Urinary incontinence is a primary symptom of a bladder fistula, because the fistula's opening can leave you unable to control the flow of urine from the bladder. Women may also leak urine through the vagina, leading to thin liquid discharge, irritation, vaginitis, or cystitis. Passing gas or stool through the urinary tract are rarer symptoms of a bladder fistula. They occur when a vesicoenteric fistula opens between the bladder and intestine. Because the intestines contain both gas and stool, the fistula can allow these to pass into the urinary tract.