Abdominal aortic aneurysm
Abdominal aortic aneurysm (AAA) is a focal dilatation of the abdominal aorta to more than 1.5 times its normal diameter. AAAs are classified by location as either suprarenal or infrarenal aneurysms. M...
A comprehensive collection of 350 medical reference articles
Abdominal aortic aneurysm (AAA) is a focal dilatation of the abdominal aorta to more than 1.5 times its normal diameter. AAAs are classified by location as either suprarenal or infrarenal aneurysms. M...
Abdominal hernias are a protrusion of intraabdominal contents through a congenital or acquired defect in the abdominal wall. Abdominal hernias are broadly classified by location (anterior wall, latera...
Abnormal labor and delivery occurs as a result of complications before and/or during birth. Prolonged stages of labor can lead to active-phase labor arrest, fetal malpresentation may cause mechanical ...
Abnormal uterine bleeding (AUB) refers to abnormal menstruation in nonpregnant individuals of reproductive age. The FIGO-AUB system 1 classifies AUB according to bleeding characteristics, i.e., freque...
Acid-base disorders are characterized by changes in the concentration of hydrogen ions (H+) in the body. Increased H+ concentration (acidosis) can lead to an abnormally low blood pH (acidemia) and dec...
Acute appendicitis is the acute inflammation of the appendix, typically due to an obstruction of the appendiceal lumen. It is the most common cause of acute abdomen requiring emergency surgical interv...
Acute cholecystitis refers to the acute inflammation of the gallbladder, which is typically due to cystic duct obstruction by a gallstone (acute calculous cholecystitis). Acalculous cholecystitis is l...
Acute heart failure is the rapid onset or worsening of heart failure symptoms, and it is a common cause of hospitalization in older patients. Multiple triggers can cause an acute decompensation of pre...
Acute leukemias are malignant neoplastic diseases that arise from either the lymphoid or myeloid cell line. Acute lymphoblastic leukemia (ALL) is the most common childhood malignancy, whereas acute my...
Acute pancreatitis is an inflammatory condition of the pancreas most commonly caused by gallstones or alcohol use in adults and biliary disease and medications in children. The typical manifestation i...
Acute respiratory distress syndrome (ARDS) is a severe inflammatory reaction of the lungs to pulmonary damage. While sepsis is the most common cause, a variety of systemic and pulmonary factors (e.g.,...
Also known as: Rheumatic fever
Acute rheumatic fever (ARF) is an inflammatory sequela involving the heart, joints, skin, and central nervous system (CNS) that occurs two to four weeks after an untreated group A β‑hemolytic streptoc...
Acyanotic congenital heart defects (ACHDs) are cardiac malformations that affect the atrial or ventricular walls, heart valves, or large blood vessels. Common causes include genetic defects (e.g., tri...
Adenomyosis is a chronic disease characterized by growth of endometrial tissue within the myometrium due to nonmalignant hyperplasia of the endometrial basal layer. Adenomyosis affects individuals of ...
Adrenal insufficiency is the decreased production of adrenocortical hormones (glucocorticoids, mineralocorticoids, and adrenal androgens) and is classified as primary, secondary, or tertiary. Primary ...
Amebiasis is an infectious disease caused by the anaerobic protozoan Entamoeba histolytica. Transmission is usually via the fecal-oral route (e.g., through contaminated drinking water) in individuals ...
Amenorrhea is the absence of menstruation. It is classified as either primary amenorrhea or secondary amenorrhea depending on whether menarche has occurred. Causes include physiological factors (e.g.,...
Amyotrophic lateral sclerosis (ALS), formerly known as Lou Gehrig disease, is a fatal neurodegenerative disease characterized by progressive upper motor neuron (UMN) and lower motor neuron (LMN) damag...
Anaphylaxis is an acute, potentially life-threatening, type 1 hypersensitivity reaction, involving the sudden IgE-mediated release of histamine mediators from mast cells and basophils in response to a...
Ankle fractures are the most common fractures of the lower extremity and most often result from twisting the ankle. Clinical features include ankle pain and decreased range of motion. If the patient h...
Anorectal abscesses are acute purulent collections in the perirectal area, which can progress to form fistulas. An anal fistula is a ductal connection between the epithelium-lined anorectal lumen and ...
Antepartum hemorrhage refers to vaginal bleeding occurring after 20 weeks of gestation. It most commonly occurs during the third trimester and is associated with significant fetal and maternal morbidi...
Asthma is a heterogeneous disease that is characterized by chronic airway inflammation and defined by a history of respiratory symptoms (e.g., wheezing, shortness of breath, chest tightness, cough). S...
Asthma is a respiratory disease that is characterized by chronic airway inflammation and commonly develops in childhood. In children ≤ 5 years of age, risk factors for asthma and asthma triggers are s...
Atrial fibrillation (Afib) is a common type of supraventricular tachyarrhythmia characterized by uncoordinated atrial activation that results in an irregular ventricular response. Afib with rapid vent...
Autoimmune hemolytic anemias (AIHAs) are a collection of disorders characterized by the destruction of RBCs through antibody-mediated hemolysis (extravascular and/or intravascular). There are two broa...
Also known as: AIH
Autoimmune hepatitis (AIH) is a rare form of chronic hepatitis that predominantly affects women. Although the etiology is unclear, it is commonly associated with other autoimmune conditions (e.g., thy...
Benign bone lesions are a heterogeneous group of slow-growing neoplasms that arise from cartilage or bone. They appear on x-ray as localized lesions with sharp margins and without soft tissue involvem...
Benign prostatic hyperplasia (BPH) is a nonneoplastic glandular and stromal hyperplasia of the transition zone of the prostate. It is a common disorder, affecting ∼ 40% of the male population by the a...
Bipolar disorder is a psychiatric condition characterized by episodes of mania (or hypomania) and major depression, interspersed with periods of normal mood and functioning. Men and women are equally ...
Birth trauma is an injury to the newborn caused by mechanical forces during birth. Risk factors include macrosomia, abnormal fetal presentation, prolonged or rapid labor, and forceps or vacuum deliver...
Blunt trauma is any nonpenetrating injury caused by the impact of a blunt object against the body, resulting in damage to underlying structures. Common causes include motor vehicle collisions and fall...
Bowel obstruction refers to the interruption of the normal passage of bowel contents through the bowel, either due to a functional or mechanical obstruction. Functional bowel obstruction, or paralytic...
Brain tumors are masses of abnormal cells within the brain. They can be primary or metastatic, benign or malignant. Common tumors in children are pilocytic astrocytomas, medulloblastomas, ependymomas,...
Bronchiectasis is an irreversible and abnormal dilation in the bronchial tree caused by cycles of bronchial inflammation leading to mucous plugging and progressive airway destruction. Bronchiectasis i...
Bronchiolitis is a lower respiratory tract infection (LRTI) characterized by inflammation of the bronchioles in children < 2 years of age. Respiratory syncytial virus (RSV) is the primary pathogen,...
Brucellosis is a zoonotic infection caused by the gram-negative coccobacillus Brucella. In countries where brucellosis is endemic, the most common vectors are cattle, sheep, goats, and pigs. Transmiss...
Cardiomyopathies are diseases of the muscle tissue of the heart. Types of cardiomyopathies include dilated (most common), hypertrophic, restrictive, and arrhythmogenic right ventricular cardiomyopathy...
Cataract is a condition characterized by clouding of the ocular lens. Acquired cataracts are more common and most frequently occur due to age-related degenerative processes in the lens; they can also ...
Also known as: Gluten‑sensitive enteropathy, Nontropical sprue
Celiac disease, also referred to as celiac sprue or nontropical sprue, is a common condition characterized by a maladaptive immune response to gluten, a protein found in many grains (e.g., wheat). The...
Cerebral palsy (CP) is a heterogenous group of disorders affecting the muscle tone and the development of movement and posture. CP results from a non-progressive damage to the brain in utero or during...
Also known as: Detection and management of cervical cancer precursor lesions
Cervical cancer is the third most common cancer of the female genital tract in the US. Persistent infection with any high-risk HPV genotype is the most common cause of cervical cancer. HPV immunizatio...
