Diagnosis and treatment of anorectal fistulas at times presents the simplest and at other times the most challenging problems encountered in surgery, is this sinus actually an anorectal fistula? Or does it originate elsewhere, such as in a region of sigmoidal diverticulitis or ileocolitis? Or does it connect with an infected precoccygeal cyst? What keeps the sinus or fistula active when the primary source has healed over spontaneously or has been erased by a previous operation? In what situations might the surgeon anticipate fecal incontinence after fistulectomy, and what can be done about it?

The purpose of this presentation is to attempt to answer these and similar questions that, in my opinion, have been inadequately answered in medical literature. I shall not dwell on the simple uncomplicated fistula with a definite primary source and secondary opening, since the principles of dealing with such a lesion have been well established.

Etiology Anorectal fistulas comprise 85 per cent of sinuses opening onto the perineum. The other 15 per cent result from hidradenitis suppurativa, pilonidal disease, and other less common causes. There are many types of anorectal fstulas, but the one feature that they have in common is that they originated inside the anus or rectum. (I use the past tense because the anorectal site of origin, the primary lesion, may have healed over, but at one time it was present.) All anorectal fistulas and most perianal sinuses originate as abscesses.