Inguinal hernia

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 subdivided based on anatomic location: an indirect inguinal hernia protrudes lateral to the inferior epigastric vessels through the deep inguinal ring, whereas a direct inguinal hernia protrudes medial to the inferior epigastric vessels through a defect in the posterior wall of the inguinal canal. An uncomplicated inguinal hernia typically manifests as a mass in the groin with or without pain (inguinodynia). Incarceration, obstruction, and strangulation of hernial contents are collectively referred to as complicated inguinal hernia. Inguinal hernia is a clinical diagnosis. Imaging, preferably with ultrasound, is indicated if the clinical diagnosis is uncertain. Surgery is the only definitive management of inguinal hernia and can be performed as an open surgery or laparoscopically. A strangulated inguinal hernia is a surgical emergency. In patients with an incarcerated hernia with or without bowel obstruction, manual reduction of the hernia may be considered as a temporizing measure before surgery. Conservative management may be considered in selected adult patients with a small, uncomplicated inguinal hernia; timely surgical intervention is recommended in children due to the risk for complicated inguinal hernia.

• Direct inguinal hernia: protrusion of abdominal and/or pelvic contents directly through the posterior wall of the inguinal canal
• Indirect inguinal hernia: protrusion of abdominal and/or pelvic contents into the inguinal canal through the deep inguinal ring
• Scrotal hernia: a large, indirect inguinal hernia that descends through the inguinal canal into the scrotum
• Uncomplicated inguinal hernia: an inguinal hernia that is completely reducible and not associated with signs of bowel obstruction or strangulation
• Complicated inguinal hernia: an inguinal hernia that is either irreducible (incarcerated) or associated with mechanical bowel obstruction and/or strangulation
• Occult inguinal hernia: an inguinal hernia that is not identifiable on physical examination

See “Femoral hernia” for further information.

• Prevalence
  • 5–10% In the US [2]
  • Inguinal hernias are the most common type of hernias (∼ 75% of all cases). [3]
  • Indirect inguinal hernia > direct inguinal hernia
  • Responsible for one of the most common general surgical procedures in the United States [2]
• Sex: ♂ > ♀
• Age
  • Indirect inguinal hernia: most commonly seen in male infants and older men
  • Direct inguinal hernia: most commonly seen in older men

Epidemiological data refers to the US, unless otherwise specified.

Inguinal canal

• Extends between the deep (internal) and superficial (external) ring
• Roof (superior): internal oblique and transversus abdominis muscles
• Floor (inferior): inguinal ligament (shelving edge of external oblique) and lacunar ligament (medially)
• Posterior wall: transversalis fascia laterally; conjoint tendon medially
• Anterior wall: external oblique aponeurosis and internal oblique muscle laterally

Hesselbach triangle borders

• Medially: rectus abdominis muscle
• Laterally: inferior epigastric vessels
• Inferiorly: inguinal ligament

References:[4]

Direct inguinal hernia

• Acquired condition
• Caused by weakening of the transversalis fascia
  • Commonly secondary to conditions resulting in increased intraabdominal pressure (e.g., chronic obstructive pulmonary disease with chronic coughing, constipation)
  • May be associated with long-term glucocorticoid use
• Medial to the inferior epigastric blood vessels (within Hesselbach triangle) and lateral to the rectus abdominis
• Hernial sac protrudes directly through the posterior wall of the inguinal canal (without involvement of the spermatic cord or round ligament of the uterus)
• Only herniates through the superficial (external) ring
• Only surrounded by the external spermatic fascia

Indirect inguinal hernia

• Most commonly results from incomplete obliteration of processus vaginalis; during fetal development (but can also be acquired)
• May not become apparent until adulthood despite being present since birth.
• Lateral to the inferior epigastric blood vessels (outside Hesselbach triangle)
• Runs from the deep inguinal ring through the inguinal canal to the superficial (external) inguinal ring (in men, along with the spermatic cord)
• Surrounded by the external spermatic fascia, cremasteric muscle fibers, and internal spermatic fascia
• Indirect inguinal hernia may be associated with a communicating hydrocele.

