Purpose: The role of a ‘rim sign’ in increasing specificity for acute cholecystitis and sensitivity for complicated acute cholecystitis has been substantiated in many small retrospective studies. We sought to corroborate this correlation in a large population, as we have encountered doubt among surgeons about the emergent implications of this sign.
Methods: We performed a small pilot interobserver reliability test with five nuclear medicine physicians from outside institutions. A total of 2881 consecutive hepatobiliary scans performed over 12 years for evaluation of acute cholecystitis were retrospectively reviewed. Available pathological (reference standard) and surgical reports were reviewed for all cases of acute cholecystitis (on scintigraphy) with a rim sign and for an equivalent set without a rim sign.
Results: There was no statistically significant interobserver agreement on the presence of a rim sign.
There was a 32.4% incidence of acute cholecystitis, based on scintigraphy, and a 10.1% incidence of rim signs. Of 63 pathologic specimens from rim-sign-positive cases, 19 (30.2%) showed acute cholecystitis and 44 (69.8%) showed chronic cholecystitis. Six (9.5%) cases were complicated.
Among 55 pathologic specimens from the acute scintigraphy cases without a rim sign, 21 (38.2%) showed acute cholecystitis and 34 (61.8%) showed chronic cholecystitis. There were eight (14.5%) complicated cases.
Conclusion: There was no interobserver reliability in the identification of a rim sign. There was almost no difference in the incidence of pathologically acute, chronic, or complicated acute cholecystitis among scintigraphically acute cases with or without a rim sign, approximately two-thirds to three-quarters of which were chronic on pathological evaluation.