An anal abscess is a painful condition in which a collection of pus develops near the anus. Most anal abscesses are a result of infection from small anal glands.
The most common type of abscess is a perianal abscess. This often appears as a painful boil-like swelling near the anus. It may be red in color and warm to the touch. Anal abscesses located in deeper tissue are less common and may be less visible.
Surgical incision and drainage is the most common treatment for all types of anal abscesses and is usually successful.
About 50% of patients with an anal abscess will develop a complication called a fistula. A fistula is a small tunnel that makes an abnormal connection between the site of the abscess and the skin.
In some cases, an anal fistula causes persistent drainage. In other cases, where the outside of the tunnel opening closes, the result may be recurrent anal abscesses. Surgery is needed to cure almost all anal fistulas.
Causes of Anal Abscesses
An anal abscess can have many different causes. These include:
- Infection of an anal fistula. An anal fistula is a small superficial tear in the skin of the anal canal.
- Sexually transmitted infections.
- Blocked anal glands.
Risk factors for anal abscesses include:
For adults, using condoms during sexual intercourse, including anal intercourse, can help prevent anal abscesses. For infants and toddlers, frequent diaper changes and proper cleaning during diaper changes can help prevent anal fistulas and perianal abscesses.
Symptoms of Anal Abscesses
Superficial anal abscesses are often associated with:
- Pain, which is usually constant, throbbing, and worse when sitting down
- Skin irritation around the anus, including swelling, redness, and tenderness
- Discharge of pus
Constipation or pain associated with bowel movements
Deeper anal abscesses may also be associated with:
Sometimes, fever is the only symptom of deep anal abscesses.
Diagnosis of Anal Abscesses
Usually, a clinical evaluation -- including a digital rectal exam -- is sufficient to diagnose an anal abscess. But some patients may require additional tests to screen for:
In rare cases, an examination may be done under anesthesia. The doctor may also ask for an ultrasound, a CT scan, or an MRI.