Ureteral stricture could have various causes, including iatrogenic origins, such as laparoscopic or endoscopic surgery, and congenital diseases. Although it is not uncommon, the optimal management still depends on the condition of each patient and practice of each urologist. Many urologists will consider conservative treatments, such as long-term ureteral stenting or balloon dilation, but the stricture might recur  and require frequent clinical visits, compromising the QoL of the patients. As regards surgery, a stricture length >2 cm may render it difficult to perform a tension-free end-to-end ureteroureterostomy anastomosis, but ureteroplasty with graft onlay might alleviate this concern. The practice of BMG onlay in the reconstruction by ureteroplasty has evolved since more than 20 years ago. However, contemporary literature is still limited to evidence level of case series and no comparative studies were available. These case series included 3–19 cases, and the repaired length ranged from 1.5 to 11 cm . After omitting duplicates, a total of 55 cases have been published since 1999 , and four (7%) of them experienced restenosis within 6 weeks to 39 months after surgery. Of these patients, one female patient having visible recurrence 6 weeks after surgery had a history of failed pyeloplasty and the area of narrowing was uncertain during repair, but she achieved stent-free condition after adjunctive balloon dilation . Another recurrence cases included long-segment ureteral stricture, 8 and 11 cm, at the middle-lower site and was treated with pelvic extirpative surgery and adjuvant radiotherapy . In our study, only one (3%) patient was unable to achieve resolution of hydronephrosis 6 weeks after ureteral stent was removed. The stricture length was 2.5 cm and was caused by a previous lithotripsy via ureteroscopy at the middle site of the ureter. However, additional intravenous pyelography and ureteroscopy were carried out to rule out restenosis and the hydronephrosis subsided 1 month after ureteral stenting and did not recur during the follow-up period. Regarding the hydronephrosis after reconstruction with buccal mucosa onlay, since it is an anatomical finding not only specific to obstruction alone but also reflects reflux or persistent chronically dilated collecting system, a hydronephrosis may persist after removing ureteral stents despite no evidence of functional obstruction. To identify the nature of hydronephrosis, CTU or fluoroscopy could be considered first. However, a ureteroscopy to rule out failure of operation is essential. Another important consideration is that hydronephrosis, an anatomical finding, is not always relevant to functional obstruction. Herein, in this study we incorporate ERPF and GFR into analysis, and we suggested other urologists should take anatomical and functional information into account when evaluating restenosis after reconstruction.
Onlay graft used in reconstruction could have other autologous components, such as ileal and appendiceal origins. In 48 cases from published literature of reconstruction with autologous graft other than BMG , restenosis occurred in two (4%) cases. However, compared with BMG, complications were difficult to manage, such as ureteral fistula requiring surgical intervention . However, a large-scale comparative study regarding different reconstruction onlay materials is still unavailable, and it is still unclear whether BMG could reduce complications requiring surgical interventions. BMG can be easily harvested from the donor site, and no complications have been reported, except for restenosis at the recipient site. To date, only one patient complained of difficulty in whistling .
Correct identification of the narrowing site to be repaired is critical to reconstruction, as failure to do so may lead to postoperative restenosis. Theoretically, the length of the incision, or augmentation, with onlay covering better substitutes for the originally unhealthy length of diseased stricture, or the remaining unhealthy tissue might result in restenosis. A study reported restenosis regarding this reason . A retrospective case–control study  found that a stent-free period over 4 weeks could significantly promote successful reconstruction by allowing stricture maturation. In that study, the authors hypothesized that improvement was attributed to the wound healing process and that a hard wire could possibly jeopardize the microvascular environment and consequently impede the inflammatory phase. Clinically, this might obscure the true narrowing segment with the swollen appearance of the diseased ureter when performing reconstruction and subsequently leave unhealthy tissues in place, causing successive restenosis. This theory is applicable to strictures caused by injuries, such as laparoscopic surgery, endoscopic surgery, or radiotherapy. However, some patients might have congenital strictures, and the role of this stent-free period remains unknown. In our study protocol, the stent-free period between two phases was 6 weeks, and the resolution rate of hydronephrosis on sonography was as high as 97%. In this study, majority of the patients experienced secondary injuries, rather than congenital disorders; thus, this stent-free period might contribute to our high successful rate to some extent.
In the assessment of the hydronephrosis grade, we deem SFU grade 2 hydronephrosis as a successful goal. In normal occasions, most nephrons are present in the cortical area, and some parts of the ascending and descending Henle’s loop might travel down to the medullary area. As a result, medullary thinning, SFU grade 3 hydronephrosis, might endanger the functions of the nephron. Based on experimental evidences and fluid mechanics, we postulated that the increased pressure resulting from the obstruction would be transported through the renal tubule and finally to Bowman’s capsule and glomerular capillary beds, and this process would reduce the GFR . Afterwards, the elevated glomerular capillary pressure further stimulates the release of angiotensin 2, which eventually affects arteriole blood flow . In our participants, although most of our patients initially presented with GFR <60 ml/min, some of their renal blood flow did not drop dramatically. This phenomenon might indicate that although they have grade 3 or grade 4 hydronephrosis anatomically, the microscopic etiology might be still in the early change process. Moreover, experiences demonstrated that SFU grade 1 and grade 2 hydronephrosis have extremely high chance of spontaneous resolution .
For an obstructive uropathy, one urgent concern is to judge the necessity to decompress the dilated collecting system. Before one is operated with reconstruction successfully, ureteral stent and percutaneous nephrostomy tube are two options for him/her. Experiences in managing obstructive urolithiasis with acute illness, these two method are both effective and similar to each other [20,21]. However, indwelling a ureteral stent will remarkably decrease the QoL of patients but placing percutaneous nephrostomy tube will not . This implies another issue when choosing ureteral stent other than reconstruction in long-segmental stenosis. For this type of stenosis will anticipate a longer indwelling periods, the impact of QoL of a patient will be considerably huge. In this study, we demonstrate that QoL after reconstruction is more improved than that after indwelling ureteral stents.
To the best of our knowledge, this is the largest validation study of BMG in reconstruction by ureteroplasty. In our experience, reconstruction with BMG could provide better improvements in renal function and image resolution of hydronephrosis than with endoscopic stenting. As regards QoL, ureteroplasty with BMG is associated with subjective improvements than with endoscopic stenting. Although our study was limited by the small sample size, it not only provides comparative results to common clinical practice, but paired data from a two-phase design reveal that our technique could lower the error term from different individuals. By accumulating published literature and results of our study, the overall successful rate is >90%. Cases with inferior outcomes may have other causes and thus should be further evaluated. Moreover, second endoscopic stenting is sufficient for restenosis and no second reconstructions are required. However, a case–control study for comparison with other autologous materials of onlay graft is warranted.