Chemical composition of urinary tract stones at the University Hospital of the West Indies.

Urinary tract stones occur frequently with the incidence being about one to fifteen per cent worldwide. Patients may be asymptomatic or sometimes they may present with haematuria. Severe lumbar pain radiating to the loin requiring immediate analgesic treatment may occur Stones generally consist of organic and inorganic material. The organic material may be present in the nidus and can contribute up to about 2.5% of the total weight. Inorganic minerals make up the bulk of the stone. Data are presented for the inorganic minerals present in the stones seen at the University Hospital of the West Indies over a 25-year period. Six hundred and forty-one (445 males and 196females) stones were analyzed by routine chemical methods. Calcium was the main constituent, being seen in 93.9% of the stones. This was followed by oxalate 60.1%, urate 37.0%, bicarbonate 16.5% and magnesium 8.6%. There were four cystine containing stones. Treatment includes medical management for the underlying cause and surgical methods for the removal of the stones. Chemical methods of analysis of the stones has its limitations and should be replaced by more sophisticated methods eg X-ray diffraction crystallography which would give more accurate details of the structure of the stones.