Gallbladder Fossa Abscess Masquerading as Cholecystitis After Cholecystectomy

DISCUSSION

Although hepatobiliary scintigraphy is typically used to evaluate disease or postprocedural iatrogenic injury of the biliary tree and gallbladder (1), it may also demonstrate any abnormality in hepatic parenchymal tissue. In the rim sign, a photopenic area in the gallbladder fossa does not show any filling with radiotracer and is surrounded by increased activity in the pericholecystic area. This sign is seen in approximately 32% of patients with acute cholecystitis and has a positive predictive value of 94% when seen in conjunction with nonvisualization of the gallbladder (2). The sign occurs secondary to several mechanisms such as increased blood flow and extraction of radiotracer by the liver, as well as decreased clearance from edema and inflammation of biliary canaliculi leading to bile stasis (3).

Because the rim sign is typically associated with a more emergent clinical picture, the importance of obtaining a proper patient history and correlative imaging cannot be underestimated. In our case, for example, if the patient had been septic and unresponsive, if the medical history had been unavailable, and if the interpreter had considered the scintigraphic findings in isolation, a case of acute cholecystitis may have erroneously been diagnosed. This diagnosis would, of course, have been impossible because of the prior cholecystectomy, leaving bile leakage or hepatic abscess to be the much more likely possibilities in the differential diagnosis. On abdominal CT, a surgical clip was seen at the proximal cystic duct, hinting not only that a prior surgical procedure was performed but also that the gallbladder fossa contained air, thus making abscess the more probable diagnosis.