UAS has many advantages, such as reducing intrapelvic pressure, providing easy and quick access to the collecting system, and lengthening the durability of flexible ureterorenoscopes. It has single and dual lumen types (3, 4). To our knowledge, there is no study evaluating renal damage or comparing patients using standard and DLUAS yet. Although stone-free rates with and without UAS differ in different studies, the rates are similar between groups (5, 10). The stone-free rates in our study were 85%, 95%, and 90% in the first group not using UAS, the second group using STUAS, and the third group using DLUAS, respectively. Although we achieved higher stone-free rates in the STUAS group, a statistically significant difference wasn't detected (p = 0.57). Stone-free data we acquired were similar to the literature.
Our study's postoperative complications were detected at rates similar to the literature for groups using and not using UAS (5, 11, 12, 13). The effect of UAS on postoperative complications wasn't observed. Although different studies were made on operation times, some provided higher results for UAS groups and some for non-UAS groups (14, 15). No difference in operation time among the groups was detected. Additionally, parallel to the literature, no difference among the groups in hospitalization times was seen (10, 16). Berquet et al. In their study, in which they evaluated the duration of hospitalization, reported that there was no difference between the patients who used UAS and those who did not (10). In their study, Traxer et al. reported that hospitalization was longer in patients who did not use UAS (15). In a meta-analysis conducted in 2018, the difference between hospitalization times was not statistically significant (16). In our study, the hospitalization was 1.67 days for all patients, 1.75 for Group 1, 1.55 for Group 2, and 1.55 for Group 3 (p = 0.99). Hospitalization times were found to be lower when compared to the literature. We think that the lower length of stay in the 2nd and 3rd groups using UAS is due to the decreased infective complications due to the decrease in intrapelvic pressure and the less postoperative analgesic requirement. A positive correlation was found between the KIM-1/Cr rate in postoperative 4th hour and hospitalization time based on the correlation analysis performed. Using a UAS during RIRS shortened the hospitalization duration and decreased renal damage.
Our study evaluated the increased pressure related to kidney damage by measuring KIM-1 levels, a phagocytic phosphatidylserine receptor present in kidney epithelial cells. It can specifically recognize phosphatidylserine epitopes on apoptotic tubule epithelial cells (17). Urine KIM-1 levels were shown to increase after renal ischemia significantly (18). Brian K et al. measured the pressures during the ureterorenoscopy procedure with a preoperatively inserted nephrostomy catheter and reported that the pressure was significantly lower for stones in all localizations when UAS was used (19). Balasar et al. measured preoperative and postoperative urine KIM-1/Cr levels in patients with micro PNL, RIRS, and PNL. A significant decrease was detected in postoperative KIM-1/Cr levels in RIRS and PNL grougroupspared to micro PNL at the end of the study (p = 0.010, p = 0.001 respectively)(20). In another study, KIM-1/Cr and NGAL/Cr levels were detected two hours after the operation at a statistically significantly increased level compared to preoperative levels (p = 0.04, p = 0.02 respectively). KIM-1 levels increasing in the postoperative 2nd hour were observed to decrease again to preoperative levels in the postoperative 24th hour (Preoperative:2.24 ± 1.14; Postoperative 2nd hour:5.16 ± 2.18; Postoperative 24th hour:2.42 ± 1.60)(21). It was observed that KIM-1 levels, which increased at the postoperative 2nd hour, decreased to preoperative levels in the measurements at the postoperative 24th hour (Preop: 2.24 ± 1.14; Postop 2. Hour: 5.16 ± 2.18; Postop 24. Hour:2, 42 ± 1.60) (21). Dağgülli et al. included 76 patients in their prospective controlled study to examine the use of biomarkers KIM-1, NAG, NGAL, and LFABP, which are indicators of AKI after PNL. Urine samples were collected 2 hours before, 2 hours after, and 24 hours after surgery. The investigators concluded that the CIM-1/Cr, NAG/Cr, and NGAL/Cr ratios increased significantly at 24 hours postoperatively (P < 0.05, compared with preoperative rates). (22). KIM-1 levels were checked preoperatively, postoperative 4th hour, and postoperative 14th days in our study. Preoperative KIM-1/Cr levels show the homogeneous distribution of the groups. But KIM-1/Cr levels in the postoperative 4th hour were significantly different increases for the three groups (Table 3). Additionally, KIM-1/Cr levels on the postoperative 14th day were decreased in all three groups, and there was no difference among the groups again. This increase in the fourth hour is an expected finding because of the damage formation occurring due to increased intrapelvic pressure during the surgery. As in other studies we mentioned above, the initial postoperative KIM-1/Cr increase is striking in our study. When postoperative 4th hour KIM-1/Cr levels were compared separately for Group-1 (non-UAS) with 2 (STUAS) and Group-1 with 3 (DLUAS), Group-1 had a significantly higher result again, and there was no significant difference among Group-2 and 3. Although kidney damage in DLUAS use was less than in STUAS, this difference wasn't significant (p = 0.7). Although postoperative 14th day KIM-1/Cr levels decreased below the preoperative level in Group-2 and 3, this decrease was sharper in Group-3 (p2vs3 = 0,35), showing that UAS use is more used efficient in postoperative kidney regeneration.
Limitations of our study were the small sample size, lack of both pathologic findings, and intrapelvic pressure measurement. As the coronavirus disease 2019 (COVID-19) pandemic burgeoned, the medical community encountered many challenges. Our study also coincided with the pandemic times; we could number of increase the patients' even though we reached a sufficient number of patients in the groups (23).
Despite its small sample size, significantly lower KIM-1/Cr levels were shown in UAS using groups (STUAS and DLUAS) compared to those not using UAS. In the presence of this sample size limitation, the damage was less in the DLUAS group, although not statistically significant.