exudate to determine the proper course of any antibiotic treatment. Diagnosis Diagnosis of anorectal abscess begins with a medical history and physical exam. Imaging studies which can help determine the diagnosis in cases of a deep non-palpable perirectal abscess include pelvic CT scan, MRI or trans-rectal ultrasound. These studies are not necessary, though, in cases which the diagnosis can be made upon physical exam. Classification Anorectal abscesses are classified according to their anatomic location and the following are the most common types: perianal abscess, ischiorectal abscess, intersphincteric abscess and supralevator abscess. Perianal abscess, which represents the most common type of anorectal abscesses accounting for about 60% of reported cases, are superficial collections of purulent material just beneath the skin of the anal canal. Ischiorectal abscess is formed when suppuration transverses the external anal sphincter into the ischiorectal space. Intersphincteric abscess results from suppuration contained between the internal and external anal sphincters. Supralevator abscess forms from cephalad extension of the intersphincteric abscess above the levator ani or from caudal extension of a suppurative abdominal process like appendicitis, diverticular or gynaecologic sepsis. Differential diagnosis This condition is often initially misdiagnosed as hemorrhoids, since this is almost always the cause of any sudden anal discomfort. The presence of the abscess, however, is suspected when the pain quickly worsens over one or two days and usual hemorrhoid treatments are ineffective in bringing relief. Furthermore, any serious abscess will eventually begin to cause signs and symptoms of general infection, including fever and nighttime chills. A physician can rule out a hemorrhoid with a simple visual inspection, and usually appreciate an abscess by touch. Treatment Anal abscesses are rarely treated with a simple course of antibiotics. In almost all cases surgery will need to take place to remove the abscess. Treatment is possible in an emergency department under local anesthesia, but it is highly preferred to be formally admitted to a hospital and to have the surgery performed in an operating room under general anesthesia. Generally speaking, a fairly small but deep incision is performed close to the root of the abscess. The surgeon will allow the abscess to drain its exudate and attempt to discover any other related lesions in the area. This is one of the most basic types of surgery, and is usually performed in less than thirty minutes by the anal surgical team. Generally, a portion of the exudate is sent for