An anal abscess or rectal abscess is the result of an infection of the lining of the anal canal. This can allow pus to collect in a cavity in the perianal area. Anorectal abscesses are quite painful and may require surgery if they fail to heal properly.
Definition & Facts
Most anal abscesses occur in the perianal area near the opening of the anus, but they can also occur in the deep tissue where they are less visible. An anorectal abscess typically starts as a boil-like nodule near the anus. The area may be painful, swollen, red, and warm to the touch.
Approximately 50 percent of people with anorectal abscesses go on to develop fistulas. A fistula occurs when the abscess breaks open, creating an abnormal opening between the abscess and the surface of the skin. Anal fistulas can lead to persistent drainage or recurrent abscesses. There are several classifications of anal abscesses based on their location in relation to other structures of the rectum and anus:
- Perianal—Approximately 60 percent of cases.
- Ischioanal—Approximately 20 percent of cases.
- Intersphincteric—Approximately 5 percent of cases.
- Supralevator—Approximately 4 percent of cases.
Most patients who develop anal abscesses are between the ages of 20 and 60. Men are twice as likely to suffer from anal abscesses than women.
Symptoms & Complaints
- Rectal bleeding or rectal discharge
- Difficulty urinating
- Fever or chills
- A boil-like nodule near the anus
- Increased irritability in young children
The most common cause of anorectal abscesses is a blocked anal gland. These blocked glands can result in a bacterial infection. Once they become filled with pus, the glands can burst inward. This releases the infected contents into the areas surrounding the anus and rectum. Sexually transmitted diseases and small tears in the skin along the anal canal can also contribute to anal abscesses. Those most at risk of developing the condition include:
- Individuals with chronic bowel conditions, including Crohn’s disease, inflammatory bowel disease, or ulcerative colitis.
- People with diabetes.
- Individuals with pelvic inflammatory disease.
- Individuals with diverticulitis.
- People using certain medications, such as prednisone.
- Individuals receiving anal sex.
- Individuals with chronic constipation or diarrhea.
- Individuals with a compromised immune system due to HIV/AIDS or other health conditions.
- Cancer patients undergoing chemotherapy.
Diagnosis & Tests
Most anorectal abscesses are diagnosed through a physical examination. The doctor will check the perianal area for the characteristic redness, swelling, and nodules. The doctor may also perform a digital exam or use an anoscope to look inside the lower rectum and anal canal.
If the physician suspects a deeper abscess, they may order a CT scan, MRI, or ultrasound. MRIs are useful in locating the openings and tracts of any fistulas and assessing the anorectal wall, perirectal spaces, and anal sphincter for any damage. Blood tests, X-rays, or a colonoscopy may be used to rule out other conditions, including diverticular disease, inflammatory bowel disease, rectal cancer, and sexually transmitted diseases.
Treatment & Therapy
Treatment can vary depending on the particular type of abscess. Treatment of perianal abscesses typically starts with surgical drainage. If the abscess is superficial, this procedure can usually be performed at the doctor’s office under a local anesthetic. A very deep or large abscess may require the patient to be hospitalized and the assistance of an anesthesiologist. Pain medications may be prescribed following the procedure to ease any discomfort. Individuals with diabetes or a weakened immune system may also require antibiotic therapy to combat the infection.
Even with drainage, it is not uncommon for a fistula to develop weeks or even months later. In this case, a second procedure is required to close the abnormal opening. The fistula correction can typically be performed on an outpatient basis or with a short hospital stay. Most people are able to return to work or school relatively quickly following abscess or fistula surgery.
Following surgery, patients are encouraged to soak the area in a warm sitz bath three to four a day. Stool softeners can help make bowel movements more comfortable. It may also be helpful to wear a gauze or mini-pad to keep clothes from being stained by any drainage. Patients should be aware of potential post-surgical complications, including infection, scarring, fissures or tears in the lining of the anus, and recurrence of the abscess.
Prevention & Prophylaxis
Individuals with abscesses should wash their hands frequently to prevent the spread of bacteria. They should also avoid sharing baths and towels with other family members. An abscess should only be drained by a medical professional to avoid spreading the bacteria and causing further infection. Individuals with health conditions that put them at risk for abscesses should work with their doctor to manage the condition.
A healthy diet high in vitamins and minerals can boost the immune system, so the body is more resistant to infection. Maintaining a healthy weight reduces the chance of developing the risk factor of diabetes. It also reduces the risk of bacteria getting trapped in skin folds.
Stopping smoking also improves the immune system as well as the body’s ability to heal from injury or infection. Anyone experiencing anal pain or other symptoms of an abscess should see their health care provider for treatment immediately to prevent complications, including fistulas, scarring, systemic infection, and recurrence. The outcome for patients with anorectal abscesses is good as long as treatment is started promptly.