53. Inguinal hernia

1. Definition

• Inguinal hernia → protrusion of abdominal contents through the inguinal canal, above the inguinal ligament
• Indirect → through the deep (internal) ring, lateral to the inferior epigastric vessels, along the canal; may reach the scrotum
• Direct → through the posterior wall (Hesselbach's triangle), medial to the inferior epigastric vessels
• Pantaloon → both, either side of the vessels

2. Epidemiology

• Most common hernia (about 75% of abdominal wall hernias)
• Men : women about 8–10 : 1; lifetime risk 27–43% in men
• More common on the right (later descent of the right testis)
• Indirect → most common type in both sexes and at all ages; all children's inguinal hernias
• Direct → older men; rare in women
• About 20 million repairs a year worldwide; 100,000 in the UK

3. Aetiology and risk factors

Anatomy of the inguinal canal (revision)

• Oblique canal, about 4 cm, above and parallel to the medial half of the inguinal ligament
• Deep ring → opening in the transversalis fascia, midpoint of the inguinal ligament (midway between ASIS and pubic tubercle), 1–2 cm above it
• Superficial ring → V-shaped gap in the external oblique aponeurosis, above and medial to the pubic tubercle
• Walls ("MALT: 2 Ms, 2 As, 2 Ls, 2 Ts"):
  • Anterior → external oblique aponeurosis (+ internal oblique laterally)
  • Posterior → transversalis fascia (+ conjoint tendon medially)
  • Roof → arching fibres of internal oblique and transversus
  • Floor → inguinal ligament (+ lacunar ligament medially)
• Hesselbach's triangle → inferior epigastric vessels (lateral), lateral edge of rectus (medial), inguinal ligament (below)
• Contents → spermatic cord (round ligament in women) and ilioinguinal nerve (outside the cord)
• Spermatic cord:
  • 3 arteries → testicular, cremasteric, artery to the vas
  • 3 nerves → genital branch of genitofemoral, sympathetics, (ilioinguinal runs alongside)
  • 3 other → vas deferens, pampiniform plexus, lymphatics
  • 3 coverings → external spermatic, cremasteric, internal spermatic fascia

Causes

• Indirect → patent processus vaginalis (congenital); prematurity in infants
• Direct → weak transversalis fascia (acquired): age, smoking, collagen defects
• Raised pressure → cough, constipation, prostate, lifting, obesity, ascites, peritoneal dialysis
• Previous appendicectomy (ilioinguinal nerve injury), family history, connective tissue disease

4. Pathogenesis

• Indirect:
  1. Processus vaginalis stays open after testicular descent
  2. Sac enters the deep ring, passes inside the cord (inside internal spermatic fascia)
  3. Exits the superficial ring → scrotum (complete, inguinoscrotal)
  4. Narrow neck → higher risk of strangulation
• Direct:
  1. Transversalis fascia stretches in Hesselbach's triangle
  2. Broad, diffuse bulge; rarely enters the scrotum
  3. Wide neck → strangulation rare
• Sliding hernia → caecum (right), sigmoid colon (left) or bladder forms part of the sac wall

5. Classification

By anatomy

• Indirect (bubonocele → in the canal; funicular → to the top of the testis; complete → in the scrotum)
• Direct
• Pantaloon
• Recurrent

European Hernia Society (EHS)

• L (lateral = indirect), M (medial = direct), F (femoral)
• Defect size → 1 (≤ 1.5 cm, one finger), 2 (1.5–3 cm, two fingers), 3 (> 3 cm)
• P (primary) or R (recurrent)

Nyhus

• I indirect, normal ring (children)
• II indirect, dilated ring
• III a direct, b large indirect, c femoral
• IV recurrent

6. Clinical picture

Symptoms

• Groin lump, often noticed after lifting or straining
• Dragging ache or discomfort, worse at the end of the day
• Many have no symptoms
• Complications → painful, tense, irreducible lump; vomiting, distension (obstruction)

