Application of omental covering technique in robot-assisted lingual mucosa graft ureteroplasty
Yuancheng Zhou1,2,3,4#, Manshun Dong1,2,3#, Shuaishuai Chai1,2,3#, Kangxiang Xu1,2,3, Ruoyu Li1,2,3, Chaoqi Liang1,2,3, Xingyuan Xiao1,2,3
, Bing Li1,2,3
Contributions: (I) Conception and design: B Li, X Xiao; (II) Administrative support: B Li; (III) Provision of study materials or patients: S Chai, C Liang; (IV) Collection and assembly of data: K Xu, R Li, M Dong; (V) Data analysis and interpretation: Y Zhou, M Dong, S Chai; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.
#These authors contributed equally to this work.
Background: Omentum has a wide application value in ureteroplasty, however, some specific situations limit its clinical application. Therefore, we modified the application method of omentum and proposed a new method named omental covering (OC) technique. This study aims to systematically evaluate the safety and efficacy of OC technique in robot-assisted lingual mucosa graft ureteroplasty (RA-LMGU).
Methods: We conducted a retrospective analysis of data from 79 patients who underwent RA-LMGU between June 2021 and October 2024 at two hospitals. Patients were divided into two groups according to the method of omental application: the omental wrapping (OW) group and the OC group. Perioperative and follow-up data were collected.
Results: A total of 79 patients were included, with 24 in the OW group and 55 in the OC group. The median ureteral stricture length was 4.3 [interquartile range (IQR), 3.7, 6.0] cm in the OW group and 3.0 (IQR, 2.1, 4.0) cm in the OC group (P<0.001). The median operative time was 181 (IQR, 139, 217) min in the OW group and 150 (IQR, 110, 198) min in the OC group (P=0.06). The median postoperative stay was 7 (IQR, 7, 8) days in the OW group and 6 (IQR, 5, 7) days in the OC group (P<0.001). The median follow-up time was 32 (IQR, 26, 39) months in the OW group and 11 (IQR, 4, 16) months in the OC group (P<0.001). It is worth noting that both groups achieved a 100% surgical success rate.
Conclusions: These short-term follow-up results demonstrated that the OC technique is also safe and effective in ureteral repair and reconstruction using lingual mucosa graft and it can reduce postoperative stay.
Keywords: Ureteral stricture; robot-assisted lingual mucosa graft ureteroplasty (RA-LMGU); omental covering (OC); omental wrapping (OW)
Submitted Mar 15, 2025. Accepted for publication May 26, 2025. Published online Jul 25, 2025.
doi: 10.21037/tau-2025-206
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Key findings
• To present a modified omentum technique for ureteral reconstruction using lingual mucosa graft (LMG), which is both safe and effective, and can potentially reduce postoperative hospitalization duration.
What is known and what is new?
• Omental wrapping (OW) technique serves as a critical technique in oral mucosal graft ureteroplasty, providing blood supply to the embedded mucosal graft, reducing the risk of anastomotic leakage, and preventing postoperative infections. Nevertheless, the applicability of OW technique is restricted in certain clinical scenarios.
• We refined the omentum technique, referred to as the omental covering (OC) technique. Specifically, rather than threading the omentum through the dorsal ureter, we eliminated the step of freeing the dorsal ureter and directly draped the pedicled omentum over the embedded mucosal graft, thereby minimizing the traction exerted on the omentum. In this retrospective study, we demonstrated that the OC technique was equally safe and effective compared to the traditional OW technique in lingual mucosa graft ureteroplasty (LMGU), while also reducing postoperative hospitalization duration.
What is the implication, and what should change now?
• OC technique provides critical vascular support for the LMG embedded within the stenotic segment, reduces manipulation of the stenotic ureter and greater omentum, thereby streamlining the LMGU procedure and minimizing the risk of unnecessary intraoperative injury. Nevertheless, the clinical significance of OC technique requires validation through larger sample sizes and more rigorous follow-up studies.
