[CT diagnosis of acute occlusion of the superior mesenteric artery]

The purpose of this study was to clarify the usefulness of CT in the early diagnosis of acute SMA occlusion. The CT scans of seven patients with surgically proved acute SMA occlusion were retrospectively reviewed. The SMV/SMA ratio, which was defined as the external diameter of the SMV divided by the external diameter of the SMA, was measured on CT scans in seven patients and in 300 control subjects. The sites of SMA occlusion were seen as high density structures on preconstrast CT scans in all seven patients and as filling defects on postcontrast CT scans in five of them. According to pathologic and angiographic studies, the high density structures represented intravascular fresh blood clots. The SMV/SMA ratios were < 1 in five of seven patients, whereas they were > 1 in 288 of 300 control subjects. Other CT findings, such as dilated fluid-filled bowel, decreased enhancement of small bowel wall and ascites, seemed to be dependent on the extent of bowel necrosis. In conclusion, focal high density in the SMA on preconstrast CT scan is a specific sign of acute SMA occlusion, and the SMV/SMA ratio might reflect the ischemic grade of mesenteric circulation.