Ch18: External Abdominal Hernia（腹外疝）

Preparatory Mindset

External abdominal hernia = abdominal contents (with parietal peritoneum) protruding through a weak point in the abdominal wall. The lecture (Bingsheng Guan) drills: the inguinal region anatomy (inguinal canal, Hesselbach's triangle, femoral canal), direct vs indirect inguinal hernia, femoral hernia, and incarcerated/strangulated hernia management. This builds directly on the Anatomy Ch16 (inguinal region).

Exam mindset: the anatomy chapter covered the structures; this surgical chapter is the disease — classifications, presentations, the direct/indirect distinction, and the repair principles (mesh, Lichtenstein, laparoscopic TAPP/TEP). The 局解 anatomy MCQ (post-appendectomy direct hernia; 15-year-old indirect) connects both.

Core Concepts

1. Concept & anatomy (MUST KNOW)

- Inguinal canal: deep ring (lateral to inferior epigastric vessels) → superficial ring (medial); walls (anterior = external oblique aponeurosis, posterior = transversalis fascia + conjoint tendon, floor = inguinal ligament, roof = internal oblique/transversus) - Hesselbach's (inguinal) triangle: medial = rectus, lateral = inferior epigastric vessels, inferior = inguinal ligament — site of direct hernias - Femoral canal: medial compartment of the femoral sheath, bounded medially by the lacunar ligament; site of femoral hernias - Deep ring: transversalis fascia opening, lateral to inferior epigastric vessels — entry of indirect hernias

• External abdominal hernia: organs/tissues in the abdominal cavity + parietal peritoneum protruding to the body surface through a weak area/pore of the abdominal wall
• Hernia components: hernia ring (neck), sac (peritoneum), contents (omentum, bowel), coverings
• Key anatomy (from Anatomy Ch16):

2. Classification of inguinal hernias (MUST KNOW)

• Inguinal hernia overall: the most common hernia; more common in males (M:F ~ 12-15:1)
• Associated: indirect hernia may be bilateral; associated with increased intra-abdominal pressure (constipation, COPD, prostatic enlargement, ascites, heavy lifting, pregnancy)

3. Femoral hernia (股疝) (MUST KNOW)

• Site: through the femoral ring → femoral canal, below & lateral to the pubic tubercle (below the inguinal ligament)
• Epidemiology: more common in women (wider pelvis); older patients
• Why dangerous: the femoral ring is narrow with the sharp lacunar ligament medially → HIGH strangulation rate (~40-60%) — more than inguinal
• Clinical: small lump below the inguinal ligament, medial thigh; may be irreducible; presents with obstruction/strangulation
• Differential (inguinal vs femoral): inguinal = above & medial to the pubic tubercle; femoral = below & lateral
• Repair: McVay (Cooper's ligament) or mesh plug; urgent for strangulation

4. Clinical features of hernia (MUST KNOW)

- Contents (bowel) blood supply compromised at the neck - Features: irreducible, tender, tense, painful, overlying erythema, fever, tachycardia, signs of obstruction → gangrene, perforation, peritonitis, shock - Management: urgent surgery (no attempt at reduction — risk of reducing gangrenous bowel); resect non-viable bowel + repair

• Reducible hernia: lump appears on standing/straining/cough, disappears lying down or with gentle pressure; cough impulse positive (palpable impulse on coughing at the superficial ring)
• Irreducible (incarcerated) hernia: contents cannot be reduced (adhesions, large neck) — at risk of obstruction/strangulation; not necessarily painful/compromised yet
• Obstructed hernia: bowel obstruction symptoms (colicky pain, vomiting, distension, no flatus) with an irreducible lump
• Strangulated hernia (绞窄性疝) — SURGICAL EMERGENCY (MUST KNOW):
• Richter's hernia: only part of the bowel wall herniates (antimesenteric) — may strangulate without complete obstruction (dangerous, easily missed)
• Littre's hernia: Meckel's diverticulum in the sac
• Sliding hernia: part of the sac wall is retroperitoneal organ (colon/bladder)