Also known as: Varicella
Chickenpox (i.e., varicella) is an infection caused by the varicella zoster virus (VZV). The condition predominantly affects children. Transmission occurs via inhalation of airborne droplets and direc...
Cholecystectomy refers to the surgical removal of the gallbladder. It is most often performed for symptomatic or high-risk cholelithiasis and acute cholecystitis. It can also be a component of a more ...
Also known as: Cholecystolithiasis
Cholelithiasis refers to the presence of abnormal concretions (gallstones) in the gallbladder. About 10–20% of American adults have gallstones. Gallstones most commonly consist of cholesterol but may ...
Also known as: Cholinergic crisis, Cholinergic toxidrome
Cholinergic poisoning is most commonly caused by exposure to substances that decrease acetylcholinesterase activity, increasing the concentration of acetylcholine at muscarinic and nicotinic receptors...
Chronic lymphocytic leukemia (CLL) is a type of B-cell malignancy that manifests with lymphocytic leukocytosis. CLL is the most common type of leukemia in adults and is typically diagnosed in older in...
Chronic obstructive pulmonary disease (COPD) is characterized by chronic respiratory symptoms resulting from airflow obstruction and alveolar gas exchange abnormalities. It is predominantly caused by ...
Chronic pancreatitis (CP) is characterized by progressive inflammation that results in irreversible damage to the structure and function of the pancreas. Chronic heavy alcohol use is the most common c...
Cirrhosis is the final stage of chronic liver disease (CLD) and it is characterized by regenerative nodules and fibrous septae in liver parenchyma in response to chronic hepatic injury. Cirrhosis is m...
Clavicle fractures are common, especially in children and adolescents, and often result from a direct fall onto the shoulder. They are classified by location using the Allman classification system, wi...
Cleft lip (CL) and cleft palate (CP) are the most common congenital orofacial deformities. A combination of genetic predisposition and in-utero exposure to teratogens (nicotine, alcohol, antiepileptic...
Colorectal cancer (CRC) is the fourth most commonly diagnosed cancer in the United States. Risk factors include a positive family history, hereditary syndromes, diet, and a number of conditions, such ...
Congenital anomalies of the kidneys and urinary tract (CAKUT) are one of the most common malformations diagnosed in newborns. The pathogenesis of CAKUT is multifactorial; both specific genes and envir...
Congenital immunodeficiency disorders are characterized by a deficiency, absence, or defect in one or more of the main components of the immune system. These disorders are genetically determined and t...
Also known as: Birth control
Contraception is the prevention of pregnancy through the use of medications, medical devices, or behaviors. Many different contraceptive options (both hormonal and nonhormonal) exist, allowing individ...
Cranial nerve palsy is characterized by a decreased or complete loss of function of one or more cranial nerves. Cranial nerve palsies can be congenital or acquired. Multiple cranial neuropathies are c...
Crohn disease (CD) is an inflammatory bowel disease (IBD) of unclear etiology. Unlike ulcerative colitis, CD is not limited to the colon but can manifest anywhere in the gastrointestinal tract. Clinic...
Also known as: Laryngotracheitis, Laryngotracheobronchitis
Viral croup (i.e., acute laryngotracheobronchitis) is an inflammation of the upper airway that occurs in young children. It is most often caused by the parainfluenza virus. This condition is character...
Also known as: Hypercortisolism
Cushing syndrome is an endocrine disorder caused by hypercortisolism, most commonly due to exogenous glucocorticoid administration (iatrogenic Cushing syndrome). Cushing syndrome can also be caused by...
Cystic fibrosis (CF) is an autosomal recessive disorder that is common in individuals of European descent. It is caused by mutations in the CFTR gene, which encodes the CF transmembrane conductance re...
Decubitus ulcers or pressure ulcers are preventable injuries frequently encountered in older, malnourished, and immobilized individuals, especially those with multiple comorbidities. These injuries ty...
Also known as: Phlebothrombosis
Deep vein thrombosis (DVT) is the formation of a blood clot within the deep veins, most commonly those of the lower extremities. The main risk factors for DVT are vascular endothelial damage (e.g., su...
Diabetes mellitus (DM) describes a group of metabolic diseases that are characterized by chronic hyperglycemia. Type 1 diabetes mellitus (T1DM) is caused by an autoimmune response that triggers the de...
Diphtheria is an infectious disease caused by Corynebacterium diphtheriae, which is usually transmitted via respiratory droplets. The clinical features of diphtheria are caused by a toxin produced by ...
Disseminated intravascular coagulation (DIC) is a disorder characterized by systemic activation of the extrinsic clotting cascade with microthrombi formation, platelet consumption, and subsequent exha...
Distal radius fracture is a common fracture of the arm, occurring most frequently in individuals 10–30 years of age and in those older than 65. The injury can be caused by low-energy trauma (common in...
Diverticulitis is a diverticular disease caused by inflammation of colonic diverticula and occurs as a complication of diverticulosis, more commonly in older adults. It may remain localized (mild unco...
Drug-induced liver injury (DILI) is most commonly caused by antibiotics, anticonvulsants, over-the-counter medications (e.g., NSAIDs, acetaminophen), and herbal or dietary supplements. Patients with D...
Also known as: Hydatidosis, Hydatid disease, Hydatid cyst, Echinocococcal cyst
Human echinococcosis, also known as hydatidosis or hydatid disease, is a parasitic disease caused by small tapeworms of the genus Echinococcus. The two most common forms of hydatidosis are cystic echi...
Also known as: Dislocation of the elbow, Elbow joint dislocation
Elbow dislocation is an atypical separation of the radial, ulnar, and humeral joint surfaces. A posterior dislocation of the elbow is common and is typically caused by a fall on an outstretched hand. ...
Endometrial cancer is the most common cancer of the female genital tract in the US, with a peak incidence between 55 and 64 years of age. It is divided into two types based on histological characteris...
Endometriosis is a common chronic disease in individuals of reproductive age characterized by growth of benign endometrial-like tissue outside the uterus. The exact etiology of endometriosis is unclea...
Intracranial epidural hematoma (EDH) refers to bleeding between the dura mater and the calvarium. Most cases of EDH are traumatic, resulting from a head injury with an associated skull fracture that r...
Erectile dysfunction (ED) is the persistent or recurrent inability to acquire or maintain an erection of sufficient rigidity or duration for sexual performance. Causative factors are vascular, neurolo...
Esophageal cancer (EC) is the eighth most common type of cancer worldwide and affects men more than women (3:1 ratio). The two main forms are esophageal adenocarcinoma and squamous cell carcinoma. Eso...
A femoral hernia is an uncommon type of inguinal hernia, in which intra-abdominal contents (e.g., intraperitoneal fat, mesentery, bowels) herniate into the femoral canal through the femoral ring. Risk...
A femoral shaft fracture is a fracture anywhere along the diaphysis of the femur. These injuries typically result from high-impact trauma (e.g., motor vehicle collisions) and are more common in younge...
Also known as: Intrauterine growth restriction, IUGR
Fetal growth restriction (FGR), also known as intrauterine growth restriction, is defined as estimated fetal weight or abdominal circumference below the 10th percentile for a given gestational age. FG...
Also known as: Vitamin B9 deficiency
Folate deficiency is most commonly caused by malnutrition, e.g., in individuals with insufficient dietary intake or alcohol use disorder. Patients typically present with signs of anemia (e.g., fatigue...
Also known as: FBA
Foreign body aspiration (FBA) is a potentially life-threatening emergency that most commonly occurs in children 1–3 years of age. A foreign body (FB) can become lodged in either the upper or lower air...
Gastroesophageal reflux disease (GERD) is a chronic condition in which stomach contents flow back into the esophagus, causing irritation to the mucosa. Reflux is primarily caused by an inappropriate, ...
Gastrointestinal (GI) bleeding can originate from the upper GI tract (proximal to the ligament of Treitz), small bowel, or lower GI tract (distal to the ileocecal valve). Overt GI bleeding is visible ...
Also known as: Bowel perforation
Gastrointestinal perforation is a full-thickness loss of bowel wall integrity that results in perforation peritonitis. Perforation of a duodenal ulcer is the most common cause of perforation peritonit...
A fracture is a partial or complete interruption in the continuity of bone. The most common cause is trauma, followed by diseases that result in weakened bone structure. Fractures are named and classi...
