Stone formation in the Middle Eastern Gulf States: A review

OBJECTIVES: To review the possible causes of the high incidence of urolithiasis in the oil-rich Gulf States. METHODS: Data were extracted from published reports on the incidence of urolithiasis, affluence and diet in the Gulf States, various Western countries and China. RESULTS: There are strong relationships: (a) between the life-expectancy of stones in men and the Gross National Income (GNI) per capita of these countries; and (b) between the daily consumption of animal protein and GNI per capita. Together these data suggest that the occurrence of stones is proportional to the intake of animal protein, although they also indicate that there are additional factors that further increase the risk of urolithiasis in the populations of the Gulf. The consumption of oxalate in the Gulf is three times higher and that of calcium a half of what it is in Western countries. Thus, the average oxalate/calcium ratio in the intestines of the Gulf populations is five to six times higher than that in Western populations, leading to enteric hyperoxaluria and an increased risk of calcium-oxalate stone formation. The risk is further accentuated by the lower urine volumes, due to the hot, dry climate of the region, and lower excretions of citrate, from the highly acidic urine resulting from the high intake of animal protein. There is a high incidence of uric acid-containing stones from the acidic urine and the hyperuricosuria caused by the high intake of purine. CONCLUSIONS: The high incidence of urolithiasis in the Gulf is due to an adverse combination of dietary and environmental factors.