Hernia — Comprehensive Overview

Definition

Epidemiology

• Hernias develop in approximately 5% of men and 2% of women
• 75% of all hernias occur in the groin (inguinal/femoral)
• In children and young adults, the majority are indirect inguinal hernias of congenital origin
• Direct hernias are acquired and become more prevalent with aging
• Incisional hernias complicate up to 20% of abdominal surgeries

Anatomy of Hernia Types

1. Inguinal Hernia (most common — ~75% of all hernias)

a) Indirect Inguinal Hernia

• Passes through the internal (deep) inguinal ring → travels down the inguinal canal → exits the external (superficial) ring → may enter the scrotum
• Runs lateral to the inferior epigastric artery
• Usually congenital: due to a patent processus vaginalis that fails to close
• Most common in children and young men; can occur at any age
• Physical exam: hernia contents strike the tip of the examining finger when palpating the canal

b) Direct Inguinal Hernia

• Protrudes directly through the posterior wall of the inguinal canal (Hesselbach's triangle), medial to the inferior epigastric artery
• Acquired — caused by weakness of the transversalis fascia from aging, heavy lifting, or increased intra-abdominal pressure
• More common in older men
• Exam: hernia contents push against the volar pad of the finger; pressure over the internal ring after reduction does NOT prevent recurrence on Valsalva (unlike indirect)

c) Pantaloon Hernia

• A combination of both direct and indirect hernias straddling the inferior epigastric artery — difficult to diagnose clinically, often found at surgery.

2. Femoral Hernia

• Protrudes inferior to the inguinal ligament through a defect in the transversalis fascia
• Contents enter the femoral canal — the space medial to the femoral vein and lateral to the lacunar ligament
• Presents as a medial thigh mass below where inguinal hernias are seen
• More common in women
• Has a narrow neck → high risk of incarceration: up to 45% are strangulated at presentation — the most dangerous groin hernia

3. Umbilical Hernia

• Traverses the fibrous umbilical ring
• In adults: acquired; associated with obesity, ascites, multiparity, and raised intra-abdominal pressure
• In neonates: usually closes spontaneously within 1–2 years
• Accounts for ~15% of emergency hernia surgery; up to 60% show strangulation at operation

4. Epigastric Hernia

• Through the linea alba above the umbilicus
• Usually contains pre-peritoneal fat; may be multiple
• Commonly tender and small

5. Incisional / Ventral Hernia

• Occurs at or near a previous surgical scar
• Complicates up to 20% of laparotomies; risk increased by wound infection, obesity, malnutrition, steroid use
• Recurrence rate after repair: 20–50%
• Larger defects paradoxically have lower incarceration risk (wide neck)

6. Spigelian Hernia

• Occurs along the lateral border of the rectus abdominis, just below the arcuate line
• Often occult — contents pass between muscle layers and may not be visible on surface exam
• CT is frequently required for diagnosis

7. Hiatal Hernia

• Herniation of the stomach (or other abdominal contents) through the esophageal hiatus of the diaphragm
• Type I (Sliding): The gastroesophageal junction slides into the chest — most common; strongly associated with GERD
• Type II (Rolling/Paraesophageal): The gastric fundus herniates alongside the esophagus; GEJ remains in place — risk of gastric volvulus
• Types III & IV: Mixed or large, containing multiple organs
• Mechanisms promoting GERD: reduced LES pressure, loss of intra-abdominal LES segment, enlarged "acid pocket" above the diaphragm, increased transient LES relaxations

8. Internal Hernias

• Congenital: Paraduodenal (most common congenital type), foramen of Winslow, transmesenteric
• Acquired/Iatrogenic: After Roux-en-Y gastric bypass, colectomy, Whipple procedure — bowel herniates through mesenteric defects
• Often only diagnosed at laparotomy

9. Other Rare Hernias

Classification by Reducibility

Key principle: smaller neck = greater risk of strangulation. Femoral and umbilical hernias have the highest strangulation rates; large incisional hernias have the lowest.

Etiology and Risk Factors

• Patent processus vaginalis → indirect inguinal hernia
• Developmental defects in abdominal wall musculature

• Aging and loss of tissue elasticity
• Raised intra-abdominal pressure: chronic cough (COPD), constipation, straining (BPH), obesity, pregnancy, ascites, heavy lifting
• Failure of wound healing: infection, malnutrition, steroids, diabetes
• Collagen disorders (Marfan, Ehlers-Danlos)

Clinical Features

Symptoms

• Reducible hernia: intermittent bulge that appears on straining/standing, disappears on lying down; often painless
• Incarcerated hernia: non-reducible lump; constant dull ache; signs of bowel obstruction (nausea, vomiting, distension, obstipation)
• Strangulated hernia: severe local pain, tender, erythematous skin overlying; systemic sepsis (fever, tachycardia); peritonitis