Giardiasis is a common parasitic infection caused by the protozoan Giardia duodenalis. Transmission usually occurs via the fecal-oral route (e.g., from contaminated drinking water) when traveling or l...
Also known as: Favism
Glucose-6-phosphate dehydrogenase (G6PD) deficiency leads to an impaired regeneration of reduced glutathione, an important antioxidant, which makes RBCs more susceptible to oxidative stress and can re...
Gout is an inflammatory crystal arthropathy caused by the precipitation and deposition of uric acid crystals in synovial fluid and tissues. Decreased renal excretion and/or increased production of uri...
Guillain-Barré syndrome (GBS) is an acute immune-mediated polyradiculoneuropathy that typically manifests with bilateral ascending flaccid paralysis and sensory involvement, e.g., paresthesia. The pat...
Hearing loss can be defined based on the general type of hearing loss (conductive or sensorineural) and the location of the dysfunction. Conductive hearing loss typically occurs due to dysfunction of ...
Heart failure (HF) is a complex clinical syndrome caused by structural or functional impairment of ventricular filling and/or ejection of blood. The three main underlying causes of HF are coronary art...
Hemolytic disease of the fetus and newborn (HDFN) is a condition characterized by the destruction of fetal red blood cells (RBC) and subsequent anemia. It is commonly caused by a Rhesus (Rh) or ABO in...
Hemolytic uremic syndrome (HUS) is a thrombotic microangiopathy, a condition in which microthrombi, consisting primarily of platelets, form and occlude the microvasculature. HUS is characterized by mi...
Hemophilia is a coagulation disorder caused by a clotting factor deficiency. The three types of hemophilia classified by deficient clotting factor are hemophilia A (factor VIII), hemophilia B (factor ...
Hemorrhoids are dilated submucosal vascular cushions within the anal canal that can be asymptomatic or manifest as painless perianal masses, pruritus, or intermittent scant hematochezia (bright red bl...
Hepatitis B is a viral infection caused by the hepatitis B virus (HBV). It occurs worldwide and is transmitted sexually, parenterally, or vertically. After an incubation period of 1–6 months, most pat...
Hereditary spherocytosis (HS) is the most common congenital hemolytic disorder among individuals of northern European descent. In most cases, it is an autosomal dominant disease that is caused by red ...
A pregnancy is considered high risk if one or more risk factors for adverse pregnancy outcomes are present at the outset or develop during the course of that pregnancy. Maternal factors that increase ...
Hip fractures are classified as intracapsular (femoral head, femoral neck) or extracapsular (intertrochanteric, trochanteric, or subtrochanteric). Hip fractures in older adults are typically low-impac...
Also known as: Lymphogranulomatosis
Hodgkin lymphoma (HL) is a malignant lymphoma of B-cell origin. Incidence follows a bimodal age distribution, with peaks in the third, and sixth to eighth decades of life. The WHO classifies HL as eit...
Infection with the human immunodeficiency virus (HIV) leads to a complex disease pattern that ultimately results in chronic immunodeficiency. HIV can be transmitted sexually, parenterally, or vertical...
Humerus fractures can result from direct or indirect trauma. They are classified by location into proximal humerus fracture, humeral shaft fracture, and distal humerus fracture. Proximal humerus fract...
Hydrocephalus is the abnormal enlargement of cerebral ventricles and/or subarachnoid space as a result of excess cerebrospinal fluid (CSF) accumulation. There are two types of true hydrocephalus: comm...
Hyperparathyroidism (HPT) is characterized by abnormally high parathyroid hormone (PTH) levels in the blood due to parathyroid gland overactivity. HPT is further classified based on the underlying cau...
Hypertension (HTN) is a common condition that affects one in every three adults in the United States and is becoming increasingly prevalent among children. The 2017 American College of Cardiology (ACC...
Thyrotoxicosis refers to the symptoms caused by the excessive circulation of thyroid hormones. It is typically caused by thyroid gland hyperactivity (i.e., hyperthyroidism), the most common causes of ...
Hypothyroidism is a condition in which the thyroid gland is underactive, resulting in a deficiency of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). Rarely, hormone production remains ...
Also known as: Henoch-Schonlein purpura, Anaphylactoid purpura
IgA vasculitis (IgAV), previously referred to as Henoch-Schonlein purpura (HSP), is an acute immune complex-mediated small vessel vasculitis that most commonly occurs in children. Onset is often prece...
Also known as: Immune thrombocytopenic purpura
Immune thrombocytopenia (ITP) is a type of thrombocytopenia involving the formation of autoantibodies against platelets. ITP may be a primary disease or occur secondary to a known trigger (e.g., SLE, ...
Infant nutrition includes the use of breast milk, infant formula, infant vitamin supplementation, and complementary feeding. Breast milk (i.e., from breastfeeding, self-expression, or donors) is the p...
Also known as: Acute gastroenteritis in children
Acute gastroenteritis is a common infection in childhood. The majority of cases are caused by viruses, while ∼20% are bacterial, and a small number are parasitic. Most children have a mild presentatio...
Also known as: Epstein-Barr virus infection
Infectious mononucleosis, also called mono or the kissing disease, is an acute condition most commonly caused by the Epstein-Barr virus (EBV). The disease is highly contagious and spreads via bodily s...
Infective endocarditis (IE) is an infection of the endocardium that typically affects one or more heart valves. The condition is usually due to bacteremia, which in adults is most commonly caused by d...
An inguinal hernia is an abnormal protrusion of intra-abdominal contents (most commonly fat) through the inguinal canal. Inguinal hernias are the most common type of groin hernia, and can be further s...
Interstitial lung diseases (ILDs) are a diverse group of rare, highly morbid pulmonary disorders characterized by inflammation and progressive scarring (fibrosis) of the lungs. The most common types o...
Also known as: ICH, Intraparenchymal hemorrhage
Intracerebral hemorrhage (ICH) refers to bleeding within the brain parenchyma. The term should not be confused with intracranial hemorrhage, which is a broader term that encompasses bleeding within an...
Also known as: Cervical cancer
Cervical cancer is the third most common cancer of the female genital tract in the US, with a peak incidence in women between 35–44 years of age. Persistent infection with any high-risk HPV genotype i...
Iron deficiency anemia (IDA) is the most common form of anemia worldwide and is caused by inadequate intake, decreased absorption (e.g., atrophic gastritis, inflammatory bowel disease), increased dema...
Irritable bowel syndrome (IBS) is a chronic condition that is very common in North America and Europe. It is thought that the underlying pathophysiology involves changes in gastrointestinal motility, ...
Ischemic stroke is an acute neurological condition caused by impaired cerebral blood flow (e.g., vascular occlusion or systemic hypoperfusion). The most important risk factors are chronic systemic hyp...
Also known as: Mucocutaneous lymph node syndrome
Kawasaki disease (KD) is an acute, necrotizing vasculitis of unknown etiology. The condition primarily affects children under the age of five and is more common among those of Asian descent. KD is cha...
Knee ligament injuries are often the result of rotational movement of the knee joint or direct trauma. Injuries to the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial colla...
A late-term pregnancy is defined as 41 0/7 to 41 6/7 weeks' gestation; at 42 weeks' gestation, it becomes a postterm pregnancy. While the causes of postterm pregnancy are generally unknown, many suppo...
Leishmaniasis is a parasitic disease caused by protozoans of the Leishmania genus, which are transmitted by infected phlebotomine sandflies. Depending on the parasite subtype and the strength of the h...
Also known as: Bronchial carcinoma, Bronchogenic carcinoma
Lung cancer is the leading cause of cancer death in the US, accounting for almost a quarter of all cancer-related fatalities; 80–90% of cases can be attributed to smoking. Lung cancer is generally div...
Also known as: Unipolar depressive disorder
Major depressive disorder (MDD) is an episodic mood disorder primarily characterized by depressed mood and anhedonia lasting for at least two weeks. Women have a higher risk of developing MDD than men...
Malaria is a potentially life‑threatening tropical infectious disease caused by Plasmodium parasites, which are transmitted through the bite of an infected female Anopheles mosquito. The disease is en...
Mastitis is inflammation of the breast tissue and most commonly affects individuals who are lactating (puerperal mastitis). Nonlactional mastitis, although rare, can also occur. Mastitis typically man...