Introduction
Ureteral repair and reconstruction surgery is an effective treatment for benign ureteral stricture (1). The application of oral mucosa graft ureteroplasty has changed the traditional approach of complex ureteral reconstruction. The operation is simple, minimally invasive, with few complications and high success rate (2). Very importantly, ensuring the survival of the oral mucosal graft is crucial for successful outcomes. The omentum, due to its unique characteristics of rich blood supply, immune function, and angiogenic properties (3), provides an optimal solution. Urologists have used adjacent omentum to wrap the oral mucosal graft attached to the ureteral stricture segment to enhance the blood supply (4,5), a technique known as omental wrapping (OW). However, for patients with severe omentum adhesion or difficulty in omentum liberation, this technique can increase the complexity and duration of surgery, and may cause unnecessary trauma. Therefore, we used a simplified approach in lingual mucosa graft ureteroplasty (LMGU) in which the omentum was used to cover and secure the graft surface of the ureteral repair segment, without the need to completely free the dorsal aspect of ureter. This modified technique is called the omental covering (OC) technique. Here, we report the application of OC technique in robot-assisted lingual mucosa graft ureteroplasty (RA-LMGU) and evaluate its safety and efficacy. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2025-206/rc).
Methods
Patient selection
Between June 2021 and October 2024, a total of 79 patients with benign ureteral strictures underwent RA-LMGU at Zhongnan Hospital of Wuhan University and Union Hospital, Tongji Medical College, Huazhong University of Science and Technology. We employed either traditional OW technique or OC technique to enhance ureter repair. Demographic data, surgical details, and perioperative information from all patients were retrospectively collected and analyzed. Inclusion criteria included patients aged 18 to 80 years with benign proximal or mid-ureteral strictures who were not suitable for conventional end-to-end anastomosis, pyeloplasty, or flap pyeloplasty. Exclusion criteria included patients with oral mucosal diseases or a history of extensive resection of the omentom. All operations were conducted by the same surgical team. We subsequently developed the OC technology as an innovative alternative. Since June 2023, OC technology has been implemented to replace OW technology in surgical procedures.
Technique selection
All operations were conducted by the same surgical team. Initially, we used OW technique in LMGU like other urologists in buccal mucosa ureteroplasty (5,6). However, as the number of cases increased, diverse reconstruction scenarios emerged. In patients with severe adhesion of tissues surrounding the ureter or omental hypertrophy, we found that implementing the OW technique was challenging. To maximize the potential blood supply support from the omentum, we developed an innovative OC technique. Postoperative follow-up revealed that LMGU patients treated with the OC technique exhibited favorable surgical outcomes. Consequently, starting in June 2023, we progressively replaced the OW technique with the OC technique in LMGU surgeries. This change may have introduced a discrepancy in follow-up durations between the two techniques.
Surgical techniques
The patient position and port placement of the RA-LMGU, as well as the identification of the stricture, have been elaborated upon in our previous study (4). Depending on the degree of ureteral stricture, LMGU involves two distinct surgical technique. The first is onlay ureteroplasty, the ureteral stricture is longitudinally incised on the ventral side, and then the lingual mucosa graft (LMG) was onlay anastomosed to the ventral defect to effectively enlarge the lumen of the stricture. The second is augmented anastomotic ureteroplasty. When the ureter was obstructed, we completely resected the obliterated stricture segment and performed the posteriorly augmented anastomosis of the ureter. Subsequently, LMG is anastomosed on the ventral side to enlarge the lumen. While the surgery was going on, the LMG was harvested by another surgeon in our team after measuring the length of the stricture. The harvesting of LMG has been previously described (4). In the OW group, the adjacent greater omentum was first pulled and padded behind the reconstructed ureter. After pulling the appropriate length of the omentum pedicle, the omentum was secured to the psoas muscle using 3-0 absorbable sutures (Figure 1A,1B). Subsequently, the reserved omental pedicle was wrapped around the ureter (Figure 1C,1D). In the OC group, the adjacent pedicled omentum was pulled near the ureter and then fixed to the connective tissue at the inner edge of the ureter with 3-0 absorbable sutures (Figure 2A,2B). In the second step, the reserved omental pedicle was covered on the LMG and secured to the psoas muscle lateral to the ureter with 3-0 absorbable sutures (Figure 2C,2D). After confirming that there was no significant active bleeding, abdominal drainage was routinely placed, and the incision was closed in layers.
