Although PCNL is a minimally invasive surgical technique, exposure to X-rays remains problematic for surgeons, patients, and operating room personnel. In many centers, access is still provided under fluoroscopy and its alternatives, such as ultrasonography and CT. This has made radiation exposure an essential issue during PCNL [19,20,21]. In a study, Dong et al. reported effective and safe surgery without radiation exposure using an ultrasound-guided two-step dilatation technique [22]. In another study, two-step dilatation was proposed by Xu et al. to minimize the risk of access failure and to prevent adverse complications such as renal pelvic perforation, extravasation, and bleeding, especially in patients with an undilated collecting system [23].

Since kidney stone disease is recurrent, and patients may require more than one procedure during their lifetimes, it is crucial to reduce their exposure to X-rays [24]. It has been reported that shortening access time through single-step dilation (OSD or BD) during tract creation decreases X-ray exposure, thus reducing operation time [10, 24, 25]. In light of this information, although single-step or tract dilatation involving a lower number of dilators reduces the FT, most studies focus on comparing OSD and SAD. However, there needs to be more precise information in the literature concerning whether all or how many dilators were used in patients undergoing SAD during PCNL. Although there are studies suggesting that OSD is effective and reliable, it may not be realistic to expect a surgeon who routinely performs PCNL with SAD to change his or her accustomed technique and perform dilation with a single 30-Fr dilator (OSD) rather than starting with a 10 F dilator and using ten dilators (SAD) in order to reduce the FT.

Total FT is a poor indicator of dilatation FT since the duration of fluoroscopy during the placement of the guide wire by entering the collecting system through a needle, and the control of residual stones may differ in each case [7]. However, a recent meta-analysis comparing four different dilatation methods stated that the heterogeneity between dilatation FTs was due to the different definitions of the duration of dilatation fluoroscopy in studies [12]. Therefore, the most accurate definition for the duration of dilatation fluoroscopy is the time from the advancement of the style over the guide wire to the placement of the working sheath. In the current study, we defined the stages of fluoroscopy during the formation of the nephrostomy tract as access 1 FT and access 2 FT. We recorded the FTs at these stages separately. To the best of our knowledge, this study is the first to compare differences in the use of different numbers of dilators for dilatation in patients undergoing SAD during PCNL.

When we compared both groups, the access 2 FT, total access FT, and total operation FT values were significantly shorter in 3SD than in the SAD group. However, the two groups had no significant difference regarding access 1 FT and post-access FT. Although the total operation time was shorter for the patients in the 3SD group than those in the SAD group, there was no statistically significant difference.

With the widespread use of PCNL in treating kidney stones, bleeding has become one of the most common and worrisome complications [26]. A correct puncture route and a proper tract dilatation method are the main factors determining the amount of intraoperative blood loss [27].

Miniaturization in PCNL was inspired by attempts to reduce blood loss during PCNL by reducing the size of the tract and, consequently, parenchymal and infundibular trauma. Miniperc was defined by Jackman et al. as a percutaneous nephrolithotomy performed through a sheath too small to accommodate a conventional rigid nephroscope [28]. In a prospective study, Kukreja et al. compared the efficacy and morbidity of reducing the tract size from the standard 24–16.5 Fr for stones measuring 16 to 30 mm. Procedure time, fluoroscopy time, blood loss, pain score, exit strategy, stone clearance status, and complications were evaluated as crucial factors. Miniperc was as effective as conventional PCNL in terms of stone clearance rates. There was no significant difference between the two groups regarding the duration of the procedure or fluoroscopy [29]. In another study, Wishahi et al. found that Mini-PCNL is significantly superior regarding hemoglobin decrease, length of hospital stay, analgesic requirement, and postoperative pain. However, they did not observe a statistically significant difference between Mini PCNL and standard PCNL X-ray exposure times [30]. It is suggested that replacing each dilator in the conventional SAD method alleviates the tamponade effect on the kidney parenchyma and may result in more blood loss during surgery, which is considered a disadvantage of the SAD method [24]. Publications show that dilatation with balloon dilators provides a lower hemoglobin drop than Amplatz and metal telescopic dilators [12]. In contrast, in the Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study, BD was associated with more bleeding and transfusion than serial dilatation [31]. In another study, Gonen et al. showed no significant difference between Amplatz dilation and BD regarding bleeding or transfusion rates. They stated that both methods resulted in similar parenchymal damage by expanding the tissue rather than tearing it [32]. However, a meta-analysis showed that OSD significantly reduced the hemoglobin drop compared to serial tract dilation [33]. The current study observed that the hemoglobin drop was statistically significantly lower in the patients in the 3SD group compared to those in the SAD group. However, the two groups had no statistically significant difference regarding the blood transfusion requirement.

Another critical point to consider is that in cases where accurate access from the kidney to the bladder cannot be achieved by the guide wire and is curved in the calyx, multiple dilator inlets and outlets increase the possibility of the guide wire slipping from the access route to the out of the body which causes re-access. Reducing the number of dilators will also reduce this risk. In a study comparing patients who underwent BD and SAD, the loss of passage due to the guide wire coming out of the access tract and the need for re-access were seen only in the SAD group [34]. In our study, four patients in the SAD group required re-access due to the displacement of the guidewire, but this was not observed in any of the cases in the 3SD group.

Open nephrolithotomy may lead to retroperitoneal and perinephric scars around the kidney, adversely affecting the needle’s entry and preventing proper canal expansion, leading to a surgical failure. However, studies have also suggested that it would be better to create the access site away from the previous scar tissue in single-step dilatation and that increasing the number of dilators or using rigid metal dilators may be preferable in cases where dilation over scar tissue is required [24, 35]. In the current study, both 3SD and SAD were successful in patients with a history of open surgery, and there was no need to increase the number of dilators due to the inability to pass the fascia in the 3SD group. We found no significant difference between the two groups regarding tract dilatation success or complications among patients with a previous history of open nephrolithotomy.

Finally, the surgery cost is the most crucial issue, especially in developing countries. Although BD during dilation has certain advantages, such as reducing complication rates related to radiation exposure, this method can be limited due to its high cost. Penbegul et al. designed and used a single 30-F dilator, a 30-F sheath, and an 8-F polyurethane dilator, a method they called the “economic one-shot PCNL set (eco set)” for patients undergoing OSD. They stated that these Amplatz dilator sets could be designed in different numbers according to the surgeon’s needs and that the sets planned this way could reduce the cost of PCNL surgery [36]. In our study, we only used three Amplatz dilators for the patients in the 3SD group. Therefore, similar to Penbegül et al., we consider that dilator sets can be manufactured in different types according to the habits or preferences of each surgeon for operations with lapsed dilatation, which can significantly contribute to the cost-effectiveness of the procedure.

This study showed that the 3SD method could be safely used in PCNL to shorten the time of surgery and fluoroscopy without compromising success or increasing complication rates. Despite our study’s strengths, we acknowledge that it also has several limitations. First, it was conducted in a single center with limited patients, and retrospectively. Second, 3SD was only compared to the conventional SAD, with no other groups being formed in which dilation was performed with OSD or with different numbers of dilators. Multicenter randomized studies with a more significant number of patients and different dilator numbers will provide more comprehensive data. Despite the limitations mentioned earlier, our results indicate that 3SD is as safe and effective as SAD.