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Urological Fistulae - Complete MBBS Guide

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Classification of Urological Fistulae

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1. Vesicovaginal Fistula (VVF)

Definition

Etiology

• Prolonged obstructed labour causes ischaemic pressure necrosis of the anterior vaginal wall, bladder, and urethra
• Risk factors: younger age at first marriage, short stature, low socioeconomic status, illiteracy, lack of prenatal care
• Large areas of bladder neck and urethra may be involved
• Concomitant rectovaginal fistulae may also be present

• Post-hysterectomy (most common): unrecognised bladder injury near vaginal cuff, diathermy injury causing delayed tissue necrosis, suture placed through bladder and vaginal wall
• Abdominal hysterectomy is 3x more likely to cause fistula than vaginal hysterectomy
• Overall rate post-hysterectomy: 0.1-4%
• Other causes: radiotherapy (may manifest years later), advanced pelvic malignancy, TB, congenital disorders, foreign body erosion

Clinical Features

• Constant urinary leakage from the vagina - the cardinal symptom
• May be intermittent in very small fistulae
• Post-hysterectomy VVF: appears in first few days post-op, or 1-3 weeks after catheter removal
• Post-irradiation VVF: may not manifest until years later
• Physical examination: fistula site on anterior vaginal wall at vaginal cuff; leakage visible on instillation of blue dye into bladder

Investigation

• CT urogram, MRI with gadolinium contrast, or cystogram - identifies fistulous tract and excludes concomitant ureteric injury

• Assess fistula: site, location, size, proximity to ureteric orifices
• Assess vaginal size, depth, and mobility for surgical planning
• Biopsy of tract to exclude malignancy in prior pelvic cancer history

• Three numbered gauze swabs placed in vagina (1 = proximal, 2 = mid, 3 = distal)
• Blue dye instilled into bladder via catheter
• Swab 1 wet + stained blue = VVF (proximal/vault)
• Swab 1 wet but NOT stained blue = ureterovaginal fistula
• Only distal swab blue = urinary incontinence (SUI/UUI)

• Oral phenazopyridine (Pyridium) colours urine orange
• Methylene blue instilled into bladder; Foley clamped
• Pad placed in vagina
• Orange stain = ureteral fistula
• Blue stain (deep pad) = vesicovaginal fistula
• Blue distal + orange proximal = both fistulae present

Classification - Goh & Waaldijk Systems

Treatment

• Indwelling catheter + anticholinergics for 2-6 weeks
• Best for newly diagnosed, small (<1 cm), non-radiated fistulae
• Spontaneous closure rates: up to 28% in obstetric fistula (Waaldijk); 13% overall from combined data
• Radiotherapy-related VVF: 0% spontaneous closure

• Required if conservative fails
• Approaches: vaginal, transabdominal (open or minimally invasive), or combined

1. Adequate exposure and debridement of ischaemic tissue
2. Adequate separation of involved organs
3. Watertight, multilayer, tension-free closure with non-overlapping suture lines
4. Use of well-vascularised tissue flaps (omentum, peritoneum, Martius labial fat pad)
5. Adequate postoperative urinary drainage
6. Treatment and prevention of infection
7. Meticulous haemostasis

• Martius labial fat pad flap (Henri Martius, 1928): labial fat pad (+/- bulbospongiosus muscle) tunneled over repair - most commonly used
• Peritoneal flap: for apical fistulae close to peritoneal reflection
• Island flap (Lehoczky): when insufficient vaginal skin for tension-free closure
• Omentum: for large/complex/irradiated fistulae

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2. Vesicointestinal Fistulae (Enterovesical)

Types and Causes

• Colovesical fistula: most common; usually from diverticulitis (sigmoid colon to dome of bladder)
• Ileovesical fistula: more common in Crohn's disease; 93% occur in men (Ben-Ami et al.)
• Previous hysterectomy increases risk 25-fold when combined with diverticulitis

Clinical Features

• Pneumaturia (passage of gas per urethra) - pathognomonic
• Fecaluria (passage of faecal debris in urine)
• Vesical irritability (frequency, dysuria, haematuria)
• Change in bowel habits (constipation, diarrhoea, distension)
• Mixed bacterial urinary infection (polymicrobial)
• Signs of bowel obstruction / abdominal tenderness if inflammatory cause