Postoperative management and follow-up
The urinary catheter is generally removed 3 to 4 days after surgery. And the abdominal drainage tube can be removed when the drainage volume is less than 50 mL. The Double-J stent is generally removed approximately 6 weeks after surgery. The nephrostomy tube was removed only when imaging confirmed the absence of ureteral stricture and the patient had no symptoms of low back pain or distention. Follow-up visits were planned at 3, 6, 12, 18, and 24 months during the 2 years after surgery and at least annually thereafter. Follow-up assessments included symptom assessment, urinalysis, renal function tests, ultrasound, computed tomography urography or magnetic resonance urography, or radionuclide renal imaging. Surgical success in this study was defined as symptomatic success (absence of stricture-related symptoms) and radiographic success (absence of radiographic ureteral stricture).
Statistical analysis
Statistical analyses were performed using SPSS® Statistics 27.0 (IBM Corporation, Armonk, NY, USA). The Shapiro-Wilk test was employed to assess the normality of data distribution. For continuous variables with a normal distribution, data were expressed as mean ± standard deviation (SD), and comparisons between two groups were analyzed using independent samples t-tests. For continuous variables with non-normal distributions, data were reported as median [interquartile range (IQR)] and analyzed using the Mann-Whitney test. Categorical variables were summarized as frequency (n) and percentage (%) and analyzed using Chi-squared tests or Fisher’s exact tests, as appropriate. Statistical significance was defined as a two-sided P value <0.05.
Ethical statement
This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study received approval from the Ethics Committee of Zhongnan Hospital of Wuhan University (No. 2024288K) and the Ethics Committee of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology (No. 2020S027). Additionally, the requirement for individual informed consent was waived for this retrospective analysis.
Results
Demographic characteristics
As shown in Table 1, a total of 79 patients were included in this study, including 24 (30.38%) in the OW group and 55 (69.62%) in the OC group. There was no significant difference in age, gender, body mass index (BMI), degree of stricture and location between the two groups (P>0.05). Forty-two (53.16%) RA-LMGU cases had left ureteral strictures, while 37 (46.84%) patients had right ureteral strictures (P=0.91). The proportion of patients with previous reconstruction was 22.78% (18/79). The proportion of patients with ureteral obliteration was 69.62% (55/79). The etiology of the strictures included endoscopic ureteral lithotripsy, laparoscopic or open ureterolithotomy, abdominal surgical injury, congenital, prior ureteral reconstruction, and polyp of ureter. Overall, endoscopic ureteral lithotripsy accounted for 58.23% (46/79) of the strictures.
Table 1
| Variables | Total (n=79) | OW (n=24) | OC (n=55) | P |
|---|---|---|---|---|
| Age (years) | 44.71±12.64 | 42.54±12.39 | 45.65±12.75 | 0.32 |
| BMI (kg/m2) | 24.34 [22.04, 26.17] | 24.80 [22.43, 27.06] | 24.14 [21.89, 25.58] | 0.17 |
| Gender | 0.45 | |||
| Male | 58 (73.42) | 19 (79.17) | 39 (70.91) | |
| Female | 21 (26.58) | 5 (20.83) | 16 (29.09) | |
| Laterality | 0.91 | |||
| Left | 42 (53.16) | 13 (54.17) | 29 (52.73) | |
| Right | 37 (46.84) | 11 (45.83) | 26 (47.27) | |
| Degree of stricture | 0.15 | |||
| Obliteration | 55 (69.62) | 14 (58.33) | 41 (74.55) | |
| Incomplete obliteration | 24 (30.38) | 10 (41.67) | 14 (25.45) | |
| Location | >0.99 | |||
| Proximal | 71 (89.87) | 22 (91.67) | 49 (89.09) | |
| Middle | 8 (10.13) | 2 (8.33) | 6 (10.91) | |
| Etiology | 0.047 | |||
| History of endoscopic ureteral lithotripsy | 46 (58.23) | 11 (45.83) | 35 (63.64) | |
| History of laparoscopic or open ureterolithotomy | 7 (8.86) | 3 (12.50) | 4 (7.27) | |
| Abdominal surgical injury | 2 (2.53) | 0 (0.00) | 2 (3.64) | |
| Congenital | 3 (3.80) | 3 (12.50) | 0 (0.00) | |
| Prior ureteral reconstruction | 18 (22.78) | 5 (20.83) | 13 (23.64) | |
| Polyp of ureter | 3 (3.80) | 2 (8.33) | 1 (1.82) |
Data are presented as mean ± standard deviation, median [Q1, Q3] or n (%). BMI, body mass index; OC, omental covering; OW, omental wrapping; Q1, 1st quartile; Q3, 3rd quartile.
