Bile Amylase levels in choledochal cysts

The etiology and pathogenesis of choledochal cysts remain unclear. The reflux of pancreatic juice into the bile duct through an abnormal pancreaticobiliary ductal junction has been incriminated as one of the major causes in forming this disorder. We investigated the levels of amylase in the bile of choledochal cysts in relation to the shape of the cysts to study pancreatic juice reflux in the etiology of this disorder. From 1980 through 1990, 38 patients with choledochal cysts underwent operations in this hospital and were included in this study retrospectively. The morphology of bile duct dilation and amylase levels aspirated from the bile of the cysts were evaluated using the Chi-Square test. There were 19 patients with cystic form cysts and 19 patients with fusiform cysts. Six (31.6%) patients with cystic form cysts had cyst amylase levels>1000 IU/L and 13 (68.4%) had levels<1000 IU/L. On the other hand, 17 (89.5%) patients with fusiform cysts had cyst amylase level>1000 IU/L and 2 (10.5%) had levels <1000 IU/L. In patients with cysts<8 cm, 21 (77.8%) had cyst amylase levels >1000 IU/L and 6 (22.2%) had levels<1000 IU/L. In contrast, in those with cysts ≤8 cm, 2 (18.2%) had cyst amylase levels >1000 IU/L and 9 (81.8%) had levels <1000 IU/L. Both of the differences are statistically significant (P<0.001). The cyst amylase levels were usually higher than 1000 IU/L in the fusiform choledochal cysts and lower in the cystic form cysts, especially in cysts larger than 8 cm. In this study, we postulate that pancreatic juice reflux may initially cause fusiform dilatation of the common bile duct. As time goes by, the distal bile duct becomes stenotic, and the cyst size increases due to this mechanical factor rather than the reflux. The cyst amylase level decreases because of the stenosis and also the dilutional effect of bile.