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:
- An anal fissure, a tear in the anal canal, that becomes infected
- Sexually transmitted infections
- Blocked anal glands
Risk factors for anal abscesses include:
- Colitis
- Inflammatory bowel disease such as Crohn's disease or ulcerative colitis
- Diabetes
- Diverticulitis
- Pelvic inflammatory disease
- Being the receptive partner in anal sex
- Use of medications such as prednisone
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:
- Fever
- Chills
- Malaise
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:
- Sexually transmitted infections
- inflammatory bowel disease
- Diverticular disease
- Rectal cancer
In rare cases, an examination may be done under anesthesia. The doctor may also ask for an ultrasound, a CT scan, or an MRI.
Treatment of Anal Abscesses
Prompt surgical drainage is important, preferably before the abscess erupts. Superficial anal abscesses can be drained in a doctor's office using a local anesthetic. Large or deeper anal abscesses may require hospitalization and the assistance of an anesthesiologist.
After the procedure, most people are prescribed medications for pain relief. For otherwise healthy people, antibiotics are usually not needed. Antibiotics may be required, though, for some people, including those with diabetes or decreased immunity.
Sometimes, fistula surgery can be performed at the same time as abscess surgery. However, fistulas often develop four to six weeks after an abscess is drained. Sometimes a fistula may not occur until months or even years later. So fistula surgery is usually a separate procedure that can be performed on an outpatient basis or with a short hospital stay.
After abscess or fistula surgery, discomfort is usually mild and can be controlled with pain medications. People can expect to lose only a minimal amount of time from work or school.
People are usually advised to soak the affected area in a warm water (sitz) bath three or four times per day. Stool softeners may be recommended to ease the discomfort of bowel movements. Some people may be advised to wear a gauze pad or mini-pad to prevent the drainage from soiling their clothes.
Complications after surgery can include:
- Infection
- Anal fissure
- An abscess returning
- Scarring
After an anal abscess or fistula has properly healed, it's unlikely that the problem will come back. To prevent one from doing so, however, it's important to follow the advice of your doctor or colon and rectal surgeon.