Perioperative and follow-up data
Perioperative and follow-up data are summarized in Table 2. All the patient underwent RA-LMGU. Augmented anastomosis was performed in 13 (54.17%) OW cases and 25 (45.45%) OC cases (P=0.48). Although not statistically significant, there was a trend that suggested the operation time being shorter in the OC group than the OW group (P=0.06). There was no significant difference in estimated blood loss between the two groups (P=0.68). The median length of ureteral stricture was significantly longer in the OW group (4.3 cm) than in the OC group (3.0 cm) (P<0.001). The postoperative hospital stay in the OW group (7 days) was significantly longer than that in the OC group (6 days) (P<0.001). In terms of postoperative follow-up time, the median follow-up time was 32 months in the OW group and 11 months in the OC group (P<0.001), reflecting the earlier implementation of the OW technique in our team. No high-grade complications occurred in all patients, and the success rate of operation was 100% in both groups (Figure 3).
Table 2
| Variables | Total (n=79) | OW (n=24) | OC (n=55) | P |
|---|---|---|---|---|
| Surgical technique, n (%) | 0.48 | |||
| Incision and onlay | 41 (51.90) | 11 (45.83) | 30 (54.55) | |
| Augmented anastomosis with onlay | 38 (48.10) | 13 (54.17) | 25 (45.45) | |
| Operation time (min) | 160 [120, 205] | 181 [139, 217] | 150 [110, 198] | 0.06 |
| Estimated blood loss (mL) | 50 [43, 70] | 50 [34, 70] | 50 [45, 68] | 0.68 |
| Intraoperative measured stricture length (cm) | 3.5 [2.5, 4.5] | 4.3 [3.7, 6.0] | 3.0 [2.1, 4.0] | <0.001 |
| Postoperative hospital stays (days) | 6 [5, 8] | 7 [7, 8] | 6 [5, 7] | <0.001 |
| Follow-up (months) | 15 [5, 27] | 32 [26, 39] | 11 [4, 16] | <0.001 |
| Complications (Clavien-Dindo III–IV) | 0 | 0 | 0 | – |
| Success rate (%) | 100 | 100 | 100 | – |
Data are presented as n (%), median [Q1, Q3] or n. OC, omental covering; OW, omental wrapping; Q1, 1st quartile; Q3, 3rd quartile.
Discussion
There are multiple etiologies for benign ureteral strictures, with the most common being calculi and endoscopic procedures (7). Other causes include trauma from abdominal or pelvic surgery, congenital factors, radiation therapy, and re-stricture following previous reconstructive surgeries (8). For complex proximal and middle ureteral strictures, LMGU is more and more favored by urologists because of its simple operation, few complications and high success rate. The LMG is easy to harvest, rich in blood vessels and anti-infection, and the scar in the donor site of LMG is concealed, which has little effect on speech and chewing function (9). To minimize the risk of postoperative stricture recurrence, fundamental principles of repair and reconstruction should be followed, including tension-free and leak-free anastomosis, as well as preservation of the blood supply to the segment of stricture. A pedicled omental flap is frequently utilized to provide supplemental blood supply to the embedded mucosal graft.
