Combined hyperdense gallbladder wall-lumen sign: new computed tomography sign in acute gangrenous cholecystitis

Purpose
The objective of our study was to evaluate the combined hyperdense gallbladder wall-lumen sign on computed tomography (CT) in diagnosing gangrenous cholecystitis.

Material and methods
We retrospectively reviewed the unenhanced CT scans of surgically proven cases of acute gangrenous (GCh) and non-gangrenous cholecystitis (nonGCh). Eleven cases of pathologically proven acute gangrenous cholecystitis and 12 consecutive cases of surgically proven acute non-gangrenous cholecystitis that underwent CT at our institute were included in the study so as to have 1 : 1 control. The Hounsfield unit (HU) value of the gallbladder wall and intraluminal bile was measured. Interobserver variability for individual CT findings was also assessed.

Results
The gangrenous cholecystitis group had significantly higher HU values of wall and bile (median value of 33 HU vs. 21 HU and median value of 21 HU vs. 8.5 HU, respectively, p < 0.05). The area under the receiver ope­rator characteristic curve for HU lumen was 0.80 (95% CI: 0.62-0.98, p = 0.014) with an ideal cut-off at 31.5 HU, where the sensitivity was 54.5% and specificity was 91.7%. HU lumen has an even better assessment for gangrenous cholecystitis with AUC of its ROC as 0.92 (95% CI: 0.80-1.00, p = 0.001) with an ideal cut-off at 12.5 HU, where the sensitivity was 81.8% and specificity was 91.7%. The combined wall-lumen cut-off is 35 HU with sensitivity of 100% and specificity of 75%.

Conclusion
A cut-off CT density value of the gallbladder wall of more than 31.5 HU, intraluminal bile more than 12.5 HU, and combined wall-lumen HU of more than 35 can predict GCh.