Epidemiological profile, mineral metabolic pattern and crystallographic analysis of urolithiasis in Kuwait

This study was conducted to determine the epidemiological profile of urolithiasis in Kuwaiti patients and the associated metabolic abnormalities favouring stone formation in this patient population. Between 1986 and 1994, a total of 421 Kuwaiti patients were studied in Al-Amiri renal stone laboratory. The mineral composition of stones was determined using a combination of stereoscopic microscopy and infrared spectrophotometry. Mineral metabolic screen (MMS) was available in 306 (72.7%) of those patients. The average annual incidence of new stone formation in Kuwaiti patients was 23.9 per 100,000 population. The incidence was only 6.9 per 100,000 population in those from pediatric age group, 33.4 in adults and 73.6 in the elderly. The frequency of new stone formation was higher among males as compared to females at different age groups. Calcium oxalate (CaO) constituted 72.1% of renal stones encountered in adults as compared to only 52.1% and 40.7% in elderly and pediatric age groups. Eighty four patients had recurrent and/or high stone load. Detailed family history was available in 57 of those 84 patients and was suggestive of strong family aggregation of stone disease in 30 (53%) patients. The proportion of urate stones was 15.4% of all stones formed and constituted a major cause of renal stones in children (24.1%), adults (14.4%) and elderly (12.5%). Cystine stones were found in 10 patients (2.4%). Hyperuricemia was detected in 1/3 of patients from pediatric age group. In adults, 89 (38.4%) of 232 patients had abnormal MMS, of which hyperuricosuria with or without hyperuricemia accounted for 79.8% of those abnormalities. In elderly patients, metabolic disorders were detected in 7 (17.5%) of the 40 patients. In the latter group, all except one, had hyperuricosuria with or without hyperuricemia. Cystinuria, distal renal tubular acidosis (d-RTA) and hyperparathyroidism constituted 6.6% of metabolic abnormalities in the patients studied. Primary abnormalities of upper and lower urinary tract was detected in 6% of adult patients as compared to 47% in children and 30% in the elderly. In conclusion; the incidence rate of new stone former in Kuwait is significantly lower from that reported in Europe and USA. This latter finding and the high familial aggregation of urolithiasis in our area constitute a cogent argument against the role of hot climate in the pathogensis of urolithiasis and are in favour of genetic predisposition. Isolated hyperuricosuria was detected in 17% of idiopathic CaO stone formers. The latter finding is of practical importance since red-meat is a common food item in our area and restriction of purine-intake may help to decrease the frequency of urate and CaO stone formation in predisposed patients.