Anal Abscess

An anal abscess is a painful, pus-filled pocket that forms near the anus or rectum when glands in the anal area become blocked and infected. Almost 90% of these abscesses are caused by blocked glands, and they require prompt medical attention to prevent serious complications.

Table of contents

• What is an Anal Abscess?
• Causes and Risk Factors
• Symptoms
• How is it Diagnosed?
• Treatment
• Complications
• Prevention

anorectal abscess, rectal abscess, perianal abscess, perirectal abscess, ischiorectal abscess, intersphincteric abscess, supralevator abscess, gland abscess

What is an Anal Abscess?

An anal abscess is a painful, pus-filled pocket that forms in or near your anus, rectum, or the area between your genitals and anus. Your anus is the opening at the end of your digestive tract where stool leaves your body. The rectum is the section where stool is held before it passes through the anus.^[1]

There are many glands inside the anus that produce mucus to help stool pass through. When one of these glands gets clogged, it can become infected. Bacteria or fecal matter can block an anal gland and tunnel into the tissue around the anus or rectum. When this happens, the infection collects into a cavity called an abscess.^[4]

The most common type of anal abscess is a perianal abscess, which appears as a painful swelling near the opening of your anus. It typically looks red and feels warm when touched. A perianal abscess may be visible on the surface of the skin.^[1] Perirectal abscesses are located deeper inside the rectum and are less common. This type is often associated with inflammatory bowel diseases (IBDs), such as Crohn’s disease.^[1]

Anal abscesses are most common in men, particularly between the ages of 20 and 60, with the average age being 40.^[2]

Causes and Risk Factors

Almost 90% of all anal abscesses are caused by blocked glands that become infected.^[4] Small glands just inside the anus are part of normal anatomy. If these glands become clogged, this may result in an infection. When the infection is serious, it often leads to an abscess.^[3]

Other causes of anal abscesses include:^[1]

• Anal fissures (tears in the anal canal) that become infected
• Sexually transmitted diseases and other infections
• Trauma to the anus or rectum
• Perianal hidradenitis suppurativa, an inflammatory condition affecting the anal glands
• Infections of tissue lining the anal canal (often related to IBD)

Several factors can increase your risk of developing an anal abscess:^[1][2]

• Inflammatory bowel diseases such as Crohn’s disease or ulcerative colitis
• Diabetes
• Being the receptive partner in anal sex
• Insertion of foreign objects into the rectum
• Being assigned male at birth
• Cigarette smoking
• Diverticulitis
• Chronic diarrhea and constipation
• Certain immune-suppressing medications, such as prednisone and chemotherapy drugs
• A weakened immune system (such as from HIV/AIDS)
• Radiation therapy
• Pregnancy
• Cancer

Symptoms

The most common symptom of a perianal abscess is a swollen and tender boil (similar to a large pimple) near the edge of your anus. It may be red, extremely painful, or constantly throbbing. Sitting down, coughing, and having bowel movements may make it hurt worse.^[2]

Symptoms of superficial perianal abscesses can include:^[1]

• Pain, which is usually constant, throbbing, and worse when sitting down
• A painful lump near your anus
• Skin irritation around your anus, including swelling, redness, and tenderness
• Discharge of pus from your anus or near your anus
• Rectal bleeding
• Constipation or pain associated with bowel movements
• Lower abdominal pain
• Flu-like symptoms such as chills and fever

Deeper anorectal abscesses may not be as painful as superficial abscesses and are not externally visible. However, they can cause fever, chills, fatigue or low energy, and lower abdominal pain.^[1]

In infants and toddlers, the abscess often appears as a swollen, red, tender lump at the edge of the anus. The infant may be fussy and irritable from discomfort. There are usually no other symptoms.^[5]

How is it Diagnosed?

