A 35-year-old presents with continuous dribbling of urine since a difficult obstructed labour 2 weeks ago. Dye test: bladder is filled with methylene blue; a tampon placed in vagina shows blue staining at the apex. Intravenous injection of indigo carmine does not stain the tampon. What type of fistula is present?

• A Ureterovaginal fistula
• B Urethrovaginal fistula
• C Combined vesicovaginal and ureterovaginal fistula
• D Vesicovaginal fistula ✓

Explanation

The 3-swab dye test differentiates types of urinary fistulae: intravesical methylene blue (via catheter) stains the upper vaginal swab/tampon in vesicovaginal fistula (VVF) — this is positive. Intravenous indigo carmine (excreted by kidneys) stains the upper vaginal swab in ureterovaginal fistula — this is negative. Here, blue staining at the apex of the vaginal tampon with methylene blue (bladder dye) positive and IV indigo carmine negative confirms an isolated vesicovaginal fistula. Ureterovaginal fistula would show a dry tampon with methylene blue but blue staining after IV carmine. Urethrovaginal fistula would stain a low (anterior) tampon with blue dye, not the apex.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.