Hernia

An abnormal protrusion of an organ or tissue through a defect in its surrounding walls.

Anatomy

• Most commonly involves the abdominal wall
• Occurs only at sites where the aponeurosis and fascia are not covered by striated muscle.
• Neck/orifice is located at the innermost musculo-aponeurotic layer
• Sac protrudes from the neck, and is lined by peritoneum
• No consistent relationship between the area of a hernia defect and size of sac

Presentation

• Reducible - when the contents can be replaced within the surrounding musculature
• Strangulated - compromised blood supply to contents
  • Occurs more often in large hernias with small orifices
  • Can be either obstructed arterial flow or venous drainage or both
• Obstructed - occurs due to adhesions between the contents of the sac and peritoneal lining
• Richter hernia - a small portion of the antimesenteric wall of the intestine is trapped within the hernia, and strangulation can occur without obstruction

Loss of domain

• Not well-defined - 'a hernia sac of great size that forms a secondary abdominal cavity'; 'large enough that primary fascial closure either cannot be achieved without additional reconstructive techniques or significant risk of complications due to raised abdominal pressure'
  • >20-50% of abdominal contents residing outside the abdomen
  • One definition from Tanaka et al: when hernia volume greater than >25% of abdominal compartment volume (excluding hernia)
• Pathophysiology
  • Abdominal contents no longer reside in the abdominal cavity, and therefore cannot simply be placed back inside
  • Natural rigidity of abdominal wall becomes compromised and musculature retracts
  • Complications:
    • MSK problems
    • Ventilatory dysfunction - cause paradoxical respiratory abdominal movement - compromised respiratory function
    • GIT dysfunction - can result in bowel oedema, stasis of the splanchnic venous system, urinary retention, and constipation
    • Psychosocial issues
• Management
  • Patient needs to understand how big of an undertaking this is going to be
  • Optimise everything medically - see separate topic under 'ventral incisional hernia'
  • May need additional techniques for closure - see 'ventral incisional hernia'
    • Usually benefits from Botox and component separation
  • Watch post-op for intra-abdominal hypertension

Classification of hernias

• Anatomical - European Hernia Working Group

• Complex vs simple
  • Patient factors
  • Anatomical factors

Management principles

• Goals
  • Fix the problem/restoration of function in line with patient expectations
  • Minimise complications, pain, disability
  • Cosmesis
  • Durable repair with low recurrence rate
  • Functional/dynamic abdominal wall
• Principles
  • Optimise patient pre-op
  • Restore anatomy and recreate linea alba
  • Reinforce the repair when possible with wide mesh overlap
  • Tension-free repair
• Contraindications to operation
  • Medically/surgically unfit
  • Absence of available tissue
  • No benefit or improvement in QoL
  • Risks outweigh benefits

Hernia emergencies

Strangulation or bowel obstruction = urgent repair

• • Ideally within 4-6 hours from onset of symptoms

Acutely incarcerated, but no signs of strangulation

• • Offer urgent repair
  • Can also attempt reduction, and if reducible, can follow up with surgeon in a few days to exclude reincarceration and arrange elective repair
  • If fails reduction, can proceed to urgent surgery
  • 'Taxis' - the rearrangement of tissues, that is, reduction of hernia, to avoid surgery
    • Contraindications: presence of strangulated bowel within the hernia (tachycardia, hypotension, peritonitis; erythema, hot and painful local skin; blood tests including WCC are unreliable)
      • Note that it's generally very unlikely that the hernia contains strangulated bowel if it's been reduced successfully
      • Obstruction but not strangulation is not necessarily a contraindication to reduction
    • >24 hours since onset of symptoms seems to be associated with higher likelihood of strangulation
      • If within 24 hours and no sign of strangulation, attempt reduction; if later, surgery and examination of sac should be preferenced
    • GPS (gentle, prepared, safe)
      • Gentle manipulation through external ring - avoid 'reduction en masse' where the herniated bowel and constricting ring are reduced together, providing a false sense of achievement
      • Prepared - consider procedural sedation/IV morphine + midaz /min bolus morphine until desired level of analgaesia achieved)
      • Safe - avoid attempting if concern for strangulation
    • Procedure
      • As much trendelenburg position as tolerated
      • Direct herniae will be easier to re-insert
      • Gentle pulling on edge of sac - will realign sac in direction of canal
      • Gently massage back into canal
      • Can take 5-10 min
      • If bowel is present, a satisfying gurgling sound is often heard on reduction
      • Need period of observation post-reduction to ensure pain resolved