Extrinsic pressure defects on the duodenal loop in mesenteric occlusive disease.

Abstract

Atherosclerotic occlusions of the mesenteric vessels can be recognized and treated in the chronic state, but frequently portions of the gastrointestinal tract are gangrenous before the diagnosis is considered. The clinical picture of postprandial abdominal pain, anorexia, and weight loss with laboratory findings of malabsorption should suggest mesenteric vascular disease (1, 3, 4, 9, 11). Thefindings, however, are often vague or may mimic other more common causes of abdominal pain. In addition, the commonly employed studies for abdominal disease have not been helpful in alerting the physician to this possibility. Gastrointestinal barium examinations have either been negative or have shown nonspecific changes in the small bowel such as those observed in the malabsorption syndrome. Confirmation and localization of the lesions have required abdominal aortography or selective visceral arteriography. Further experience in mesenteric vascular disease has suggested to us that the collateral circulation developing after major mesenteric occlusion may on occasion be demonstrable by barium studies of the upper gastrointestinal tract. The major collateral flow after marked narrowing or occlusion of the celiac and superior mesenteric vessels is derived from the inferior mesenteric artery, although smaller collaterals have been seen coming from the phrenic and esophageal arterial branches. Flow from the inferior mesenteric artery passes around the splenic flexure of the colon through what has been called the central anastomotic artery of the colon or the “meandering mesenteric artery” (17). This vessel communicates with the middle colic artery, and flow proceeds into the superior mesenteric trunk. Collateral flow between the superior mesenteric artery and the celiac axis has not been as well defined. The major pathway, when one or both of these vessels become occluded at their origins, has, in our experience, been from the superior mesenteric artery through the inferior to the superior pancreaticoduo-denal arcades and then into the celiac axis distribution. These vessels become quite large as the upper abdominal viscera become increasingly dependent upon them for survival. The appearance by arteriography of these collateral channels is that of a single large vessel from the superior mesenteric artery to the gastroduodenal artery around the head of the pancreas and the medial aspect of the descending portion of the duodenum (Figs. 1 and 2). For descriptive purposes, we have called this large collateral channel the pancreaticoduodenal artery loop. Enlargement of this collateral loop as it passes along the medial aspect of the descending portion of the duodenum may produce extrinsic pressure on the duodenum or expansion of the duodenal loop. These changes when observed in barium studies suggest an increase in the size of the head of the pancreas.