Upper urinary tract stones and dietary habits

The objective of the present study was to determine the relationship between dietary intake and the formation of idiopathic upper urinary tract stones. More specifically, the aim of this study was to test the relationship between the formation of idiopathic upper urinary tract stones and diet in new cases and demonstrate how the inclusion of recurrent cases in a study could affect the relationship mentioned above.A case-control approach was used. A total of 61 new cases was compared to 58 controls. A parallel analysis was made for 62 recurrent cases and 59 controls in order to demonstrate the possible effect of dietary advice received in the past in relation to previous episodes of kidney stones. All controls were selected from patients who had an intravenous pyelogram for a reason other than one related to the formation of a kidney stone and were matched to cases for age and sex. The dietary history of patients was established and constituted the main part of a home interview. Logistic regression was used and potential confounding factors were adjusted for, including family history of stones, ethnic group, and source of the patients.Some differences in nutrient intake were observed between new cases and their controls. Differences involved oxalates, vitamin D and the combination of proteins, purines and magnesium. As the direction of the observed differences did not fit the research hypotheses and likely explanations were found, it was concluded that there was no relationship between diet and kidney stone formation.The analysis involving recurrent cases and their controls revealed that there was effectively a dietary bias which affected the estimated intake of calcium, water, magnesium, purines, and possibly proteins and vitamin C as well. It is concluded that any case-control study on kidney stone formation should be done separately for new and recurrent cases