Perianal abscess overview

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

A perianal abscess is a collection of pus outside the anus. It arises from an infection at one of the anal crypts of Morgani which leads to inflamation and abscess formation. Most cases of perianal abscesses are sporadic, though there are certain situations which elevate the risk for developing the disease, such as diabetes mellitus, crohn's disease, chronic steroid treatment and others.

Pathophysiology

The abscess usually begins when bacteria enters through a tear in the lining of the rectum or anus. Most often, this occurs between the internal and external sphincters (intersphincteric abscess), where the perianal glands are located. As the abscess increases in size, most will follow the plane of least resistance and spread towards the surface, creating a perianal abscess. Occasionally, the infection can spread into the ishiorectal fossa or above the level of the levator muscles, creating ischiorectal and/or supralevator abscesses, respectively. Although supralevator abscesses are difficult to diagnose, perianal and ischiorectal abscesses still seem to account for the majority of the ones encountered.

Differentiating Perianal Abscess from other Diseases

This condition is often misdiagnosed initially by the patient as a bad case of hemorrhoids, since this is almost always the cause of any sudden anal discomfort. The presence of the abscess, however, is to be suspected when the pain quickly worsens over one or two days and the 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.

Risk Factors

In terms of risk, those individuals with diabetes, immunocompromised states, those with inflammatory bowel disease, or who engage in receptive anal sex, appear to be at higher risk for developing an abscess, than those without these risk factors.

Natural History, Complications and Prognosis

An anorectal abscess that is untreated or not fully drained can get worse and cause a severe local or systemic infection which can be life-threatening (Fornier's gangrane or sepsis). On the long run, a perianal fistula can arise from the abscess cavity - an abnormal tract that connects the rectum and the external perianal region. After successful treatment and recovery, a person can generally return to normal activities. However, someone with inflammatory bowel disease often needs lifelong monitoring by a healthcare provider. Any new or worsening symptoms should be reported to the healthcare provider.

Diagnosis

Imaging Findings

CT

Imaging study which can help determine the diagnosis in cases of a deep non-palpable perirectal abscess includes CT scan.

MRI

Imaging study that can help determine the diagnosis in cases of a deep non-palpable perirectal abscess includes pelvic MRI.

Ultrasound

Imaging study that can help determine the diagnosis in cases of a deep non-palpable perirectal abscess includes trans-rectal ultrasound.

Treatment

Surgery

Treatment of perianal abscesses include examination under anesthesia (regional or general) as well as incision and drainage of the pus. Antibiotics to cover rectal flora (and not skin flora) should be prescribed perioperatively.