Utility of diffusion-weighted MRI for differentiating acute from chronic cholecystitis

Purpose: To assess the use of diffusion-weighted imaging (DWI) for differentiating acute from chronic cholecystitis, in comparison with conventional magnetic resonance imaging (MRI) features. Materials and Methods: Liver MRI including DWI (b-values 0/500/1000s/mm²) was performed at 1.5T ≤30 days before cholecystectomy in 83 patients with abdominal pain. Two radiologists assessed cases for conventional (gallstones, wall thickening, pericholecystic fluid, pericholecystic fat changes, gallbladder distension, pericholecystic liver enhancement, mural T₂-hyperintensity, mural hyperenhancement, mural striations, abscess, intraluminal membranes, and mural defect) and DWI (increased mural signal on high b-value images, visually low apparent diffusion coefficient [ADC], and ADC values) features. Results: Acute cholecystitis was present in 43%; chronic cholecystitis was present in 57%. Nine of 12 conventional features were more frequent in acute cholecystitis for both readers (P ≤ 0.003). Increased mural signal on high b-value images was more frequent (P < 0.001) in acute than chronic cholecystitis for R1 (92% vs. 32%) and R2 (83% vs. 30%). Sensitivity and specificity of increased signal on high b-value images were: R1, 92%/68%; R2, 83%/70%. Visually low ADC was more frequent in acute cholecystitis for R2 (P < 0.001) but not R1 (P = 0.406); ADC values were not different between groups for either reader (P = 0.104–0.139). Among conventional and DWI features, only increased signal on high b-value DWI was independently associated with acute cholecystitis for both readers (P = 0.006–0.012). Conclusion: Visually increased mural signal on high b-value DWI was highly sensitive and moderately specific for acute cholecystitis, being an independent predictor relative to conventional features for both readers. Although requiring larger studies, DWI (particularly the high b-value images) may have additive value relative to conventional MRI-suspected acute cholecystitis. J. Magn. Reson. Imaging 2016;44:89–97.