Extrahepatic bile duct on MRCP: Does incidentally detected dilation in the absence of signs or symptoms of obstruction require further investigation?

OBJECTIVE

Dilation of the extrahepatic bile duct (EHD) on imaging, which includes the common hepatic and bile ducts, is often assumed to be due to obstruction. The purpose of this study was to determine if EHD diameter differs between patients with and without active EHD obstruction.

METHODS

All patients ≥ 18 years who underwent MRCP 2017-2024 were eligible. Patients with EHD dilatation due to a known etiology were excluded. EHD diameter was measured from inner-wall to inner-wall perpendicular to the long axis of the duct by two investigators independently, then averaged. Biliary obstruction was confirmed or excluded using a composite reference standard.

RESULTS

121 patients (50 men, 71 women) mean age 65 years (range 20-95 years) met the inclusion criteria. 38% (46/121) had right upper quadrant pain, 10% (12/121) dilated main pancreatic duct, and 26% (31/121) had a prior cholecystectomy. Median EHD diameter was 6.5 mm (range 2-16 mm). There was no difference in EHD diameter between patients with and without active biliary obstruction (median 7 mm vs 6.5 mm), P = 0.60, regardless of cholecystectomy status or age. EHD diameter was larger in patients with prior cholecystectomy (median 8 mm vs 6 mm), P = 0.03. Only an abrupt CBD "cutoff" on imaging was associated with obstruction (P = 0.03).

CONCLUSION

EHD diameter as a standalone finding does not have a clear association with biliary obstruction and may not require further workup in the absence of signs or symptoms of obstruction. An abrupt CBD cutoff was the only imaging feature associated with obstruction.