Upper urinary tract stone analysis using X-ray diffraction: results from a tertiary referral centre in northern India

The spectrum of urinary stone disease has changed considerably in India from the common childhood bladder stone to the more frequent upper tract calculi. We analysed the gravel retrieved from the upper urinary tract using X-ray diffraction analysis in an attempt to evaluate the composition of the stones.

We analysed 434 upper urinary tract calculi from May 1993 to June 1994 obtained endourologically, as well as by extracorporeal shock wave lithotripsy and open surgery. The stones were analysed using a Phillips compact X-ray diffractometer (PW1840). The PC-APD software was used for data collection and peak search. The phase matching was done by the software using the JCPDS reference database.

Oxalate stones comprised 97% of the total stones with calcium oxalate monohydrate forming 90% and calcium oxalate dihydrate and mixed stones forming the remainder. Struvite stones were found in 1.4%, while uric acid and apatite stones were less than 1%. There were no cystine calculi. Seventy per cent of calcium oxalate monohydrate and 40% of calcium oxalate dihydrate stones were pure. All the struvite and apatite calculi were almost pure. Only 15% of staghorns did not consist of oxalate. Nine of the ten stones in children were of the calcium oxalate monohydrate variety. The stone composition in females was similar to that in males.

X-ray diffraction data indicate that urinary stone disease in north India is different from that in the western world. Calcium oxalate monohydrate stones predominate. These stones are hard to break and have a different metabolic origin from those consisting of calcium oxalate dihydrate. These findings might help in selecting the most appropriate method of treatment in north India and they indicate directions in which further metabolic studies might be planned.