In a case of incontinence of urine, dye filled into the urinary bladder does not stain the pad in the vagina, yet the pad is soaked with clear urine. Most likely diagnosis is :

Ans. is b i.e. Uretero -- vaginal fistula The three swab test helps to confirm the Vesico Vaginal Fistula and to differentiate between vesico vaginal fistula, uretero vaginal and urethrovaginal fistula. Procedure of Three swab test __ A catheter is introduced into the bladder through the urethra. Three cotton swabs are placed in the vagina as follows : One at vault, One at the middle One just above the introitus. Methylene blue dye is instilled into the bladder through a rubber catheter and swabs are removed for inspection. Observation Interpretation Upper most swab soaked with urine but unstained with dye Uretero -- vaginal fistuladeg Upper and lower swab remain dry but the middle swab soaked with dye Vesico -- vaginal fistuladeg The upper two swab remain dry but lower one soaked with dye Urethro -- vaginal fistuladeg