"The DIRECT path leads through the MiDdle, the INDIRECT path goes beLow." (DIRECT hernias lie MeDial and INDIRECT hernias lie Lateral to the inferior epigastric vessels)

References:[2][3][4][5]

Uncomplicated inguinal hernia [6][7][8]

• Typically manifests as an ill-defined mass in the inguinal region with the following features:
  • Increases in size when coughing or straining
  • Decreases in size on lying supine
  • Inguinal pain; (inguinodynia) or vague inguinal discomfort that increases with physical activity; can also be painless
• Inguinodynia with no palpable groin mass is typically the only manifestation of an occult inguinal hernia. [9]
• Physical examination
  • Ask the patient to perform the Valsalva maneuver and observe for an expansile cough impulse in the inguinal region.
  • Palpate the inguinal canal.
    • Male patients: Invaginate the scrotal skin toward the superficial inguinal ring with the index or little finger.
    • Female patients: Palpate the area over the inguinal ligament.
    • Ask the patient to perform the Valsalva maneuver.
    • A palpable bulge confirms the diagnosis of an inguinal hernia.
  • The hernia is completely reducible and soft.

Female patients rarely present with visible bulges but often report a sensation of heaviness or dull discomfort in the groin or pelvis that is worsened by lifting, straining, or prolonged standing. [10]

Complicated inguinal hernia [7][8][11]

• Incarcerated hernia
  • The hernia is irreducible.
  • Skin overlying the hernia: normal
• Obstructed hernia: : symptoms of mechanical bowel obstruction (sudden onset of pain, nausea, vomiting, abdominal distention, constipation or obstipation)
• Strangulated hernia
  • Sudden, severe groin pain caused by constriction and ischemia (or necrosis) of hernial contents
  • Signs of sepsis or signs of shock
  • Features of bowel obstruction if the hernia contains intestinal loops
  • Skin overlying the hernia: warm, erythematous, tender, and may appear exfoliated or blistered

Manual reduction of an inguinal hernia should not be attempted if there are any signs of strangulated hernia!

Inguinal hernia is typically a clinical diagnosis; however, imaging may be useful if the clinical diagnosis is unclear or to investigate an underlying cause.

Clinical evaluation

• Medical history should include:
  • Identification of typical clinical features (e.g., of uncomplicated inguinal hernia)
  • Onset and duration of symptoms [12]
  • Evaluation of risk factors for an acquired inguinal hernia.
• Physical examination should include:
  • Palpation of the inguinal canal
  • Evaluation for signs of complicated inguinal hernia
  • Identification of signs of underlying etiologies, e.g., ascites, BPH

To avoid missing inguinal hernias, routinely examine the inguinal canal in patients with unexplained acute abdominal pain and/or clinical features of bowel obstruction, especially in those with verbal impairment.

Imaging for inguinal hernia [6][13]

Indications

• Uncertain clinical diagnosis
• Suspected recurrent or occult inguinal hernia
• Consider preoperative imaging for complicated inguinal hernia.

Modalities [6]

• First line: ultrasound of the groin [7][13]
• Inconclusive ultrasound findings: CT or MRI abdomen and pelvis
• Complicated inguinal hernia: Consider CT abdomen and pelvis with IV contrast. [11][14]
• Suspected occult inguinal hernia or recurrent inguinal hernia; consider any of the following modalities: [9]
  • MRI groin [15]
  • Dynamic CT or dynamic MRI, if available
  • Herniography [15][16][17]

Supportive findings

• Visualization of the hernial sac with its contents (e.g., bowel, omentum)
• Uncomplicated inguinal hernia
  • Visible expansile cough impulse
  • Direct inguinal hernia: fascial defect in the posterior wall of the inguinal canal
  • Indirect inguinal hernia: widening of the deep inguinal ring
• Obstructed hernia [18]
  • Free fluid and thickening of bowel wall within the hernial sac
  • Dilated bowel loops within the abdomen (see “Radiological signs of mechanical bowel obstruction” for details)
• Strangulated inguinal hernia [19][20]
  • Absence of blood flow to the hernial contents
  • Absence of peristalsis in bowel loops within the hernial sac

Do not delay emergency surgery for imaging in unstable patients with signs of strangulated hernia or obstructed hernia. [6]

Laboratory studies [19]

The following tests should be obtained in patients with strangulated inguinal hernia or incarcerated inguinal hernia with bowel obstruction for supportive diagnostic evidence and to assess for complications. [21]

• CBC
• Blood glucose
• Serum electrolytes
• BMP
• Serum lactate
• Urinalysis

Maintain a high index of suspicion for strangulation in patients with an incarcerated hernia and leukocytosis. [12]

Groin or scrotal mass [7][8]

• Hydrocele
• Varicocele
• Spermatocele
• Round ligament varicosities
• Large cutaneous or subcutaneous masses in the inguinal region
  • Lipoma
  • Sebaceous cyst
  • Hematoma
• See also “Overview of scrotal abnormalities.”

