Differences of pancreatic stone morphology and content in patients with pancreatic lithiasis.

Pancreatic stones from 25 patients were compared by morphological and/or radiological examination. Twenty patients, mostly alcoholics, had calcified stones. Five (four nonalcoholic women) had radiolucent stones. Aspect and consistency of calcified stones varied from compact and resistant to coralliform and brittle but were identical in the same patient. In the coralliform type, organic fibrils with a diameter up to 10 microm and a length up to a few centimeters were observed, strongly attached to mineral crystals. The lithostathine (formerly called pancreatic stone protein, PSP) content was estimated in each stone significantly lower in the populations with larger stone mass, compared to populations with small amounts of stones. Transparent stones were built up of an amorphous material solubilized at acidic pH and corresponding to degraded forms of lithostathine-S (S for secretory). In one patient, we followed over seven years the evolution of a radiolucent calculus. We observed that the radiolucent core occurred first, and was secondarily wrapped in a calcified shell. We conclude that morphological differences observed in this study among pancreatic stones suggest that different mechanisms have been involved in their formation. Among them, lithostathine transformation into insoluble polypeptides may provide different types of protein aggregates, some of them being able to promote CaCO(3) apposition and others having no affinity for calcium.