[Concentrically layered microconcrements in the renal medulla of nephrolithiasis patients. A contribution to the renal stone pathogenesis (author's transl)].

The electron microscopic investigation of the renal medulla in calcium oxalate stone patients has shown the frequent occurrence of globoid microconcrements in the basal laminae of the collecting ducts and of the thin limbs in Henle's loop. They have a concentrically layered structure, the diameter is usually below 1.5 microns, rarely more than 3 microns. Some of these objects were also seen in the interstitial connective tissue. Tissue of stone-free patients exhibited either no or only few such microconcrements which were usually located in the interstitial space. Histochemical tests and energy dispersive microprobe analysis suggest that calcium phosphate and acid mucopolysaccharides are principal components of the microconcrements. There are indications that some microconcrements might be expelled from the basal laminae into the urinary space and may form agglomerations. They might then furnish nuclei for heterogeneous crystallization especially in cases without hypercalciuria or hyperoxaluria.