[Cystine calculi: x-ray diffraction study. Infrared spectroscopy and SEM]

The present study investigated cystinuria and cystine calculi. Inexplicably, of 987 calculi that had been analyzed ultrastructurally at the Department of Urology of the University Hospital of Salamanca over a period of 15 years only 3 (0.3%) were cystine. The foregoing finding does not coincide with the 0.5-1% incidence reported in the world literature. Apart from the chemical analyses, infrared spectroscopy disclosed the typical findings of multiple bands 1600-625 cm-1. Analysis by x-ray diffraction revealed a slight variation from the ASTM values. One of the calculi, which we considered to be a mixed calculus (probably of calcium phosphate), showed a peak at 43 degrees, instead of the usual 34.5. Scanning electron microscopy disclosed two forms of crystallization: The typical hexagonal form of cystine stones and the rectangular form of different sizes. The material comprising the matrix was observed in many areas, covering and joining the crystals as if it were cement. Whenever possible, treatment of these recurrent calculi should be conservative. Some advocate the use of ESWL, although others consider these calculi to be extremely hard and, therefore, not amenable to ESWL. Chemical dissolution is advocated by some, although its critics consider it to be of little use. Concerning prophylaxis, forced fluids and alkalinization may reduce recurrence. Ultrastructural studies have provided further insight into the structure and composition of cystine calculi. The foregoing may be useful in determining the most appropriate form of treatment based upon stone size, shape, composition (pure or mixed), etc.