Subtrigonal Inlay and Related BMG Approaches for Posterior Stenosis
Subtrigonal inlay refers here to the specific robotic transvesical buccal graft operation described by Avallone, Flynn and colleagues. Perineal dorsal onlay and transurethral grafting are related tissue-augmentation approaches but are different named techniques, with different anatomy, selection and evidence. These techniques augment the stenosis with buccal mucosa without primary reanastomosis.[1] The open subtrigonal approach includes excision of fibrotic trigonal tissue before graft placement.[11]
Robotic subtrigonal inlay
The original report involved one 70-year-old man with refractory bladder-neck contracture after photovaporization of the prostate. Multiple endoscopic interventions had failed.[1]
The robotic transvesical approach provides intravesical exposure of the bladder neck. The stenosis is opened and buccal mucosa is inlaid at the subtrigonal (posterior bladder-neck) defect, beneath the trigone. Viable tissue is preserved, the ureteral orifices are protected, the graft is secured against its recipient bed and the cystotomy is closed. The original video shows the incision and graft orientation. The pubic-periosteal quilting used in the perineal operation does not apply here.
| Index-case finding | Result |
|---|---|
| Graft dimensions as reported | 5 × 5 × 4 cm |
| Hospital discharge | Postoperative day 2 |
| Catheters | Urethral catheter 2 weeks; suprapubic catheter 4 weeks |
| Healing assessment | VCUG at 4 weeks without obstruction or extravasation |
| Flow and residual | Qmax 2 to 27 mL/s; PVR 200 to 3 mL[1] |
| Recurrence | None at reported last follow-up |
Its catheter schedule is a case-specific protocol.[1] In a distinct single-surgeon open subtrigonal inlay series, one of 11 men required bladder-neck reintervention at 44 months; median cohort follow-up was 36 months (range 13–56). None had prior radiotherapy or pelvic-malignancy surgery.[11] One developed urge incontinence and four reported retrograde ejaculation.[11]
Related approaches
| Approach | Anatomical distinction | Evidence scope |
|---|---|---|
| Perineal dorsal BMG | Dorsal urethral opening reached from below; graft bed depends on technique | Observational cohorts with different stenosis sites and radiation exposure |
| Endoscopic BMG | Transurethral recipient-bed preparation and graft delivery | Small cohorts and technical cases; no proven superiority |
| Single-port robotic BMG | Midline single-port access, intraabdominal or extraperitoneal transvesical, with perineal dissection if needed; graft anastomosis with rectus abdominis, omental or gracilis flaps as needed | Liu's nine-patient series (7 VUAS, 4 urethral strictures, 1 pubic fistula after posterior urethroplasty and 1 anastomotic distraction, with overlapping diagnoses) had mean defect length 3.9 cm; 5 required ancillary procedures (rectus flap in 3, omental in 1, gracilis in 1). Median operative time was 377 minutes, blood loss 200 mL and stay 2 days; urethral patency was 6/9 (67%) across the mixed diagnoses at median 11.7-month follow-up. Thirty-day complications were UTI, epididymitis, anemia, recurrent stricture and SBO requiring surgery (one each). It had no open comparator.[2] |
| Y-V plasty | Native bladder-flap advancement into an opened stenosis | It is not synonymous with circumferential excision and primary reanastomosis |
Interpreting posterior BMG evidence
Angulo's 107-patient study involved membranous or bulbomembranous stenoses after benign prostate surgery and excluded BNC. At mean follow-up of 59.3 months, it reported 10 recurrences and one de novo SUI event in the 107-patient cohort. In Angulo's 107-patient cohort with ten recurrences, postoperative complications within 90 days (adjusted OR 12.5), prior radiation (OR 8.3), and at least two prior dilations (OR 7.2 in Results; 8.3 in the abstract) were associated with recurrence on multivariable analysis.[3]
Sterling's 45-patient cohort comprised men treated with both prostatectomy and radiotherapy for prostate cancer; 21 had anastomotic and 24 had bulbomembranous stenoses, with seven recurrences.[4] No de novo SUI was reported, but the publication's continence counts differ between sections, so a 0/45 at-risk rate cannot be derived. Policastro's 79-patient post-radiation series (median stenosis length 3.0 cm) reported 14 recurrences (17.7%) and 3/37 new SUI cases (8.1%) among initially continent patients, at median 21 months. Of 29 men with SUI before surgery, all but one remained incontinent.[4][5]
In Viegas's robotic Y-V series, 5 of 6 VUAS patients were reported to have postoperative SUI; one already had an AUS and three underwent concomitant AUS implantation.[6] The earlier cited cohorts did not directly compare BMG with excisional repair after radiation.[6][4][5] A 2026 two-center retrospective cohort compared BMG onlay (49 men) with anastomotic repair (163 men) for radiation-induced bulbomembranous stenosis (median length 2.0 cm).[12] BMG was associated with more cystoscopically defined recurrence (lumen <16 Fr; adjusted HR 3.43, 95% CI 1.03–11.47); median follow-up among men without recurrence was 97 months, and incontinence was reported in 18% of each group.[12]
Clinical role
BMG augmentation needs a viable graft bed, secure fixation and drainage. Patients are counseled about oral donor-site morbidity and the possibility of recurrence or incontinence. Augmentation can preserve urethral continuity in appropriate anatomy.
