Background:
A critical factor for survival of acute mesenteric ischemia is early diagnosis and intervention, a goal that has been hindered by lack of an accurate diagnostic imaging tool. Multidetector row CT, with its relatively short scanning time and 3-D reformation algorithms, has led to the development of CT angiography as a viable imaging alternative to traditional, invasive angiography. We sought to examine the utility of 16-multidetector row CT angiography in diagnosing acute mesenteric ischemia in a porcine model. Following induction of ischemia, pigs were imaged, and the radiographic findings were compared to the gross and histopathological findings after the affected bowel was surgically removed.

Methods:
Following administration of general anesthesia, ischemia was induced by cannulation of a femoral artery, selective catheterization of the ileocolic branch of the superior mesenteric artery, and embolization with 500-micron microspheres. At specified time points, pigs underwent contrast angiography using 16-multidetector row CT with 3-D reconstruction. Exploratory laparotomy was then performed and the ischemic bowel segment was surgically excised en bloc with the mesenteric arcade. The radiologic findings were then confirmed by gross and microscopic pathological examination.

Results:
Control animals demonstrated bowel wall enhancement in the arterial phase on CT angiogram. In ischemic animals, segmental arterial embolic occlusion was reliably seen on CT angiogram. Resected bowel segments that were noted on histopathological examination to be cyanotic, but viable, with early ischemic changes, demonstrated hyperemia with normal arterial enhancement on multi-detector row CT. In contrast, irreversibly necrotic bowel showed lack of bowel wall enhancement and focal dilation of the mesenteric veins at the site of embolization on CT angiogram.

Conclusions:
Using a state-of-the-art 16-multidetector row CT angiography in the porcine model, definitive radiographic evidence of an ischemic event was seen in the acute setting, one hour after the onset of ischemia. The associated hyperemia and vascular changes correlated with the gross pathological findings of cyanosis and hypothermia, as well as the microscopic finding of thrombosis. Since acute mesenteric ischemia has had reported mortality rates of at least 60%, this imaging modality holds promise for the early detection necessary for successful treatment.