Childhood urolithiasis in Iran: a comparative study on the calculi composition of 121 cases.

Within 12 years, 165 cases of urolithiasis were observed at the Children's University Hospital of Teheran. The incidence of urolithiasis amounts to 1 case in 300 paediatric hospitalizations. 160 calculi from 121 children were analysed by various methods: semiquantitative chemical analysis (Mercognost), x-ray diffraction, polarising microscopy on thin sections. In about 25% of the cases metabolic disorders or malformations were found responsible for urolithiasis. In 100 cases, stone formation was attributed to the upper and in 21 cases to the lower urinary tract. Calcium oxalates are the most frequent constituents, followed by ammonium acid urate. The core of the stones in the upper tract was mostly composed of calcium oxalate. Ammonium acid urate was the second important core component, but occurred especially enriched in the lower urinary tract. On the basis of these and literature data, the lack of ammonium acid urate in juvenile stones in Europe and the USA seems surprising. Thus, it must be assumed therefore, that ammonium acid urate is a key to understanding the formation of endemic calculi. The cases studied support that with increasing standard of living, the incidence of bladder stones decreases.