Papillary stones: calcified renal tubules in Randall's plaques.

Papillary stones are small, rounded concretions with one smooth convex face and one concave face which corresponds to its implantation on the papilla and in which a whitish Randall's plaque is often present. Eighty-seven papillary stones were studied with stereoscopic, scanning electron microscopic and x-ray dispersive energy analysis. Sixty-three stones had a plaque and 13 of these showed calcified renal tubules that demonstrated their intrapapillary origin and a link between partial papillary nephrocalcinosis and renal stones.