MRI of acute cholecystitis: comparison with the normal gallbladder and other entities.

Our purpose was to prospectively compare MRI findings with histopathologic findings in the evaluation of suspected acute cholecystitis. Fourteen patients with clinically suspected acute cholecystitis were entered into the study. MR sequences included T1-weighted fat-suppression and breath-hold spoiled gradient echo (SGE) before and after intravenous gadolinium chelate administration. Percent contrast enhancement (%CE) of the gallbladder wall and gallbladder wall thickness (WT) were measured and liver enhancement patterns determined prospectively on MR images. Correlation was obtained with pathological findings at cholecytectomy in all patients. In a second phase of the study MR images on 10 additional subjects who underwent MR examination for reasons other than hepatobiliary disease were analyzed to determine normal values for %CE and gallbladder wall thickness. Mean %CE was 124.0% in patients with acute cholecystitis (10 patients), 58.0% in patients with chronic cholecystitis (2 patients), and 73.0% in patients with gallbladder malignancy (2 patients). Mean gallbladder WT was 6.1 mm in acute cholecystitis, 4.5 mm in chronic cholecystitis, and 6.0 mm in malignant disease. There was a significant difference in %CE between acute and chronic cholecystitis (p = 0.03); no other significant differences in %CE or WT were observed among the patients with gallbladder disease. Patients without biliary disease had %CE of 37.3% and WT of 2.9 mm, which were both significantly less (p < 0.001) than in patients with acute cholecystitis. Transient enhancement of pericholecystic hepatic parenchyma on immediate postgadolinium SGE images was seen in 7 of 10 patients with acute cholecystitis, and not observed in other patients. Patients with acute cholecystitis had increased %CE and WT on MR images that were significantly greater than normal and %CE that was significantly greater than in patients with chronic cholecystitis. Transient increased pericholecystic hepatic enhancement was observed in 70% of acute cholecystitis patients and in no other patient groups.