Maternal complications during pregnancy include metabolic conditions, hemorrhage, infectious diseases, and dermatologic conditions. Hyperemesis gravidarum is a severe form of nausea and vomiting in pr...
Also known as: Rubeola
Measles (rubeola) is a highly infectious disease caused by the measles virus. There are three phases of disease: a prodromal stage, an exanthem stage, and a recovery stage. The prodromal stage is char...
Meningitis is an infection of the meninges in the brain or spinal cord. Common causes include viruses and bacteria, although fungal, parasitic, and noninfectious causes of meningitis are possible. The...
Metabolic dysfunction-associated steatotic liver disease (MASLD) is the accumulation of excess fat in hepatocytes in individuals with at least one cardiometabolic risk factor (e.g., hypertension, impa...
Migraine is a primary headache characterized by recurrent episodes of unilateral, localized pain that are frequently accompanied by nausea, vomiting, and sensitivity to light and sound. In approximate...
Also known as: Multiple pregnancy
Multifetal gestation is a pregnancy with two or more fetuses. Previous multifetal gestation and use of assisted reproductive technology increase the risk of multifetal gestation, which may be fraterna...
Multiple endocrine neoplasia (MEN) is a term used to describe three autosomal dominant syndromes that are associated with certain hormone-producing neoplasias. There are three subtypes: MEN 1, MEN 2A,...
Multiple myeloma (MM) is a malignant plasma cell dyscrasia characterized by uncontrolled proliferation and diffuse infiltration of monoclonal plasma cells in the bone marrow. Malignant plasma cells pr...
Multiple sclerosis (MS) is a chronic degenerative disease of the CNS characterized by demyelination and axonal degeneration in the brain and spinal cord, which are caused by an immune-mediated inflamm...
Mumps is a highly contagious viral infection that is transmitted via infectious respiratory particles and primarily affects children. Since the introduction of the measles, mumps, and rubella (MMR) va...
Also known as: Heart attack
Myocardial infarction (MI) refers to ischemic necrosis of myocardial tissue. The most common underlying cause is coronary artery disease. Type 1 myocardial infarction occurs when an unstable plaque ru...
Also known as: Icterus neonatorum
Neonatal jaundice is one of the most common conditions occurring in newborn infants and is characterized by elevated levels of bilirubin in the blood (total serum bilirubin concentration > 5 mg/dL)...
Also known as: Infant respiratory distress syndrome, Surfactant deficiency disorder, Hyaline membrane disease
Neonatal respiratory distress syndrome (NRDS), or surfactant deficiency disorder, is a lung disorder in infants that is caused by a deficiency of pulmonary surfactant. It is most common in preterm inf...
Also known as: Urolithiasis
Nephrolithiasis encompasses the formation of all types of urinary calculi in the kidney, which may be deposited along the entire urogenital tract, from the renal pelvis to the urethra. Risk factors in...
Nephrotic syndrome is characterized by massive proteinuria (e.g., > 3.5 g/24 h), hypoalbuminemia, and edema and indicates damage to the glomerular filtration barrier. In adults, the most common typ...
Nipple discharge can be physiological or pathological. Physiological discharge is typically bilateral, multiductal, with a milky appearance; causes include lactation and galactorrhea. Pathological dis...
Childbirth begins with the onset of labor, which consists of contractions that lead to progressive cervical dilation and effacement, eventually resulting in the birth of the infant and expulsion of th...
Also known as: Osteoarthrosis
Osteoarthritis is a disabling joint disease characterized by degeneration of the joint complex (articular cartilage, subchondral bone, and synovium) that can have various causes, most notably advanced...
Osteoarthritis of the hip and knee is characterized by joint degeneration, which can lead to functional impairment. Although the exact etiology is unknown, risk factors include older age, overuse of t...
Osteomalacia and rickets are disorders of bone mineralization. In osteomalacia, remodeling of preexisting bone is defective; in rickets, new bone formation is defective. Osteomalacia can affect indivi...
Osteomyelitis is an infection of the bone; it occurs following hematogenous (seeded from a remote source) or exogenous (expansion from nearby tissue) spread of pathogens, most commonly Staphylococcus ...
Osteoporosis is a skeletal condition in which the loss of bone mineral density (BMD) leads to decreased bone strength and increased susceptibility to fractures. Postmenopausal women and older adults a...
In the US, ovarian cancer is the second most common gynecologic cancer and has the highest mortality rate of any gynecologic cancer. Incidence increases with age (peak incidence at 55–64 years of age)...
Ovarian cysts are fluid-filled sacs within the ovary. The most common types are functional follicular cysts, corpus luteum cysts, and theca lutein cysts, which all develop as part of the menstrual cyc...
A number of conditions affect the breasts, including disorders of breast development (e.g., congenital anomalies, breast hypertrophy), fibrocystic breast changes, inflammatory conditions (e.g., mastit...
Viral hepatitides comprise the infectious diseases hepatitis A, B, C, D, and E, which have various routes of transmission (e.g., fecal-oral, sexual, parenteral, and perinatal transmission). Most patie...
Overweight and obesity are characterized by an accumulation of excess body fat (adiposity) associated with the risk of developing weight-related complications. Multiple underlying factors (e.g., genet...
Parkinson disease (PD) is a neurodegenerative condition that involves the progressive depletion of dopaminergic neurons in the basal ganglia, particularly the substantia nigra. The disease most common...
Parvovirus B19 is transmitted through respiratory droplets and has a wide range of clinical presentations. Infections occur most frequently in children, with peak incidence between 5 and 15 years of a...
Also known as: Pelvic relaxation disorder
Pelvic floor dysfunction (PFD) refers to laxity (low-tone PFD) or tension (high-tone PFD) of the pelvic floor muscles and/or connective tissue. Causes include muscle or nerve damage (e.g., from surger...
Pelvic inflammatory disease (PID) is caused by a bacterial infection that spreads beyond the cervix to infect the upper female reproductive tract, i.e., the uterus (endometritis), fallopian tubes (sal...
Also known as: PUD
Peptic ulcer disease (PUD) is the presence of one or more ulcerative lesions in the stomach or duodenum. Etiologies include Helicobacter pylori infection (most common), prolonged NSAID use (NSAID-indu...
Pericardial effusion is the acute or chronic accumulation of fluid in the pericardial space (between the parietal and the visceral pericardium) and is often associated with a variety of underlying dis...
Pericarditis is inflammation of the pericardium and may be acute or chronic. Acute pericarditis is most commonly caused by a viral infection; however, a number of conditions can cause an inflammatory ...
Peripheral nerve injuries result from systemic diseases (e.g., diabetes, autoimmune disease) or localized damage (e.g., trauma, compression, tumors) and manifest with neurological deficits distal to t...
Also known as: Whooping cough, 100-day cough
Pertussis, or whooping cough, is a highly infectious disease of the respiratory tract caused by the gram-negative bacterium Bordetella pertussis. This disease spreads via droplet transmission (and to ...
Also known as: Pituitary neuroendocrine tumor
Pituitary adenomas (also known as pituitary neuroendocrine tumors) are benign tumors that arise sporadically from the anterior pituitary gland. They are classified as either microadenomas or macroaden...
Plantar fasciitis is a common condition that affects the deep plantar fascia, resulting in foot and heel pain. Although it is traditionally thought to be an inflammatory-driven process, histological a...
Pleural effusion is the abnormal accumulation of fluid in the pleural cavity between the lining of the lungs and the thoracic cavity (i.e., the visceral and parietal pleurae). Normally, a small amount...
Pneumonia is a respiratory infection characterized by inflammation of the alveolar space and/or the interstitial tissue of the lungs. In industrialized nations, it is the leading infectious cause of d...
Also known as: Pediatric community-acquired pneumonia
Pneumonia, a common infection in children, is a respiratory illness characterized by inflammation of the alveolar space and/or the interstitial tissue of the lungs. The etiology is typically bacterial...
Polyneuropathy is a disorder that involves damage to multiple peripheral nerve fibers. Causes include diabetes mellitus, alcohol use disorder, hereditary diseases, toxins, infection, or other inflamma...
