56. Incisional, Spigelian, Petit's and Grynfeltt's hernias

1. Definition

• Incisional hernia → hernia through a defect in the scar of a previous abdominal incision (or port site)
• Spigelian hernia → hernia through the Spigelian aponeurosis, along the linea semilunaris, usually at or below the arcuate line
• Lumbar hernia → hernia through the posterolateral abdominal wall:
  • Petit's → through the inferior lumbar triangle
  • Grynfeltt's (Grynfeltt-Lesshaft) → through the superior lumbar triangle

2. Epidemiology

• Incisional hernia → 10–20% of midline laparotomies (up to 30% at 5 years with risk factors); most appear within the first 2–3 years
• Port-site hernia → about 1%, mostly at umbilical ports 10 mm or more
• Second commonest abdominal wall hernia after inguinal
• Spigelian → rare (1–2% of hernias); age 40–70; slightly more in women
• Lumbar → very rare (about 300 cases each in the old literature); superior more common than inferior; about 20% congenital, most acquired (flank incision, trauma)

3. Aetiology and risk factors

Incisional hernia

• Patient factors:
  • Obesity
  • Wound infection (strongest single factor; doubles or triples the risk)
  • Smoking, diabetes, malnutrition, anaemia, jaundice, uraemia
  • Steroids, chemotherapy, immunosuppression
  • Chronic cough, constipation, prostatism, ascites
  • Collagen disorders, abdominal aortic aneurysm
• Technical factors:
  • Midline incision (more than transverse or paramedian)
  • Poor closure: wrong suture, large bites, too much tension
  • Emergency surgery, re-opening, drains through the wound
• Prevention → small bites (5 mm bites, 5 mm apart), slowly absorbable continuous suture, suture to wound length ratio at least 4 : 1 (STITCH trial); prophylactic mesh in high-risk patients (for example aortic aneurysm, BMI over 27)

Spigelian hernia

• Weak Spigelian aponeurosis (internal oblique and transversus) below the arcuate line, where no posterior rectus sheath
• Obesity, pregnancy, rapid weight loss, COPD, laparoscopic ports

Lumbar hernias

• Anatomy (revision):
  • Inferior (Petit's) triangle → iliac crest (below), latissimus dorsi (posterior), external oblique (anterior); floor internal oblique
  • Superior (Grynfeltt's) triangle → 12th rib (above), quadratus lumborum and erector spinae (medial), internal oblique (lateral); floor transversalis fascia; roof latissimus dorsi
• Acquired → flank incisions (nephrectomy), iliac crest bone graft, trauma (seat belt), infection
• Congenital → in children, with other defects

4. Pathogenesis

• Incisional:
  1. Early fascial separation (often in the first weeks, silent)
  2. Scar stretches, sac of peritoneum forms
  3. Defect enlarges with time; contents adhere to the sac
  4. Large hernias → loss of domain (contents live outside the abdomen; cannot return without raising pressure)
  5. Many defects in one scar → "Swiss cheese" pattern
• Spigelian → interparietal: sac lies under the intact external oblique aponeurosis; narrow neck → high risk of incarceration (about 20%)
• Lumbar → wide neck mostly; incarceration rare (about 10%)

5. Classification

Incisional (European Hernia Society)

• Midline (M) → M1 subxiphoid, M2 epigastric, M3 umbilical, M4 infraumbilical, M5 suprapubic
• Lateral (L) → L1 subcostal, L2 flank, L3 iliac, L4 lumbar
• Width → W1 < 4 cm, W2 4–10 cm, W3 > 10 cm
• Recurrent or not; length

Lumbar

• Superior (Grynfeltt) or inferior (Petit)
• Diffuse (after a flank incision)
• Congenital or acquired (primary or secondary)

6. Clinical picture

Symptoms

• Incisional → bulge in a scar, larger on standing and coughing; ache, dragging; skin changes in large hernias
• Spigelian → pain at the lateral edge of rectus, below the umbilicus; lump often hard to feel (lies under external oblique)
• Lumbar → flank or back bulge, back ache; may be mistaken for a lipoma
• Complications → painful, irreducible lump, vomiting, distension

