Obesity linked to metabolic changes, stone recurrence

Berlin-Obesity is definitively associated with both metabolic alterations and urinary stone recurrence, according to a recent study from South Korea.

"There have been several studies that have suggested the association between obesity and increased urine metabolites, such as calcium, uric acid, citrate, oxalate, and phosphate, as well as the possible sequelae and repercussions of the increase of these metabolites in the body, such as urinary stone formation and urinary stone recurrence," lead author Yong-June Kim, MD, reported at the European Association of Urology annual congress here.

Dr. Kim and his team of researchers in the department of urology, Chungbuk National University College of Medicine, Cheongju, South Korea, conducted a study to assess the influence of obesity on urinary metabolic abnormalities and on the rate of stone recurrence.

"The results of our stone analysis showed that there was a significant increase in the frequency of stones composed of uric acid in the obese patients as compared to the non-obese patients," Dr. Kim said.

The study was based on analysis of a database of 855 consecutive stone formers who underwent a comprehensive metabolic evaluation that included medical history, body mass index, and metabolic assessment. Of the patients in the study, 542 were first-time stone formers and 313 were recurrent stone formers. Obesity was defined as a body mass index >25 kg/m² . Follow-up was conducted in 289 patients (33.8%) for up to 12 months, at which time a multivariate analysis was performed. Stone analysis was available in 150 patients (17.5%).

Rresults showed that among first-time stone formers, obesity was highly correlated with the rate of urinary stone recurrence. Furthermore, Cox regression analysis revealed that obesity was the only predictor of urinary stone recurrence.

"In my opinion, weight control may be considered as one of the possible preventive modalities against recurrent stone formation. This prevention in the form of weight control can especially play a role in those patients who are first-time stone formers," Dr. Kim said.

Pierre J. Conort, MD, of Hôpital Pitié-Salpêtrière, Paris, who co-chaired the session, said it is well known that obesity is related to stones and stone formation and, specifically, uric acid stones.

"We have to stress that it is in the field of the metabolic syndrome," Dr. Conort said. "This aspect should be added to the study, as well as the insulin-resistance explanation for this lower pH and higher rate of uric acid stone formation."