Small Bowel Ischaemia

Small bowel ischaemia is inadequate intestinal perfusion causing reversible or progressive bowel injury. It may result from arterial occlusion, mesenteric venous thrombosis, nonocclusive low flow states, strangulated obstruction, volvulus or internal hernia.

The operative distinction is reversible ischaemia versus irreversible necrosis.

Ischaemia begins with mucosal injury and can progress rapidly to full thickness infarction, bacterial translocation and perforation.

Severe pain disproportionate to initial examination is characteristic of vascular mesenteric ischaemia.

Mechanical strangulation may produce severe continuous pain superimposed on previous colic.

Progression to focal guarding or generalised peritonitis strongly suggests transmural injury.

Gastrointestinal bleeding can occur when mucosal ischaemia becomes advanced.

CT angiography: first line when a vascular cause is suspected; identify the vascular lesion and determine whether bowel enhancement is impaired.

A normal lactate does not exclude early ischaemia. Rising lactate and metabolic acidosis suggest advanced injury but are late enough that treatment should never wait for them.

Correct hypovolaemia without excessive crystalloid loading and treat the underlying mechanism immediately.

For arterial occlusion, pursue urgent revascularisation where bowel remains potentially salvageable.

For mesenteric venous thrombosis without peritonitis, therapeutic anticoagulation is first line.

For a strangulated obstruction or volvulus, release the mechanical cause urgently.

Start broad spectrum antibiotics when significant bowel ischaemia is suspected because mucosal barrier failure allows bacterial translocation.

A practical regimen is:

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

At operation, restore blood flow or release strangulation before deciding how much bowel to resect whenever feasible.

Questionable bowel should be warmed and allowed time to reperfuse. Frankly necrotic bowel requires resection.

When substantial bowel remains of uncertain viability, use temporary abdominal closure and perform a second look operation approximately 24 to 48 hours later rather than sacrificing potentially viable small bowel.