You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Most useful investigation for VVF and explain in detail?
Big fistula Fistula tract is available Obvious escape of urine Tiny fistula Dye test Knee chest position: Escape of bubbles on coughing Three-swab test Gold Standard Cystoscopy Ref: D.C.DUTTA&;S TEXTBOOK OF GYNAECOLOGY; 6th edition; Pg no: 420