Signs

• Examine standing, then lying, both sides
• Lump above and medial to the pubic tubercle (femoral hernia lies below and lateral)
• Cough impulse
• Reducible; you cannot get above a scrotal hernia (unlike a hydrocele)
• Deep ring occlusion test → reduce the hernia, press over the deep ring, ask the patient to cough:
  • Controlled → indirect
  • Appears medially → direct
  • Not reliable; the type is confirmed at operation
• Indirect → descends obliquely along the canal into the scrotum; reduces upwards and laterally
• Direct → forward bulge, reduces straight back, rarely scrotal
• Examine the testes, abdomen (masses, ascites), chest, prostate

7. Diagnosis

• Clinical in most
• Ultrasound → uncertain lump, occult hernia, groin pain
• MRI → occult hernia, athletes' groin (most accurate)
• CT → obese patients, complications
• Herniography → rarely
• Emergency → FBC, U&E, lactate; abdominal X-ray for obstruction

8. Differential diagnosis

• Femoral hernia (below and lateral to the pubic tubercle)
• Hydrocele (can get above it, transilluminates), encysted hydrocele of the cord
• Varicocele ("bag of worms")
• Undescended or ectopic testis
• Inguinal lymph nodes
• Saphena varix, femoral artery aneurysm, psoas abscess
• Lipoma of the cord
• Groin pain → adductor strain, athletic pubalgia, hip disease

9. Treatment

Conservative

• Watchful waiting → men with no or few symptoms:
  • Incarceration risk very low (about 0.2–0.3% a year)
  • About 70% need surgery within 10 years because of pain
• Unfit patients → observe; truss gives little relief
• Women → repair all (risk of a missed femoral hernia)
• Children → repair all promptly (high incarceration risk, especially < 1 year)

Surgical

• Indications → symptomatic hernia, history of irreducibility, all women and children, complications
• Infants and children → herniotomy only (ligate and excise the patent processus vaginalis); no repair of the wall
• Adults: open tension-free mesh repair (Lichtenstein) → standard open operation; local, regional or general anaesthesia:
  1. Skin crease incision above the inguinal ligament
  2. Open the external oblique aponeurosis; protect the ilioinguinal and iliohypogastric nerves
  3. Mobilise the cord
  4. Indirect sac → separate from the cord, reduce or ligate and excise at the deep ring
  5. Direct sac → invert; plicate the transversalis fascia
  6. Polypropylene mesh → from 1–2 cm over the pubic tubercle to beyond the deep ring; sutured to the inguinal ligament below and internal oblique above; tails cross behind the cord to make a new deep ring
  7. Close external oblique
• Laparoscopic repair → mesh behind the transversalis fascia (preperitoneal); covers all three sites (direct, indirect, femoral):
  • TEP (totally extraperitoneal) → peritoneum not opened
  • TAPP (transabdominal preperitoneal) → peritoneum opened, then closed over the mesh
  • Best for bilateral and recurrent hernias (after open repair) and women (NICE, EHS)
  • Less chronic pain, faster return to work; needs general anaesthesia
  • Danger zones → "triangle of doom" (vas medially, testicular vessels laterally; external iliac vessels inside) and "triangle of pain" (lateral to the testicular vessels, below the iliopubic tract: lateral femoral cutaneous and genitofemoral nerves); no tacks in these
• Tissue (non-mesh) repairs:
  • Shouldice → four-layer imbrication of transversalis fascia; low recurrence in expert hands
  • Bassini, McVay (Cooper's ligament) → historical, contaminated fields
• Recurrence after open repair → laparoscopic; after laparoscopic → open
• Strangulated → emergency open (or laparoscopic) repair; resect dead bowel

10. Complications

Early

• Haematoma (2%), seroma
• Wound infection (< 5%)
• Urinary retention (older men, spinal anaesthesia)
• Ischaemic orchitis, testicular atrophy (< 1%) → damage to the pampiniform plexus
• Bowel or bladder injury (sliding hernia, laparoscopy)

Late

• Chronic postoperative groin pain (inguinodynia) → 10–12% some pain, 1–3% severe; ilioinguinal, iliohypogastric, genital branch of genitofemoral nerves; treatment → analgesia, nerve block, triple neurectomy, mesh removal
• Recurrence → 1–3% with mesh, higher with tissue repairs
• Mesh infection, mesh migration
• Vas injury → infertility
• Port-site hernia (laparoscopic)