Objective: To evaluate the clinical and epidemiological factors associated with residual lithiasis among patients who underwent flexible ureteroscopy with laser lithotripsy (FURSLL). Materials and methods: An observational, analytical, retrospective and cross-sectional study, using a non-probability sampling method through consecutive case series. Demographic and clinical variables were collected from the medical records of patients who underwent FURSLL. Descriptive statistics, including measures of central tendency and dispersion, were applied. Pearson’s chi-square test and Fisher’s exact test were used to assess the associations, with statistical significance set at p ≤ 0.05. Results: A total of 24 medical records from patients with nephrolithiasis who underwent FULL were analyzed. The sample consisted of eight males (33.33 %) and 16 females (66.70 %), with a mean body mass index...