Boari Flap & Psoas Hitch
The psoas hitch and Boari flap are bladder-mobilization techniques used when distal ureteral reconstruction cannot be completed with a direct tension-free ureteral reimplantation. The psoas hitch brings the bladder cephalad to the ureter; the Boari flap converts a full-thickness bladder flap into a tubularized bladder-based ureteral substitute.[1][2][3]
The reconstructive rule is simple: move bladder before stretching ureter. Direct ureteroneocystostomy is used when the ureter reaches easily, psoas hitch when bladder fixation removes tension, and Boari flap when a longer bladder tube is needed to reach the mid or upper ureter.[1][3][4]
For the parent reimplantation framework, see Ureteral Reimplantation. For general upper-tract reconstruction rules, see Principles of Upper Tract Reconstruction. For distal stricture workup, see Ureteral Stricture.
Indications
Psoas hitch
Psoas hitch is the preferred bladder-based adjunct for lower and selected middle ureteral defects when direct reimplantation would be under tension.[1][3][5]
Common indications:
- iatrogenic distal ureteral injury during gynecologic, colorectal, urologic, vascular, or pelvic oncologic surgery,
- distal ureteral stricture from prior surgery, stones, endometriosis, radiation, ischemia, or retroperitoneal fibrosis,
- distal ureterectomy with bladder preservation,
- failed prior ureteroneocystostomy,
- congenital distal ureteral anomalies in adults or older children,
- ureteral reimplantation where tension persists after routine bladder mobilization.[1][2][6]
Boari flap
Boari flap is used when the defect is too long for direct reimplantation or psoas hitch alone and the bladder has enough capacity and mobility to donate a flap.[4][7][8]
Common indications:
- long distal or mid-ureteral loss,
- selected upper ureteral or lumbar-level defects when combined with psoas hitch or downward nephropexy,
- radiation-induced or ischemic distal/mid ureteral strictures,
- ureteral injury after pelvic surgery,
- distal ureterectomy for malignancy,
- salvage after failed reimplantation when bladder tissue remains usable.[4][8][9]
In contemporary Boari flap series, a psoas hitch is commonly added first to stabilize the bladder and increase reach; one female reconstruction cohort used a concurrent psoas hitch in 62% of Boari flap cases.[8]
Contraindications and Caution Zones
| Problem | Why It Matters | Practical Response |
|---|---|---|
| Small-capacity or contracted bladder | Cannot reach or donate a useful flap without unacceptable storage morbidity | Consider augmentation, ileal ureter, TUU, or autotransplantation |
| Neurogenic high-pressure bladder | Reimplanting into hostile storage can threaten the kidney | Treat bladder storage first; consider augmentation or diversion |
| Frozen pelvis | Bladder cannot be mobilized safely | Delay after drainage, use alternate route, bowel substitution, or autotransplantation |
| Severe radiation injury to bladder | Flap may be ischemic, noncompliant, or too small | Assess cystoscopic capacity and tissue quality carefully |
| Bilateral long ureteral defects | A single bladder may not supply enough reach/capacity | Individualize; consider staged or bowel-based reconstruction |
| Active infection or urinoma | High leak and fibrosis risk | Drain first, control infection, reconstruct electively |
The bladder is the limiting organ. A technically beautiful Boari flap is a bad operation if it leaves the patient with an intolerable small-capacity, high-pressure bladder.
Reconstruction Ladder
| Defect / Reach Problem | Usual Move | Approximate Reach Logic |
|---|---|---|
| Distal ureter reaches bladder easily | Direct ureteroneocystostomy | No adjunct needed |
| Distal ureter reaches only under tension | Psoas hitch | Bladder is fixed cephalad to remove tension |
| Mid-ureter defect or long distal loss | Boari flap +/- psoas hitch | Tubularized bladder flap bridges the gap |
| Upper ureter / lumbar-level reach | Boari flap + psoas hitch +/- downward nephropexy | Bladder tube plus kidney descent shortens both sides |
| Beyond bladder reach or hostile bladder | BMG ureteroplasty, ileal ureter, TUU, autotransplantation | Salvage ladder outside bladder-based repair |
Psoas Hitch
Concept
The psoas hitch mobilizes the bladder cephalad and anchors it to the ipsilateral psoas tendon or fascia. This brings a fixed, immobile bladder segment to the ureter and prevents the anastomosis from being pulled by a mobile bladder dome.[3][5][10]
Step-by-step technique
- Expose and stage the ureter. Identify the ureter proximal to the diseased segment, preserve periureteral adventitia, and debride back to healthy bleeding tissue.
