Hepatobiliary rim sign: new implications for acute and complicated cholecystitis.

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.

Tc-99m sestamibi parathyroid gland scintigraphy: added value of Tc-99m pertechnetate thyroid imaging for increasing interpretation confidence and avoiding additional testing.

PURPOSE: To evaluate the benefit of adding a pertechnetate parathyroid scan (dual-isotope imaging) in the interpretation of sestamibi dual-phase parathyroid scintigraphy. MATERIAL AND METHODS: One hundred and sixteen dual Tc-99m sestamibi (MIBI) and Tc-99m pertechnetate subtraction parathyroid studies, performed between January 2000 and February 2006, were retrospectively reviewed. Dual-phase technetium sestamibi examinations were initially interpreted, with blinding to the technetium pertechnetate findings. Subsequently, technetium pertechnetate scan findings were added, and changes in interpretation were recorded. RESULTS: By adding Tc-99m pertechnetate imaging, the interpretation of 17 scans (17/116=14.6%) was substantially altered. This included 5 scans (4%) that changed from negative to positive and 9 scans (8%) that changed from equivocal to positive, excluding ectopic tissue and directing minimally invasive surgery, without the need for further imaging, such as ultrasound, in 12% of cases. One examination changed from positive to negative. In addition, 2 scans changed from equivocal to negative, necessitating further preoperative imaging for the evaluation of additional pathology such as thyroid nodules and lymph nodes and the consideration of hyperplasia. Among the remaining 99 patients, Tc-99m pertechnetate scans may also have contributed to the diagnosis in the 66 positive Tc-99m MIBI scans by increasing confidence in the interpretation and obviating additional imaging. Ten cases remained equivocal. CONCLUSION: By adding Tc-99m pertechnetate imaging, scan interpretation was changed in 14.6% of cases, and interpretation confidence was enhanced in all but 10 remaining equivocal cases. The addition of a dual-isotope subtraction also eliminated the need for additional testing, such as ultrasound, in 12% of our cases. Increased confidence in interpretation that comes with dual-isotope subtraction may come at the cost of slight lengthening of imaging time but likely simplifies preoperative localization and decreases intraoperative time for many patients with primary hyperparathyroidism.