Portal hypertension is the pathological elevation of portal venous pressure resulting from obstructions in portal blood flow, which can be prehepatic (e.g., portal vein thrombosis), hepatic (e.g., liv...
Postpartum complications include infectious, vascular, genitourinary, musculoskeletal, and behavioral conditions. Infectious complications include postpartum endometritis, postpartum sepsis, mastitis,...
Poststreptococcal glomerulonephritis (PSGN) is an acute glomerular inflammation that follows infection with nephritogenic strains of streptococci. Although most commonly seen in children following gro...
Pregnancy begins with the fertilization of the ovum and its subsequent implantation into the uterine wall. The duration of pregnancy is counted in weeks of gestation from the first day of the last men...
Pregnancy loss can occur even in previously healthy pregnancies. If it occurs before 20 weeks' gestation (∼ 10% of pregnancies), it is called miscarriage or spontaneous abortion. If it occurs after 20...
Preterm labor is defined as regular uterine contractions and cervical changes before 37 weeks' gestation. Preterm birth is defined as live birth between 20 0/7 weeks and 36 6/7 weeks' gestation. Risk ...
Also known as: Premature ovarian failure
Primary ovarian insufficiency (POI) is impaired ovarian function before the age of 40 years due to a defect in the ovaries that decreases follicle numbers or results in an insufficient follicular resp...
Prostate cancer is one of the most common cancers that affect men, especially those > 50 years of age. Typically, prostate cancer has an indolent course and is usually discovered while still locali...
Pulmonary embolism (PE) is the obstruction of one or more pulmonary arteries by an embolic solid, fluid, or gas. In the majority of cases, PE is caused by a venous thrombus that originated in the legs...
Pyelonephritis is an infection of the renal pelvis and parenchyma that is usually associated with an ascending bacterial infection of the bladder. It occurs more commonly in women and risk factors inc...
Rabies is a neurotropic virus transmitted through the bite of an infected animal. The virus enters via the animal saliva, traveling along peripheral nerves to the central nervous system (CNS). The ons...
Renal replacement therapy (RRT) is used to support or replace kidney function (i.e., remove toxins, metabolites, and/or water from the body). RRT is indicated in various acute (e.g., acute renal injur...
Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory autoimmune disorder that primarily affects the joints (e.g., causes pain, swelling, synovial destruction, deformities), but may also mani...
Also known as: Exanthem subitum, Sixth disease
Roseola infantum is an infectious disease most commonly caused by human herpesvirus 6 (HHV-6). It occurs most frequently in children between 6 months and 2 years of age. Roseola infantum is characteri...
Also known as: German measles
Rubella (German measles) is an infectious disease caused by the rubella virus and transmitted via airborne droplets or transplacentally (see “Congenital rubella syndrome”). Since the introduction of t...
The scaphoid bone is the most commonly fractured carpal bone. Fractures are most often localized in the middle third of the scaphoid bone. Generally, scaphoid bone fractures result when an individual ...
Also known as: Second disease
Scarlet fever is an acute syndrome caused by Streptococcus pyogenes, a highly contagious toxin-producing group A Streptococcus (GAS). The syndrome most commonly occurs in children and in less than 10%...
Also known as: Seizure disorders
A seizure is a transient manifestation of abnormal excessive or synchronous electrical brain activity that causes convulsions, loss of consciousness, and/or lapses of consciousness. The underlying cau...
Sepsis is an acute life-threatening condition characterized by organ dysfunction due to a dysregulated immune response to infection. Without prompt intervention, patients frequently progress to septic...
Sexually transmitted infections (STIs) are a group of infections that are primarily transmitted via sexual intercourse and intimate physical contact. Some of the most common STIs include HPV infection...
In shoulder dislocation, the head of the humerus dislocates completely or partially (subluxation) in one of three directions: anterior (most common), posterior, or inferior. Shoulder dislocation is us...
Sickle cell disease is caused by hereditary hemoglobinopathy, which includes sickle cell anemias (i.e., HbSS and HbSβ0thal) and other compound heterozygous genotypes (e.g., HbSC, HbSβ+thal). Mutations...
Volvulus is defined as the twisting of a loop of bowel on its mesentery and is one of the most common causes of intestinal obstruction. The sigmoid colon, and less frequently, the cecum, are the commo...
Skeletal dysplasias are a group of genetic disorders that affect the development of bone and cartilage. The disorders may be inherited in an autosomal dominant, autosomal recessive, or X-linked manner...
Somatic symptom and related disorders are characterized by prominent somatic symptoms associated with significant distress and psychosocial impairment, and cannot be fully explained by a recognized me...
Spinal cord injuries (SCIs) result from trauma (e.g., motor vehicle crashes and falls) or nontraumatic causes (i.e., ischemic, compressive, or inflammatory). SCIs initially manifest with an acute phas...
Also known as: Subdural hemorrhage
Subdural hematoma (SDH) refers to bleeding into the intracranial subdural space that is typically caused by a rupture of the bridging veins. Trauma, including minor falls, cerebral atrophy, and condit...
Supraventricular tachycardias (SVTs) are a group of tachyarrhythmias arising from abnormalities in pacemaker activity and/or conduction involving myocytes of the atria and/or AV node. Types of SVT inc...
Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease that predominantly affects women of childbearing age and is the most common form of lupus. The exact cause is still unknown, but ...
Testicular torsion is the sudden twisting of the spermatic cord within the scrotum. It most commonly affects neonates and young men. Because of the risk of ischemia and possible infarction of the test...
Also known as: Lockjaw
Tetanus (lockjaw) is an acute disease caused by neurotoxins from the bacterium Clostridium tetani. C. tetani is ubiquitous in spore form and enters the body through broken skin (e.g., deep puncture wo...
Thalassemias are a group of hereditary hemoglobin disorders characterized by mutations on the α- or β-globin chains (resulting in alpha or beta thalassemia). Thalassemias can be further classified acc...
The menstrual cycle is a highly regulated physiological process required for conception and pregnancy. From the start of menstruation (menarche) to its cessation (menopause), menstrual bleeding (menst...
Also known as: Thyroid carcinoma
Thyroid cancer is a malignant tumor that arises from either the thyrocytes or the parafollicular cells of the thyroid gland. It is more common in women, especially between 30–50 years of age. The pred...
Thyroid nodules are abnormal growths within the thyroid gland. They are present in approximately 50% of the general population but only palpable in 5–10% of the population. They are more common in wom...
Tibial and fibular fractures are common types of long bone injuries and are usually caused by direct trauma. Fractures may occur proximally, at the shaft, or distally. Since only a small amount of sof...
Toxoplasmosis is a disease caused by the obligate intracellular parasite Toxoplasma gondii. Transmission occurs either through ingestion of cysts found, for example, in raw meat or cat feces, or from ...
Traumatic brain injury (TBI) is defined as a structural injury to the brain or a disruption in the normal functioning of the brain as a result of a blunt or penetrating head injury. Head injury refers...
Tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis, which typically affects the lungs. It is a common infectious cause of morbidity and mortality worldwide. Primary infection, transmi...
Typhoid and paratyphoid fever (sometimes referred to together as enteric fever) are infectious diseases caused by the bacteria Salmonella Typhi and Salmonella Paratyphi. Transmission occurs via the fe...
Ulcerative colitis is a type of chronic inflammatory bowel disease (IBD) characterized by mucosal inflammation of the colon that typically starts in the rectum and may extend proximally affecting the ...
Urinary incontinence (UI) is a common condition characterized by involuntary leakage of urine. Causes and representations are variable. Stress urinary incontinence (SUI), urgency urinary incontinence ...
Urinary tract cancer most commonly involves the bladder, although it may also occur in the renal pelvis, ureters, and, rarely, the urethra. The most common histological type of urinary tract cancer is...
Urinary tract infections (UTIs) are infections of the bladder, urethra, ureters, or kidneys that are most commonly caused by bacteria, especially E. coli. Infections of the bladder or urethra are call...
Urticaria is an inflammatory skin disorder characterized by hives (wheals) with or without angioedema. Urticaria is classified as acute (≤ 6 weeks duration) or chronic (> 6 weeks duration). Causes ...
Vaccination is a very effective measure for providing immunity to many infectious diseases. The discovery of vaccines played a central part in the eradication of smallpox and helped significantly redu...
