Vesicovaginal fistula after hysterectomy — structured SAQ (15 marks)

(a) Most likely diagnosis and one alternative (2 marks)

• Most likely: Vesicovaginal fistula (VVF) — iatrogenic, post-hysterectomy, presenting day 6 with continuous leakage.^[1]
• Alternative on differential: Ureterovaginal fistula (UVF) — the patient also voids normally, which raises the possibility that one ureter has been injured at the vault and is leaking into the vagina while the bladder continues to fill via the contralateral ureter.^[1][3]

(b) Bedside investigations to discriminate (3 marks)

One mark per step with rationale. ^[2]

• Methylene blue dye test — fill the bladder with 200 to 300 mL of dilute methylene blue saline via Foley catheter; insert a high and a low tampon; ask the patient to walk for 15 to 30 minutes.^[2]
• Interpretation: blue staining of either tampon = VVF (the level of staining localises the fistula). If the bladder is blue but the tampons remain unstained and leakage continues, the fistula is NOT vesicovaginal.^[2]
• If methylene blue is negative — administer IV indigo carmine and repeat the tampon test; a positive stain on the tampon with a blue bladder confirms ureterovaginal fistula.^[2][3]
• Vaginoscopy / Sims speculum examination — localise the fistula on the anterior vaginal wall; note any tissue loss, scarring or vault defect.^[1]

(c) Imaging — what to arrange and why (3 marks)

One mark per modality with rationale. ^[1][3]

• CT urogram — identifies the upper tracts, demonstrates any ureteric injury (extravasation, hydronephrosis), and shows the level of injury to plan ureteric reimplantation if a UVF is confirmed.^[3]
• Cystoscopy — identifies the fistula opening in the bladder, assesses surrounding mucosa and bladder capacity, excludes calculus, foreign body or synchronous pathology.^[1]
• Midstream urine / catheter urine culture — confirms sterile urine; treat any UTI before repair to reduce the risk of wound infection and breakdown.^[1]

(Examination under anaesthesia in theatre is reserved for cases where the fistula cannot be localised in clinic.)^[1]

(d) Counselling on timing of repair (3 marks)

One mark per point with rationale. ^[1]

• Minimum delay of 3 months from the date of injury before definitive repair — this is the standard for an iatrogenic post-hysterectomy VVF and is supported by FIGO, WHO and contemporary case series.^[1]
• Rationale — tissue inflammation and oedema need to settle, the ischaemic slough needs to demarcate, and the tissues need to become pliable again. Operating on inflamed tissue is the commonest cause of repair failure.^[1]
• Earlier repair is acceptable in selected clean intra-operative cases where the fistula is recognised at the original operation and the field is clean — but day 6 post-operatively with a sloughing fistula is NOT one of those cases.^[1]
• What to do in the meantime — barrier cream for ammoniacal dermatitis, sanitary protection, treatment of any UTI, contraception discussion, and psychological support; the patient should be referred to a centre experienced in fistula repair.^[1]

(e) Named operation and interposition (4 marks)

One mark per element with rationale. ^[1][4][5]

• Approach: Vaginal Latzko repair (partial colpocleisis) — appropriate for a clean, accessible supratrigonal post-hysterectomy fistula; first-attempt closure 85 to 95% in experienced hands.^[4][5]
• Steps in summary — excise the epithelialised tract, mobilise the bladder wall from the vagina, three-layer closure (bladder in two layers, vaginal fascia, vaginal epithelium) without tension.^[4]
• Interposition to consider — Martius labial fat pad flap (vascularised pedicle from the labia majora based on the pudendal artery branches) is the interposition of choice when there is any scarring, prior repair, or moderate size fistula; for a small clean first-attempt fistula, primary closure without interposition is acceptable.^[4]
• Post-operative care — indwelling catheter for 14 to 21 days, cystogram before removal, pelvic rest for 6 to 8 weeks, clinic review at 6 weeks, 6 months and 12 months.^[1][4]