Results
A total of 176 patients who had initial RIRS for kidney stones were
included in this study. Age, gender, follow-up period, stone side, BMI,
operative difficulty were not significantly different between groups,
except for size and density (detailed demographic and clinical data of
the patients are summarized in Table 1).
Immediate intraoperative SFRs for the group 1 and group 2 were 43.14%
(n=22/51) and 57.6% (n=72/125), respectively. Postoperative
radiologically controlled residual stone fragments after initial RIRS
for group 1 and group 2 were 37.25% (n=19/51) and 40.8% (n=51/125),
respectively. SFR after second-look flexible URS improved from 40.8% to
93.6% (n=117/125); for the eight patients who were not considered
stone-free, the RSFs were visibly smaller than 1 mm and were not
retrievable with a basket.
The univariable analysis indicated that BMI, size, operative difficulty,
and type of intervention (group 1 vs. group 2) were significantly
associated with SREs (Table 2). The SRE rate increased by 19.6% for
each 5 mm increment in stone size.
Age, stone density, stone type, side,
gender, and radiologic RSF were not significantly associated with SREs
(data not shown).
Accordingly, the final model variables were the type of intervention,
operative difficulty, stone size, BMI, residual stone, and stone density
(p<0.001). Type of intervention, stone size, and BMI were
independent prognostic factors for SREs. When group 2 was taken as a
reference, the odds ratio was 8.48 (95% CI: 2.95-24.42) for SREs in
group 1. The odds ratio was 1.62 (95% CI: 1.21-2.18) for increasing
stone size (Table 2).
In 69% (n=121) of the whole cohort, no postoperative SRE was recorded.
Urinary infection, asymptomatic stone growth, and re-operation were
recorded in 10.2% (n=18), 6.8% (n=12), and 6.2% (n=11) of the
patients, respectively. Nine patients had postoperative SWL, four
patients reported renal colic, and one patient was admitted to the
emergency room due to unrelieved colic symptoms.
Renal colic (5.9% vs. 1%), urinary tract infection (16% vs. 8%),
emergency room admission (2% vs. 0), SWL (15.69% vs. 0.8 %), and
reoperation (13.8% vs. 3%) rates were significantly higher in the
group 1, while asymptomatic stone growth (4% vs. 8%) was higher in the
group 2 (Table 1). Initial stone sizes were larger than 20 mm in
patients who had reoperations in group 2.