Your healthcare provider diagnoses anal abscesses with a rectal examination. They insert a gloved, lubricated finger into your rectum and feel around for irregularities. A speculum (a device that helps open hollow body parts) may help your healthcare provider view your entire rectum. They may be able to see external abscesses during this examination.^[2]

Most anal abscesses are diagnosed and managed based on clinical findings. Your healthcare provider will ask about your symptoms and health history and give you a physical examination.^[3]

Occasionally, imaging studies may be used to help diagnose and manage deeper abscesses. These tests can include:^[3]

• Ultrasound
• CT scan (computed tomography)
• MRI (magnetic resonance imaging)

A proctosigmoidoscopy may be done to check for other diseases. This is a procedure where a flexible tube with a light and camera is placed in the anus to allow your provider to look at the area.^[7]

Treatment

The problem rarely goes away on its own. As a rule, the presence of an abscess is an indication for surgical drainage. Antibiotics alone usually cannot treat an abscess because they are unable to penetrate the abscess cavity.^[4][12]

Treatment involves surgery to open and drain the abscess. An incision is made in the skin near the anus to surgically drain the infected cavity. This can usually be done in a doctor’s office with local anesthetic. Some patients require deeper anesthesia in an operating room.^[4] Simple perianal abscesses may be treated in the emergency department, while more complex abscesses are treated by an experienced surgeon.^[12]

Surgery is most often an outpatient procedure, which means that you go home on the same day. The surgeon cuts open the abscess and drains the pus. Sometimes a drain is put in to keep the incision open and draining, and sometimes the abscess cavity is packed with gauze.^[5] Drained abscesses are usually left open and no stitches are needed.^[5]

If the pus collection is deep, you may need to stay in the hospital longer for pain control and nursing care of the abscess drainage site. Hospitalization and antibiotics are rarely required except for patients with severe infections or decreased immunity.^[4]

The need for routine use of antibiotics in patients with anorectal abscesses has not been established. However, antibiotics may be warranted in patients with conditions such as:^[12]

• Systemic inflammatory response or sepsis
• Extensive cellulitis
• Diabetes
• Immunosuppression
• Heart valve abnormalities or prostheses

After surgery, your healthcare provider may recommend:^[5][16]

• Warm sitz baths (sitting in 8 to 10 centimeters of warm water) for 15 to 20 minutes, 3 times a day and after bowel movements
• Pain medicines as directed
• Keeping the anal area clean and dry
• Using a gauze bandage to absorb drainage if needed
• Stool softeners to avoid constipation and straining

Complications

With prompt treatment, people with anal abscesses usually do well. Most of the pain caused by the abscess goes away right after surgery.^[16] However, complications can occur when treatment is delayed.^[5]

As much as 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 inside of your anus and your skin.^[1] Fistulas usually develop when anal glands become infected. Your body creates the fistula as a way to drain pus from the infection.^[1]

Symptoms of anal fistulas include pain, swelling, itching, and redness around the anus. In some cases, fluids — including pus, stool, and blood — may drain from the fistula opening in your skin. In other cases, the opening of the fistula to the skin can become blocked, which may lead to recurrent anal abscesses.^[1] Most fistulas need to be treated surgically. Fistulas can develop before or after an abscess is treated.^[1]

Other possible complications of anorectal abscess include:^[5][6]

• Infection that spreads to the blood (sepsis), a life-threatening condition
• Continuing pain
• Problem keeps coming back (recurrence)
• Fournier’s gangrene, a rare but potentially life-threatening infection

Prevention

Prevention or prompt treatment of sexually transmitted infections may prevent an anorectal abscess from forming. Using condoms during intercourse, including anal sex, can help prevent such infections.^[5]

In infants and toddlers, frequent diaper changes and proper cleaning during diaper changes can help prevent both anal fissures and abscesses.^[5]

To help avoid recurrence of perianal abscesses, several steps can be helpful:^[17]

• Maintain good hygiene in the anal area by washing regularly with mild soap and water after bowel movements
• Follow a high-fiber diet to regulate bowel movements and prevent constipation
• Stay hydrated by drinking at least eight glasses of water a day
• Avoid straining during bowel movements
• Practice regular physical activity to maintain proper bowel function
• Avoid tobacco and limit alcohol consumption
• Manage chronic conditions such as Crohn’s disease or diabetes properly
• Seek regular medical follow-up

Unfortunately, despite proper treatment and complete healing, an abscess can come back. If an abscess comes back, it suggests that perhaps there is a fistula that needs to be treated.^[3] It will probably take about 3 to 8 weeks for the abscess to completely heal, and most people can go back to work or their normal routine 1 or 2 days after surgery.^[16]