Apparent diffusion coefficient by magnetic resonance cholangiopancreatography is useful for grading cholecystitis and surgery planning.

The ADC value was significantly lower in the severe inflammation group ( grade 3) than in the weak inflammation group (grades 1 and 2) (1.93 ± 0.22 vs 2.38 ± 0.67, respectively; P = .02). Ulceration and wall thickness in the gallbladder neck were significantly correlated with ADC values (P = .04 and .006, respectively), and lymphoid follicle formation was marginally correlated with ADC values (P = .06). The diagnostic utility of the ADC values decreased as the interval between imaging and cholecystectomy increased. [Correction added on 19 October 2022, after first online publication: [On the first sentence of the Results section, (grades 2 and 3) for weak inflammation group has been changed to (grades 1 and 2).] CONCLUSION: ADC values were inversely associated with the pathologic intensity of cholecystitis. We recommend that the ADC value be measured before surgery, so that the procedure can be accordingly planned.