An anorectal abscess (also called an anal abscess, rectal abscess, perianal abscess, or perirectal abscess, depending on its location) is a pus-filled cavity that forms in the grooves of the anal canal (called anal sinuses).
Anorectal abscesses are usually caused by the accumulation of common bacteria in vulnerable or damaged tissues. When your body tries to control an infection, dead white blood cells and other bodily fluids begin to accumulate in your tissues, forming a pocket of pus.
Abscesses can form near or inside the anus, and they can also develop much higher up in the rectum. Although an abscess can form spontaneously for no apparent reason, it is usually associated with gastrointestinal problems, intestinal problems, weakened immune systems, and even certain medications .
Symptoms of anorectal abscess
Anorectal abscesses are usually recognized initially due to a dull, throbbing pain in the anus or rectum, often accompanied by sharp pain during bowel movements.
Perianal abscesses ("perianal" means "around") are the most common type and can usually be identified visually as they occur in the upper layers of tissue. When touched, the bump usually becomes tender, red, and warm.
In contrast, perirectal abscesses tend to form deeper tissues and often feel more than visible. Of the two types, perirectal infection tends to be more serious.
When the pus begins to consolidate and form a palpable mass, other symptoms of an anorectal abscess appear, including:
- Rectal bleeding and discharge
- Feeling like you need to use the bathroom when you don't
- Increasing and often persistent pain that is worse when moving or sitting
If you experience any of these symptoms, it is important to see your doctor and undergo a full examination.
If left untreated, an abscess can lead to an anal fistula , an abnormal tunnel junction between the skin around the anus and the rectal or anal canal through which stool and pus can drain. This may require intensive surgery and a long recovery period.
If you have a fever (over 100.4 degrees), chills, persistent vomiting, an inability to empty your intestines, or severe anal or rectal pain (with or without a bowel movement), go to the emergency room right away. This may indicate a systemic infection that has spread from the abscess site to the bloodstream.
Without proper treatment, this type of systemic infection can lead to sepsis , toxic shock, and even death.
Anorectal abscess can develop in isolation, often due to the overgrowth of common bacteria in the digestive tract, such as Escherichia coli ( E. coli ).
However, in recent years, an increasing number of cases have been linked to methicillin-resistant Staphylococcus aureus (MRSA) , a difficult-to-treat bacterial strain that can be transmitted through skin-to-skin contact .
Although anyone, young or old, can get an anorectal abscess, there are several conditions that can increase your risk. They include:
Most anorectal abscesses are diagnosed based on your medical history and physical exam. If the abscess is inside the anal canal, your healthcare provider may want to do an endoscopy with a lighted, flexible scope to better see inside.
Less commonly, imaging tests such as computed tomography (CT) or transrectal ultrasound (TRUS) may be used if the abscess is particularly deep.
During your physical exam, your healthcare provider will want to find out if the lump is an abscess or a hemorrhoid . These two conditions can usually be distinguished by their symptoms.
With an abscess, the pain worsens over time and does not respond to standard hemorrhoid treatment . There may also be common symptoms of infection that you don't usually experience with hemorrhoids, such as fever and chills at night.
If IBD, HIV, or diabetes is suspected, other tests may be ordered, including blood tests and colonoscopy .
Anorectal abscesses rarely go away on their own or only resolve with antibiotic therapy . In most cases, the doctor will need to drain the abscess , a relatively simple office procedure that involves a local pain reliever, a scalpel, and a pair of forceps.
If the abscess is particularly deep or located high in the rectum, the procedure should be done in a hospital under general anesthesia. The operation usually takes about 30 minutes. Some of the extracted pus can be sent to a laboratory to identify the pathogen.
After the procedure is complete, antibiotics are prescribed for about a week to help treat the infection and prevent it from spreading further. You may also be advised to use a sitz bath , a shallow bath used to soak and clean your anal area.
Tylenol (acetaminophen) is sometimes prescribed for pain relief. During recovery, stool softeners may be needed to reduce abrasion and allow the drained abscess to heal better.
After defecating, pat dry with toilet paper and rinse with a syringe filled with warm water. Wash lightly with soap, but avoid using alcohol or hydrogen peroxide, which can slow healing. Place gauze or large gauze over the wound as needed.
You can also ask your doctor about short-term use of over-the-counter topical creams and gels that can help soothe the tissues of the anus.
Drainage of the abscess is almost immediate. Although there may be some pain after the procedure, it is generally mild in comparison. However, if you experience severe rectal bleeding, fever, chills, or vomiting after returning home from the procedure, call your doctor immediately.
Frequently asked questions
If you have recurring abscesses around the anus, you may have an anal fistula. This is an abnormal tunnel that develops between the inside of the anal canal and the outer opening of the skin. Your doctor will need to surgically remove the fistula and prescribe antibiotics to treat the infection and prevent recurrence.
No. Both diseases are painful and develop around the rectum. However, anal abscesses are infections and hemorrhoids are swollen and bulging veins. Hemorrhoids can get infected, but they are not the same type of infection as abscesses. Hemorrhoids usually come back, but abscesses don't usually come back after treatment.
No. What looks like a small boil or abscess can be a much deeper and more extensive infection. Heating can help the boil to open on its own, causing it to drain. However, it is best to ask your doctor to drain the abscess during an in-office procedure, which can keep the area sterile. Your doctor will usually also prescribe antibiotics and may do a pus test to determine the type of infection.