A groin bulge with an expansile cough impulse above the inguinal ligament is diagnostic of an inguinal hernia. A femoral hernia typically manifests as a groin bulge below the inguinal ligament and lateral to the pubic tubercle. [8]

Groin pain [7]

If these diagnoses are chronic or recurrent, they may cause inguinodynia.

• Sports hernia: chronic groin pain due to an injury or weakness of the posterior wall of the inguinal canal; an actual hernia may or may not be present [22]
• Muscular strain or injury
• Pathology of the hip joint
• Lumbar disk herniation
• Osteitis pubis
• Neuropathy
• See also: “Causes of pelvic pain”

The differential diagnoses listed here are not exhaustive.

Overview [6][7]

Critically ill patients with complicated inguinal hernias need to be stabilized and evaluated concurrently. Well-appearing patients with easily reducible hernias typically do not need further workup in the emergency department.

• Complicated inguinal hernias
  • Strangulated hernia and/or signs of mechanical bowel obstruction: emergency surgery (within hours)
  • Incarcerated hernia without strangulation: Consider manual reduction of the inguinal hernia.
    • Successful manual reduction: Close monitoring is required; consider surgery during the same hospital admission.
    • Unsuccessful manual reduction: urgent surgery
• Uncomplicated inguinal hernia: Recommend elective surgery; consider watchful waiting in selected patients.

Strangulated inguinal hernias and obstructed hernias are surgical emergencies.

Initial management and disposition [19][23]

• All patients
  • Assess hernia reducibility.
  • Consider ultrasound if the diagnosis is unclear.
  • Provide analgesia as needed.
• Reducible hernia: Refer for outpatient surgical management (watchful waiting or elective hernia repair).
• Incarcerated hernia
  • Provide resuscitation as needed; see “ABCDE survey.”
  • Assess for signs of obstruction and strangulation.
  • Establish NPO status and provide supportive care as needed (e.g., antiemetics, parenteral analgesics, fluid resuscitation, and electrolyte repletion).
  • No signs of strangulated hernia: Consider manual reduction of the inguinal hernia as a temporizing measure. [23][24]
    • Attempt to reduce the hernia 1–2 times.
    • Consider admission or discharge after observation in the emergency department if reduction is successful.
    • Consult surgery urgently for operative management if reduction is unsuccessful.
  • Signs of strangulated hernia
    • Consider broad-spectrum IV antibiotics (see “Empiric antibiotic therapy for intraabdominal infection”). [25][26]
    • Consider NG tube insertion for obstructed hernias.
    • Consult surgery urgently for operative management; do not attempt manual reduction.

Intestinal infarction can occur within 6 hours of strangulation. [12]

Risk factors associated with poor outcomes in incarcerated and strangulated hernias include older age, obesity (BMI > 30 kg/m²), prolonged duration of symptoms, female sex, and a delayed diagnosis. [6]

Manual reduction of an inguinal hernia is a bedside procedure where hernia contents are manually guided back into the abdominal cavity through the fascial inguinal defect. [19][23][27]

• Indication: Consider as a temporizing measure before surgery in patients with an incarcerated hernia with or without bowel obstruction.
• Contraindication: strangulated inguinal hernia
• Preparation
  • Informed consent
  • NPO, parenteral analgesia, consider procedural sedation
• Procedure
  • Place the patient in the Trendelenburg position.
  • Apply an ice pack to the affected area to reduce the swelling.
  • Manually guide the hernia through the fascial defect with slow, steady pressure.
• Successful hernia reduction: Observe the patient for 12–24 hours with serial abdominal examination. [23]
  • Symptoms improve: Schedule an elective hernia repair as soon as possible.
  • Symptoms worsen: immediate surgical consult to evaluate for recurrence or reduction en masse [28]
• Unsuccessful hernia reduction: urgent surgery (see “Surgeries for inguinal hernia”)

