Key Facts

Inguinal hernias are extremely common and represent a significant surgical workload. Understanding the anatomy of the inguinal canal is essential for diagnosis and surgical management.

Epidemiology

Lifetime risk ~27% in men, ~3% in women. ~70,000 inguinal hernia repairs performed annually in England. Peak incidence: Infants (indirect) and men aged 40-60 (direct). Indirect:direct ratio ~2:1.

Aetiology

Indirect: Patent processus vaginalis (congenital) or acquired; passes through deep ring lateral to inferior epigastric vessels. Direct: Weakness in posterior wall of inguinal canal (Hesselbach's triangle); acquired — chronic raised intra-abdominal pressure. Risk factors: Male sex, increasing age, chronic cough, constipation, prostatism (straining), heavy lifting, obesity, previous surgery, connective tissue disorders.

Pathophysiology

• Inguinal canal: Runs from deep ring (midpoint of inguinal ligament) to superficial ring (above pubic tubercle)
• Contents: Spermatic cord (males) or round ligament (females)
• Hesselbach's triangle: Bounded by inferior epigastric artery (lateral), rectus sheath (medial), inguinal ligament (inferior)
• Direct hernias protrude through this triangle; indirect hernias pass lateral to it through the deep ring

Typical Presentation

• Groin lump: Increases with coughing, straining, standing; reduces when lying down
• May be asymptomatic or cause dragging/aching discomfort
• Lump above and medial to pubic tubercle (inguinal) — below and lateral = femoral
• Cough impulse: Palpable expansion on coughing

Indirect vs Direct

• Indirect: May descend into scrotum; controlled by pressure over deep ring; more common in young males
• Direct: Rarely enters scrotum; not controlled by deep ring pressure; bulge appears on standing, reduces on lying; older males

Complications

• Irreducibility: Cannot reduce contents — often omentum
• Incarceration: Contents trapped — risk of obstruction
• Obstruction: Bowel trapped → colicky abdominal pain, vomiting, constipation
• Strangulation: Blood supply compromised → bowel ischaemia/necrosis — surgical EMERGENCY (tenderness, erythema over hernia, systemic sepsis)

Red Flags

• Tender, irreducible hernia with vomiting — strangulation until proven otherwise
• Overlying skin erythema or peritonitis — bowel may be gangrenous
• Signs of bowel obstruction — emergency surgery required

Bedside

• Clinical diagnosis in most cases
• Examine standing and lying; cough impulse; attempt reduction; deep ring occlusion test
• Check contralateral groin

Imaging (if diagnostic uncertainty)

• Ultrasound: Useful for occult hernias (groin pain without obvious lump)
• CT abdomen/pelvis: If complicated hernia, incarceration, or obstruction
• MRI: Occasionally for complex or recurrent hernias

Conservative

• Watchful waiting: Option for asymptomatic/minimally symptomatic direct hernias in patients with significant comorbidities
• Trusses are NOT recommended — do not prevent complications and delay definitive treatment

Surgical (Definitive)

Open repair:

• Lichtenstein tension-free mesh repair: Gold standard; local/regional/GA; recurrence <2%
• Mesh placed to reinforce posterior wall of inguinal canal

Laparoscopic repair:

• TEP (Totally Extraperitoneal): Preperitoneal mesh placement without entering peritoneal cavity
• TAPP (Transabdominal Preperitoneal): Enters peritoneal cavity, mesh placed preperitoneally
• Advantages: Faster recovery, less chronic pain, better for bilateral/recurrent hernias
• NICE IPG252 supports laparoscopic repair

Emergency

• Strangulated/incarcerated hernia: Emergency surgery
• Resuscitate, IV antibiotics (co-amoxiclav 1.2g IV)
• Emergency repair with possible bowel resection if gangrenous

Referral Criteria

• All symptomatic inguinal hernias — surgical referral for repair
• Irreducible hernia — urgent referral
• Incarcerated/strangulated — emergency admission

• Mesh repair: Recurrence rate ~1-2%
• Laparoscopic: Slightly lower chronic pain rates than open (~5% vs ~10%)
• Chronic groin pain: Occurs in ~5-12% after repair — nerve entrapment (ilioinguinal, iliohypogastric, genital branch of genitofemoral)
• Mesh infection: ~1-2% — may require mesh removal
• Strangulated hernia: Mortality ~2-5% — higher in elderly and if bowel resection required
• Without repair: Annual risk of strangulation ~0.5-3%

Inguinal Canal Anatomy

Indirect vs Direct