Vulvar cancer is a rare carcinoma that predominantly occurs after menopause. Major risk factors include HPV infection, smoking, vulvar intraepithelial neoplasia, and cervical intraepithelial neoplasia...
Vulvovaginitis refers to a large variety of conditions that result in inflammation of the vulva and vagina. The causes may be infectious (e.g., bacterial vaginosis in most cases) or noninfectious. Phy...
The well-child visits are a vital component of pediatric and public health care, allowing for the prevention of disease through immunizations and anticipatory guidance, and early detection of existing...
Also known as: Hepatolenticular degeneration
Wilson disease is an autosomal recessive metabolic disorder in which impaired copper excretion causes copper to accumulate in the body. Early-stage Wilson disease is characterized by the presence of c...
Wounds are a break in the skin and/or a disruption of the skin's normal barrier function. Wound healing is a step-wise cellular response involving fibroblasts, macrophages, endothelial cells, and kera...
Also known as: Factor VIII-related antigenic protein deficiency
Von Willebrand disease (vWD) is a bleeding disorder characterized by a deficiency or dysfunction of von Willebrand factor (vWF). vWD is the most common congenital bleeding disorder, affecting approxim...
Acute compartment syndrome (ACS) is caused by tissue ischemia due to increased pressure within a fascial compartment. It is a surgical emergency that is characterized by rapidly progressive pain and s...
Also known as: Osteonecrosis
Avascular necrosis is a condition in which bone tissue becomes ischemic and begins to suffer pathologic decomposition, leading to joint dysfunction. Avascular necrosis (AVN) affects all age groups and...
Also known as: Behcet syndrome
Behcet disease is a type of variable vessel vasculitis that most commonly affects young adults (20–40 years of age) from the Mediterranean region to eastern Asia. Patients typically present with recur...
Breast cancer is the second most common malignancy in women (after nonmelanoma skin cancer). In the US, the lifetime risk of a woman developing breast cancer is approximately 13%. The most important r...
Burns can be caused by heat, chemicals, electricity, friction, and radiation. Injury severity is determined by the depth and extent of the burn. Burn depth is classified as first degree (superficial),...
Cervical lymphadenopathy (LAD) is a > 1 cm enlargement of lymph nodes in the neck. In children, cervical LAD is common and most often represents an inflammatory response to an acute infection, such...
Early childhood, which typically spans from birth to 8 years of age, is characterized by rapid growth and development. Close monitoring during this period ensures children are meeting age-specific mil...
Also known as: Child abuse and neglect
Child maltreatment is any act or failure to act that results in potential or actual harm to a child, usually involving a caregiver. Types of child maltreatment include neglect, physical abuse, sexual ...
Also known as: Chromosomal anomalies
Structural and numerical chromosomal abnormalities affect either the autosomes or gonosomes and are a common cause of spontaneous abortion. The most frequently observed autosomal abnormalities are tri...
Connective tissue is an important biological tissue composed of an extracellular matrix that binds, anchors, and supports organs. There are various types of connective tissue, all of which consist of ...
Also known as: Corneal diseases
The cornea is the external, transparent layer of the eye covering the iris and pupil. The cornea is highly sensitive, and corneal disorders (e.g., abrasions, infection, erosion, ulcers, foreign bodies...
Cyanotic heart defects (CHDs) are congenital cardiac malformations that commonly affect the atrial walls, e.g., the right atrium (RA) or left atrium (LA); ventricular walls, e.g., the left ventricle (...
Deep neck infections include peritonsillar abscess, parapharyngeal abscess (PPA), and retropharyngeal abscess (RPA). While uncommon, deep neck infections are clinically significant because of their po...
Diabetes mellitus (DM) in pregnancy consists of gestational diabetes mellitus (GDM) and pregestational diabetes mellitus. GDM is an abnormal glucose tolerance that develops during pregnancy, while pre...
Differences (disorders) of sex development (DSDs; formerly known as “intersex conditions”) are a group of congenital conditions characterized by the atypical development of chromosomal, gonadal, and/o...
Down syndrome, also called trisomy 21, is the most common autosomal chromosomal irregularity, occurring in approximately 1:700 live births. The risk of a trisomy 21 pregnancy increases with maternal a...
Encephalitis is the inflammation of brain parenchyma with neurological dysfunction. Infectious encephalitis is caused by viral (most common), bacterial, parasitic, or fungal pathogens. Autoimmune ence...
Erythema multiforme is a rare, acute hypersensitivity reaction most commonly triggered by the herpes simplex virus (HSV). Additional triggers include infections (e.g., Mycoplasma pneumonia) and certai...
Febrile seizures affect children aged 6 months to 5 years and are associated with fever in the absence of CNS infection. They are one of the most common pediatric emergencies. Simple febrile seizures ...
Food poisoning is a specific subset of foodborne illnesses and is caused by the ingestion of any substance that is contaminated with a preformed toxin. Symptoms usually occur within hours of ingesting...
Genitourinary trauma includes injury to the kidneys, ureters, bladder, urethra, and genitals, and is associated with a high level of morbidity if not properly identified and managed. Classic symptoms ...
Gestational trophoblastic disease (GTD) is a class of neoplastic conditions characterized by abnormal trophoblast-cell growth in the uterus. GTD is classified into hydatidiform moles (molar pregnancy)...
Glaucoma is a group of eye diseases associated with acute or chronic destruction of the optic nerve with or without concomitant increased intraocular pressure (IOP). In the US, glaucoma is the second ...
Renal glomeruli excrete urinary substances and excess water as an ultrafiltrate into the urine by selectively filtering the blood. Any damage to the glomeruli disrupts the filtration process and resul...
Also known as: Helminthiasis, Worm infections
Helminths (i.e., parasitic worms) are a group of macroparasites encompassing a variety of species that can infect their hosts in three different ways: ingestion of eggs or larvae (e.g., via contaminat...
Also known as: Iron overload disease
Hemochromatosis refers to a group of conditions characterized by excess iron deposition (or increased risk of excess deposition) in the body as a result of increased iron absorption. Increased iron ab...
Bleeding disorders are a group of heterogeneous conditions characterized by defects in hemostasis that lead to an increased susceptibility to bleeding (also known as hemorrhagic diathesis). They are c...
Hyperglycemic crisis is a condition characterized by severe hyperglycemia and metabolic disturbances and may be the initial manifestation of diabetes mellitus or a complication of diabetes or another ...
Hypertensive crises refer to acute increases in blood pressure (generally defined as ≥ 180/120 mm Hg) that cause or increase the risk of end-organ damage, i.e., damage to the brain (e.g., encephalopat...
Hypertensive pregnancy disorders, also called hypertensive disorders of pregnancy (HDP), are among the most common complications during pregnancy and the early postpartum period. There are four major ...
Idiopathic inflammatory myopathies (IIM) are a group of rare systemic diseases characterized by progressive weakness due to chronic skeletal muscle inflammation. They are classified based on clinicopa...
Vaccinations are one of the most effective methods of disease prevention, drastically reducing illness, hospitalizations, and deaths from infectious diseases. In order to prevent a resurgence of vacci...
Infectious gastroenteritis is an inflammation of the gastrointestinal tract that is most commonly caused by viruses (e.g., norovirus, rotavirus, enteric adenovirus). However, it can also be caused by ...
Infertility is the inability to achieve pregnancy after 12 months of regular unprotected sexual intercourse in female individuals < 35 years of age and after 6 months in those ≥ 35 years of age, or...
Myelodysplastic syndromes (MDSs) are a group of clonal hematopoietic stem cell neoplasms characterized by impaired proliferation and differentiation of myeloid stem cells within the bone marrow. Prima...
Myeloproliferative neoplasms (MPNs) are a group of disorders characterized by a proliferation of normally developed (nondysplastic) multipotent hematopoietic stem cells from the myeloid cell line. The...
Neurodevelopmental disorders are a group of conditions that begin in early childhood and affect the development of the brain and nervous system. These disorders impact areas such as learning, communic...
Lymphomas are malignancies that arise from lymphocytes and are classified as either Hodgkin lymphomas (characterized by Reed-Sternberg cells) or non-Hodgkin lymphomas (NHLs), which comprise all other ...
