What is an anal abscess, main causes and how to treat

Anal, perianal or anorectal abscess is the formation of a cavity full of pus in the skin around the anus, which can cause symptoms such as pain, especially when evacuating or sitting, the appearance of a painful lump in the anal area, bleeding or elimination of yellowish secretion.

The abscess usually forms when bacteria infect the region and cause intense inflammation, with an accumulation of pus. Treatment is done by the surgeon, requiring drainage of the abscess and, in some cases, the use of antibiotics for a few days. 

What are the causes

Perianal abscess is caused by a bacterial infection of the skin of the anus and perineum region, usually due to the obstruction of glands that produce mucus in the anal region, facilitating the installation of bacteria. Some of the conditions that cause a risk of abscess formation are:

  • Inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis;
  • Hidradenite supurativa;
  • Infections of the rectum, such as amoebiasis, venereal lymphogranuloma, tuberculosis or rectal schistosomiasis;
  • Anal fissure;
  • Anorretal cancer;
  • Compromised immunity;
  • Having undergone surgery in the anorectal region, such as hemorrhoidectomy, episiotomy or prostatectomy, for example. 

Generally, these conditions cause inflammation in the tissue of the rectum and anus, facilitating the accumulation of bacteria and the formation of pus. Better understand the causes, symptoms and treatment of proctitis .

Main symptoms

The main symptom of perianal abscess is pain in the anus and perineum region, especially when evacuating or sitting, but it can become constant as the injury worsens. Also check out other  major causes of pain when evacuating .

If the location of the abscess is more external, a painful, hot, reddish lump may also be seen in the anal area. In some cases, there may be bleeding and fever. When the abscess is ruptured, purulent secretion may escape, and with that, the pressure in the skin and pain will decrease.

The diagnosis of anal abscess is made by the general surgeon or coloproctologist, through analysis of the region and tests such as anoscopy, ultrasound, computed tomography or magnetic resonance, which identify the size and depth of the lesion. Blood tests, such as a complete blood count, can help assess the severity of the infection.

How the treatment is done

The treatment of the anal abscess is done with its drainage, by the general surgeon or coloproctologist, as soon as possible, as the persistence of the abscess increases the risk of a generalized infection. 

Depending on the size and location of the abscess, drainage surgery can be performed with local anesthesia or with more powerful ones such as spinal or epidural. In large abscesses, it may be necessary to leave a drain for a few days at the site.

To treat a fistula, the doctor may make a cut or place a material to stimulate healing and the closure of the path. In addition, antibiotics can be indicated if the abscess is large and has a large inflammatory area, or if the patient presents risks of generalized infection, such as in cases of diabetes, compromised immunity or obesity, for example.

Postoperative care

After surgery, the doctor may recommend rest, use of painkillers and sitz baths with warm water, due to its anti-inflammatory effect.

The doctor will schedule reevaluations in 1 to 2 weeks, to observe healing and to identify if there is drainage of secretions that indicate fistulas. In some cases, the abscess may return, especially if the initial treatment was not done correctly or if there is a disease that causes inflammation of the site and facilitates the formation of the lesion.

Possible complications

It is very common for the abscess to give rise to an anal fistula, which is the formation of a path that connects two regions, which can arise between the anus and the vagina, the uterus, the urinary tract or other parts of the intestine, for example. Find out what anal fistula is and how to treat it .

In addition, other complications that the anal abscess can cause are the involvement of the anal sphincter, causing fecal incontinence, or a necrotizing infection, which is when the bacteria reach neighboring tissues, such as skin, muscles and fat.

In addition, if the treatment is not done correctly, it is possible that the bacteria reach the bloodstream, causing a generalized infection, which can even lead to death.

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