Strangulated Hernia

A strangulated hernia is an incarcerated hernia in which blood supply to the herniated tissue has been compromised.

Venous obstruction occurs first, producing congestion and bowel wall oedema. Increasing pressure eventually compromises arterial inflow, causing ischaemia, transmural necrosis, bacterial translocation and perforation.

A strangulated hernia is an operative emergency. Delay increases bowel resection, sepsis and mortality.

The most concerning pattern is an acutely painful irreducible hernia with persistent rather than intermittent pain.

Features include:

• Severe local tenderness
• Continuous pain
• Vomiting and bowel obstruction
• Progressive abdominal tenderness
• Fever and persistent tachycardia
• Overlying erythema, dusky skin or oedema
• Peritonism if perforation has occurred

Late disease produces hypotension, metabolic acidosis and septic shock.

Normal lactate or absence of skin changes does not exclude early strangulation.

Richter strangulation can occur without complete bowel obstruction.

Diagnosis is principally clinical.

Check full blood count, renal function, electrolytes, blood gas and lactate. Crossmatch blood when bowel resection may be required.

CT abdomen and pelvis with IV contrast: useful in a stable uncertain case; determine whether trapped bowel shows compromised perfusion or closed loop obstruction.

Do not delay emergency operation for CT when the clinical diagnosis is convincing.

Begin resuscitation while theatre is being prepared.

Keep fasting, establish large bore IV access and correct intravascular depletion with balanced crystalloid. Use nasogastric decompression when bowel obstruction and vomiting are significant.

Do not attempt manual reduction when strangulation is suspected. Reduction can return necrotic bowel to the abdominal cavity and remove the ability to assess it directly.

Begin antibiotics when bowel ischaemia is suspected.

A practical adult regimen is:

Ceftriaxone 2 g IV every 24 hours plus metronidazole 500 mg IV every 12 hours.

For septic shock, perforation or major contamination:

Piperacillin tazobactam 4.5 g IV every 8 hours by extended infusion, with renal dose adjustment.

Proceed urgently to operative exploration.

Release the constricting defect and assess bowel viability. Allow potentially recoverable bowel to reperfuse before committing to resection.

Viability assessment incorporates:

• Return of normal colour
• Mesenteric arterial pulsation
• Peristaltic activity
• Bleeding from a cut bowel edge when required
• Doppler flow or fluorescence assessment where available

Frankly gangrenous or perforated bowel requires resection.

Primary anastomosis is reasonable when bowel margins are healthy and the patient is physiologically stable.

Septic shock, severe bowel oedema, heavy contamination, high vasopressor requirement or uncertain perfusion should lower the threshold for diversion, bowel discontinuity or staged reconstruction.

If the strangulated contents reduce spontaneously during induction before viability has been assessed, inspect the bowel laparoscopically or through another appropriate abdominal approach rather than assuming it is healthy.

Synthetic mesh is appropriate in a clean field and can be considered when bowel resection occurs without gross enteric spillage. Gross contamination, bowel perforation or established infection should generally avoid permanent synthetic mesh during the contaminated operation.