Abscesses & Fistulas

Unhappy African American woman feeling cold, covered with warm blanket
Anal abscess. Vector illustration

An abscess occurs when infected tissue forms a pocket of pus under the skin. These painful lumps may heal on their own, but often they need to be drained, naturally or surgically. When abscesses are left to drain naturally, they can form a fistula (an opening or connection between two body parts).

Perianal abscesses and fistulas occur in or around the anus or rectum. They are often painful and may require surgery to drain the infected fluid and close the opening.

Perianal abscesses

Perianal abscesses are infections that appear under the skin near the anus, typically causing a painful, hardened lump or swelling from the buildup of fluid and bacteria (pus). The abscesses can also occur farther up in the anal canal and may not cause pain during a physical exam.

Causes of perianal abscesses

Everyone has small glands inside their anal canal. An infection can occur if stool or bacteria get trapped in these glands. As the amount of fluid and bacteria increases, the abscess grows and eventually can reach skin level.

Symptoms of perianal abscesses

Abscesses can cause severe discomfort in the anal area. Other symptoms can include:

  • Chills
  • Difficulty urinating
  • Fever
  • General flu-like symptoms
  • Pain that worsens when sitting or using the restroom

Treatment for perianal abscesses

Treatment for perianal abscesses is drainage of the fluid. Antibiotics are not often required for perianal abscesses, but they may occasionally be used if there is significant cellulitis on the skin, if you have undergone another drainage procedure already, or if you are immunosuppressed.

Surgical treatment for a perianal abscess can usually happen right in our clinic. The procedure includes cutting into the infected tissue and draining the fluid. Once the abscess drains, symptoms typically improve. However, if the abscess is deeper in your anal canal or more severe, your surgeon may recommend having the procedure while you are under light anesthesia (or sedation) in the operating room.

Perianal fistulas

A perianal fistula is an opening connecting the anal canal or lower rectum where the abscess started and the area where it drains. Fistulas can be simple or complex. A complex fistula occurs when the fistulas are located deeper in the rectum, involve more tissue or muscle, or when there are multiple connections.

Causes of perianal fistulas
About 30 percent of perianal abscesses turn into perianal fistulas. Unfortunately, there is no way to predict whether an abscess will turn into a fistula. If the area where the abscess initially develops (typically the anal gland) remains open even after it drains, then the abscess can create a fistula.
Symptoms of perianal fistulas
Fistulas typically do not cause discomfort; however, they can cause long-term drainage of blood, pus or mucus as well as irritation in the surrounding skin. In addition, a chronic fistula allows bacteria to continue seeping from the gastrointestinal (GI) tract to the surrounding tissues and skin. This seepage causes abscesses to continue to form until the opening is successfully closed.
Treatment for perianal fistulas

The goal with any fistula surgery is to maintain the normal function of your anal sphincter muscle, so the surgery does not affect your ability to control your stool. Therefore, your surgeon may need to thoroughly evaluate the fistula and your surrounding tissue and muscle during surgery before deciding the best approach for your situation.

Surgery for an anal fistula varies depending on how much muscle is involved:

  • If the opening is superficial (shallow) and involves little to no muscle, your surgeon can perform a fistulotomy (surgery to open a fistula). Complete healing after surgery takes about four to six weeks, depending on the size of the fistula.
  • If the opening is complex or deeper in the anal space, your surgeon may place a drain (a seton) to help it remain open. The seton allows the surrounding abscess area to heal. Setons can stay in place as long as needed.
  • Once a seton has been placed and the fistula tract is ready to be surgically closed, your surgeon will perform a follow-up procedure to close the opening internally a few months later. This follow-up procedure is called an endorectal advancement flap.

Learn more about the procedures and surgeries that our team offers.