Comparison of hepatobiliary iminodiacetic acid (HIDA) scan, ultrasound (US), computer tomography (CT) in evaluation of acute cholecystitis

Learning Objectives The purpose of this exhibit is to compare HIDA scan and US in evaluation of acute cholecystitis and to illustrate characteristic findings of HIDA scan, abdominal US and CT.

Methods: We retrospectively reviewed 174 patients with pathologically proven acute cholecystitis who underwent both HIDA scan and abdominal US exam prior to cholecystectomy. Twenty-one of 174 patients also underwent CT scan prior to cholecystectomy. Results: Nonvisualization of the gallbladder at 4 hours post radiotracer injection was seen in 58 of 174 patients, consistent with acute cholecystitis. Nubbin sign and Rim sign on HIDA scan are characteristic findings of acute cholecystitis seen in 12 patients and 1 patient respectively. US findings in acute cholecystitis include the presence of cholelithiasis, sonographic Murphy sign, gallbladder wall thickening (> 3mm) and pericholecystic fluid. These signs were identified in 112 patients, 55 patients, 31 patients and 25 patients respectively. CT showed acute cholecystitis in 9 out of 21 patients including cholelithiasis, gallbladder distension, gallbladder wall thickening, mural or mucosal hyperenhancement, pericholecystic fluid and inflammatory fat stranding. HIDA scan had a greater sensitivity, specificity, and accuracy in diagnosing acute cholecystitis when compared to US and CT. Conclusion: US is the preferred initial modality in evaluation of cholecystitis because US is more readily available and less costly. HIDA scan is unable to demonstrate the complications of acute cholecystitis. Although the CT scan is readily available, the radiation of the CT scan should also be taken into account, especially in young patients. HIDA scan and CT can be used for the evaluation of sonographically equivocal cases. It is also paramount that the radiologists are familiar with the characteristic appearance of acute cholecystitis.