- Spatulate the ureter. Spatulate the proximal ureter for 1-1.5 cm to create a broad mucosa-to-mucosa anastomosis.
- Mobilize the bladder. Develop the space of Retzius, divide lateral peritoneal attachments as needed, and mobilize the bladder enough that it reaches the ureter without stretch.
- Add length if needed. Division of the contralateral superior vesical pedicle can add several centimeters of bladder reach in selected open or robotic cases.[1][3]
- Choose the hitch point. Bring the bladder dome to the ipsilateral psoas tendon or fascia while confirming that the future ureteral course is straight.
- Protect the genitofemoral nerve. The nerve runs on the anterior psoas surface. Hitch sutures should avoid incorporating or compressing it.
- Fix the bladder. Place two or three durable nonabsorbable or delayed-absorbable sutures from bladder wall to psoas tendon/fascia.
- Create the reimplant. Use refluxing direct mucosa-to-mucosa anastomosis, intravesical antireflux tunnel, or extravesical Lich-Gregoir-style onlay depending on context.
- Stent and drain. Place a double-J stent, Foley catheter, and closed suction drain when appropriate.
- Close the bladder. If a cystotomy was used, close in two layers with absorbable suture and verify watertightness.
Technical rules
- The ureter should enter the bladder in a straight, non-kinked axis.
- The reimplant should sit in the fixed portion of bladder, not on a mobile dome under traction.
- The hitch should remove tension before the anastomosis is sewn; it is not a rescue stitch after a tight reimplant is already completed.
- Do not trade ureteral tension for bladder ischemia: preserve vesical blood supply unless extra reach truly requires pedicle division.
Outcomes
| Study | N | Approach | Key Result |
|---|---|---|---|
| Riedmiller 1984 | 181 | Open | Classic large psoas-hitch series; durable ureteroneocystostomy across broad indications[5] |
| Mathews & Marshall 1997 | 20 | Open | Long-term adult durability with most patients avoiding reintervention[11] |
| Manassero 2012 | 24 | Open | Contemporary long-term adult series; no reinterventions at mean 53 months[3] |
| Wenske 2013 | 58 psoas hitch cases | Open | Distal reconstruction series including ureteroneocystostomy, psoas hitch, and Boari flap[2] |
| Dell'Oglio 2021 | 30 total robotic psoas/Boari cases | Robotic | Median OR time 180 min, EBL 100 mL, LOS 4 d; no open conversions[12] |
Urodynamic data are reassuring when the bladder is normal preoperatively. In endometriosis-related hydronephrosis, psoas hitch did not produce durable adverse urodynamic changes, and bladder capacity normalized by 3 months in a prospective series.[13]
Boari Flap
Concept
The Boari flap creates a full-thickness anterior bladder wall flap, rotates it cranially, and tubularizes it into a bladder-based neo-ureter. The flap can bridge a much longer defect than psoas hitch alone, especially when combined with psoas hitch and selective downward nephropexy.[4][7][14]
Step-by-step technique
- Prepare the ureter. Mobilize only as much proximal ureter as needed, debride scarred or ischemic tissue, and spatulate the ureter.
- Fully mobilize the bladder. Release the bladder from the anterior pelvis and lateral attachments; decide whether contralateral superior vesical pedicle division is needed.
- Perform psoas hitch when useful. Hitching first stabilizes the bladder and shows the true residual gap.