Choose reconstruction according to stenosis site, length, residual lumen, radiation or tissue damage, bladder function, continence and the patient's goals. The 2023 AUA urethral stricture guideline states that surgeons may perform robotic or open reconstruction for recalcitrant bladder-neck stenosis or post-prostatectomy VUAS .[8] EAU 2026 weakly recommends Y-V or T-plasty for treatment-refractory BNS after surgery for benign prostatic obstruction and redo VUA for obliterative or treatment-refractory VUAS in nonirradiated men or irradiated men with adequate bladder function; it describes robotic subtrigonal BMG inlay as a case report needing further investigation.[7] Neither guideline identifies subtrigonal inlay or dorsal BMG as the preferred repair for radiated or nonradiated VUAS.[7][8] Complete posterior obliteration is not treated endoluminally.[7] Sterling's dorsal onlay BMG technique also requires a traversable lumen and does not address obliterative stenosis or anastomotic disruption.[4] AUS surgery follows stable patency, with individualized risk assessment.[7]
Graft choice
The 2023 AUA urethral stricture guideline amendment states that surgeons should use oral mucosa as the first choice when grafts are used for urethroplasty , and that buccal or lingual mucosa may be used as equivalent alternatives .[8] A 2025 meta-analysis of eight comparative studies (655 patients) of bulbar strictures found similar success for dorsal and ventral onlay (RR 1.00, 95% CI 0.94–1.06) and lower transient erectile dysfunction with ventral onlay (RR 0.24); permanent ED was similar.[9] In a 2022 survey of GURS members (134 of 350 responded), 99% preferred buccal mucosa as the primary site, and 66% favored dorsal graft placement for bulbar urethroplasty. The majority preferred anastomotic urethroplasty to BMG for short post-radiation bulbomembranous stenosis (63% vs 37%).[10] Graft biology is covered in the foundations pages.
Videos
References
1. Avallone MA, Quach A, Warncke J, Nikolavsky D, Flynn BJ. "Robotic-Assisted Laparoscopic Subtrigonal Inlay of Buccal Mucosal Graft for Treatment of Refractory Bladder Neck Contracture." Urology. 2019;130:209. doi:10.1016/j.urology.2019.02.048
2. Liu W, Shakir N, Zhao LC. "Single-Port Robotic Posterior Urethroplasty Using Buccal Mucosa Grafts: Technique and Outcomes." Urology. 2022;159:214-221. doi:10.1016/j.urology.2021.07.049
3. Angulo JC, Dorado JF, Policastro CG, et al. "Multi-Institutional Study of Dorsal Onlay Urethroplasty of the Membranous Urethra After Endoscopic Prostate Procedures: Operative Results, Continence, Erectile Function and Patient Reported Outcomes." Journal of Clinical Medicine. 2021;10(17):3969. doi:10.3390/jcm10173969
4. Sterling J, Simhan J, Flynn BJ, et al. "Multi-Institutional Outcomes of Dorsal Onlay Buccal Mucosal Graft Urethroplasty in Patients With Postprostatectomy, Postradiation Anastomotic Stenosis." The Journal of Urology. 2024;211(4):596-604. doi:10.1097/JU.0000000000003848
5. Policastro CG, Simhan J, Martins FE, et al. "A Multi-Institutional Critical Assessment of Dorsal Onlay Urethroplasty for Post-Radiation Urethral Stenosis." World Journal of Urology. 2021;39(7):2669-2675. doi:10.1007/s00345-020-03446-y
6. Viegas V, Freton L, Richard C, et al. "Robotic YV Plasty Outcomes for Bladder Neck Contracture vs. Vesico-Urethral Anastomotic Stricture." World Journal of Urology. 2024;42(1):172. doi:10.1007/s00345-024-04814-8
7. European Association of Urology. EAU Guidelines on Urethral Strictures. 2026. Disease management in males, sections 6.3.5–6.3.6. Guideline.
8. Wessells H, Morey A, Souter L, Rahimi L, Vanni A. "Urethral Stricture Disease Guideline Amendment (2023)." The Journal of Urology. 2023;210(1):64-71. doi:10.1097/JU.0000000000003482
9. Hassan AA, Soliman AM, Shouman HA, et al. "Dorsal- vs Ventral-Onlay Buccal Mucosal Graft Urethroplasty for Urethral Strictures: A Meta-Analysis." BJU International. 2025;136(3):385-394. doi:10.1111/bju.16811
10. Berg C, Singh A, Hu P, et al. "Current Trends in the Use of Buccal Grafts During Urethroplasty Among Society of Genitourinary Reconstructive Surgeons." Urology. 2024;191:139-143. doi:10.1016/j.urology.2024.06.019
11. Bozkurt O, Sarıkaya EA, Ozer MS, Şen V, Demir Ö, Esen AA. "Long-Term outcomes of subtrigonal inlay patch in case series – Buccal mucosal graft technique for recurrent bladder neck stenosis." BMC Urol. 2025;25:253. doi:10.1186/s12894-025-01947-9
12. Rourke K, Gelman J. "Anastomotic Urethroplasty Is Associated With a Lower Risk of Stricture Recurrence Compared With Buccal Mucosa Graft Onlay After Reconstruction for Radiation-Induced Bulbomembranous Urethral Stenosis." J Urol. Published online August 26, 2026. doi:10.1097/JU.0000000000005279