Acute mesenteric ischaemia with vascular occlusion could result from venous or arterial occlusion.
CT features of acute mesenteric ischaemia with arterial or venous occlusion are correlated with the results of published histopathological reports. In arterial mesenteric ischaemia, pathological findings demonstrate transmural infarction and the bowel wall is very thin. CT shows a dilated bowel segment, lack of bowel wall enhancement, thin bowel wall, and pneumatosis. In venous mesenteric thrombosis, there is oedema and vascular engorgement associated with varying degree of oedema and haemorrhage in the submucosa. CT shows concentric bowel wall thickening, and enhancement of bowel without evidence of pneumatosis.
It is important to differentiate arterial occlusion from venous occlusion in acute mesenteric ischaemia because treatment and prognosis are different. When venous thrombosis is diagnosed early, the ischaemia may be reversible with anticoagulant therapy and the prognosis is good; on the other hand, in arterial thrombosis, emergency surgery is required with resection of ischaemic bowel segments, if possible, and the prognosis is grave.