Signs

• Incisional → reducible lump in the scar, cough impulse; feel the edges of the defect lying down; look for several defects
• Large hernia → thin skin, ulceration, intertrigo; loss of domain
• Spigelian → tender spot on the linea semilunaris, often no lump; ask the patient to lift the head (tense the wall)
• Lumbar → reducible flank swelling above the iliac crest, cough impulse; examine sitting up

7. Diagnosis

• Clinical in most incisional hernias
• CT → test of choice for planning: size and number of defects, loss of domain (ratio of hernia volume to abdominal volume), muscle quality, contents
• Ultrasound → small or occult hernias, Spigelian (dynamic, with straining)
• Spigelian → ultrasound or CT; laparoscopy confirms
• Lumbar → CT (defect, contents, rule out a mass)
• Preoperative → weight, smoking, diabetes control, nutrition

8. Differential diagnosis

• Divarication of the recti (no defect, no sac)
• Lipoma, desmoid tumour, abscess, haematoma in the scar
• Rectus sheath haematoma (Spigelian area)
• Endometriosis in a caesarean scar
• Lumbar → lipoma, abscess, kidney tumour, flank bulge from nerve injury (denervation) without a defect

9. Treatment

Conservative

• Small, asymptomatic, wide-necked hernias in unfit patients → watchful waiting; abdominal binder or corset
• Prehabilitation before elective repair → stop smoking (4–6 weeks), weight loss (BMI under 35 ideally), control diabetes (HbA1c), nutrition
• Loss of domain → progressive preoperative pneumoperitoneum or botulinum toxin A into the lateral muscles (2–6 weeks before)

Surgical: incisional hernia

• Principles:
  1. Reduce the contents, excise or keep the sac
  2. Close the fascia (restore the linea alba) where possible
  3. Reinforce with mesh, overlap at least 5 cm beyond the defect
• Defects under 1–2 cm → sutured repair can be enough; above that, mesh (lower recurrence: suture alone recurs in up to 50%)
• Mesh positions:
  • Sublay (retromuscular, Rives-Stoppa) → mesh behind rectus, in front of the posterior sheath; preferred open position
  • Onlay → on the anterior sheath; more seroma and infection
  • Preperitoneal → below the arcuate line
  • Intraperitoneal onlay mesh (IPOM) → laparoscopic; coated mesh against bowel; fixed with tacks or sutures
  • Inlay (bridging) → only when the fascia cannot be closed; high recurrence
• Laparoscopic IPOM → less wound infection, shorter stay; best for defects up to about 10 cm
• Component separation for large defects:
  • Anterior → divide the external oblique lateral to the linea semilunaris (Ramirez); perforator-sparing or endoscopic forms reduce skin necrosis
  • Posterior: transversus abdominis release (TAR) → extends the retromuscular space laterally; large sublay mesh
• Robotic eTEP and TAR → newer options
• Contaminated field → sutured repair, biological or absorbable synthetic mesh, or staged repair
• Strangulation → emergency repair; resect dead bowel

Surgical: Spigelian hernia

• All are repaired (narrow neck, incarceration risk)
• Laparoscopic TAPP or TEP with preperitoneal mesh (preferred), or IPOM
• Open → incision over the defect, open external oblique, reduce the sac, close the defect, mesh preperitoneally

Surgical: lumbar hernia

• Small, primary → open repair with sublay or preperitoneal mesh
• Large or diffuse → laparoscopic or robotic transabdominal preperitoneal mesh; fix to the iliac crest and 12th rib with wide overlap
• Watch the subcostal, iliohypogastric and ilioinguinal nerves

10. Complications

• Hernia → incarceration, strangulation, skin ulceration, loss of domain
• Repair:
  • Seroma (common, mostly settles), haematoma
  • Wound infection, skin necrosis (anterior component separation)
  • Mesh infection, mesh erosion, enterocutaneous fistula (IPOM)
  • Recurrence → up to 50% after suture alone; about 10–20% with mesh
  • Abdominal compartment syndrome after reducing a large hernia
  • Bowel injury (adhesiolysis)
  • Chronic pain