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Acute cholecystitis: MR findings and differentiation from chronic cholecystitis.

PURPOSE
To retrospectively determine the sensitivity and specificity of magnetic resonance (MR) imaging for differentiation between acute and chronic cholecystitis, with histopathologic analysis as the reference standard.


MATERIALS AND METHODS
Institutional review board approval with waived informed consent was obtained for this HIPAA-compliant study. Four reviewers blinded to the cholecystitis type but aware that cholecystitis was present retrospectively evaluated MR images for predetermined findings in 32 patients (15 male, 17 female; mean age +/- standard deviation, 55 years +/- 20) with histopathologically proved acute or chronic cholecystitis. The final MR diagnoses and MR findings in both groups were compared with each other and with the histopathologic diagnoses to determine the sensitivity and specificity of MR imaging. Chi(2) tests were used to detect differences in MR findings between the acute and chronic cholecystitis groups.


RESULTS
MR imaging sensitivity and specificity for detection of acute cholecystitis were 95% (18 of 19 patients) and 69% (nine of 13 patients), respectively. The sensitivities of increased gallbladder wall enhancement and increased transient pericholecystic hepatic enhancement were 74% (14 of 19 patients) and 62% (10 of 16 patients), respectively. Both findings had 92% (12 of 13 patients) specificity. Sensitivities of increased wall thickness, pericholecystic fluid, and adjacent fat signal intensity changes were 100% (19 of 19 patients), 95% (18 of 19 patients), and 95% (18 of 19 patients), respectively; specificities were 54% (seven of 13 patients), 38% (five of 13 patients), and 54% (seven of 13 patients), respectively. Pericholecystic abscess, intraluminal membranes, and wall irregularity or defect each had 100% (13 of 13 patients) specificity; sensitivities were 11% (two of 19 patients), 26% (five of 19 patients), and 21% (four of 19 patients), respectively. Increased gallbladder wall enhancement (P<.001) and increased transient pericholecystic hepatic enhancement (P=.003) were the most significantly different between acute and chronic cholecystitis.


CONCLUSION
Increased gallbladder wall enhancement and increased transient pericholecystic hepatic enhancement had the highest combination of sensitivity and specificity for the diagnosis and differentiation of acute and chronic cholecystitis.