The most frequent structures of the majority of possible urolith components are assessed by scanning electron microscopic investigations. Typical examples of the conversion of uric acid dihydrate into uric acid, weddellite into whewellite and MgHN4PO4 . 6 H20 into MgNH4PO4 . H2O are given.

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In uroliths various phosphate phases can be detected which indicate different formation conditions. Structure and topography of the respective phosphate phases are characterized by scanning electron microscopy and microprobe techniques. Trace element enrichment is investigated and illustrated; for example, sulfur is found preferentially in carbonate apatite. From the distribution of the phosphate phases, conclusions can be drawn concerning the urolith genesis.

Rabbits were given glyoxylic acid to induce intrarenal calcium oxalate crystal formation. The point of crystallisation in the renal tubule, the structure and the composition of the intrarenal crystals were studied. The initial crystallisation takes place in the proximal tubule. Calcium phosphate formation was excluded by microprobe examination. The comparison of the structures of the intrarenally formed crystals with those of Whewellite stones by scanning electron microscopy and the examination of isolated crystals by x-ray diffraction showed the intratubular crystals to consist of Whewellite.

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