5. Examination (MUST KNOW)

- Indirect: controlled (stays reduced) — deep ring defect - Direct: bulges again (posterior wall defect, medial)

• Inspect standing & supine; locate the lump relative to the pubic tubercle & inguinal ligament
• Reduce & test: reduce the hernia, place a finger over the deep ring (midpoint of the inguinal ligament) → ask the patient to cough:
• Invaginate the scrotal skin into the superficial ring (finger invagination) to feel the cough impulse
• Examine for lymph nodes (femoral canal may be a node, not hernia); differentiate from hydrocele (transillumination, above the testis), varicocele, undescended testis, lipoma, femoral artery aneurysm

6. Complications & natural history

• Irreducibility, obstruction, strangulation (the serious one — gangrene, perforation, death if untreated)
• Repair is elective for asymptomatic/reducible hernias (strangulation risk ~1-3%/year for inguinal; higher for femoral)
• Emergency presentation = obstructed/strangulated → urgent operation with bowel resection if needed

7. Surgical treatment (MUST KNOW)

- Lichtenstein tension-free mesh repair — most common open technique (mesh over the posterior wall) - Shouldice (tissue repair, historical), Bassini/McVay (tissue repairs) - Indirect in children: high ligation of the sac only (patent processus vaginalis — no mesh)

• Principles: reduce contents, excise the sac (high ligation at the deep ring for indirect), repair the defect — tension-free mesh is standard (lower recurrence)
• Open repairs:
• Laparoscopic repairs: TAPP (transabdominal preperitoneal) & TEP (totally extraperitoneal) — mesh in the preperitoneal space; advantages: less pain, faster recovery, bilateral/ recurrent hernias; requires general anesthesia
• Femoral hernia repair: low approach (Lockwood), high approach (Lotheissen), or laparoscopic; strangulated → urgent
• Strangulated hernia operation: open the sac, assess bowel viability (color, pulsation, peristalsis; warm saline), resect non-viable bowel & anastomose, repair the hernia
• Incarcerated hernia reduction attempt: ONLY if recent (<6-8 h), no signs of strangulation; after reduction, observe; elective repair

High-Yield Points

• Indirect = lateral to inferior epigastric vessels (deep ring), congenital, may reach scrotum; Direct = medial (Hesselbach triangle), acquired, older men — the classic distinction
• Femoral = below & lateral to the pubic tubercle, women, high strangulation (lacunar ligament)
• Strangulated hernia = irreducible + tender + obstruction ± toxicity → URGENT surgery, resect gangrenous bowel
• Cough impulse test: reduce → press the deep ring → indirect controlled, direct not
• Inguinal vs femoral: above & medial (inguinal) vs below & lateral (femoral) to the pubic tubercle
• Tension-free mesh (Lichtenstein) = standard; children: high ligation only
• Laparoscopic: TAPP/TEP — less pain, faster recovery
• Richter's: partial bowel wall — strangulates without obstruction (missed)
• Inguinal hernia = most common hernia; M > F

Topic Summary

External abdominal hernia: contents + peritoneum through a weak point. Inguinal hernias: indirect (deep ring lateral to inferior epigastric vessels, congenital patent processus vaginalis, may reach the scrotum) vs direct (Hesselbach triangle medial to inferior epigastric vessels, acquired weak posterior wall, older men). Femoral hernia: below & lateral to the pubic tubercle, more common in women, high strangulation (lacunar ligament). Clinical: reducible (cough impulse) → irreducible/incarcerated → obstructed → strangulated (emergency — tender irreducible + obstruction, resect non-viable bowel). Examination distinguishes by pubic tubercle & deep-ring pressure. Treatment: tension-free mesh repair (Lichtenstein), laparoscopic TAPP/TEP, high ligation in children; urgent surgery for strangulation. Richter's hernia is the dangerous partial-wall variant.