A Boari flap is a reconstructive technique for a longer lower or middle ureteric defect when the remaining ureter cannot reach the bladder directly. A flap of bladder wall is raised, fashioned into a tube and brought upward to meet the healthy ureter. It can be combined with a psoas hitch for additional reach. Boari flap is useful after surgical ureteric injury or long distal stricture, provided the bladder has adequate capacity and healthy tissue. A DJ stent and bladder catheter are usually used temporarily while the reconstruction heals.

When is a Boari flap considered?

• Long distal ureteric stricture.
• Mid-ureter defect that cannot be bridged by direct reimplant or psoas hitch alone.
• Ureteric injury after pelvic or gynecological surgery with loss of length.
• Selected redo reconstruction when bladder tissue is suitable.

How is the flap made?

• The bladder is mobilised.
• A broad-based flap is designed to preserve blood supply.
• The flap is advanced toward healthy ureter.
• It is tubularised to create a new urinary conduit.
• The ureter is joined to the flap without tension.
• A DJ stent bridges the repair and the bladder is drained with a catheter.

Why bladder capacity matters

The technique borrows bladder wall. A very small, severely scarred or radiated bladder may not provide a reliable flap and may worsen storage symptoms. Bladder health and prior radiation therefore matter.

Boari flap compared with other repairs

Recovery

The bladder catheter remains until bladder healing is satisfactory and the DJ stent is removed later. Temporary frequency, urgency or stent discomfort can occur. Heavy activity is restricted during early healing.

Risks

• Urine leak from bladder or ureteric anastomosis.
• UTI.
• Recurrent narrowing.
• Stent-related symptoms.
• Bladder storage symptoms or reduced capacity in some patients.
• Bleeding or injury to nearby structures.

A practical postoperative timeline

• Early recovery: both the bladder and ureteric anastomosis need protection, so a Foley catheter, DJ stent and sometimes a drain are used.
• Before catheter removal: some surgeons confirm bladder healing with imaging, particularly after a large flap or complicated repair.
• After catheter removal: frequency and urgency can occur because the bladder has been remodelled. These often improve with healing.
• After stent removal: imaging assesses the kidney for drainage. Hydronephrosis may take time to improve, so symptoms and functional testing may be needed if uncertainty remains.
• Later: recurrent infection, flank pain or worsening kidney function can signal narrowing at the ureter-flap junction and should prompt reassessment.

Why bladder quality can rule out a Boari flap

A Boari flap borrows bladder wall to create a tube, so the bladder must have enough capacity, mobility and healthy vascularised tissue to spare. A small, severely inflamed or heavily radiated bladder may not tolerate the required mobilisation or loss of reservoir volume.

This is why preoperative planning looks beyond the ureteric stricture itself. Previous pelvic radiation, bladder surgery, lower urinary tract symptoms and sometimes bladder-function testing can influence whether a Boari flap is sensible or whether another reconstructive option is safer.

The quoted centimetres are a guide, not an operative guarantee

Published descriptions often give approximate defect lengths that a psoas hitch or Boari flap can bridge. In an individual patient, actual reach depends on kidney and ureter position, bladder capacity, scar fixation and how much healthy ureter remains after damaged tissue is removed.

The surgeon therefore judges tension after mobilisation rather than choosing a flap solely from the CT-measured stricture length. A slightly longer healthy reconstruction is preferable to a shorter repair that places ischemic ureter under tension.

What to bring for consultation

• Ultrasound, CT urography/CT abdomen or MR urography reports and images if available.
• Renogram report (DTPA/MAG3) if performed.
• Serum creatinine and recent kidney-function reports.
• Urine routine and culture reports.
• Previous operative notes, discharge summaries and pathology reports if the problem followed surgery.
• Details of any DJ stent or nephrostomy: side, date placed and last change.
• A list of current medicines and any history of radiation, stones, endoscopy or pelvic surgery.

Why a Boari flap can bridge a longer distal or mid-ureteric defect

A Boari flap turns a broad flap of bladder wall into a tube that reaches upward toward the remaining healthy ureter. It is useful when a simple reimplant or psoas hitch cannot bridge a mid/lower ureteric gap without tension. The bladder is therefore being used as living, well-vascularised urinary tissue rather than inserting a foreign tube.

The operation requires an adequately capacious, mobile and healthy bladder. Previous radiation, severe bladder contracture or significant bladder disease can make a long flap unsuitable. The flap must be broad enough at its base to preserve blood supply and long enough to reach the ureter without tension; over-narrow tubularisation risks ischaemia.

A stent crosses the ureter-flap connection while it heals, and a bladder catheter protects the bladder closure. Because this is more extensive bladder reconstruction than a simple reimplant, catheter duration and postoperative urinary frequency can be greater. Long-term follow-up focuses on drainage, recurrent stricture and bladder symptoms.

How the bladder flap becomes part of the urinary tract

A broad flap of bladder wall is designed with enough blood supply at its base. The flap is raised toward the remaining healthy ureter and tubularised to create a conduit. The ureter is then joined to the tip of this bladder tube over a DJ stent. A psoas hitch is often combined to reduce tension further.

Because the flap is made from living bladder tissue, preserving a wide vascular base is essential. An excessively narrow or long flap risks ischemia. The operation also requires enough bladder capacity and mobility; a small fibrotic or heavily radiated bladder may not be a good donor.

A bladder catheter allows the flap and bladder closure to heal at low pressure. Some surgeons obtain imaging before catheter or stent removal. Long-term success is judged by symptoms, renal function and unobstructed drainage rather than simply by whether the external incisions have healed.

Recovery after a Boari flap

The bladder has been used to construct a tubular flap, so postoperative drainage is especially important. A urethral catheter keeps the bladder decompressed, a DJ stent bridges the ureter-flap anastomosis and a drain may monitor for urinary leak. Catheter duration is usually longer than after a very simple ureteric repair, according to surgeon protocol and healing.

Frequency and urgency can be noticeable after catheter removal because the bladder has been surgically remodelled. These symptoms often improve as inflammation settles. Persistent fever, rising drain output, severe flank pain or reduced urine output requires evaluation.

Long-term surveillance focuses on patency at the ureter-flap junction and along the tubularised flap, renal function and bladder symptoms. A successful Boari flap can avoid bowel interposition for a substantial distal or mid-ureteric defect.

FAQs

Related reading

• Psoas Hitch Surgery Explained
• Ureteric Reimplantation Explained
• Buccal Mucosal Graft Ureteroplasty
• Ileal Ureter Replacement for Long Ureteric Stricture
• Urologist in Latur

References

• European Association of Urology. EAU Guidelines on Urological Trauma, 2026 https://uroweb.org/guidelines/urological-trauma
• Bourillon A, et al. Ureteral stricture: current treatment algorithm and key surgical principles in the robotic upper urinary tract reconstruction era. World J Urol. 2026;44:102. PMID: 41546831 https://pubmed.ncbi.nlm.nih.gov/41546831/
• Hook S, et al. Update on ureteral reconstruction 2024. Die Urologie. 2024;63:25-33. PMID: 37989869 https://pubmed.ncbi.nlm.nih.gov/37989869/