Lithofibrin. A new remarkably stable substance found in renal stones

Besides inorganic constituents, renal stones contain organic matter known as stone matrix. We have examined such matrix obtained from stones that had been crushed by extracorporeal shock-wave lithotripsy, in order to determine its chemical properties. Morphologically, the matrix was composed of fibers of different colors, most of them exhibiting autofluorescence. Proteins or any other well-known biochemical material were not present. It was remarkably stable against chemical degradation, and could not be dissolved in hot concentrated acids or bases or any common organic solvent. Elementary analysis revealed carbon (60.8%), oxygen (26.9%), nitrogen (7.6%), hydrogen (5.3%) and sulfur (0.77%) to be present. Furthermore, X-ray emission spectroscopy revealed the presence of titanium and chromium. Solid-phase 13C NMR spectroscopy revealed the presence of aromatic and aliphatic carbon as well as carbon bound to O and/or N. The material was paramagnetic. All findings indicated the matrix to be composed of a new class of organic compound, probably a polyaromatic heterocyclic organic material. We welcome suggestions on further methods that can ultimately elucidate the nature of lithofibrins.