Question

A 52 year old lady presents with constant leakage of urine and dysuria two weeks after a complicated total abdominal hysterectomy. A diagnosis of vesicovaginal fistula is suspected. The most important test for the diagnosis is:

• A. Triple swab test
• B. Urine culture
• C. Cystoscopy
• D. Intravenous pyelography (IVP)

Hint:

The bedside dye test both confirms and localises the fistula first.

Answer 1

The Correct Option is A

Step 1: Understand the clinical picture. Constant urine leakage after a hysterectomy strongly suggests a urinary fistula. The two candidates are vesicovaginal fistula (bladder to vagina) and ureterovaginal fistula (ureter to vagina). The first diagnostic step is to confirm a fistula exists and to localise it.
Step 2: Recall the triple swab test (three swab or dye test). Three cotton swabs are placed in the vagina, then dye such as methylene blue is instilled into the bladder. The pattern of staining tells you the source:
top swab stained with clear urine suggests a ureterovaginal fistula (urine bypasses the bladder dye),
middle or lower swab stained blue suggests a vesicovaginal fistula,
blue staining at the introitus suggests urethral leak or stress incontinence.
Step 3: This simple bedside test both confirms the fistula and helps localise it, so it is the most important first diagnostic test.
Step 4: Why the others are not the first test.
Urine culture (option B): only checks for infection causing dysuria, does not diagnose a fistula.
Cystoscopy (option C): useful to see the fistula and plan repair, but it is a later, more invasive step.
IVP (option D): used mainly to exclude an associated ureteric injury, not the primary test for vesicovaginal fistula.
So the triple swab test is the answer, option A.