• Clinical science

Inguinal hernia

Abstract

An inguinal hernia is an abnormal protrusion of intra-abdominal contents either through the deep inguinal ring (indirect inguinal hernia; lateral to the inferior epigastric artery) or through the weakened posterior wall of the inguinal canal (direct inguinal hernia; medial to the epigastric artery). Inguinal hernias are often asymptomatic, presenting as a painless swelling in the groin. Pain and features of intestinal obstruction are signs of a complicated inguinal hernia (obstructed/strangulated hernia). Diagnosis is mainly based on clinical findings. Surgical repair is the definitive treatment. Elective open/laparoscopic mesh repair of the inguinal hernia is the standard of care for uncomplicated inguinal hernias. Emergency surgery which may include resection of gangrenous bowel is indicated in patients with complicated inguinal hernias.

Epidemiology

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[1][2][3][4]

Classification

Anatomy of the inguinal canal and the inguinal triangle (the Hesselbach triangle)

  • 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
  • Borders of Hesselbach's triangle
    • Medially: rectus abdominis muscle
    • Laterally: inferior epigastric vessels
    • Inferiorly: inguinal ligament

Direct inguinal hernia

  • Medial to the inferior epigastric blood vessels (within Hesselbach's triangle)
  • 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

  • Lateral to the inferior epigastric blood vessels (outside Hesselbach's triangle)
  • Runs from the deep (internal) 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

'MD': medial = direct References:[4]

Clinical features

  • Visible, palpable groin protrusion or bulge
  • Inguinal pain (does not have to correlate with the size of the hernia)
  • Increase of symptoms during physical activity (walking or standing, coughing, sneezing, abdominal pressure)
  • Indirect inguinal hernia may be associated with a communicating hydrocele
  • Palpation of the inguinal canal
    1. With the patient standing, palpate from the scrotal skin towards the superficial (external) inguinal ring.
    2. Ask the patient to cough or strain and bear down (Valsalva maneuver).
      • Bulging can be felt with a fingertip (expansile cough impulse).
  • For other possible symptoms, see “Complications” below.

References:[2]

Diagnostics

Inguinal hernia diagnosis is typically established based on medical history and physical exam findings!

  • Ultrasound
    • Imaging test of choice
    • Visualization of the hernial orifice and hernial contents may be possible.
  • CT/MRT: to distinguish from differential diagnoses in ambiguous cases

References:[2]

Differential diagnoses

The differential diagnoses listed here are not exhaustive.

Treatment

Indications for surgery

  • Complicated hernia (see “Complications” below)
  • Uncomplicated hernia + moderate symptoms:
    • Inguinal pain associated with exertion
    • Daily activities are limited due to pain
    • Manual reduction is not possible
  • Uncomplicated hernia + mild symptoms: elective hernia repair

Open vs. laparoscopic hernia repair

  • Indications for open hernia repair
    • Complicated hernias
    • Previous preperitoneal surgeries (e.g., hysterectomy, cesarean section)
    • Presence of ascites
    • Inability to undergo surgery under general anesthesia
    • Recurrent hernia (if the patient initially had a laparoscopic hernia repair)
  • Indications for laparoscopic hernia repair
    • Bilateral hernia
    • Recurrent hernia (if the patient initially had an open hernia repair)

Surgical management

  • Main idea: reinforcement of the posterior wall of the inguinal canal with synthetic mesh or primary tissue approximation
    • Mesh vs. nonmesh repair: Mesh is preferred because of decreased recurrence rates and postoperative pain. It is contraindicated in the case of inguinal infection or contamination.
  • Most common surgical procedures
    • Conventional (open) surgical procedures
      • Lichtenstein repair: reinforcement by implementation of a synthetic mesh between the abdominal internal oblique muscle and the aponeurosis of the abdominal external oblique muscle
      • Shouldice repair: doubling of the transverse fascia and fixation of the abdominal internal oblique muscle and transverse muscle at the inguinal ligament by suture (a nonmesh repair)
    • Laparoscopic surgical procedures
      • 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
    • The choice of which repair to perform depends on the type of hernia and patient's risk factors.
  • Recurrence after surgical intervention is 0.5–15% depending on the surgical procedure (see “Therapy” above).

Risks of surgery

References:[5][6][7][1]

Complications

References:[2][5]

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

Special patient groups

Inguinal hernia in infants

  • Epidemiology
    • Incidence: ∼ 1–5% of all children
    • > (∼ 4:1)
    • Occurs more often on the right side
  • Etiology and risk factors
  • Therapy: surgery
    • Premature infants with uncomplicated inguinal hernia: Surgery should be performed after discharge from the neonatal intensive care unit (NICU).
    • If hernia can be reduced manually: Wait 24–48 hours before performing surgery to allow enough time for edema to decrease.
    • If hernia cannot be reduced manually: immediate surgery
    • Asymptomatic inguinal hernia: within 14 days of diagnosis

References:[8][9]