Manual reduction of hernial contents is contraindicated in patients with signs of a strangulated hernia, as necrotic bowel or omentum may be pushed into the abdominal cavity, which can lead to serious complications including peritonitis. [23]

Manual reduction can be performed in patients with an incarcerated inguinal hernia causing bowel obstruction provided there is no evidence of strangulation. [27]

• Surgical repair of the hernial defect is the only definitive treatment for inguinal hernia.
• The management of direct inguinal hernia and indirect inguinal hernia does not differ.
• Once the hernial contents are reduced (i.e., returned to the abdominal cavity), the goal of hernia surgery is to reinforce the posterior wall of the inguinal canal with a synthetic mesh or through primary tissue approximation.
• Emergency surgery is associated with an increased risk of complications; elective surgery is preferred when it is an option.

Indications

• Elective surgery
  • Significant inguinodynia limiting daily activities.
  • Female patients
  • Worsening of symptoms during watchful waiting.
  • Patient prefers surgery to watchful waiting.
• Emergency surgery: complicated inguinal hernia

Hernioplasty (mesh repair)

• Definition: repair of a hernial defect using a synthetic mesh
• Indication: gold standard for inguinal hernia repair [6]
• Open surgery
  • Preferred in patients with complicated inguinal hernia or contraindications for laparoscopic repair [8]
  • Procedures include Lichtenstein repair, in which a synthetic mesh is placed between the transversalis fascia and the external oblique aponeurosis to reinforce the posterior wall of the inguinal canal. [11]
• Laparoscopic surgery: preferred in patients with bilateral or recurrent inguinal hernia [8]
  • Transabdominal preperitoneal repair (TAPP): laparoscopic, preperitoneal mesh implementation between the parietal peritoneum and transverse fascia
  • Total extraperitoneal repair (TEP): laparoscopic, extraperitoneal mesh implementation between parietal peritoneum and transverse fascia

Herniorrhaphy (non-mesh repair)

• Definition: open surgical repair of a hernial defect using autologous tissue
• Indication: Consider in patients at high risk of surgical site infection. [8][25]
• Options: Shouldice repair
  • A pure tissue repair that involves a multilayer imbricated repair of the posterior wall of the inguinal canal with a continuous running suture technique. [8]
  • Preferred procedure when hernioplasty is not feasible
  • Has a lower recurrence rate than other non-mesh repairs
• Important consideration: Herniorrhaphy is associated with a greater risk of recurrence than hernioplasty. [29]

Most patients who are managed conservatively will eventually require surgical repair. [6][19]

• Indications [30]
  • Asymptomatic or minimally symptomatic, completely reducible hernia in a male patient
  • Uncomplicated inguinal hernia in patients unfit for surgery or anesthesia
• Contraindications [6]
  • Symptoms significant enough to limit daily activities [30]
  • Complicated inguinal hernia
  • Female patients
• General recommendations [6]
  • Consider the use of a truss.
  • Advise against lifting heavy weights.
  • Advise returning to seek care if symptoms worsen. [6]
  • Evaluate and treat potential risk factors of hernia.

All patients with inguinal hernia

• Examine the inguinal canal, assessing for hernia reducibility and signs of obstruction and strangulation.
• If signs of strangulated hernia are present, see “Acute management of strangulated inguinal hernia.”
• Order abdominopelvic imaging (e.g., pelvic ultrasound) if the diagnosis is unclear.
• Refer easily reducible uncomplicated inguinal hernias for outpatient elective surgical management.
• Attempt manual reduction of the inguinal hernia if for incarcerated hernias without signs of strangulated hernia (maximum 2 attempts).
• Observe patients with successful manual reduction with serial abdominal examinations (e.g., for 12–24 hours).
• Consult surgery urgently if manual reduction is unsuccessful.

