Since how long is it draining pus? Was a swab / culture done? Where is the exact location on the butt? Are you diabetic? Are you on any medications?
This is unlikely to be related to the lymph nodes. With its location there is a possibility of it being the anorectal fistula. For the diagnosis, a fistulogram would be essential to see the communication with the anal canal or rectum (called as high rectal fistula). If the fistulogram shows the communication whole tract needs to be excised. That only would prevent recurrence. Another possibility is a sinus. That too would entail surgical excision of the tract. A tubercular infection is another possibility which causes recurrence unless specific medications are given for the treatment. A culture of the pus/swab is an essential component of the management.
Read about the anorectal fistula;
Please feel free for your follow up questions.
You are welcome.
CA-125 is a blood test for ovarian cancer. But there are many benign conditions also which can cause its elevation. Please read this resource;
Please click accept, if it has been helpful to you, as it is the only way we get credit for the time and work.
Best wishes and kindest regards.
It is pleasure assisting you.