Differential Diagnosis

• Single most likely diagnosis
  • Acute cholecystitis: The "nubbin sign" of the cystic duct, nonvisualization of the gallbladder, and complete evacuation of activity from the hepatic parenchyma through the CBD are highly suggestive of acute cholecystitis, especially in the appropriate clinical setting.
• Other Likely diagnoses
  • Chronic cholecystitis: Chronic inflammation of the gallbladder could lead to similar findings, including nonvisualization of the gallbladder and abnormal uptake in the cystic duct.
  • Cystic duct obstruction: Obstruction of the cystic duct, whether due to stones, inflammation, or other causes, could result in the observed pattern of radiotracer uptake and nonvisualization of the gallbladder.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Gallbladder perforation: Although less likely, gallbladder perforation is a serious condition that requires prompt diagnosis and treatment. The presence of focal uptake in the region of the gallbladder fossa could potentially represent leakage of radiotracer into the peritoneal space.
  • Mirizzi syndrome: This rare condition, where a gallstone becomes impacted in the cystic duct and causes obstruction of the common bile duct, could lead to similar imaging findings and requires timely intervention to prevent serious complications.
• Rare diagnoses
  • Porcelain gallbladder: A rare condition characterized by calcification of the gallbladder wall, which could potentially lead to nonvisualization of the gallbladder on imaging studies.
  • Gallbladder diverticulum: A congenital or acquired outpouching of the gallbladder wall, which could potentially cause abnormal radiotracer uptake and mimic other conditions.