Duplex ultrasound of the superior mesenteric artery in chronic pancreatitis

Blood flow in the superior mesenteric artery (SMA) increases after a meal due to a vasoactive effect of the decomposed food. In exocrine pancreatic insufficiency, the digestion of food is compromised. We used duplex ultrasound to test the hypothesis that blood flow in the SMA after a meal increases less in patients with pancreatic insufficiency than in control persons. We studied 16 patients with chronic pancreatitis, eight of them with exocrine insufficiency, and eight healthy volunteers. The resistive index (RI) in the SMA was determined before and after a liquid meal. The RI reflects the downstream circulatory resistance, giving a precise description of mesenteric hyperaemia. Both groups of patients with chronic pancreatitis unexpectedly had lower fasting RI than controls, 0.818 and 0.815 vs 0.851, p = 0.028 and p = 0.0030, respectively. Postprandialy there was significantly less decrease in RI (less increase in flow) in patients with exocrine insufficiency than in controls, 0.055 vs 0.099, p = 0.0047. There was a significant trend for a less pronounced postprandial decrease in RI with more impaired pancreatic function (p = 0.0036). Our study thus demonstrates a reduced postprandial increase in SMA flow in patients with exocrine pancreatic insufficiency, and suggests an increased fasting SMA flow in chronic pancreatitis. Further studies are needed to evaluate the possible role of the test-meal-induced shift in RI in the SMA and of a lower-than-normal fasting RI in the diagnosis and monitoring of chronic pancreatitis.