Hernia: Complete Overview

Definition

• Sac - a peritoneal pouch
• Contents - bowel, omentum, or other abdominal viscera
• Coverings - layers of abdominal wall overlying the sac

Classification

By Reducibility

By Location: Abdominal Wall (External) Hernias

Types of Hernia

1. Inguinal Hernia (most common overall)

• Lateral border of the rectus sheath (medially)
• Inferior epigastric vessels (superolaterally)
• Inguinal ligament (inferiorly)

2. Femoral Hernia

• Exits inferior to the inguinal ligament through a defect in the transversalis fascia
• Contents enter the femoral canal: medial to the femoral vein, lateral to the lacunar ligament
• Appears as a mass in the medial thigh below the groin crease
• Relatively uncommon; more frequent in women
• High incarceration risk: up to 45% of cases (Roberts and Hedges' Emergency Medicine)
• Up to 40% are strangulated at initial presentation (Tintinalli's Emergency Medicine)

3. Umbilical Hernia

• Traverses the fibromuscular ring of the umbilicus
• Common in infants/children - congenital, often resolves by age 5 without treatment
• Surgical repair if: persists beyond age 5, size >2 cm, or if incarcerated/strangulated
• Adults: acquired; associated with obesity, ascites, pregnancy; more prone to strangulation than in children
• Accounts for ~15% of emergency hernia surgery; strangulation seen in up to 60% at operation (Sleisenger & Fordtran)

4. Incisional Hernia

• Occurs in up to 1 in 5 patients after abdominal surgery
• Poor wound healing (e.g., infection) increases risk
• Recurrence rate of 20-50% after repair
• Larger defects have a lower risk of strangulation (paradoxically, wider neck = less constriction)

5. Epigastric Hernia

• Midline, through the linea alba, between xiphoid and umbilicus
• Usually small and contains preperitoneal fat in adults
• Found in ~4% of pediatric patients evaluated for hernias

6. Spigelian Hernia

• Rare; through a defect at the lateral edge of the rectus muscle at the level of the arcuate (semilunar) line
• Often interparietal (between muscle layers), making it difficult to detect clinically

7. Hiatal Hernia

8. Internal Hernias

• Congenital types: mostly paraduodenal or through the foramen of Winslow
• Most common type is iatrogenic - after Roux-en-Y gastric bypass, colectomy, or pancreaticoduodenectomy (mesenteric defect)
• Also: obturator hernia and sciatic hernia (uncommon)

Pathophysiology

• Deficiency of elastic fibers in the transversalis fascia
• Decreased tropoelastin and lysyl oxidase-like 1 synthesis
• Overexpression of matrix metalloproteinases (MMPs) and elastase
• TGF-beta1 overexpression
• Raised intra-abdominal pressure (obesity, chronic cough, constipation, ascites)

Complications

Incarceration

• Hernia is irreducible but not necessarily ischemic
• Chronically incarcerated hernias (due to adhesions) may be painless with normal overlying skin
• An acutely incarcerated, painful hernia requires careful assessment
• Taxis (manual reduction technique): Trendelenburg position + gentle guiding pressure at the neck - NEVER forceful; contraindicated if strangulation is suspected
• "Reduction en masse" is a danger - the constricting ring comes in with the bowel

Strangulation

• Ischemia/obstruction from compression at the hernia neck
• Signs: severe tenderness, skin erythema, fever, peritonism
• A surgical emergency - prompt exploration required
• Strangulation risk is inversely proportional to the size of the defect (small neck = higher risk)
• Among patients undergoing surgery for hernia-related small bowel obstruction: ischemia in up to 75% and necrosis in more than 25% (Sleisenger & Fordtran)

Obstruction (Hernia Accident)

• Bowel obstruction from incarceration historically prompted prophylactic repair of all hernias
• However, randomized controlled trials have shown that watchful waiting is safe for asymptomatic inguinal hernias in men (Mulholland & Greenfield's Surgery)

Diagnosis

• Clinical: Visible/palpable lump; increases with coughing/straining; history of groin/abdominal swelling
• Hernia examination: Standing and supine; cough impulse; reducibility; transillumination (differentiates hydrocele - transilluminates; hernia - does not)
• Imaging:
  • Ultrasound: useful for groin hernias, especially in obese patients
  • CT: best for incisional hernias, internal hernias, and complex/obese cases; CT confirms incarceration and strangulation (pneumatosis, free fluid)
  • Barium study: useful for hiatal hernias (though sliding hernias may reduce spontaneously)

Surgical Management

Inguinal Hernia Repair Options

• Lichtenstein repair - gold standard open approach; flat polypropylene mesh; tension-free

• Bassini, Shouldice, Desarda, Maloney darn

• TEP (Total Extraperitoneal) - preperitoneal dissection without entering the peritoneal cavity
• TAPP (Transabdominal Preperitoneal) - laparoscopic entry into the peritoneum then preperitoneal mesh

Emergency Hernia Surgery

• ~5% of inguinal hernias present as an emergency
• ~20% require bowel resection at emergency repair
• Synthetic mesh is still acceptable in most emergency cases if appropriate antibiotics are given (unless significant contamination)

Postoperative Complications

Key High-Yield Points

• Indirect inguinal hernia is the most common hernia in both sexes
• Femoral hernias are uncommon but have the highest risk of strangulation at presentation
• Incarceration ≠ strangulation; strangulation implies ischemia and is a surgical emergency
• The "smaller the neck, the greater the strangulation risk" - hence femoral hernias strangulate more than incisional hernias
• Watchful waiting is acceptable for asymptomatic inguinal hernias in men
• Lichtenstein repair (open tension-free mesh) and TEP/TAPP (laparoscopic) are equivalent in outcomes
• Chronic pain after groin hernia repair is a major concern, affecting up to 20% of patients