HEPATOBILIARY IMAGING WITH Tc-99m-HIDA

Abstract

Availability of the Tc-99m-hepatobiliary agents has permitted an evaluation of the liver-biliary tree-gallbladder-small bowel complex even in the face of elevated bilirubin levels. Although the sequence of events is usually well defined, variations can be found which tend to contribute to diagnostic uncertainties. We wish to point out 2 major variants, which are likely related to increased pressure in the biliary system. 1) Stasis pattern. As long as hepatic ability to extract the radiotracer is still present, the blood level of Tc-99m-HIDA will progressively fall and that within the liver will increase. Once within the liver however, the radiolabel may not progress into the biliary system. This stasis pattern has been recognized in patients with intrahepatic cholestasis. An identical pattern has been noted in 2 males with acute high obstruction of the biliary tree. Hepatic accumulation of tracer occurred, but there was total lack of collection in the larger biliary radicals and no excretion. The diagnosis of high obstruction was confirmed surgically. The presence of acute high obstruction should be considered when a stasis pattern is accompanied by signs and symptoms of cholecystitis (severe pain was present in both cases). 2) Intrahepatic reflux. As the gallbladder contracts, the pressure generated is usually greater than that in the cystic and common bile ducts; hence, the pathway of excretion is from gallbladder toward the small bowel. If this pathway is obstructed, then bile may pass in another direction. A woman was seen with intermittent right upper quadrant pain. The Tc-99m-HIDA study proceeded normally with filling of the gallbladder. Upon administration of a fatty meal, there was prompt emptying of the gallbladder with reflux of activity into the major intrahepatic ducts. At ERCP, there was delayed runoff, and an inferred elevated pressure gradient preventing downward drainage. Hence, increased pressure within the bile excretory pathway can result in unusual distribution of the Tc-99m-HIDA. (Supported by USPHS CA 17802).