A decreased waist area is a risk factor of recurrent nephrolithiasis after ureteroscopy for Nonobese female patients: a retrospective study from a regional referral hospital in Japan.

Background: Obesity and metabolic syndrome have been identified as risk factors for nephrolithiasis. Although dietary improvements and exercise effectively prevent cardiovascular disease, their impact on recurrent nephrolithiasis has not been well studied. We investigated the associations between changes in body shape and recurrent nephrolithiasis.

Methods: Patients who underwent computed tomography (CT) twice at intervals of more than 12 months after retrograde ureteroscopy to treat upper urinary stones of the calcium component from January 2014 to December 2021 at our hospital were retrospectively included. The changes in waist area (WA) according to CT, age, sex, previous stone episodes, number of stones at surgery, residual stones after surgery, and body mass index (BMI) at surgery were compared with those of patients who experienced recurrence and those who did not experience recurrence via univariate and multivariate analyses.

Results: A total of 96 patients were included in this study, with 48 patients in the recurrence group and 48 patients in the nonrecurrence group. The median age was younger in the recurrence group than in the nonrecurrence group (61.5 versus 70.5 years). The median BMI was 23 in both the recurrence group and the nonrecurrence group. The rate of recurrence in female patients with a decreased WA was greater than that in those with an increased WA (n = 9/5 versus 4/16) (p = 0.0137). Age under 70 years and a decreased WA were significant risk factors for the recurrence of renal stones according to multivariate analysis (p < 0.05).

Conclusion: A decreased WA on CT images is a risk factor for recurrent nephrolithiasis after ureteroscopy, especially in nonobese female patients.

Trial registration: Trial registration was not performed, and the number of clinical trials was not suitable because this was a retrospective observational study at a single institution. All participants were retrospectively registered, and the study was approved by the Institutional Review Board and Ethics Committee of the Faculty of Medicine, Saga Japan (number 2023-11-R-4) at the date of 2/02/2024.