Anal swelling can occur for a variety of reasons. Most causes of a swollen anus are temporary and harmless, but some require medical attention.

The anus is at the end of the rectum, and muscle surrounds it. Depending on the cause of the swelling, people may have additional symptoms, such as pain, itching, burning, or bleeding around the anus.

In this article, we discuss the possible causes of a swollen anus and explain how doctors diagnose and treat these conditions.

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Anal swelling may make bowel movements painful.

An anal fissure is a small rip or tear that occurs in the lining of the anus.

Damage to the lining of the anus or overstretching it, possibly during a bowel movement, can cause an anal fissure. An anal fissure is most common when a person has either a dry, hard bowel movement or frequent, loose stool.

Less commonly, an infection or tumor can cause an anal fissure.

Other symptoms of an anal fissure include:

  • pain accompanying bowel movements
  • bright red blood with a bowel movement
  • a small lump near the anal fissure

A perianal abscess is a collection of fluid that gathers in the glands near the anus. In most cases, the abscess arises as a result of an infection.

A person might notice fluid or drainage coming from a perianal abscess. Other symptoms include fever, pain, and problems urinating.

Hemorrhoids are a common cause of anal swelling.

Hemorrhoids are swollen veins that occur in the anus and lower rectum. They can be external, appearing around the skin of the anus, or internal, which means that they arise in the lining of the anus or rectum.

Hemorrhoids are more common in older people and those who eat low fiber diets, strain during bowel movements, and have chronic constipation. They are also more likely to occur during pregnancy.

Other symptoms include:

  • anal itching
  • rectal bleeding
  • pain
  • a palpable lump near the anus

Anusitis is a disorder that involves inflammation of the anal canal. People often mistake anusitis for hemorrhoids.

Inflammatory bowel disease, infections, and chronic diarrhea can cause anusitis. However, the most common cause is a diet that contains a lot of acidic or spicy foods, such as coffee, citrus, and spices.

Other symptoms of anusitis include:

  • bleeding with a bowel movement
  • pain with a bowel movement
  • anal itching

An anal fistula is a large tear or tunnel that develops under the skin and connects the end of the bowel to either the anus or an abscess.

According to the American Society of Colon and Rectal Surgeons, an anal fistula will occur in about 50% of people with an abscess.

People with an anal fistula might experience:

  • pain
  • fluid drainage from the skin
  • rectal bleeding

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A person with perianal Crohn's may experience fever, perianal swelling, or fecal incontinence.

Crohn's disease is a type of inflammatory bowel disease that causes inflammation anywhere in the gastrointestinal tract, including the anus.

Perianal Crohn's disease signifies more severe disease, and it can be challenging to manage.

Symptoms include:

  • perianal swelling
  • fever
  • fecal incontinence
  • drainage from the anus, vagina, or scrotum

Anal symptoms can sometimes be due to anal cancer, although this disease is quite rare.

Anal cancer is less common than colon cancer or rectal cancer. The American Cancer Society estimate that there will be about 8,300 new cases of anal cancer in 2019 in the United States.

The symptoms can be similar to those of other anal disorders and include:

  • anal bleeding
  • anal itching
  • pain
  • a feeling of fullness in the rectal area
  • abnormal discharge
  • changes in bowel movements

Friction from sexual activity involving the anus can irritate the sensitive tissues around it, causing swelling, small tears, or bleeding.

Anal sex is mostly safe, but because there is a risk of bacterial infections, people should consider the risks. Learn about how to practice anal sex safely here.

A doctor will typically begin the diagnostic assessment by taking a thorough medical history and carrying out a physical examination.

Sometimes, a doctor can diagnose an anal disorder upon visual inspection or with a digital exam, which involves inserting a gloved finger into the anal canal.

However, they will investigate internal problems using other tests, which might include:

  • Anoscopy. An anoscope is a lighted tube that a doctor uses to examine the lower rectum and anal lining.
  • Flexible sigmoidoscopy. A doctor will perform flexible sigmoidoscopy using a flexible tube with a light and camera on the end to look inside the rectum and lower colon.
  • Colonoscopy. A colonoscopy also involves a long, flexible tube with a light and camera. This tube is called a colonoscope, and doctors use it to view the rectum and large intestine, usually to screen for colorectal cancer.

The underlying cause of a swollen anus will determine the treatment.

Anal fissure

At-home treatment options for an anal fissure include:

  • having warm baths or sitz baths, especially after a bowel movement
  • adopting a high fiber diet or taking fiber supplements
  • using stool softeners
  • drinking more water
  • applying topical medications to relieve pain

Chronic anal fissures might require surgical repair.

Sometimes, injections of botulinum toxin (Botox) into the anal sphincter help heal chronic anal fissures.

Perianal abscess

Perianal abscesses often require surgical drainage, particularly in people with weakened immune systems and those with diabetes. After surgical drainage, the wound can take 3–4 weeks to heal.

Hemorrhoids

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A warm bath several times per day may help to treat hemorrhoids.

Treatments for hemorrhoids include:

  • a high fiber diet
  • stool softeners or fiber supplements
  • drinking more water
  • warm baths or sitz baths several times per day
  • not straining during a bowel movement and avoiding sitting on the toilet for too long

Prolapsed or internal hemorrhoids may require medical treatment, including laser procedures or surgery.

Anusitis

The type of treatment for anusitis will depend on the underlying cause. If the cause is inflammatory bowel disease or an infection, a person will need medical treatment.

Other treatments include:

  • diet changes, including eating more high fiber foods
  • stress management
  • applying ice or cold packs

Anal fistula

Surgery is almost always necessary to treat an anal fistula.

Perianal Crohn's disease

The treatment of perianal Crohn's disease is often multifactorial and may include:

  • antibiotics
  • immunosuppression drugs
  • biologic drugs
  • surgery

Anal cancer

When deciding how to treat anal cancer, doctors will consider several factors, including the type of tumor and how far it has spread into the body. They will also take into account a person's age and overall health.

A treatment plan for anal cancer might consist of a combination of chemotherapy, radiation, and surgery.

A swollen anus may be very uncomfortable, but in most cases, the causes are temporary and pose no long term risk.

Home remedies for anal swelling include warm baths, a high fiber diet, hydration, and topical medications.

A person should contact their doctor if they experience persistent symptoms, such as pain, bleeding, or changes in bowel habits.