Methylene blue 3 swab test is done for urinary fistulae. Source of leakage if the lowermost swab gets stained: March 2010

Ans. C: Urethra Methylene blue 3 swab test is useful for diagnosing site of leakage. In this test, Catheter is introduced in to the bladder through the urethra. Vaginal cavity is packed with 3 sterile swabs 50-100 ml of dilute methylene blue dye is injected into the bladder through the catheter (methylene blue turns urine blue). If VVF is present, methylene blue will stain the uppermost swab. If lowermost swab gets stained, the leak is from the urethra If the swab do not take up the stain but gets wet, leak is from the ureter.