Objective: 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.
Patients: 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).
Results: 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).
Conclusion: 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.