Hernia — Comprehensive Overview

Definition

Classification

By Location

Anatomical locations of common abdominal hernias — Bailey & Love's Surgery, p. 1086

By Reducibility / Clinical Status

"Strangulation occurs when any degree of ischaemia or obstruction results from compression of a loop of bowel within the neck of a hernia." — Sleisenger & Fordtran's GI and Liver Disease, p. 2494

Epidemiology & Risk Factors

• Inguinal hernias are ~10× more common in men than women.
• Femoral hernia is relatively more common in women, though inguinal hernias still predominate in women too.
• Right side more common than left for indirect inguinal (due to later descent of the right testis).
• Risk factors include: male sex, advanced age, previous hernia/repair, connective tissue disorders, increased intra-abdominal pressure (chronic cough, constipation, prostatism, heavy lifting, obesity, ascites, pregnancy), and prior abdominal surgery.

Anatomy of the Inguinal Canal

• Deep (internal) inguinal ring: Defect in transversalis fascia, lies midway between anterior superior iliac spine (ASIS) and pubic tubercle, 2–3 cm above and lateral to the femoral artery pulse; inferior epigastric vessels lie just medial to it.
• Superficial (external) inguinal ring: Inverted-V defect in external oblique aponeurosis, just above and lateral to pubic tubercle.
• Conjoint tendon: Fusion of transversus abdominis and internal oblique muscles; forms the posterior wall medially.
• Hesselbach's triangle: Bounded by inferior epigastric vessels (lateral), inguinal ligament (inferior), rectus sheath (medial) — site of direct hernia.
• Indirect hernia passes lateral to inferior epigastric vessels, through the deep ring, along the canal.
• Direct hernia passes medial to inferior epigastric vessels, through Hesselbach's triangle.

Laparoscopic posterior (TAPP) view showing a direct inguinal hernia, the Triangle of Doom (iliac vessels), and Triangle of Pain (sensory nerves).

Pathophysiology

Indirect Inguinal Hernia

Direct Inguinal Hernia

Femoral Hernia

Hiatal Hernia

• Displacing the LES above the diaphragm → reduced LES pressure
• Eliminating the "pinch-cock" mechanism of the crural diaphragm
• Creating an acid pocket in the hernia sac that acts as a reservoir for acid reflux
• Large (≥3 cm), non-reducible hernias are especially prone to reflux.

Clinical Features

• Dragging or aching discomfort in the groin, especially on standing or straining.
• Visible/palpable bulge that enlarges on coughing (cough impulse).
• Sudden severe pain + irreducibility = incarceration/strangulation — surgical emergency.

Investigations

• Diagnosis is primarily clinical in most cases.
• USS: Useful for groin hernias, especially in obese patients or when diagnosis is uncertain; useful for distinguishing inguinal hernia from femoral hernia, hydrocele, or lymphadenopathy.
• CT scan: Gold standard for complex or internal hernias; identifies incarceration and strangulation; required in obese patients where clinical examination is unreliable. CT in Roux-en-Y gastric bypass patients should specifically look for internal hernia through mesenteric defects.
• MRI/MRI herniography: Occasionally used for occult hernias.

Special Hernia Types

Richter's Hernia

Maydl's Hernia (Hernia-en-W)

Pantaloon Hernia

Sliding Hernia

Parastomal Hernia

Internal Hernias

Complications

1. Incarceration — Irreducible contents; may not compromise blood supply initially.
2. Obstruction — Incarcerated bowel causing small bowel obstruction (SBO). Hernia is the second most common cause of SBO (after adhesions) in the West but has a higher rate of strangulation per episode than adhesions.
3. Strangulation — Ischaemia/necrosis of contents; surgical emergency. Up to 75% of hernias causing SBO have associated intestinal ischaemia; >25% have intestinal necrosis.
4. Incisional hernia recurrence — Open suture repairs: 20–50% recurrence.

Treatment

Conservative

• Watchful waiting for minimally symptomatic inguinal hernias in men (acceptable as initial approach; annual risk of acute incarceration ~0.2–0.3% per year for non-strangulated hernias).
• Never watchful waiting for femoral hernias (too high a risk of strangulation).
• Trusses: Largely obsolete; not recommended for definitive management.

Open Surgical Repair

Laparoscopic Repair

• TEP (Totally Extraperitoneal): Surgeon develops the extraperitoneal plane without entering the peritoneal cavity.
• TAPP (Transabdominal Preperitoneal): Enter the peritoneal cavity first; incise peritoneum above the hernia defect.

• Less post-operative pain (short- and long-term)
• Faster return to normal activity
• Fewer wound complications
• Particularly beneficial for bilateral and recurrent hernias

Emergency Management (Incarcerated/Strangulated)

1. Urgent resuscitation and antibiotics.
2. Attempt manual reduction only if no signs of strangulation (no skin erythema, severe tenderness, systemic toxicity) — contraindicated if strangulation suspected.
3. Emergency surgery: hernia reduction, bowel viability assessment; resection if necrotic.
4. Mesh use in contaminated field is controversial — clean cases: mesh acceptable; contaminated (bowel resection/perforation): tissue repair preferred for primary repair, mesh reserved for later.

Paediatric Considerations

• All congenital inguinal hernias in children are indirect (patent processus vaginalis).
• Incidence higher in premature neonates.
• Incarceration risk is higher in infants due to narrow inguinal ring.
• Operation = herniotomy (sac ligation only); no floor repair needed as the posterior wall is normal.
• Umbilical hernias commonly resolve by age 5 without treatment; surgery if persists beyond 5 years, >2 cm, or incarcerated.

Hernia and Small Bowel Obstruction (SBO)

Summary of Key Numbers