Bahadır Reis, Faruk Enes Yazar
Advanced Radiology and Imaging - 2026;3(1):8-14
Objectives: Computed tomography (CT) is frequently the first cross-sectional imaging modality obtained in patients presenting with suspected biliary obstruction, yet its sensitivity for direct detection of common bile duct (CBD) stones is known to be variable. This study aimed to determine the rate of CT-missed findings in patients with magnetic resonance cholangiopancreatography (MRCP)-confirmed choledocholithiasis and to identify stone and protocol characteristics associated with CT nondetection. Methods: In this single-center retrospective study, 33 adults with MRCP-confirmed choledocholithiasis who had undergone abdominal CT within seven days of MRCP were included. CT images were independently re-evaluated by two blinded radiologists; discordant readings were resolved by consensus. MRCP served as the reference standard. CT sensitivity and its 95% confidence intervals (CI) were calculated using the Wilson method. Intergroup comparisons were performed using the Mann-Whitney U test and Fisher's exact test. Agreement between MRCP and CT measurements of CBD diameter was assessed by Spearman correlation and Bland-Altman analysis. Results: CT sensitivity was 48.5% (16/33; 95% CI, 32.5-64.8%), corresponding to a missed finding rate of 51.5%. MRCP stone diameter was significantly larger in the CT-detected group (median 9.0 mm vs. 5.0 mm; p=0.001), and CT-measured CBD diameter was likewise larger (median 14.0 mm vs. 10.0 mm; p=0.017). Stones measuring <=5 mm were missed on CT in 83.3% of cases versus 33.3% for stones larger than 5 mm (odds ratio, 10.00; p=0.010). MRCP and CT CBD diameters were strongly correlated (Spearman r=0.793; p<0.001), with negligible bias on Bland-Altman analysis (+0.18 mm). The Median stone attenuation in CT-detected cases was 78 hounsfield units (HU) (interquartile range, 56-114 HU). Conclusion: CT failed to identify CBD stones in more than half of patients with MRCP- confirmed choledocholithiasis. Stone diameter <=5 mm was the strongest predictor of CT non-detection. These findings support a low threshold for MRCP referral when CT does not directly demonstrate a CBD stone in patients with clinically suspected biliary obstruction.
