3 pad test is done for:

Ans: c (Urinary fistula) Ref: Shaw, 13th ed, p. 182Methylene blue - 3 swab test is an investigation for urinary fistula.ObservationInferenceUppermost swab soaked with urine but unstained with dye. The lower two fistula swabs remain dryUretero-vaginal fistulaUpper and lower swabs remain dry but the middle swab stained with dyeVesico-vaginal fistulaThe upper two swabs remain dry but the lower swab stained with dyeUrethro-vaginal fistulaCommonest cause of VVF in developing countries - Obstetrical causeCommonest cause of VVF in developed countries - GynecologicalCommonest cause of uretero vaginal fistula - Difficult abdominal hysterectomyCommonest cause of RVF - incomplete healing or unrepaired recent complete perineal tear