Definition of age dependent reference values for diameter of the common bile duct and pancreatic duct on MRCP from a population based cohort study

Introduction:

Changes in diameters of the pancreaticobiliary ducts are markers of benign and malignant pancreaticobiliary conditions. MRCP is first line, non-invasive imaging modality. The reference ranges in asymptomatic individuals have only been studied in small cohorts.

Aims and Methods:

To define new reference values for diameters of pancreaticobiliary ducts on MRCP in the general population. Study subjects were recruited from the SHIP cohort and had whole body MRI+MRCP (1,5T MRI system). Diameters of pancreatic duct (PD) and common bile duct (CBD) were measured on MRCP before and after administration of secretin.

Results:

1385 subjects were initially scanned, 774 PDs and 938 CBDs were included for analysis. Subjects were excluded for missing data or evidence of pancreaticobiliary disease. Median age 53y (21 – 89y) and 48.5% female. The diameters increased with age (PD median (range) 1.–3. Quartile: 20 – 29 years 1,48 cm (1,03 – 1,2,91), > 70 years 2,50 (1,11 – 4,81); CBD median (range) 1.–3. Quartile: 20 – 29 years 4,57 (2,52 – 7,51), > 70 years 6,60 (2,80 – 15,94)) and the historic upper limit of normal of 3 mm for PD and 7 mm for CBD were exceeded by 10,9% and 18,2%. Subjects that underwent cholecystectomy presented with significantly increased diameter of CBD, but not PD (CBDw/oCCE: 5.60 mm, (1,9 – 16,9 mm range) vs. CBDw/CCE: 8.42 mm, (2,3 – 15,3 mm range), p < 0.01; PDw/oCCE: 2,04 mm, (1,0 – 6,7 mm range) vs. PDw/CCE: 2.26 mm, (1,0 – 5,0 mm range), p > 0.01). Duct size was not correlated to liver function tests (ASAT, ALAT, GGT). Using 95th percentile quantile regression age dependent upper limits for normal were defined (< 65 years PD 3,30 mm; CBD 8,31 mm; > 65 years PD 4,00; CBD 10,48 mm). PD but not CBD diameters significantly changed after administration of secretin.

Conclusions:

Up to 18,2% of healthy volunteers would have undergone diagnostic workup for enlarged CBD or PD above the current reference standard. The width of the pancreaticobiliary ducts increases in an age dependent manner in asymptomatic volunteers. An increase of the CBD after cholecystectomy can be observed. In absence of cholastatic liver disease a moderately increased duct diameter is most likely non-pathologic. To reduce unnecessary workup age related adjustments of reference values are suggested.