Trying to find information on a "sinus tract in lower portion of the vagina"

My sibling has had 4 surgeries on a sinus tract in the lower portion of her vagina. The tract is in the wall between the vagina and the rectum. She is a diabetic and we are concerned that if she continues to have this issue it may become extremely serious. Her gynocologist lanced it and it got worse. The gynocologist said she was going to have do surgery on it. The morning of the surgery the cyst ruptured and left a huge hole. Surgery was performed to clean it out. It never completely healed and continued to bleed. After a time it began to bleed worse and surgery was performed again. When it didn't heal the 2nd time the gynocologist sent her to a specialist.  

The specialist has presented her case at 2 medical conferences to no avail. He is at a loss as to how to proceed since he has done surgery twice with indigo carmine dye and cut out everything that showed blue. He stated that he probed at least 2.5 cm in depth. He was positive the last time that he got it all but here is again! She is supposed to have surgery again but considering that the previous 4 times have been fruitless we are at our wits end as to what to do. Maybe someone out there has had some experience with this sort of thing.    

She asked if it would hurt to do research on her own and he basically said "by all means, please do". The doctors that she has been to have called it a sinus tract, a perineal sinus tract, a possible perineal-rectal abscess. (He later goes on to say that it was away from the rectal canal and he could not feel the defect from the rectum. He also said that he thought that originally it may have involved the Bartholin's gland although he also said that pathology never proved that. She has had 4 previous attempts at resection. She trusts his opinion but we are open to anyone who may have some previous experience with this.