Strangulated Bowel Obstruction

Strangulated obstruction is mechanical bowel obstruction accompanied by compromised blood supply.

Venous obstruction initially produces oedema and haemorrhage within the bowel wall and mesentery. Progressive pressure then compromises arterial inflow, resulting in transmural ischaemia, necrosis, bacterial translocation, perforation and septic shock.

Strangulation can complicate adhesive obstruction, closed loop obstruction, hernia, volvulus or intussusception.

It is an operative emergency.

Pain often changes from intermittent colic to persistent severe pain.

Suspicious findings include:

• Continuous abdominal pain
• Focal or generalised guarding
• Persistent tachycardia
• Fever
• Localised severe tenderness
• Gastrointestinal bleeding in some ischaemic processes
• Haemodynamic deterioration

Late findings include rigidity, shock, metabolic acidosis and organ dysfunction.

Absence of fever or leukocytosis does not exclude early strangulation.

Obtain full blood count, renal function, electrolytes, coagulation, blood gas and lactate. Crossmatch blood when bowel resection or major contamination is likely.

CT abdomen and pelvis with IV contrast: confirms obstruction and should be assessed specifically for impaired bowel enhancement or other evidence of ischaemia. CT evidence of ischaemia should prompt a low threshold for immediate exploration.

Do not undertake prolonged conservative management.

Begin resuscitation immediately with balanced crystalloid, correction of electrolyte abnormalities, nasogastric decompression and urinary output monitoring where systemic compromise is present.

Start broad spectrum antibiotics because loss of mucosal integrity and necrosis expose the patient to enteric Gram negative and anaerobic organisms.

A suitable adult regimen is:

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

For severe sepsis or extensive necrosis:

Piperacillin tazobactam 4.5 g IV every 8 hours by extended infusion, adjusted for renal function.

Resuscitation must not become a reason to postpone source control. Correct major physiological abnormalities while theatre preparation proceeds.

At laparotomy or laparoscopy, relieve the constricting lesion and assess the entire affected segment. Necrotic bowel requires resection back to clearly perfused margins.

Primary anastomosis is reasonable in a stable patient with viable margins and limited contamination. Shock, high vasopressor requirement, gross contamination, severe bowel oedema or questionable perfusion should lower the threshold for diversion or staged reconstruction.

Where viability remains uncertain after reperfusion, second look laparotomy is appropriate, particularly when extensive bowel resection would otherwise be required.

Postoperatively, persistent acidosis, rising lactate, vasopressor requirement, worsening abdominal findings or ongoing organ dysfunction should raise concern for residual ischaemic bowel or inadequate source control.