Given that hepatobiliary clearance is the predominant pathway for the ^99mTc MPI radiopharmaceuticals, it is expected that the components of the biliary system (intrahepatic ducts, common hepatic duct, common bile duct) might be visualized and that the gallbladder will be visualized (Figs. 20.1 and 20.2) (Shih et al. 2002). A normal common bile duct is not uncommonly visible and should not be misconstrued as pathologic. While there are relatively few biliary conditions (biliary ectasia, common bile duct obstruction) that can be seen on SPECT MPI, there are multiple physiologic and pathologic conditions of the gallbladder (Table 20.1) (Hesse et al. 2005).

The gallbladder should fill with radioactive bile and appear quite “hot,” often the “hottest” finding in the field-of-view. The patient is typically fasting for the stress test, and the gallbladder, as in ^99mTc iminodiacetic acid (IDA) hepatobiliary scintigraphy, should fill. Diaphragmatic motion may produce a moving (“beating”) gallbladder (Fig. 20.3). The gallbladder generally has a characteristic round to ovoid shape and is tucked under the inferior right lobe; however, it may be intrahepatic in location (Howarth et al. 1996). Figure 20.4 shows an unusually elongated and superiorly displaced gallbladder; it is adjacent to the right hemidiaphragm by anatomic CT correlation. A very “hot” and “high” gallbladder may create a processing artifact on the reconstructed MPI (Fig. 20.5). The degree of gallbladder visualization can vary from rest to stress imaging on both 1-day and 2-day protocols (Figs. 20.6 and 20.7). The gallbladder is usually well-distended and a contracted gallbladder is considered abnormal (Fig. 20.8).