Diffusion-Weighted Magnetic Resonance Imaging of the Gallbladder in Acute Cholecystitis: Diagnostic Performance Compared to Histopathological Findings

Purpose: To evaluate the diagnostic performance of gallbladder (GB) wall diffusion restriction on MRCP with diffusion-weighted imaging (DWI) for diagnosing acute cholecystitis (AC), with histopathological findings as the reference standard, and to assess the added value of GB wall thickness and interobserver agreement. Methods: In this retrospective multicenter study, 270 patients underwent MRCP with DWI followed by cholecystectomy within seven days. Three experienced abdominal radiologists independently assessed GB wall diffusion restriction and measured GB wall thickness. Diagnostic accuracy was calculated for DWI, GB wall thickness, and a combined model compared to histopathology-confirmed AC diagnosis. Interobserver agreement was assessed with kappa and intraclass correlation. Subgroup analyses examined the influence of MRI-to-surgery interval and magnetic field strength. Results GB wall diffusion restriction showed high diagnostic accuracy, with sensitivity of 94%, specificity 84%, PPV 77%, and NPV 96% (AUC 0.89). Sensitivity was 100% for surgery performed within 24 hours, but declined with longer intervals. GB wall thickness alone reached an optimal cutoff at 4.3 mm (sensitivity 84%, specificity 72%). The combined model slightly increased AUC (0.92) without significant improvement over DWI alone. Interobserver agreement was substantial for DWI (κ = 0.63) and good for wall thickness (ICC = 0.80). Diagnostic performance was similar across 1.5T and 3.0T field strengths (p = 0.23). Conclusion GB wall diffusion restriction on MRCP with DWI is a reproducible and accurate marker for AC diagnosis. GB wall thickness adds information but only modestly affects overall accuracy. DWI is a robust imaging marker that could be integrated into diagnostic algorithms for suspected AC.