Investigation

• CT scan/MRI: most sensitive - shows bladder wall thickening, adjacent bowel mass, air in bladder (CT triad for colovesical: (1) bladder wall thickening adjacent to thickened colon loop, (2) air in bladder, (3) fistulous tract)
• Cystoscopy: localised inflammatory reaction; bowel contents may exude; catheterisation of tract
• Urinalysis: pyuria, bacteriuria, mixed flora on culture
• Poppy seed / charcoal test (historical): oral ingestion followed by urine collection

Treatment

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3. Ureterovaginal Fistula

Aetiology

• Most common cause: iatrogenic ureteric injury during pelvic surgery (hysterectomy, colorectal surgery, caesarean section)
• Delayed presentation - patient complains of ongoing incontinence after surgery

Diagnosis

• Double-dye test: IV methylene blue + clamp Foley → orange stain on vaginal pad = ureteral fistula
• CT urogram: localise level and extent of ureteral injury
• Retrograde ureterography + cystoscopy

Treatment

• Endoscopic first: ureteral stent or percutaneous nephrostomy with antegrade stenting (for partial transections/small leaks)
• Stents maintained 4-8 weeks
• Surgical repair if endoscopic management fails:
  • Wait 6 weeks (inflammation subsides) before open repair
  • Early repair (within 7 days) possible if detected immediately post-op
  • Options: ureteroneocystostomy, ureteroureterostomy, Boari flap, ileal ureter

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4. Urethrovaginal Fistula

Features

• Distal urethrovaginal fistulae: often asymptomatic
• Proximal fistulae: intermittent or constant urinary leakage
• Caused by surgical trauma (anterior vaginal wall surgery, sling procedures, diverticulectomy) - difficult to visualise on physical exam or cystoscopy
• Diagnosis best made with voiding cystourethrogram (VCUG)

Treatment

• Challenging repair; almost always requires interpositional tissue flap due to lack of surrounding connective tissue in mid/distal urethra
• Martius flap is standard

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5. Rectourethral Fistula (RUF)

Aetiology

• Most common cause: surgical treatment of localised prostate cancer (radical prostatectomy, cryotherapy, HIFU, radiotherapy)
• Radiotherapy/ablation-related RUF is far more difficult to manage

Clinical Features

• Passage of urine per rectum
• Faecal soiling of urine
• Recurrent UTI

Diagnosis

• Confirmed with VCUG

Treatment

• Conservative: Foley catheter drainage (select patients)
• Surgical repair (majority) - but radiation-induced RUF has much higher morbidity:
  • 86% require permanent colostomy (vs 0% for non-radiated)
  • 93% require permanent urinary diversion (vs 6% for non-radiated)

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6. Urethrocutaneous Fistula

Aetiology

• Most common surgical complication after hypospadias repair (~10% incidence)
• Occurs anywhere along urethroplasty; most often at original meatal site or coronal margin
• Causes: ischaemia, oedema, infection, haematoma, meatal stenosis, overlapping suture lines, poor tissue perfusion
• "Watering-can perineum": multiple urethrocutaneous fistulae from periurethral abscess complicating urethral stricture

Management

• Surgical repair delayed 6-12 months after initial hypospadias repair
• Pre-op: calibration with bougie à boule + urethroscopy to assess urethral patency
• Stress test: saline injected into clamped urethra to identify concealed tracts
• Small shaft fistulas: excise tract + primary multilayer closure
• Large/coronal/complex fistulas: trap-door or island flap with vascularised tissue coverage
• Smaller fistulas (<1 cm) noted immediately post-op without stenosis: rarely close spontaneously; most require repair

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7. Urovascular Fistulae (Rare but Life-Threatening)

Ureteroarterial Fistula

• Predisposing factors: radiation, vascular pathology, chronic ureteral stenting
• Massive haemorrhage, high mortality
• Treatment: endovascular stenting (initial modality of choice in stable patients)

Renovascular / Pyelovascular Fistula

• Most common cause: percutaneous nephrolithotomy (PCNL) - puncture of intrarenal vessel
• Bleeding may be tamponaded by catheter; brisk haemorrhage on removal
• Incidence of post-PCNL bleeding requiring transfusion: ~11%; requiring intervention: ~1.2%
• Also: penetrating/blunt trauma, infection, renal surgery
• Treatment: angioembolisation; surgical repair if needed

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Summary Table: Key Points for Exams

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