[Structural studies of infection stones: structure of the nuclei].

The composition and structure of nuclei of infection stones were investigated. Twenty seven out of 40 renal stones were found to contain struvite and/or carbonate apatite in the nuclei as well as peripheral layers, and 13 contained calcium oxalate. Some bladder stones also contained different substances in the nuclei. In some infection stones whose architecture was studied in thin section and with scanning electron microscopy, we found large numbers of bacteria in the nuclei composed of struvite and/or apatite. Though we could find no bacteria within the nuclear parts composed of oxalate, we found them in apatite layers outside the nuclei. Urea-splitting bacteria are suggested to participate both in the initial formation of struvite stones and in the diversion of oxalate stones into phosphate stones. Such bacteria may play important roles in stone formation, not only as promotors of crystallization of struvite and apatite but also as a component such as of an organic matrix.