Radiolucent pancreatic lithiasis: a precursor stage for calcified pancreatic lithiasis or a new entity?

Radiolucent pancreatic lithiasis (RPL) has been identified as a different entity from calcified pancreatic lithiasis. The purpose of this study is to evaluate the frequency, characteristics and evolution of RPL.

Between 1983 and 1995, 278 consecutive patients who presented with pancreatic lithiasis were studied. Forty-four patients had RPL (15.8%): 27 had pure radiolucent stones (PRS) (group 1), 5 had pure radiolucent stones combined with evenly calcified stones (ECS) (group 2), 2 had target calculi (TC) (radiolucent core with calcified shell) (group 3), 10 had TC combined with ECS (group 4).

Among the 27 patients with PRS, there were 19 males with a mean age of 41 years. PRS were mainly located in the head of the pancreas with a mean diameter of 5 mm (range 3-26 mm). Seven patients among 27 with PRS (26%) were less than 20 years old (juvenile form) or more than 60 years old (senile form). They were characterized by no or low alcohol consumption and a high rate of attacks of acute pancreatitis. In group 1, PRS turned to more advanced calcified stages in 6/16 of patients (37%) followed in 30 to 144 months with a prior stage of TC in 2 cases. An evolution toward more calcified stages (TC or ECS) occurred in half of the patients belonging to group 2 and 4 in 36 to 84 months. Genetic disposition and alcohol consumption could account for the evolution toward more calcified stages. A genetic factor is suggested by a rapid evolution to evenly calcified stones in two aged children 8 and 10 years and by a high frequency of familial cases in patients belonging to groups 2 and 4 (60% and 20%) as compared to group 1 with PRS (4%). Alcohol consumption could accelerate the calcifying process since patients belonging to groups 2 and 4 had a significantly higher alcohol consumption than those with PRS (group 1).

RPL is a heterogeneous pancreatic disease including juvenile and senile presentation which may represent about 15% of pancreatic lithiasis. Evolution towards calcified stages (PRS then TC then ECS) occurred in 37-50% of cases and could be related to a genetic factor and increased alcohol consumption.