The SIFUT (Stress Incontinence Fistula Urethra Test) distinguishes vesico-vaginal fistula from urethro-vaginal fistula. Which dye test is used and what result confirms a urethro-vaginal fistula?

• A Methylene blue instilled intravesically; vaginal gauze stains blue throughout
• B Methylene blue intravesically — vaginal gauze distal portion stains blue while proximal is unstained ✓
• C Phenazopyridine orally; orange discolouration of entire vaginal gauze confirms VVF
• D Methylene blue intravesically — proximal gauze stains blue (near cervix) while distal remains unstained

Explanation

In the 3-swab/dye test for urinary fistulae: methylene blue is instilled into the bladder (intravesically) via catheter with three swabs placed sequentially (proximal, middle, distal) in the vagina. In VVF, the proximal/middle swabs stain blue. In urethro-vaginal fistula, the distal swab near the introitus stains blue (as the fistula communicates with the urethra), while the proximal swabs remain unstained. If all three are unstained, a ureteric fistula (ureterovaginal) is suspected, confirmed by phenazopyridine (turns urine orange) staining the gauze without methylene blue staining.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

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