Three cotton swabs are placed in the upper, middle, and lower vagina of a woman leaking urine continuously since a hysterectomy, and methylene blue is instilled into the bladder. The upper swab remains dry, the middle swab becomes stained with clear fluid, and the lower swab stays dry. This pattern indicates:

• A Vesicovaginal fistula
• B Urethrovaginal fistula
• C Ureterovaginal fistula ✓
• D No fistula present

Explanation

In the three swab test, staining of the middle swab with clear urine while the upper swab stays dry means urine is entering the vagina above the bladder level, that is, from the ureter, confirming a ureterovaginal fistula. A vesicovaginal fistula would stain the uppermost swab blue because dye-filled bladder urine escapes there. Clear wetness on the lowest swab alone suggests urethral involvement. Confirmation is by CT urogram showing contrast extravasation at the distal ureter.

Reference: Berek and Novak's Gynecology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.