Is CCK administration or delayed imaging necessary when bowel excretion does not occur but gallbladder fills promptly?

Objectives: On Tc-99m HIDA scans, “preferential gallbladder (GB) filling without tracer excretion into the small bowel (SB) up to an hour [pGB-no-SB]” is occasionally seen after cholecystokinin (CCK) pretreatment or in the fasting state. While pGB-no-SB is known as a normal variant, many nuclear medicine physicians still seem to choose to administer CCK (even when estimation of GBEF is not requested) or obtain delayed images (DI) to exclude the possibility of common bile duct (CBD) obstruction as the cause of the patient’s symptoms. We assessed: 1) the prevalence of clinically relevant CBD obstruction found by administering CCK or DI in this circumstance, and 2) imaging findings that can be used to triage which patients do or do not need additional CCK or DI.

Methods: 1,244 HIDA scans were retrospectively reviewed. Of these, 1,089 were excluded because of one or more of the following reasons: SB visualized within 60 minutes (min), GB not visualized within 60 min, severely decreased hepatic function, and less than 1 month of clinical follow-up after the date of HIDA scan. The remaining 155 scans with pGB-no-SB were reviewed. The time of GB visualization and liver parenchymal clearance was qualitatively assessed.

Results: Of the 155 scans, 142 showed visually prompt clearance of liver parenchymal activity (Group 1), while 13 scans showed mild to moderately delayed clearance of liver parenchymal activity (i.e., mild cholestatic pattern) with or without initial decreased hepatic uptake (Group 2). In Group 1, 113 GBs were visualized ≤15 min, and 29 GBs at 16-30 min. 13 GBs in Group 2 were visualized at 19-35 min. The median GB visualization time was 12 min in Group 1 and 25 min in Group 2. 134 of 142 in Group 1 had additional imaging (99 CCK or 35 DI); all 134 showed SB visualization. 8 remaining scans in Group 1 were terminated without additional imaging. None of the 142 had any event attributable to CBD obstruction on follow-up. All 13 in Group 2 had additional imaging (9 CCK, 4 DI); SB visualized in 11, but not in 2; clinical follow-up revealed no CBD-related issues in 11. ERCP revealed CBD obstruction in the latter 2.

Conclusion: When a HIDA scan shows p-GB-no-SB, the probability of identifying clinically relevant CBD obstruction by additional imaging with CCK or DI is virtually zero in acute clinical setting, if liver parenchymal clearance is prompt. Additional imaging with CCK or DI can be reserved for only those showing abnormal liver parenchymal clearance.