Oncologic emergencies are a group of potentially life-threatening conditions that can manifest as a result of malignant disease and/or their treatment. These conditions include, but are not limited to...
Also known as: Clinically relevant neonatal conditions
Neonatal conditions manifest during the first 28 days of life and can affect any organ system. This article includes an overview of neonatal conditions by organ system with additional information on m...
The ovaries consist of different types of tissue (epithelial, germ cells, and sex cord tissue), which may give rise to benign or malignant tumors. Epithelial ovarian tumors are the most common tumor s...
Pelvic fractures most often occur in patients with multiple trauma caused by impact injuries such as motor vehicle crashes or falls. Patients present with pelvic pain, reduced range of motion, and hem...
Penetrating trauma is an injury caused by a foreign object piercing the skin, resulting in damage to underlying structures and an open wound. The most common types of penetrating injuries are gunshot ...
Poisoning describes the harmful effects of exposure (i.e., inhalation, ingestion, injection, absorption) to a potentially toxic substance. The degree of harm depends on substance factors (e.g., type, ...
Also known as: Stein–Leventhal syndrome, Hyperandrogenic anovulation
Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders in women. It is characterized by hyperandrogenism (which primarily manifests as hirsutism, acne vulgaris, and androgenic ...
Also known as: Puerperal hemorrhage
Postpartum hemorrhage (PPH) is an obstetric emergency and is defined as a blood loss ≥ 1000 mL or blood loss presenting with signs or symptoms of hypovolemia within 24 hours of delivery. It is the num...
Liver diseases unique to pregnancy include intrahepatic cholestasis of pregnancy, acute fatty liver of pregnancy (AFLP), hyperemesis gravidarum, and HELLP syndrome. The diagnostic evaluation of abnorm...
The purpose of a preoperative evaluation is to assess whether a patient is medically optimized for the stress of surgery and to identify reversible factors that may increase the perioperative risk for...
Primary malignant bone tumors are rare malignant tumors that arise from native bone tissue, such as osteoblasts, chondrocytes, and mesenchymal stem cells. Osteosarcoma and Ewing sarcoma are the most c...
Psoriasis is a common chronic inflammatory skin disorder affecting individuals with an underlying genetic predisposition. Triggering events (e.g., infection, medication) can lead to disease manifestat...
Puberty is the phase of development between childhood and complete, functional maturation of the reproductive glands and external genitalia. Puberty typically starts with gonadarche, which is the stim...
This article provides an overview of inherited symptom complexes that occur rarely in the general population. These syndromes are caused by inherited genetic defects, which occur either due to chromos...
Also known as: Hypernephroma, Grawitz tumor
Renal cell carcinoma (RCC), which originates from the renal tubular epithelium, is the most common renal malignancy in adults. Most cases are sporadic, but some hereditary disorders are also associate...
Scrotal abnormalities include various conditions such as varicoceles, hydroceles, and malpositioning of the testicles (e.g., cryptorchidism, retractile testes). The differential diagnosis is broad and...
Also known as: Infectious arthritis
Septic (infectious) arthritis is an infection of the joint space, which can occur in a native joint or a prosthetic joint. Patients with underlying joint diseases (e.g., rheumatoid arthritis) are at a...
Sjogren syndrome is a chronic inflammatory autoimmune disease that most commonly occurs in middle-aged women. Primary Sjogren syndrome is idiopathic; Sjogren syndrome that occurs concomitantly with an...
Skin and soft tissue infections (SSTIs) are a group of heterogeneous conditions affecting the epidermis, dermis, subcutaneous tissue, or superficial fascia. Uncomplicated infections are most commonly ...
Soft tissue injuries of the head and neck are usually caused by blunt or penetrating trauma and require careful clinical assessment. Imaging may be required to rule out fractures and other complicatio...
Soft tissue lesions of the shoulder involve the shoulder's ligaments, tendons, cartilage, and/or capsule. The rotator cuff is the most commonly affected structure. Rotator cuff disease includes a rang...
Infants are usually born at term between 37 and 42 weeks of gestation. This time period can be further divided into early term (37 to 38 weeks), full term (39 to 40 weeks), and late term (41 weeks) de...
This article provides an overview of the most common thyroid disorders (hypothyroidism and hyperthyroidism) and thyroid function testing. For more information on specific conditions, see the articles ...
Blood component transfusions are usually safe and, given extensive screening and pretransfusion testing, serious adverse events are uncommon. When acute reactions occur they are typically mild, with t...
Also known as: Fibroid, Uterine fibromyoma
Uterine leiomyomas (also known as fibroids) are benign, hormone-sensitive uterine neoplasms. They are classified as either submucosal (beneath the endometrium), intramural (within the muscular uterine...
Also known as: Valvular heart defects
Valvular heart diseases (VHDs) comprise a group of conditions that affect the heart valves. Valvular defects are either acquired or congenital and manifest as stenosis and/or insufficiency (regurgitat...
Vasculitides are a heterogeneous group of rare autoimmune diseases characterized by blood vessel inflammation (vasculitis). Inflammation can lead to ischemia, necrosis, and/or hemorrhage, with subsequ...
Vertebral injuries consist of fractures, subluxations, dislocations, and ligamentous injuries with or without consequent nerve root and/or spinal cord injury. They are usually caused by high-energy bl...
Acute abdomen refers to severe abdominal pain lasting for hours to a few days. The underlying pathology may be intraabdominal, thoracic, or systemic and may require urgent surgical intervention. The i...
Also known as: Acute renal failure
Acute kidney injury (AKI) is a sudden loss of renal function with a subsequent rise in creatinine and blood urea nitrogen (BUN). It is most frequently caused by decreased renal perfusion (prerenal) bu...
Also known as: Fulminant hepatic failure
Acute liver failure (ALF) is a severe condition characterized by rapidly progressive liver injury, hepatic encephalopathy, and impaired synthetic function, which results in coagulopathy. The most comm...
Anemia is defined as a decrease in the quantity of circulating red blood cells (RBC), represented by a reduction in hemoglobin concentration (Hb), hematocrit (Hct), or RBC count. It is a common condit...
Back pain is experienced by most adults. The majority of cases are benign, nonspecific back pain (pain that is not attributable to a specific pathology). Spinal causes of acute back pain are condition...
Chronic kidney disease (CKD) is defined as an abnormality of kidney structure or function that persists for > 3 months and affects health. The most common causes of CKD in the United States are dia...
Congenital infections are caused by pathogens transmitted from mother to child during pregnancy (transplacentally) or delivery (peripartum). They can have a substantial negative impact on fetal and ne...
Diarrhea, defined as three or more loose stools per day or more frequent stool passage than is normal for the individual, is a common disease with a monthly prevalence of around 5% in the United State...
Ectopic pregnancy occurs when an embryo attaches outside the uterine cavity, most commonly in the fallopian tubes. Risk factors include conditions that alter the anatomy of the fallopian tubes (e.g., ...
Eye pain and redness are symptoms that often manifest together, but not always. They present a diagnostic challenge due to the wide range of possible causes requiring quick risk stratification and app...
Also known as: FUO
Fever of unknown origin (FUO) is defined as a temperature of > 38.3°C (> 100.9°F) lasting for > 3 weeks with no clear etiology despite appropriate diagnostics. Infections, malignancy, and inf...
Also known as: Thyromegaly
Goiter is any abnormal enlargement of the thyroid gland. The condition has various causes, with the most common worldwide being iodine deficiency. In the US, however, Hashimoto's and Graves' disease a...
Also known as: Failure to thrive
Growth faltering is defined as a pattern of slow growth in children when compared to the predicted values for their age and sex. It is seen in up to 10% of children in the United States and often occu...
Also known as: Pediatric viral exanthems
Infectious rashes are common in children and are caused by viruses, bacteria, fungi, or parasites. In acutely ill patients, perform initial management of rash to identify red flags for a life-threaten...
Also known as: Juvenile rheumatoid arthritis
Juvenile idiopathic arthritis (JIA; formerly called juvenile rheumatoid arthritis) is a broad term for childhood rheumatic diseases that begin before the age of 16 and are characterized by joint infla...
Malabsorption is the impaired absorption of nutrients caused by functional or structural alterations of the intestinal mucosa or inadequate breakdown of food in the intestinal lumen (i.e., maldigestio...
