UC is a rare procedure. Initially, Neuwirt described this operation in 1947 primarily as a salvage operation after pyeloplasty failure [2], which provides a direct channel from the lower calyx to the ureter. UC was not commonly used because of the high possibility of anastomotic stenosis [7]. Subsequently, Hawthorne et al. proposed technical improvements in 1976 [8], emphasizing the importance of lower pole nephrectomy. The key elements of this salvage surgery include complete resection of the lower pole of the kidney; preservation of the surrounding tissue and blood supply of the ureter; establishment of extensive, tension-free mucosal-mucosal anastomosis; and appropriate ureteral stent placement [9]. UC was initially described as a “salvage” operation after pyeloplasty failure [2]. With the increase in UC experience, its indications have changed. UC is considered the first choice for treating most recurrent PUJO cases [3, 4]. In addition to its role as a ' salvage ' surgery, UC is used for primary repair in specific cases. When PUJO is secondary to complex renal anatomical abnormalities, such as horseshoe kidney, renal malrotation, intrarenal pelvis, or proximal ureteral long-segment stenosis, it is a good indication for UC [5, 6]. There are few reports on the reconstruction of ureterocalicostomy for treating complex proximal ureteral stenosis after endoluminal laser lithotripsy [6, 10, 11].
We reviewed the patients with LUC in the past five years. Two patients (2/9) developed primary UPJ obstruction, and seven patients (7/9) developed complicated proximal ureteral stenosis after intracavitary laser lithotripsy. The two patients with primary UPJ obstruction developed severe hydronephrosis in the renal pelvis, which was unsuitable for standard dismembered pyeloplasty, and underwent LUC. In comparison, the other seven patients developed proximal ureteral strictures secondary to previous endoluminal laser lithotripsy. During the operation, dense scars around the renal pelvis were found, the adhesion was severe, and the proximal ureter and renal pelvis could not be dissociated. The surgery was switched to LUC to avoid nephrectomy or permanent nephrostomy. The literature review shows few reports on the application of UC reconstruction in treating complex proximal ureteral stenosis secondary to endoluminal laser lithotripsy. Herein, patients with LUC were primarily those with proximal complex ureteral strictures after intracavitary laser lithotripsy. UC has undergone a clear change in contemporary indications.
Urolithiasis is a major global health problem, and its incidence varies from 1–13% depending on location, climate, race, diet, and genetic factors [12]. Urinary calculi treatment is a major problem for most urologists. Intracavitary technology has several applications, a high stone clearance rate, and a relatively low incidence of complications. It is the preferred treatment for urinary calculi [13]. The current gravel tools based on intracavitary technology mainly include laser gravel, pneumatic ballistic gravel, and ultrasonic gravel. Holmium laser is the dominant lithotripsy tool, and the early stone-free rate reaches 80.0%, while the long-term stone-free rate remains at 84% [14]. Ureteroscopic holmium laser lithotripsy is currently the first-line treatment for ureteral calculi, which has associated complications. Ureteral stricture is one of the common complications after ureteroscopic holmium laser lithotripsy, with an incidence of 1.7–4.9% [15–16], which can increase to 24% in patients with incarcerated ureteral calculi [17]. With the development of endoluminal technology and the wide application of various lasers in surgery, the incidence of ureteral stricture caused by iatrogenic ureteral injury is on the increase [18].
Previously, mechanical injury caused by ureteroscopy was the primary cause of ureteral stenosis. However, studies have shown that the thermal effect of holmium laser can directly damage the ureteral wall; without mechanical damage, it may cause thermobiological effects [19]. Holmium laser can damage the ureteral mucosa, causing pale and ureteral contracture and leading to stenosis, which is related to the excessive proliferation of ureteral fibroblasts and muscle cells [20]. The muscular layer of the ureteral wall continues to undergo fibrosis and gradually develops into a scar [21]. The incidence of ureteral stricture caused by thermal injury from intracavitary laser lithotripsy is increasing rapidly, which has become an urgent problem to be solved.
With the development of endoluminal technology and the wide application of various lasers in surgery, the location of ureteral stricture has changed. Previous literature reported that iatrogenic ureteral injury occurred in the lower part of the ureter (approximately 91%) [22], in the middle part (approximately 7%), and in the upper part (approximately 2%), which is mainly related to gynecological pelvic surgery and general surgery. With the increasing application of urological intracavitary surgery, proximal ureteral stenosis is becoming increasingly common [23]. Although retrograde and antegrade endovascular interventional therapy has become a recognized form of treatment [1], its success rate is not close to the success rate of reconstruction surgery, which may lead to more patients' treatment failure and require more complex reconstruction.
The long proximal ureteral stricture reconstruction remains challenging for urologists because of the complexity of end-to-end ureteral anastomosis. Previously, ileal ureter replacement surgery [24] or autologous kidney transplantation [25] were generally used for treatment. However, these procedures may lead to higher vascular or intestinal complications. The development of autologous patch technology has brought new hope for patients with long proximal ureteral strictures. The technique forms a ureteral plate by longitudinal incision of the narrow ureter or resection of the occluded ureter combined with posterior wall reinforcement anastomosis, and the autologous patch is covered at the ureteral defect to complete the reconstruction. This technique can expand the narrow ureteral lumen while retaining part of the blood supply of the ureter, thereby preventing severe postoperative complications caused by ileal ureter replacement and autologous kidney transplantation. Autologous patch technology is an ideal alternative treatment [26, 27].
