Patients and Methods
We retrospectively analyzed 282 consecutive patients treated with RIRS and laser lithotripsy for kidney stones between October 2013 and December 2017. A total of 106 patients were excluded: cases in the learning curve (n=50); patients who did not have double-J stent placement (n=29); cases with incomplete data on the stone type, CT scan, or follow-up (n=18); patients with poor visibility secondary to bleeding during RIRS (n=6); and cases of intra-operative complications necessitating secondary procedures (n=3). The remaining 176 patients comprised the study sample. They were divided into two groups based on the type of management utilized: the standard of care (group 1) group (n=51), which had only an RIRS, and the second-look flexible URS (group 2) group (n=125), which had a second-look flexible URS after RIRS.
We routinely performed second-look flexible URS after January 2015 to increase SFRs following a single RIRS within 2 to 3 weeks.
All operations were performed by a single surgeon using general anesthesia, and prophylactic intravenous antibiotics were used routinely. Before placement of the ureteral access sheet, the ureter was examined with a rigid URS for the presence of ureteral stones and any other unexpected pathology. A ureteral access sheath (9.5 Fr, Flexor Cook) was used. At the end of the RIRS procedure, 4.7 F double-J stents were placed routinely.
RIRS was performed using a 7.5 Fr Flex X2s (Karl Storz, Germany) URS. For stone fragmentation, a Quantasystem-Litho Holmium: YAG laser (Milan, Italy) with 200-micron fiber was used. All stone fragments were extracted with a 1.7 F stone basket (NGage Nitinol stone extractor, Cook, Bloomington, IN, USA) whenever possible. The second-look flexible URS procedure was performed similarly in patients who had double-J stent placement during the RIRS except for stent placement. The double-J stent was not placed after the second-look flexible URS. Extracted stone fragments were sent for X-ray diffraction stone analysis.
An immediate intraoperative SFR was defined as no stone fragments left behind and reported by the surgeon at the end of the procedure. In group 1, following RIRS and group 2 after second-look flexible URS, X-ray KUB (kidneys, ureters, and bladder), and ultrasound were performed on all patients to determine whether RSFs were present. A detectable stone of any size (> 1 mm) was considered as a residual stone.
Unless a complication was observed, patients were discharged on postoperative day 1. The double-J stent was removed at the second postoperative week, and a second-look flexible URS was performed at the time of stent removal. Single or multiple calyceal stones with sizes ranging from 1 to 4 mm were extracted with a basket. Patients with a stone size larger than 4 mm where laser lithotripsy needed were considered candidates for a second RIRS and thus were not included in the study. Patients who had a second-look flexible URS were discharged on the same day of the procedure.
Preoperatively, all patients had routine laboratory work and a CT scan. Unless earlier intervention was indicated, patients received follow-up for SREs every six months after that.
We analyzed the potential risk factors associated with SREs, including age, gender, body mass index (BMI), stone size, operative difficulty, CT stone density and size (centralized to the mean and scaled to 5 mm), RSF, stone type, and stone management groups. SREs were defined as urinary infection, renal colic, stone growth, and any additional intervention with shockwave lithotripsy or reoperation. The operative difficulty was categorized, based on the stone location, as easy (isolated mid or upper calyx or renal pelvis stones), moderate (middle or upper calyx stones, with pelvis stones), or hard (lower calyx stone, with or without pelvis stones).
Histograms and the Shapiro-Wilk’s test were used to test whether variables were normally distributed. Descriptive analyses were presented using mean±standard deviation. The chi-square test was used to compare categories, and the t-test was used for continuous variables.
Univariable and multivariable analyses with logistic regression were used to assess the association between covariates. All analyses were performed using STATA 14.2 (StataCorp, TX). Statistical significance was set at 0.05, and all tests were two-tailed.