Acute management of strangulated inguinal hernia

• Perform ABCDE assessment.
• Consult surgery immediately and do not attempt manual reduction.
• Establish NPO status.
• Establish IV access and obtain CBC, BMP, lactate, and other studies required for emergency preoperative assessment.
• Administer IV fluids, analgesics, and antiemetics.
• Start empiric antibiotic therapy for intraabdominal infection.
• Consider CT abdomen and pelvis with IV contrast once stable.
• Consider NG tube placement for obstructed hernia.
• Consider Foley catheter placement

Preoperative complications [6]

• Incarcerated hernia: progression to mechanical bowel obstruction or strangulation of hernia sac contents
• Strangulated hernia
  • Necrosis of bowel or other hernia sac contents
  • Gastrointestinal perforation and/or peritonitis
  • Systemic inflammatory response syndrome (SIRS)

Postoperative complications [6]

• Early
  • Surgical site infection
  • Urinary retention
  • Hematoma
  • Seroma
  • Visceral and vascular injuries (rare)
• Delayed
  • Inguinodynia; paresthesia or anesthesia over the surgical site [31]
  • Paresthesia or anesthesia over the surgical site
  • Sexual dysfunction
  • Recurrence

We list the most important complications. The selection is not exhaustive.

Epidemiology

• Incidence: up to 5% in term infants and up to 20% in preterm infants [32][33][34]
• ♂ > ♀ (4–5:1) [33][34]

Etiology [32][33]

• Anatomical causes
  • Indirect (most common): due to a patent processus vaginalis
  • Direct (rare in children): due to weakening of the transversalis fascia
• Risk factors
  • Male sex
  • Premature birth
  • Low birth weight
  • Increased intra-abdominal pressure (e.g., from ventriculoperitoneal shunt, ascites)
  • Family history
  • Connective tissue disease

Clinical features [33]

• Groin mass
  • More common on the right side (in ∼ 60% of patients) [32]
  • Increases in size with coughing or crying
  • Can extend to the scrotum or labia majora
  • May be reducible or incarcerated [32][34]
  • Typically painless; large hernias can cause discomfort [32][34]
• Features of associated conditions may be present, e.g.:
  • Nonpalpable testes in cryptorchidism [35]
  • Joint hypermobility, skin hyperextensibility in connective tissue disorders (e.g., Ehlers-Danlos syndrome) [33]
  • Ambiguous genitalia or palpable testes in phenotypic female individuals with differences of sex development (e.g., androgen insensitivity syndrome) [34]
• Features suggestive of incarcerated or strangulated hernias [36]
  • Similar to those in adults; see "Complicated inguinal hernia."
  • Inconsolable crying and fussiness suggests complicated hernia in nonverbal children.

In children, the risk of inguinal hernia incarceration is highest in infancy. [32][34]

Diagnosis [33][34]

• Inguinal hernia is a clinical diagnosis.
  • A reducible hernia may be detectable only during crying or coughing.
  • Use caregiver reports of intermittent mass in the groin as supportive evidence.
• Laboratory studies and imaging are not routinely indicated.
• Ultrasound may be used in case of diagnostic uncertainty. [33][37]

Management [32][33][34]

Surgery is recommended for all patients as hernia in children is associated with a significant risk of incarceration and, consequently, strangulation.

• Reducible hernia [34]
  • Refer to a specialist (e.g., pediatric surgery, pediatric urology) for elective surgery.
  • Timing of surgery [32][33]
    • Premature neonates: Surgery performed after discharge from neonatal ICU may be associated with optimal outcomes. [33][38]
    • Older infants and children: Timing depends on patient factors such as risk of incarceration. [32]
• Incarcerated hernia [33][34][36]
  • Perform manual reduction of the inguinal hernia; sedation or analgesia may be required.
  • Consult a specialist for urgent surgery.
  • Timing of surgery
    • Irreducible hernia: emergency surgery [36]
    • Successful manual reduction: typically during the same admission (within 24 hours to 5 days) to minimize risk of recurrent incarceration [39][40]
• Strangulated hernia
  • Immediate referral for surgery.
  • Initiate management for pain and associated complications (e.g., bowel obstruction, shock).
  • Manual reduction is contraindicated.

Hernia surgery in children [33][36]

• Herniorrhaphy is typically performed; mesh repair (hernioplasty) may be considered in selected patients.
• Surgery can be performed using an open or laparoscopic approach. [32][41]
• Evaluation for contralateral hernia during surgery is controversial. [32][33][34]
• Counsel patients and/or caregivers on the small risk of recurrence. [32][36]