Correlation between body size and stone composition in pediatric stone patients

Abstract Purpose Due to the lack of stone composition data, the relationship between BMI and stone composition in children is rarely reported. Our study encompassed more cases than previous studies, aim to examine the correlation between BMI and stone composition in pediatric stone patients. Methods Clinical date of pediatric patients who underwent minimally invasive surgery for urolithiasis from 2009 to 2019 were retrospectively reviewed. Patient's gender, age, BMI, stone location, stone size, stone composition, serum uric acid, urine culture, urine pH and other clinical data were collected. According to BMI, children were divided into overweight/obese group and normal group, stone composition and other related indicators were compared between the two groups. Results A total of 71 children were included in the study, consisting 49 males and 22 females, with an average age of 4.9 ± 3.87 years. The overweight/obese group included 16 children (22.5%) and the normal group included 55 children (77.5%). Kidney stone was seen in 49 cases (69%), ureteral stone in 17 cases (24%) and bladder/urethral stone in 5 cases (17%). Twenty-seven cases (38%) had pure stones, and 44 cases (62%) had mixed stones. Among the main stone composition, calcium oxalate was the most common (41/71, 57.7%), followed by ammonium urate (10/71, 14.1%), carbonate apatite (6/71, 8.5%) and cystine (6/71, 8.5%). There was no statistical difference in the main stone composition between the two groups. Also, no significant difference was seen in gender, age, stone location, stone size, and urine culture positive rate. However, the overweight/obese group had higher serum uric acid (361 ± 139.3umol/L vs 271 ± 140.3umol/L, p = 0.027) and lower urine pH (6.1 ± 0.63 vs 6.4 ± 0.57, p = 0.048) than the normal group. Conclusion Our study showed that there was no apparent correlation between BMI and stone composition in pediatric stone patients. But overweight or obese children had higher serum uric acid and lower urine pH.