Medicina, Vol. 58, Pages 1769: Clinical Application of the Computed-Tomography-Based Three-Dimensional Models in the Surgical Planning and Intraoperative Navigation of Ureteropelvic Junction Obstruction Complicated with Renal Calculi

1. IntroductionUreteropelvic junction obstruction (UPJO) is characterized by decreased flow of urine down the ureter and increased fluid pressure inside the kidney. Additionally, a delayed washout of crystalline aggregates may promote crystal agglomeration, nucleation, and final stone formation. It is reported that the incidence of UPJO with ipsilateral renal calculi is approximately 16–30% [1,2,3], and this coexistence might propose a management dilemma for urologists [4].A detailed understanding of stones and their anatomical relationships prior to surgery is required to optimize the stone clearance rate and minimize complications. However, ultrasonography, X-ray, and computed tomography (CT) urography provide the images simply in a two-dimensional level. A recently developed three-dimensional (3D) reconstruction technique based on preoperative CT scans provides stereoscopic and lifelike anatomical understanding for surgeons, and allows full surgical planning, from intraoperative orientation to lesions removal, in many fields including renal tumors and urinary lithiasis [5,6]. Prior studies had shown the benefits of 3D reconstruction in minimizing the risks of percutaneous nephrolithotomy and achieving higher intraoperative stone-free rates for patients with complex renal calculi [5], but no study exists evaluating the efficiency of 3D reconstruction technique as a preoperative planning tool for patients with UPJO and renal calculi.

In this retrospective study, individualized surgical planning and grouping for included patients with UPJO and renal calculi according to the 3D CT reconstruction models were developed preoperatively. We also compared the variables of renal stones and hydronephrosis, and the perioperative data of patients in different groups. In addition, intermediate follow-up outcome data of these patients were presented.

4. DiscussionRecently, 3D reconstruction technology has been increasingly adopted to facilitate the surgeon in better developing surgical planning and navigation. The 3D virtual models are constructed based on preoperative cross-sectional images, including CT and magnetic resonance imaging (MRI). Moreover, these virtual models can be printed by the 3D printers for better preoperative training and preparation. Shin et al. reported that the life-size 3D printing models based on the MRI data provided surgeons with precise knowledge of the location of prostate cancer and its relationships with neurovascular bundles [10]. In addition, Bertolo et al. investigated the role of 3D virtual models in complex renal masses [11]. The authors found that the surgeons changed their indication from radical to partial nephrectomy after viewing the respective 3D virtual models in about 27% of the cases [11].Concomitant renal calculi are not uncommon in patients with UPJO, with an incidence of 16-30% [4,12]. The key to successful operation of UPJO and ipsilateral stones lies in thorough preoperative evaluation. Compared with prostate cancer and kidney tumors, 3D reconstruction technology may be more suitable for complex renal stone diseases, as the 3D virtual models can accurately represent the interrelationships between the collecting system, stones, and adjacent anatomical structures with the aim of minimizing the risks of lithotomy procedures. Brehmer et al. reported that the 3D CT reconstruction technique optimized the selection of the access route into the renal pelvis, improved stone clearance rate, and reduced surgical complications during percutaneous nephrolithotomy (PCNL) [13].In this study, the affected renal parenchymal volume and affected renal hydronephrosis volume, the number, maximum cross-sectional area, location distribution and the number of affected calyces of stones were quantitatively analyzed (Table 1). Preoperatively, the surgeon subjectively divided the included patients into three groups based on the quantitative assessment of renal calculi by 3D CT reconstruction models. The three groups were named LP, LP with pyelolithotomy, and LP with endoscopy, respectively. The quantitative analysis of stones showed that the mean number of involved renal calyces (p = 0.041), the maximum cross-sectional area of stones (p = 0.036) was statistically different among the three groups.The treatment of renal calculi has developed from open surgery to several minimally invasive options. Extracorporeal shock wave lithotripsy, ureteroscopy, and PCNL have been reported to effectively minimize the morbidity of stones removal, and PCNL is considered as the main treatment for large and staghorn stones [14]. The treatment of renal calculi with concomitant UPJO is complex and intractable, and it remained diverse without a standard protocol. PCNL combined with endopyelotomy may not succeed when UPJO is caused by anterior crossing vascular compression [15]. At present, minimally invasive pyeloplasty (TLP or RALP) in combination with pyelolithotomy, rigid nephroscope, flexible ureteroscope, or cystoscope lithotomy have been reported with satisfactory outcomes [16,17,18,19]. Kadihasanoglu et al. reported that the intraoperative stone clearance rate of TLP combined with pyelolithotomy was 93.3% (26/28), but the operative time was no significant difference (p = 0.88) when compared with pyeloplasty without pyelolithotomy [16]. Yin et al. reported that the stone clearance rate of TLP in combination with flexible ureteroscope lithotomy was 100% (16/16), and there was no recurrence of stone and obstruction in the follow-up of average 29.3 months [17].Koh et al. reported 28% (16/57) renal stones measuring 5 mm or less passed spontaneously, significantly more likely than stones that were larger (p = 0.006), and there was no difference in the incidence of passage when the stone located the lower, mid or upper renal calyx [20]. In our study, six patients with concomitant stones in the depth of renal calyx with the mean maximum cross-sectional area of 51.50 mm2, underwent pyeloplasty alone in group 1. Urinary ultrasound at the last follow-up showed that there were no renal stones in 66.7% patients (4/6), indicating the stone had passed out. In patients with stones not discharged, one patient had symptomatic stones that needed to be managed, and the remaining two patients had stones without progression. The incidence of spontaneous passage in our study was significantly higher than Koh et al. reported, probably because the obstructive of ureteropelvic junction was relieved and the number of included cases was deficient. Based on the evidence, we hypothesized that relief of obstruction may improve metabolic disorder of affected renal unit, and then facilitate the expulsion of stones and reduce the formation of new stones. Thus, conservative management for asymptomatic small concomitant nephronlithiasis (2) is viable and reasonable.To the best of our knowledge, our study presents the first report of using 3D reconstruction technique as a preoperative planning tool for the pyeloplasty with concomitant stone extraction. According to our initial experience, in UPJO patients with small calculi located deep in the renal calyx, if the diameter of the stone is 2, and the number of involved renal calyces is 20,21]. Regular observation is needed because the stones might become larger gradually and then cause symptoms. As for ipsilateral renal calculi with larger sectional area and more involved renal calices, either concomitant pyelolithotomy or endoscopic lithotomy can be adopted. However, we think that concerning complex stones with large quantity, large sectional area (>200 mm2), concomitant lithotomy under endoscopies such as ureteroscopy, cystoscopy, and nephroscopy should be given priority.

There are several limitations in this study, including a small number of cases, single-center design, and short-term follow-up. Thus, additional studies with multicenter data, a larger sample size, and long-term follow-up are required to further validate the efficiency of the 3D CT reconstruction technique for the surgical planning and intraoperative navigation of UPJO patients with ipsilateral renal calculi.

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