Incisional Hernia

Definition

Incidence

• 10-50% after open laparotomy incisions
• 1-5% after laparoscopic port-site incisions
• Midline incisions carry the highest risk compared to off-midline incisions
• Rates can reach 50% in specific high-risk populations

Aetiology and Risk Factors

Patient Factors

• Obesity (increases intra-abdominal pressure AND wound infection risk)
• Diabetes (impairs wound healing)
• Malnutrition
• Immunosuppression / steroid therapy
• Smoking
• Chronic cough / COPD (elevated intra-abdominal pressure)
• Genetic collagen disorders
• Previous wound infection

Wound Factors

• Poor-quality tissue
• Wound tension
• Wound infection / surgical site infection (SSI) - an independent predictor of early (<6 months) incisional hernia formation

Surgical/Technical Factors

• Inappropriate suture material
• Poor closure technique
• Drains brought through the midline wound (prevents fascial apposition)
• Ostomies through the midline incision
• Incorporating fatty/muscular tissue in fascial bites (causes ischemia and necrosis)

Pathophysiology

• Progress rapidly to full-thickness wound dehiscence, heralded by serosanguineous discharge around the 6th postoperative day
• Pass unnoticed if overlying skin has healed, with a visible swelling appearing weeks, months, or years later

Clinical Features

• Localised swelling at the surgical scar, OR diffuse bulging along the whole incision length
• Multiple discrete defects within the same scar are very common (always check full incision length)
• Hernia tends to increase in size over time
• Overlying skin may become thin, atrophic, and prone to ulceration
• Obstruction is common (due to coexisting internal adhesions)
• Strangulation is less frequent - most incisional hernias are shallow and wide-necked; strangulation is most likely when the fibrous defect is small and the sac is large

Risk Stratification

Prevention

1. Preoperative optimisation - smoking cessation, weight loss, glycaemic control, nutritional support
2. Fascial closure technique:
   • Close the linea alba only - do not incorporate fat or muscle
   • Small-stitch, small-bite technique (STITCH trial): 5 mm fascial bites spaced 5 mm apart
   • Suture length:wound length ratio of ≥4:1 (European Hernia Society guideline)
   • Use slowly absorbable monofilament suture (e.g. 2-0 PDS with 30-40 mm needle)
   • Avoid closing under excessive tension
3. Drains must exit through separate stab incisions, never through the midline wound
4. Prophylactic mesh augmentation (PMA) in high-risk patients - reduces incisional hernia formation regardless of mesh plane (onlay, retrorectus, preperitoneal, or intraperitoneal)
5. Use laparoscopic approach when safe and feasible (lower hernia risk vs open)

Treatment

Conservative

• Asymptomatic hernias may not require immediate surgery
• Abdominal binder/belt provides symptomatic relief and may limit enlargement
• Patients with significant comorbidities: balance benefits vs operative risks carefully

Preoperative Optimisation ("Prehabilitation")

• Weight loss (loss of 7% bodyweight achieves significant metabolic improvement; 5 kg body weight ~1 extra litre of intra-abdominal space in adult males)
• Smoking cessation
• Fitness improvement and core-strengthening exercises
• Multidisciplinary team assessment is increasingly standard

Surgical Principles

1. Repair must cover the entire length of the previous incision
2. Musculofascial approximation with minimal tension
3. Prosthetic mesh should be used to reduce recurrence risk
   • Contraindicated in grossly contaminated field (e.g. perforated strangulated bowel)
   • May be used in clean-contaminated field (e.g. elective bowel resection) with strict hygiene and prophylactic antibiotics
4. Mesh should augment primary fascial closure - not "bridge" a gap (bridging repair leads to central mesh bulge)

Mesh Placement Planes (ICAP Classification, 2019)

Surgical Approaches

Open Repair

• Open previous incision along its full length to expose unsuspected defects
• Expose hernial sac, neck, and margins; reduce contents; divide adhesions; excise redundant sac
• Primary suture repair alone (Mayo/da Silva overlap) - NOT recommended due to unacceptable recurrence rates; only acceptable in gross contamination where mesh is contraindicated
• For small hernias (<2 cm): primary closure may be acceptable
• For larger defects: mesh-based repair is standard

Laparoscopic Repair

• Laparoscopy and adhesiolysis performed first
• Hernia contents reduced
• Mesh placed intraperitoneally and fixed with tacks/sutures
• Advantages: less wound morbidity, shorter hospital stay
• Access ports at a distance from the hernia; may need robotic assistance for complex cases

Component Separation

Complications of Repair

• Wound seroma (very common, especially with large flap elevation)
• Wound infection / SSI
• Mesh infection (may require mesh removal)
• Recurrence (lower with mesh vs suture alone)
• Adhesive bowel obstruction (especially with intraperitoneal mesh)
• Visceral erosion/fistula

Key Points Summary

• Incidence: 10-50% after laparotomy; 1-5% after laparoscopic ports
• Most important modifiable prevention factor: fascial closure technique (small-bite, ≥4:1 suture:wound ratio)
• Obstruction is common; strangulation is rare (wide-necked)
• Multiple defects in same scar are very common - always explore full incision
• Mesh repair is standard - simple suture repair has unacceptable recurrence
• Retromuscular/sublay plane is preferred for mesh placement
• Prehabilitation (weight loss, smoking cessation) is important preoperatively