- Design the flap. Mark a wide-based anterior bladder flap. A broad base preserves vascularity; narrow flaps risk ischemia and stricture.
- Open the bladder and raise the flap. Raise a full-thickness mucosa-plus-detrusor flap sized to reach the ureter without tension.
- Create the ureter-flap anastomosis. Anastomose the spatulated ureter to the cranial flap end over a stent, using fine absorbable suture.
- Add antireflux design selectively. A submucosal tunnel or mucosal flap modification can be used when reflux prevention is important and tissue geometry permits.
- Tubularize the flap. Close the flap around the stent with running or interrupted absorbable suture, avoiding narrowing or twisting.
- Close the bladder donor site. Close the bladder in two layers and test for watertight closure.
- Drain. Leave Foley catheter, ureteral stent, and a closed suction drain; many surgeons obtain cystography before catheter removal in large flaps or hostile fields.
Flap design
The flap must be wide, well vascularized, and long enough before tubularization. Practical design rules:
- keep a generous base-to-length ratio,
- avoid a narrow distal flap tip,
- ensure the flap reaches the ureter before committing to tubularization,
- tubularize over a stent without twisting,
- preserve bladder capacity and avoid excessive anterior wall harvest.
Simmons and Gill described laparoscopic Boari modifications, including mucosal flaps to improve anastomotic circumference and support the suture line.[14]
Outcomes
| Study | N | Approach | Key Result |
|---|---|---|---|
| Wenske 2013 | 18 Boari cases | Open | Hydronephrosis resolution/patency in most patients within a 100-case distal reconstruction series[2] |
| Mauck 2011 | 20 Boari flaps | Open | Boari flap central to upper ureteral reconstruction; downward nephropexy frequently used for proximal reach[7] |
| Dell'Oglio 2021 | 30 robotic psoas/Boari cases | Robotic | Demonstrated feasibility of robotic Boari flap and psoas hitch with acceptable perioperative morbidity[12] |
| Corse 2023 | 50 | Robotic | Largest multi-institutional robotic Boari flap series; 90% success, with failures early[15] |
| Hardesty 2024 | 29 women | Mixed | 93.1% patency; 6.9% stricture; 27.6% new-onset LUTS after Boari reconstruction[8] |
| Xu 2025 | 76 robotic reimplants +/- psoas/Boari | Robotic | 94.5% success with antireflux technique; reflux-like symptoms often did not require reintervention[16] |
Downward Nephropexy
When Boari flap reach remains marginal, downward nephropexy mobilizes the kidney and secures it in a lower position, reducing the ureteral gap from above.[7][17]
Use cases:
- upper ureteral or lumbar-level defects,
- failed prior reconstruction with shortened ureter,
- Boari flap that reaches only under tension,
- reconstruction where renal pelvis dissection is hostile but kidney mobility is available.
Downward nephropexy can add several centimeters of reach, but it marks a higher-complexity reconstruction. In upper-ureter Boari reconstruction, nephropexy is associated with longer operations, greater blood loss, and higher complication burden than distal reconstructions, while still allowing comparable failure rates in experienced hands.[7][17]
Robotic Approach
Robotics is well suited to psoas hitch and Boari flap because the hard parts are deep pelvic suturing, bladder mobilization, tubularization, and ureterovesical anastomosis.[12][15][16]
Common robotic sequence:
- Identify the ureter and define healthy proximal margin.
- Mobilize the bladder and assess direct reach.
- Add psoas hitch if direct reach is tight.
- Decide whether Boari flap is required after the hitch.
- Use ICG selectively to define ureteral perfusion and flap viability.
- Complete stented ureterovesical or ureteroflap anastomosis.
- Close bladder/flap and test watertightness.
