Ischaemic Disorders

The pathogenesis of intestinal ischaemia has been previously discussed and in the large intestine is often due to mesenteric vascular insufficiency because of systemic hypotension (myocardial infarction, cardiac arrhythmia, blood loss) or mesenteric atheroma/thrombosis/embolism. Acute lesions may resolve if mucosa-confined but are potentially fatal if transmural. Late or chronic ischaemia has a predilection for the splenic flexure and rectosigmoid watershed areas of vascular supply. This can result in non-specific ulceroinflammatory and stricturing lesions - endstage changes that can be produced by various other conditions, e.g., CIBD, infection (E. coli 0157:H7 bacterium), pseudomembranous colitis due to Clostridium difficle overgrowth, obstructive enterocolitis and stercoral trauma. Occasional cases are due to vasculitis or amyloid infiltration. Assessment of resection limit viability and mural/mesenteric vessels is necessary in ischaemia.

A vascular abnormality that can present with an iron deficiency anaemia in elderly patients is colonic angiodysplasia. Thought to be degenerative in nature due to increased intraluminal pressure compressing mural vessels, the commonest site is the caecum. Operative injection of radio-opaque contrast may be needed to demonstrate areas of vascular ectasia so that targeted blocks can be sampled. The ectatic vessels involve the submucosa and lamina propria.

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