As the superior mesenteric vein thrombosis, back pressure builds as arterial supply to the bowel is uninterrupted. This leads to bowel wall oedema (and thus bowel wall thickening) and possible intramural haemorrhage (leading to hyperdense bowel wall) 1. Depending on the how complete occlusion is, and whether or not collateral drainage is available, the combination of back pressure, and bowel wall thickening can lead to inadequate tissue perfusion leading to intestinal ischaemia, infarction and eventual necrosis 1.