Inguinal Hernia

Definition

Anatomy of the Inguinal Canal

• Deep inguinal ring - defect in transversalis fascia, midway between ASIS and pubic tubercle; the inferior epigastric vessels lie just medial to it
• Superficial inguinal ring - inverted V-shaped gap in external oblique aponeurosis
• Contents in males: testicular artery, veins, lymphatics, vas deferens, cremasteric muscle; ilioinguinal, iliohypogastric, and genital branch of genitofemoral nerves
• Contents in females: round ligament

• Laterally: inferior epigastric vessels
• Medially: lateral edge of rectus abdominis
• Inferiorly: inguinal ligament

Figure: The close relationships of direct inguinal, indirect inguinal and femoral hernias - Bailey & Love

Types

1. Indirect (Lateral) Inguinal Hernia

• Enters through the deep inguinal ring, passes along the inguinal canal, exits through the superficial ring - can descend into the scrotum
• Lies lateral to the inferior epigastric vessels
• Sac lies superior and medial to the pubic tubercle
• Can be congenital (due to patent processus vaginalis) or acquired
• All pediatric hernias are of this type
• More prone to strangulation due to narrow neck

2. Direct (Medial) Inguinal Hernia

• Passes directly through the posterior wall of the inguinal canal through Hesselbach's triangle
• Lies medial to the inferior epigastric vessels
• Usually acquired, more common in elderly men
• Broadly based - less likely to strangulate
• The bladder can be pulled into a direct hernia (sliding hernia component)

3. Sliding Hernia

• Retroperitoneal fat pushed into the canal; as more tissue enters, peritoneum is pulled along to form the sac secondarily
• Sigmoid colon may descend on the left; caecum on the right
• Caution during repair: bowel may form part of the sac itself

4. Pantaloon Hernia

• Both lateral and medial hernias present simultaneously in the same patient

Classification (European Hernia Society)

• P or R - Primary or Recurrent
• L, M, or F - Lateral, Medial, or Femoral
• 1, 2, 3 - Defect size in fingerbreadths (<1.5 cm, 1.5-4.5 cm, >4.5 cm)

Epidemiology / Risk Factors

• Male sex (M:F = 10:1)
• Right side more common than left
• Premature infants (failure of processus vaginalis closure before birth)
• Family history, chronic cough, straining, heavy lifting, obesity
• 50% lifetime risk of contralateral hernia after unilateral presentation

Clinical Features

• Swelling appears on standing or coughing (cough impulse)
• Can get above the swelling (differentiates from scrotal swelling)
• Transillumination negative (unlike hydrocele)
• Deep ring pressure test distinguishes indirect (controlled) from direct (not controlled)

Complications of Hernia

1. Reducible - contents return spontaneously or on pressure
2. Irreducible (incarcerated) - contents cannot be returned, no vascular compromise yet
3. Obstructed - bowel lumen occluded (may have no vascular compromise)
4. Strangulated - vascular compromise of hernia contents; surgical emergency; edematous, tender, erythematous; absent cough impulse; signs of bowel obstruction and systemic toxicity
   • ~5% of inguinal hernias present as emergencies
   • ~20% of emergency cases require bowel resection

Differential Diagnosis

• Femoral hernia (below and lateral to pubic tubercle)
• Lymph node (inguinal lymphadenopathy)
• Hydrocele (transilluminates, can get above it)
• Saphena varix (disappears on lying, bluish, thrill on coughing)
• Psoas abscess (fluctuant, may have back pain)
• Lipoma of cord
• Undescended testis
• Femoral artery aneurysm

Investigations

• Usually clinical - no investigations required in most cases
• Ultrasound: useful for uncertain diagnosis, especially occult hernias; patient examined standing and with Valsalva
• CT / MRI: for complex cases, obese patients, suspected complications; may miss hernias if patient is supine
• Herniography rarely used now

Management

Conservative

• Watchful waiting is safe for asymptomatic direct hernias, especially in elderly patients who decline surgery
• Trusses are not recommended (uncomfortable, ineffective long-term, can cause complications)
• Patients should seek early advice if hernia enlarges or becomes symptomatic

Surgical - Pediatric (Herniotomy)

• In children, simply excise and close the sac (herniotomy) - no floor repair needed
• Performed promptly because incarceration risk is high in infants due to narrow internal ring

Surgical - Adult Open Techniques

Surgical - Laparoscopic/Minimally Invasive

• Less post-operative and chronic pain
• Faster return to activity
• Fewer wound complications
• Preferred for bilateral hernias and recurrences after open surgery

Emergency Surgery

• Principles same as elective
• Mesh use acceptable even in contaminated field if antibiotics given
• ~20% require bowel resection; may need conversion to laparotomy

Complications of Repair

Pediatric Inguinal Hernia (Special Points)

• Male:female = 10:1; right > left (due to later testicular descent on right)
• All are indirect (patent processus vaginalis)
• Premature infants at highest risk (processus vaginalis not yet closed)
• High risk of incarceration in infants (narrow inguinal ring)
• An incarcerated hernia can usually be reduced with gentle pressure (sometimes light sedation); if not reducible or strangulated - emergency operation
• Treatment is prompt herniotomy (not hernioplasty) - Schwartz's Principles of Surgery 11th Ed., p.1771

Recent Evidence

• Robotic repair: A 2024 systematic review (PMID 37985490) shows robotic-assisted inguinal hernia repair is feasible and safe, but no clear superiority over standard laparoscopic repair; cost remains a barrier.
• TAPP vs TEP: The 2024 Cochrane review (PMID 38963034) found no clinically meaningful difference between TAPP and TEP for recurrence, chronic pain, or complications.
• Emergency hernia: A 2025 EAST practice management guideline (PMID 40671180) addresses management of incarcerated/strangulated inguinal hernias requiring urgent surgery.