Obesity and urolithiasis: evidence of regional influences

Abstract

There is evidence that obese patients have an increased risk of renal stone formation, although this relationship could be less evident in some populations. The aim of this study was to evaluate the impact of overweight and obesity on the risk of renal stone formation in a population consuming a Mediterranean diet and to better elucidate the mechanisms underlying the increased risk of urolithiasis observed in obese subjects. We performed a retrospective review of 1698 stone forming patients (mean age 45.9 ± 14.6 years; 984/714 M/F), attending outpatient stone clinics in Milan and Florence, seen between January 1986 and June 2014. Records were reviewed and data collected pertaining to age, gender, weight, height, stone composition, association with diabetes type 2 or gout and metabolic profile of 24-h urine to perform a descriptive study. We estimated prevalence ratios for body mass index (BMI) categories (underweight: BMI <18.5, normal: BMI 18.5-24.9, overweight: BMI 25-29.9 and obese ≥30). Overweight and obesity were present in 40.7 and 8 % of the men and in 19.9 and 8.7 % of the women in the study population. The mean BMI of patients with urolithiasis was found to be 24.5 ± 7.5 kg/m. BMI values were positively correlated with age (p = 0.000) and mean BMI was higher in males than in females (25.5 ± 8.9 vs 23.2 ± 4.4 kg/m). In males, rates of overweight and obesity in renal stone formers were higher than the rates reported in the Italian general population in 2004 only for the age group 25-44 years, whereas males in all the other age groups and in females the rates of overweight and obesity in renal stone formers were similar to rates reported in the Italian general population. The rates of overweight and obesity were significantly different in patients with different chemical stone composition. In particular, patients with uric acid stones have rates of overweight and obesity higher than patients with calcium stones or other types of calculi. Also the rates of type 2 diabetes and gout were greater in patients with overweight and obesity. In overweight and obese patients, the urinary excretion of risk factors for stone formation, such as calcium, oxalate and urate, and also of inhibitory substances, such as citrate, were significantly higher than in patients with normal weight or underweight. The prevalence of overweight and obesity in patients with urinary calculi from a country consuming a Mediterranean diet is not higher than in the general population. It should be taken into account that not all the dietary patterns that are associated with obesity may involve a parallel increase in the risk of forming kidney stones and that epidemiological findings from one country could not be confirmed in other countries with different climatic, socioeconomic and cultural features.

The influence of metabolic syndrome and its components on the development of nephrolithiasis

“…In addition, a greater proportion of obese kidney stone formers had hyperoxaluria. Others have demonstrated this relationship between obesity and urinary oxalate excretion [48] , [49] . Urinary oxalate excretion has also been reported to be higher in diabetic kidney stone formers than those who do not form calculi [44] , [50] , [51] .…”

The Association of Uric Acid Calculi with Obesity, Prediabetes, Type 2 Diabetes Mellitus, and Hypertension

“…Further investigation revealed that type 2 diabetes mellitus (T2DM) and high body mass index (BMI) were particularly attributed to uric acid calculi formation [ 11 – 13 ]. Besides, a recent study indicated that increased levels of calcium, oxalate, and uric acid, known as risk factors for developing urolithiasis, were observed in the urinary excretion of the obese population, while the urinary concentration of citrate, which prevented urinary stone formation, was also increased in the same population [ 14 ]. The role of urinary stone composition in these metabolic disorders remains obscure and further investigation is required.…”

Chronic Kidney Disease as a Result of Secondary Oxalate Nephropathy From Excess Dietary Intake of Peanut Butter and Coffee

“…Thus, while any comorbid conditions may have led to slight progression of his renal interstitial fibrosis, both his past medical history and the biopsy results suggested his acute renal injury was a result of a hyperoxaluric state. Moreover, previous studies have shown that patients with a high BMI are more likely to develop calcium oxalate kidney stones, and since our patient had a BMI of 40, it is likely that his weight played a factor in oxalate deposition despite his negative history of nephrolithiasis [18,19].…”