A successful outcome from any type of fistula operation is dependent on accurate clinical assessment and classification. Generally, surgeons rely on a detailed history and careful physical examination.

The history of an anal fistula is often quite typical. The patient gives a history of a prior episode of perianal swelling and pain (low abscess) or deep rectal pain with fever and systemic symptoms (high abscess). The abscess either ruptures spontaneously and drainage of pus and blood is followed by resolution of acute pain or alternately the abscess may be drained by a surgeon to relieve the symptoms and prevent spreading sepsis. The spontaneously or surgically drained abscess will take one of three courses: (1) complete healing and no recurrence (less likely), (2) nonhealing and continuous drainage (more likely), or (3) healing and recurrence of the abscess (most likely).

The patient must be told that the infectious process begins in the anal canal and spreads outward and drainage of the abscess alone may not be adequate to eradicate the infection. Therefore, the patient should not blame the subsequent recurrent infections on the inadequacy of the original surgical drainage or the surgeon’s skill.

This typical history can be found in the overwhelming majority of patients with fistula in ano. However, if the abscess is due to an ingested foreign body (e.g., fish bone, chicken bone, toothpick, needle, etc.), the sign and symptoms of anorectal abscess might be more muted and insidious until a full-blown abscess presents itself a few days later. On the other hand, the history of an infection caused by external penetrating injury is much clearer and the clinical course easier to follow. Abscesses due to inflammatory bowel disease are often much less painful, contain very thin pus and the patient may present with some pain and drainage for weeks without a significant acute illness. Patients with hematologic disorders such as acute myelogenous leukemia (AML) often present with pain, erythema, fever, and tachycardia; but due to lack of leukocytosis (due to the original illness or as a result of chemotherapy) are unable to produce pus because of severe leukopenia. This is more likely to be seen in hematology–oncology units of major medical centers than in physician/surgeon’s offices. When such patients are encountered, the surgeon must not rush into attempting to drain the abscess especially when in the majority of cases severe thrombocytopenia is part and parcel of pancytopenia. Aggressive board spectrum antibiotic therapy, patient isolation and supportive therapy including liberal use of granulocyte stimulating factor (GSF) should be instituted and the patient reexamined every few hours.

Recurrent fistulas appear at the exact same anatomic location after an abscess has apparently healed [1]. Intermittent swelling and pain followed by drainage and relief of pain are typical symptoms of anal fistulas. It should be noted that although horseshoe fistulas may drain on one side and later on the contralateral perianal space, their incidence are much less frequent than “regular” fistulas.