However, these techniques cannot be applied herein. Seven patients (7/9) had previous upper ureteral calculi and underwent intracavitary laser lithotripsy. During the operation, obvious scars and fibrosis were found around the renal pelvis and proximal ureter. The ureter was often engulfed by scar tissue, rendering it difficult to identify. It is possible that the urine extravasation after laser treatment of intracavitary calculi and subsequent repeated infection led to extensive scar formation around the renal pelvis, proximal ureter, and kidney. Due to the obvious fibrosis and scar at the ureteropelvic junction, the proximal ureter and renal pelvis cannot be entirely free. Consequently, further fine reconstruction surgery cannot be performed at this site. When the renal pelvis cannot be fully approached and dissected, nephrectomy or permanent nephrostomy can only be considered. Calyceal ureteroplasty is an important option for these patients because it bypasses extensive peripelvic scars, provides drainage-dependent care, and compensates for insufficient ureteral length. The surgeon switched to UC to avoid nephrectomy or permanent nephrostomy.
Our study demonstrated that UC remains essential in modern urology. Additionally, we believe that the wide application of intracavitary techniques and various types of lasers in urology may lead to a new epidemic of UPJO [22, 28], which is characterized by severe scars and fibrosis, which may hinder in situ reconstruction surgery, and necessitate UC.
Anastomotic stenosis is the most common complication of calyceal ureteroplasty[9]. The key elements of the operation, including complete resection of the lower pole of the kidney, preservation of all periureteral tissue and blood supply, establishment of extensive, tension-free mucosal-mucosal anastomosis, and appropriate stent placement, are required to prevent anastomotic stenosis and ensure the effectiveness of the operation[9]. Among them, lower pole nephrectomy is considered one of the most important technical steps in this operation [7, 8]. For the thick and well-functioning renal parenchyma, ureterocalicostomy requires routine lower pole nephrectomy. However, some scholars believe that appropriate resection of the renal parenchyma around the anastomosis is desirable for the thin renal parenchyma of the lower pole of the kidney [10, 29]. However, in our study, all patients developed severe hydronephrosis with a thin parenchyma of the lower pole of the kidney. We performed a complete tension-free anastomosis with the ureteral mucosa, removed the surrounding renal parenchyma, and completely cut the lower pole of the kidney to expose the calyceal mucosa. Thus, we prevented unnecessary loss of nephron caused by transecting the lower pole of the kidney. Additionally, because only the lower pole of the kidney needs to be anastomosed, there is no need to dissociate a long, normal ureter and retain the blood supply of the ureter as much as possible, which is a protective factor to avoid postoperative anastomotic stenosis. Herein, all patients underwent hypotonic intravenous pyelography at 6 and 12 months after surgery, and no patients showed signs of anastomotic obstruction. However, during the median follow-up period of 35 (4–59) months, one patient (1/9) developed right lower back pain two years after surgery. Re-implanting and replacing the ureteral stent regularly was necessary due to anastomotic stenosis. Anastomotic stenosis may be the consequence of postoperative recurrent urinary tract infections and pyelonephritis.
Previous studies reported that ureteral stent implantation can reduce anastomotic stenosis. The possible mechanism is that ureteral stent implantation can reduce urinary leakage, thereby reducing fibrosis around the anastomosis and subsequent anastomotic stenosis [5, 30]. Herein, ureteral stents were routinely implanted during surgery for all patients. Ureteral stents were removed from all patients between 4 and 12 weeks after surgery, and no urinary leakage was found during that period (Fig. 6).
Control of anastomotic bleeding during ureterocalicostomy is another key issue [30]. Patients with renal cortical thickness may experience a substantial quantity of bleeding during lower pole nephrectomy. Clamping the renal pedicle blood vessels is an alternative method to control bleeding. However, this method has disadvantages, including long ischemia time, possible damage to the renal pedicle blood vessels, and increased operation time. Herein, the renal parenchyma of the lower calyx was thin enough to be incised without the risk of bleeding, and we did not block the renal pedicle vessels. Furthermore, we found that an ultrasound scalpel can minimize bleeding when performing a lower pole nephrectomy. The ultrasonic scalpel transfers substantial energy and heat to the tissue, which is beneficial for hemostasis. However, when using the ultrasonic scalpel, it is necessary to be careful when approaching the collection system because the thermal damage caused by the energy of the ultrasonic scalpel may lead to urinary leakage or anastomotic stenosis. Since only the subrenal pole incision was performed to maximize the preservation of the renal parenchyma, we succeeded without clamping the renal hilum. Herein, the average blood loss was 77 mL (10–300 mL), and no patient required a blood transfusion. If significant bleeding occurs during renal parenchyma incision, particularly when transecting the kidney's lower pole, controlling the renal hilum may be necessary. There are some limitations to this study. First, this study did not have a control group. Due to the rarity of the surgery and the lack of good alternatives for these patients, it is difficult to find a control group. Second, this was a retrospective study without the comparison of other types of treatments; therefore, we cannot conclude that laparoscopic ureterocalicostomy is the best treatment choice. However, we confirmed that the surgery was effective and safe.