ICG fluorescence can help distinguish healthy from diseased ureteral segments and confirm perfusion of reconstructive tissue, particularly in robotic reoperative or radiated fields.[18]
Complications
| Complication | Mechanism / Pattern | Prevention |
|---|---|---|
| Anastomotic stricture | Ischemia, tension, narrow anastomosis, tight tunnel, radiated tissue | Preserve adventitia, debride to healthy ureter, spatulate, avoid tension |
| Urine leak / urinoma | Non-watertight closure, distal obstruction, stent malfunction | Stent, bladder drainage, watertight test, drain near repair |
| Persistent hydronephrosis | Edema, reflux, stricture, aperistalsis | Trend imaging; investigate worsening or symptomatic obstruction |
| UTI / pyelonephritis | Stent, reflux, residual obstruction, colonized urine | Pre-op culture strategy, stent removal, evaluate obstruction |
| Reflux symptoms | Refluxing adult reimplant or imperfect antireflux geometry | Counsel; treat only clinically meaningful cases |
| Genitofemoral neuralgia | Hitch suture or dissection on anterior psoas | Identify nerve trajectory; avoid nerve in hitch bites |
| Reduced bladder capacity / LUTS | Boari flap harvest, radiation, baseline bladder dysfunction | Pre-op bladder assessment; avoid excessive flap harvest |
| Flap ischemia | Narrow base, over-tension, radiated bladder | Broad base, perfusion assessment, alternate reconstruction if tissue poor |
Boari flap can create meaningful postoperative lower urinary tract symptoms. In a female Boari reconstruction cohort, new-onset LUTS occurred in 27.6% and was generally manageable medically, but it is important preoperative counseling for patients whose indication is benign obstruction rather than life-threatening injury.[8]
When Bladder-Based Reconstruction Is Not Enough
If psoas hitch, Boari flap, and downward nephropexy cannot create a durable tension-free repair, the surgeon should leave the bladder ladder rather than forcing it.[10][19][20]
Next options include:
- Buccal mucosa graft ureteroplasty for long strictures with a usable ureteral plate,
- appendiceal flap or appendiceal interposition for selected right-sided defects,
- transureteroureterostomy when the contralateral ureter is healthy and reachable,
- ileal ureter replacement for long-segment or full-length defects,
- renal autotransplantation when bowel is undesirable or anatomy demands pelvic relocation of the renal unit,
- nephrectomy when function is poor and reconstruction risk outweighs benefit.
Ileal ureter can also be combined with Boari flap-psoas hitch for full-length defects, using bladder reach to reduce bowel length and preserve upper-tract drainage.[19]
Operative Pearls
- Assess bladder before ureter. Capacity, compliance, mobility, and radiation history determine whether psoas/Boari is even fair to the patient.
- Hitch before flap when the gap is borderline. The hitch shows how much defect remains.
- Never hitch across the genitofemoral nerve. Postoperative neuralgia is avoidable.
- Keep the ureter straight. A tension-free anastomosis can still fail if the ureter kinks at bladder entry.
- Make the Boari base generous. A narrow flap is a future ischemic stricture.
- Do not harvest a flap that the bladder cannot afford. Storage morbidity is a reconstructive complication.
- Use nephropexy deliberately. It is useful reach, but it signals a complex upper-ureter reconstruction.
- Escalate early when tissue is hostile. Radiated, infected, or multiply reoperative fields may be better served by delayed reconstruction or non-bladder substitution.
References
1. White C, Stifelman M. Ureteral reimplantation, psoas hitch, and Boari flap. J Endourol. 2020;34(S1):S25-S30. doi:10.1089/end.2018.0750
2. Wenske S, Olsson CA, Benson MC. Outcomes of distal ureteral reconstruction through reimplantation with psoas hitch, Boari flap, or ureteroneocystostomy for benign or malignant ureteral obstruction or injury. Urology. 2013;82(1):231-236. doi:10.1016/j.urology.2013.02.046
3. Manassero F, Mogorovich A, Fiorini G, et al. Ureteral reimplantation with psoas bladder hitch in adults: a contemporary series with long-term followup. ScientificWorldJournal. 2012;2012:379316. doi:10.1100/2012/379316
4. Andrade C, Narducci F, Bresson L, Leblanc E. Boari flap ureteroneocystostomy in an oncological patient. Gynecol Oncol. 2016;143(1):193. doi:10.1016/j.ygyno.2016.07.115
5. Riedmiller H, Becht E, Hertle L, Jacobi G, Hohenfellner R. Psoas-hitch ureteroneocystostomy: experience with 181 cases. Eur Urol. 1984;10(3):145-150. doi:10.1159/000463777
6. Middleton RG. Routine use of the psoas hitch in ureteral reimplantation. J Urol. 1980;123(3):352-354. doi:10.1016/S0022-5347(17)55931-5
7. Mauck RJ, Hudak SJ, Terlecki RP, Morey AF. Central role of Boari bladder flap and downward nephropexy in upper ureteral reconstruction. Int Braz J Urol. 2011;37(5):648-654.
