Hello! Thank you for the query. If you had recto-vaginal fistula, the stool would come from your vagina and you would suffer from severe vagina infection, urinary tract infection and bad smelling from vagina. So if you do have such extreme symptoms, the answer is yes, it can be such fistula, if no, there is no fistula. Rectal bleeding is most likely caused by hemorrhoids or anal fissure. It is possible that both hemorrhoids and fissure can be invisible for endoscopy as usually the very first part of rectum is missed during this test. Such blood is usually bright red, on the surface of the stool. If your blood is bright red and mixed with the stool the reason can be large intestine polyp or even cancer. Sigmoidoscopy is not enough to rule it out, you should have full colonoscopy. Endometriosis gives pain during intercourse, abdominal pain and very rarely bleeding from anus. Hope this will help. Regards.