Physical Examination (Groin Hernia)

1. Examine in both standing and supine positions
2. In males: invaginate scrotal skin and palpate inguinal canal; ask patient to cough or Valsalva
3. Indirect vs. direct distinction:
   • Indirect: starts lateral to inferior epigastric vessels; tip of finger impulse; occlusion of internal ring prevents recurrence
   • Direct: medial to epigastric vessels; pad of finger impulse; internal ring occlusion doesn't prevent bulge
4. A hernia descending into the scrotum is almost always indirect

Investigations

• Diagnosis is clinical in most cases
• Ultrasound: useful for groin hernias, especially in obese patients or equivocal examination; sensitivity ~86%
• CT scan: investigation of choice for suspected internal hernias, occult hernias (e.g., Spigelian), assessing complications (strangulation — bowel wall thickening, fat stranding, fluid within sac), and preoperative planning for large incisional hernias
• MRI: occasionally used for athletic pubalgia / groin pain differentiation
• Plain X-ray: may show dilated bowel loops in obstruction

Complications

1. Incarceration — irreducibility; may lead to obstruction
2. Strangulation — ischemia → gangrene; up to 75% of hernias causing SBO have intestinal ischemia; >25% have intestinal necrosis at surgery
3. Bowel obstruction — hernias are second only to adhesions as causes of small bowel obstruction in Western countries
4. Recurrence — after primary repair (tissue repairs: higher rate; mesh repairs: lower rate)
5. Haematoma / seroma
6. Wound infection — especially with mesh
7. Chronic groin pain — ilioinguinal/iliohypogastric/genitofemoral nerve injury

Emergency Management (ED)

Assessment Priorities

1. Is the mass truly a hernia?
2. Is it reducible, incarcerated, or strangulated?
3. Is there bowel obstruction?

Manual Reduction (Taxis)

• Appropriate for incarcerated but non-strangulated hernias
• Position patient supine with hips slightly flexed (Trendelenburg)
• Apply gentle, sustained pressure directed toward the defect — do NOT use excessive force
• More reliable for groin and umbilical hernias than large incisional defects
• Contraindications: fever, skin erythema, severe tenderness, systemic signs of strangulation — these require urgent surgical referral, not reduction attempts

Strangulated Hernia (Surgical Emergency)

• IV access, fluid resuscitation, NBM
• IV antibiotics (cover gram-negative and anaerobes)
• Urgent surgical consultation → laparotomy or laparoscopy; bowel resection if necrotic; hernia repair

Surgical Management

Principles

• Elective repair is preferred (lower morbidity, better outcomes than emergency repair)
• Emergency repair carries significantly higher rates of short-term complications and recurrence

Techniques

Open Tissue Repair (Non-mesh)

• Shouldice repair: multi-layer imbrication of the posterior inguinal wall; recurrence ~1–2% in expert hands
• Bassini repair: classical; less used now
• Preferred in contaminated fields (strangulation, bowel resection) where mesh infection risk is high

Open Mesh Repair

• Lichtenstein tension-free repair: mesh sutured to inguinal ligament and conjoint tendon; standard for elective inguinal hernia
• Plug-and-patch and other variants exist
• Mesh significantly reduces recurrence rates compared to tissue repairs

Laparoscopic Repair

• TAPP (Trans-Abdominal Pre-Peritoneal): mesh placed in pre-peritoneal space via intra-abdominal approach; excellent visualization of triangle of doom (external iliac vessels) and triangle of pain (femoral/lateral cutaneous nerve)
• TEP (Totally Extra-Peritoneal): pre-peritoneal dissection without entering peritoneal cavity; avoids intra-abdominal complications
• Benefits: less post-operative pain, faster return to activity, lower chronic pain rates, better for bilateral or recurrent hernias

Mesh Use in Emergency

• In emergency hernia repair with contamination or bowel resection, tissue repair is preferred (mesh infection risk); mesh deferred to later stage if recurrence occurs
• Without contamination, mesh can be used with acceptable outcomes

Special Considerations

• Hiatal hernia: managed with proton pump inhibitors (medical); surgery (Nissen fundoplication ± mesh hiatal cruroplasty) for symptomatic paraesophageal or failed medical therapy
• Incisional hernia: component separation techniques for large defects; biologic meshes in contaminated fields
• Parastomal hernia: difficult to manage; mesh repair via laparoscopic Sugarbaker technique or open repair

Summary Table

• Roberts and Hedges' Clinical Procedures in Emergency Medicine, Chapter 44
• Sleisenger and Fordtran's Gastrointestinal and Liver Disease, Chapters 46 & 123
• Mulholland and Greenfield's Surgery: Scientific Principles and Practice, 7e, Chapter 49
• Bailey and Love's Short Practice of Surgery, 28th Edition