8. Hardesty JK, Burns RT, Soyster ME, Jansen NE, Mellon M. Female bladder dysfunction following Boari bladder flap ureteral reconstruction. Urology. 2024;186:31-35. doi:10.1016/j.urology.2024.01.020
9. Sutherland RS, Pfister RR, Koyle MA. Endopyelotomy associated ureteral necrosis: complete ureteral replacement using the Boari flap. J Urol. 1992;148(5):1490-1492. doi:10.1016/S0022-5347(17)36946-X
10. de'Angelis N, Schena CA, Marchegiani F, et al. 2023 WSES guidelines for the prevention, detection, and management of iatrogenic urinary tract injuries during emergency digestive surgery. World J Emerg Surg. 2023;18(1):45. doi:10.1186/s13017-023-00513-8
11. Mathews R, Marshall FF. Versatility of the adult psoas hitch ureteral reimplantation. J Urol. 1997;158(6):2078-2082. doi:10.1016/S0022-5347(01)68160-6
12. Dell'Oglio P, Palagonia E, Wisz P, et al. Robot-assisted Boari flap and psoas hitch ureteric reimplantation: technique insight and outcomes of a case series with at least 1 year of follow-up. BJU Int. 2021;128(5):625-633. doi:10.1111/bju.15421
13. Carmignani L, Ronchetti A, Amicarelli F, et al. Bladder psoas hitch in hydronephrosis due to pelvic endometriosis: outcome of urodynamic parameters. Fertil Steril. 2009;92(1):35-40. doi:10.1016/j.fertnstert.2008.05.034
14. Simmons MN, Gill IS, Fergany AF, Kaouk JH, Desai MM. Technical modifications to laparoscopic Boari flap. Urology. 2007;69(1):175-180. doi:10.1016/j.urology.2006.10.023
15. Corse TD, Dayan L, Cheng N, et al. A multi-institutional experience utilizing Boari flap in robotic urinary reconstruction. J Endourol. 2023;37(7):775-780. doi:10.1089/end.2022.0618
16. Xu L, Yu X, Huang Y, et al. Robot-assisted laparoscopic ureteral reimplantation and Boari flap with anti-reflux technique: do postoperative reflux related symptoms matter? World J Urol. 2025;43(1):716. doi:10.1007/s00345-025-06096-0
17. Hofer MD, Aguilar-Cruz HJ, Singla N, et al. Expanding applications of renal mobilization and downward nephropexy in ureteral reconstruction. Urology. 2016;94:232-236. doi:10.1016/j.urology.2016.04.008
18. Drain A, Jun MS, Zhao LC. Robotic ureteral reconstruction. Urol Clin North Am. 2021;48(1):91-101. doi:10.1016/j.ucl.2020.09.001
19. Zhong W, Du Y, Yang K, et al. Ileal ureter replacement combined with Boari flap-psoas hitch to treat full-length ureteral defects: technique and initial experience. Urology. 2017;108:201-206. doi:10.1016/j.urology.2017.07.014
20. Knight RB, Hudak SJ, Morey AF. Strategies for open reconstruction of upper ureteral strictures. Urol Clin North Am. 2013;40(3):351-361. doi:10.1016/j.ucl.2013.04.005