The omentum is extensively utilized in reconstructive surgery due to its unique proangiogenic properties, stem cell characteristics, and immune function. It serves as a protective envelope for various wounds or as packing material for lacunae (10). The OW technique has been demonstrated to be safe and effective in RA-LMGU (4,11). This is mainly attributed to the structure of the greater omentum, four-layered peritoneal structure linking the stomach’s greater curvature to the transverse colon, contains vascular, neural, and lymphatic networks that promote rapid collateral circulation (12). It mediates containment of abdominal inflammation and infection, while its absence or damage increases susceptibility to adhesion-related ileus (10,13). However, excessive mobilization of the omentum may have potential effects on the visceral organs of the abdominal cavity (14). Our clinical experience has revealed some limitations of the OW technique. Firstly, excessive mobilization of the omentum may have potential effects on abdominal organs, stimulating the gastrointestinal tract. Secondly, OW technique requires complete mobilization of the dorsal ureter, which will destroy the ureteral blood supply to a certain extent. Moreover, for patients with failed ureteral reconstruction surgery, the narrow ureter is likely to adhere to the surrounding tissues (15,16), complicating the dorsal anatomy of the ureter and increasing the risk of injury. Finally, the greater omentum, as visceral adipose tissue, has a mass and volume that are closely correlated with BMI (12). The greater omentum is thicker in patients with higher BMI. When this thickened omental flap is used to wrap around the reconstructed ureter, it may artificially elevate the ureter, impeding its peristalsis and obstructing urine excretion. This condition may persist even after the obstruction is relieved.
In order to alleviate the above limitations, we invented the OC technique, which used the pedicled omentum flap to cover the repaired ureteral segment at 180° plane, without the need to free the dorsal ureter to ensure the maximum blood supply. Therefore, we initiated a comparative study aimed at assessing the safety and efficacy of the OC technique. The results showed that there was no statistically significant difference in estimated blood loss and postoperative success rates between the OW and OC groups. Compared with the OW group, the OC group had a shorter postoperative hospital stay (P<0.001), which may be due to less impact on abdominal organs and faster recovery of postoperative gastrointestinal function. Although not statistically significant, there was a trend that suggested the operation time being shorter in the OC group than the OW group (P=0.06). This may be due to the time saved by not having to perform dorsal ureteral mobilization. The disparity in follow-up duration suggests that we are progressively adopting OC technology as a replacement for OW technology following validation of its effectiveness. Overall, the OC technique provides vascular support for the LMG embedded within the segment of stricture, minimizes intraoperative manipulation of both the ureteral stricture segment and the omentum, thereby simplifying the surgical procedures of LMGU and reducing the risk of unnecessary injury during the operation.
There are some limitations in this study. First, our study was retrospective, a prospective study is necessary to further determine whether there is a direct causal relationship between the OC technique and high surgical success rates. Future research should adopt a prospective design with multi-institutional collaboration. Second, the total sample size was small in our study. The clinical value of OC technique requires larger sample sizes and more effective follow-up validation.
Conclusions
Compared with the OW technique, the OC technique is also safe and effective in ureteral repair and reconstruction using oral mucosal grafts, and it can reduce postoperative stay. However, its long-term efficacy needs to be validated and evaluated by extensive studies with large samples and extended follow-up periods.
Acknowledgments
None.
Footnote
Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-206/rc
Data Sharing Statement: Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-206/dss
Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-206/prf
Funding: This work was supported by
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2025-206/coif). B.L. was supported by Zhongnan Hospital of Wuhan University, China (No. rcyj20230102). The other authors have no conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study received approval from the Ethics Committee of Zhongnan Hospital of Wuhan University (No. 2024288K) and the Ethics Committee of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology (No. 2020S027). Additionally, the requirement for individual informed consent was waived for this retrospective analysis.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
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