Pelvic organ prolapse (POP) is the protrusion of the uterus, vaginal apex, or surrounding pelvic structures (e.g., bladder, rectum) into the vaginal vault due to decreased pelvic floor support. It mos...
Rash is a common presenting symptom with many different causes. A systematic approach is necessary to identify life-threatening conditions and reach a definitive diagnosis. Initial management steps in...
Respiratory failure is the acute or chronic inability of the respiratory system to maintain gas exchange (PaO2 < 60 mm Hg, PaCO2 > 50 mm Hg). Causes can be extrapulmonary (e.g., CNS depression d...
Schizophrenia is a psychiatric disorder that manifests with a variable collection of clinical features. Negative symptoms of schizophrenia (e.g., flat affect, inattention, and/or social withdrawal) ty...
Semen analysis is an important test in the evaluation of male infertility and is also used to confirm sterility after a vasectomy. A semen sample is examined for sperm concentration, morphology, motil...
Transplantation is the process of transferring an organ or part of an organ (known as a graft) from one donor to either themselves (autologous transplantation) or another recipient (allogeneic transpl...
Upper respiratory tract infections (URTIs) involve structures at or above the vocal cords, e.g., the nasal cavity, sinuses, pharynx, and/or larynx. URTIs include the common cold, acute rhinosinusitis,...
Also known as: Urinary tract infections in children
A urinary tract infection (UTI) is an infection of the bladder, urethra, ureters, and/or kidneys and is a common infection in infancy and childhood. Risk factors include congenital anomalies of the ki...
Viral hemorrhagic fevers (VHFs) are a group of viral infections caused by viruses from five different families: Arenaviridae, Bunyaviridae, Filoviridae, Flaviviridae, and Paramyxoviridae. The most wel...
Weakness is a common symptom that can occur in a wide variety of conditions. In medical settings, “weakness” is best used to refer to decreased strength specifically attributable to neuromuscular abno...
Acute coronary syndrome (ACS) is a group of conditions caused by acute myocardial ischemia, including unstable angina, non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation...
Acute wounds are disruptions of the normal structure and function of skin and underlying soft tissue caused by trauma or chronic mechanical stress. Acute wounds may be open or closed. All wounds shoul...
Cardiac arrest is the sudden cessation of cardiac function and blood circulation, manifesting as apnea, pulselessness, and loss of consciousness. In adults, cardiac arrest is most commonly caused by c...
Hypovolemia refers to a state of intravascular volume depletion, while dehydration describes a state of reduced total body water volume, mostly affecting the intracellular fluid compartment. In clinic...
Also known as: Parenteral fluid therapy
Intravenous fluid therapy involves the intravenous administration of crystalloid solutions and, less commonly, colloidal solutions. The type, amount, and infusion rates of fluids are determined based ...
Magnetic resonance imaging (MRI) is a tomographic imaging modality that employs electromagnetic fields and radio waves rather than ionizing radiation to visualize structures and processes within the b...
Trauma is one of the leading causes of death worldwide and, in the United States, the leading cause of death in young adults. Traumatic injuries range from isolated wounds to life-threatening multi-or...
Mechanical ventilation is used to assist or replace spontaneous breathing to reduce the work of breathing and/or reverse life-threatening respiratory derangement in critically ill patients or to maint...
Neonatal bacterial infections include neonatal sepsis, neonatal meningitis, neonatal urinary tract infection, neonatal pneumonia, neonatal conjunctivitis, and omphalitis. Neonatal bacterial infections...
The neonatal resuscitation algorithm provides a structured approach to care of neonates immediately after birth. Initial interventions include drying, warming, and stimulating the neonate while assess...
Postoperative management of the surgical patient has two important components: supporting the patient's return to baseline health and recognizing and treating adverse events that may occur following s...
Prenatal care is the health care provided throughout a pregnancy; it is aimed at optimizing maternal and fetal outcomes. Prenatal visits allow high-risk pregnancies to be identified and are used to mo...
Regional anesthesia involves the injection of local anesthetic agents around nerves in the peripheral nervous system or central nervous system to achieve reversible numbing of pain conduction in the c...
Shock is a life-threatening circulatory disorder that leads to tissue hypoxia and a disturbance in microcirculation. The numerous causes of shock are classified into hypovolemic shock (e.g., following...
Transfusion of whole blood or fractionated blood components is a widely used method for managing numerous conditions. Packed red blood cells (pRBCs), the most commonly transfused products, are primari...
Also known as: Benign tumors of the endometrium
Endometrial hyperplasia is an abnormal proliferation of the endometrium caused by increased estrogen stimulation. It manifests with abnormal uterine bleeding (AUB) or postmenopausal bleeding (PMB) and...
Also known as: Bone scintigraphy
A bone scan (skeletal scintigraphy) is an imaging modality in which an intravenously administered radioactive tracer with an affinity for bone (e.g., Tc99m-methylene biphosphonate) is used to visualiz...
Critically ill patients are typically cared for in intensive care units (ICUs), which are designated hospital units dedicated to managing patients who require a higher level of care than that availabl...
This article covers important clinical findings of urological and renal conditions, including changes in micturition (e.g., dysuria, anuria) and changes in urine (e.g., hematuria, proteinuria) as well...
Oncology is the science of tumors. This article explains basic concepts relevant to the development, progression, spread, and diagnosis of cancer. Histological analysis helps to determine tumor type a...
The process of taking a history and performing a physical examination (H&P) in OB/GYN patients presents unique challenges. Because of the intimate aspect of an OB/GYN examination, it is important ...
The postpartum period (fourth trimester) is the 12 weeks after childbirth in which the body recovers from the changes of pregnancy and labor. During this period, individuals are at risk of a range of ...
Also known as: Dwarfism
Short stature (dwarfism) in children is defined as a height that is at least two standard deviations (SDs) below the mean for children of the same age and sex. In adults, the condition is commonly def...
Thyroid surgery is a procedure commonly performed to treat benign and malignant thyroid disorders. Total thyroidectomy entails the removal of the entire thyroid gland and is indicated in the managemen...
Also known as: Sonography
Ultrasound is a radiological technique that involves sending soundwaves with very high frequencies (∼ 2–20 MHz for diagnostic imaging) through the body and receiving their echoes to visualize internal...
Also known as: Chest radiograph
Chest x-ray (CXR) is one of the most commonly performed imaging studies in clinical practice. CXR is a quick, noninvasive, and relatively low-radiation method to evaluate conditions and monitor proced...
Fractures of the radius and/or ulna occur frequently. Important forearm fracture patterns include complete forearm fractures, Galeazzi fractures, and Monteggia fractures. Fractures of the forearm bone...
Local anesthesia refers to the reversible numbing of pain conduction by blocking nerve endings at and around the site of administration. It is commonly used in both adults and children for minor proce...
Pancreatic and hepatic surgeries are indicated in the management of malignant/symptomatic benign tumors and traumatic lacerations of the liver and pancreas. The choice of surgery depends on the locati...
Wound closure is the approximation of wound edges with materials such as sutures, staples, wound tape, and/or tissue adhesive, and may be performed for the primary or tertiary closure of wounds. Prima...
The adrenal gland is a paired retroperitoneal organ located on the upper pole of each kidney. It receives its arterial supply from the superior, middle, and inferior suprarenal arteries and drains int...
Structural anomalies of the female genital tract may be present at birth or may be acquired later in life. Common congenital anomalies of the female genital tract are anomalies of Müllerian duct fusio...
The lymphatic system is part of the adaptive immune system as well as the circulatory system and comprises the thymus and bone marrow (primary lymph organs); mucosa-associated lymphatic tissue (MALT),...
Radiography is an imaging technique that employs x-rays (high-energy electromagnetic radiation of a wavelength between UV light and gamma rays) to visualize internal structures of the body for diagnos...
Also known as: Volatile anesthetics
Inhalational anesthetics are used for the induction and maintenance of general anesthesia as well as sedation. The exact mechanisms by which they act are still unknown. The most common inhalational an...
Lipid disorders in adults encompass a spectrum of metabolic conditions that affect blood lipid levels. They are generally characterized by elevated levels of cholesterol, triglycerides, and/or lipopro...