Key Facts

Inguinal hernias are the commonest type of hernia and one of the most frequent conditions managed surgically. Understanding the anatomy and distinguishing indirect from direct hernias is essential for examinations and clinical practice.

Epidemiology

Lifetime risk: ~27% in men, ~3% in women. Peak incidence in early childhood (indirect, congenital) and >40 years (direct, acquired). ~80,000 inguinal hernia repairs performed annually in England. M:F ratio 9:1.

Aetiology

• Indirect: congenital — patent processus vaginalis (failure of obliteration after testicular descent); can present at any age
• Direct: acquired — weakness of posterior wall of inguinal canal (transversalis fascia); associated with: chronic cough, constipation/straining, heavy lifting, obesity, smoking, connective tissue disorders, previous surgery
• Risk factors: male sex, age, family history, chronic cough (COPD), chronic constipation, prostatic symptoms (straining), ascites, previous hernia repair (recurrence), collagen disorders (Ehlers-Danlos, Marfan)

Pathophysiology

The inguinal canal transmits the spermatic cord (males) or round ligament (females). The deep inguinal ring is the point of entry of the spermatic cord into the canal (lateral to inferior epigastric vessels). Indirect hernias pass through this ring, following the cord. Direct hernias push through a weakness in the posterior wall (Hesselbach's triangle), medial to the inferior epigastric vessels. Complications arise when hernia contents become trapped (incarceration) → venous congestion → arterial compromise → strangulation → ischaemic necrosis.

Typical Presentation

• Groin lump/swelling — worse on standing, coughing, straining
• Reduces on lying down (if reducible)
• Dragging/aching discomfort in groin
• May extend into scrotum (indirect hernia)

Examination Findings

• Reducible hernia: soft swelling, expansile cough impulse, reduces with gentle pressure
• Indirect: controlled by pressure over the deep ring (midpoint of inguinal ligament); may descend into scrotum; can get above it (distinguishes from testicular pathology)
• Direct: not controlled by deep ring pressure; broad-based; does not typically descend to scrotum
• Incarcerated (irreducible): tender, cannot be reduced, no cough impulse

Red Flags

• Strangulation: severe pain, tenderness, irreducible, signs of bowel obstruction (vomiting, distension, absolute constipation), erythematous overlying skin, systemic toxicity (fever, tachycardia)
• Bowel obstruction: may be presenting feature of strangulated hernia
• Incarcerated hernia in elderly: can deteriorate rapidly

Clinical Diagnosis

• Diagnosis is primarily clinical — no imaging required if typical presentation

Imaging (if diagnostic uncertainty)

• USS groin: helpful if clinical examination equivocal; can distinguish hernia from other groin lumps; operator-dependent
• CT abdomen/pelvis: for suspected strangulation/obstruction or complex/recurrent hernias
• MRI: rarely needed; for occult or complex hernias

Bloods (if strangulation suspected)

• FBC: leucocytosis
• CRP/lactate: raised in strangulation
• U&Es: dehydration from vomiting
• Group and save: for emergency surgery

Non-pharmacological

• Conservative/watchful waiting: asymptomatic or minimally symptomatic hernias in patients unfit for surgery; risk of strangulation is low (~0.2-1.8% per year for inguinal hernias)
• Lifestyle modification: weight loss, smoking cessation, treat chronic cough/constipation
• Trusses: rarely used; not a definitive treatment; for patients declining/unfit for surgery

Surgical (Definitive)

• Open repair: Lichtenstein tension-free mesh repair (gold standard for primary unilateral inguinal hernia); local/general/spinal anaesthesia; day-case surgery
• Laparoscopic repair: TEP (totally extra-peritoneal) or TAPP (trans-abdominal pre-peritoneal); preferred for bilateral hernias and recurrent hernias (NICE IPG); less post-op pain, faster return to activity; learning curve
• Emergency surgery: for strangulated hernia — open approach; assess bowel viability; resect non-viable bowel
  • If viable: reduce and repair
  • If non-viable: bowel resection ± anastomosis or stoma

Referral Criteria

• 2WW referral: NOT applicable (hernia is benign)
• Routine surgical referral: symptomatic inguinal hernia
• Emergency referral: irreducible, painful hernia (suspected strangulation/obstruction)
• Watchful waiting: acceptable for asymptomatic/minimally symptomatic if counselled about strangulation risk

Elective inguinal hernia repair: mortality <0.5%; recurrence rate 1-5% (mesh repair). Laparoscopic repair: faster recovery (~1 week vs 2-3 weeks for open). Strangulated hernia: mortality 2-5% (higher in elderly with comorbidities; much higher if bowel resection required). Chronic groin pain after hernia repair (inguinodynia): affects 5-10% (nerve entrapment/damage — ilioinguinal, iliohypogastric, genital branch of genitofemoral). Most hernias can be repaired as day-case surgery.

Indirect vs Direct Inguinal Hernia

Hesselbach's Triangle