Impairment of Changes in the Diameter of the Pancreatic Portion of the Superior Mesenteric Vein

Abstract

A new ultrasonographic technique for detecting parenchymal stiffness of the pancreas is proposed. This technique measures changes in the diameter of the origin of the superior mesenteric vein (SMV) induced by deep inspiration. The origin of the SMV has extensive attachments to the pancreatic parenchyma; therefore, both physiologic enlargement and shrinkage of the venous lumen cannot occur without changes in the shape of the surrounding parenchyma. Therefore, increased parenchymal stiffness due to chronic pancreatitis (CP) may result in impaired changes in the venous diameter. To confirm this hypothesis, patients with CP and those with a normal pancreas were examined in this study. Twelve patients in each group were examined. Images of the origin of the SMV were obtained with a commercial ultrasound system. The smallest diameter of the SMV was measured during normal breathing. The patients were then asked to take a deep breath to increase the portal blood pressure followed immediately by the same measurements as performed during normal breathing, and the ratio of the change was calculated. In the normal group, the diameter of the SMV changed by 79.5% +/- 43.8% (mean +/- SD), whereas a change of 1.4% +/- 7.3% was observed in the CP group. The difference between the two groups was statistically significant (P < .0001). The physiologic change in the diameter of the origin of the SMV enhanced by deep inspiration may reflect the stiffness of the pancreatic parenchyma. Therefore, detection of an impaired diameter change may be useful for screening of CP.