Infectious colitis and ulcerative colitis cause colon inflammation but have different causes.

Infectious colitis and ulcerative colitis have similar symptoms. It’s important to speak with a doctor if you develop diarrhea, abdominal pain, or blood in your stool, especially if these persist.

Let’s discuss the similarities and differences of infectious colitis and ulcerative colitis. We look at the causes, symptoms, and risk factors, among other considerations.

Infectious colitis refers to colon or intestinal inflammation that results from a bacterial or viral infection. Bacteria and viruses that cause this condition include:

  • Salmonella
  • Escherichia coli (E. coli)
  • Rotavirus
  • Adenovirus

Ulcerative colitis is the most common form of inflammatory bowel disease (IBD) and causes inflammation and bleeding.

Researchers do not know the exact cause of ulcerative colitis. However, they believe it could be an autoimmune condition in which your immune system mistakenly attacks healthy tissue.

Stress may worsen IBD symptoms or increase your chance of experiencing a flare-up.

IBD (including ulcerative colitis) can cause:

  • diarrhea
  • tenesmus (frequent and urgent feeling that you need to pass stool, even if your bowels are already empty)
  • abdominal pain
  • blood in the stool
  • fecal urgency (a sudden need to relieve yourself)

If your condition is severe, you may also feel very tired, nauseated, or develop a fever.

Remission can also occur sometimes. For example, symptoms may disappear for weeks or years, but then they may return.

If you have infectious colitis, your symptoms may be similar to those of IBD, including:

  • rectal pain
  • tenesmus
  • diarrhea

You may want to seek medical care if you have any of the above symptoms or diarrhea that lasts for more than 4 weeks. A doctor may evaluate your symptoms, provide a diagnosis, and also a treatment plan.

A 2022 study notes that bacterial and viral infections are risk factors for infectious colitis. You may also develop colitis if you have a parasitic infection or a sexually transmitted infection (STI) that affects the rectum, especially if you have HIV.

Rectal infections include:

  • Chlamydia trachomatis
  • herpes simplex 1 and 2
  • Neisseria gonorrhoeae

Ulcerative colitis is not an infection, so you cannot get it if you come into contact with someone with the condition.

It can affect people of any sex.

You may have an increased chance of developing ulcerative colitis if your parents or siblings already have it, though this is not always the case.

Infectious colitis

To diagnose infectious colitis, a healthcare professional may ask about your symptoms and medical history.

They may also perform other tests, such as:

  • Stool test: This test checks whether there are bacteria present in your stool.
  • Abdominal CT scan: This scan may be used to diagnose bacterial colitis if you have an empty colon or no enlarged lymph nodes.
  • Pelvic CT scan: This scan may show whether you have a thickened colonic wall.
  • Colonoscopy: This procedure is used to check for colonic ulcerations.

Ulcerative colitis

For ulcerative colitis, blood and stool tests are also common.

A doctor may recommend other tests, including:

  • colonoscopy
  • chromoendoscopy, which checks whether you have polyps or precancerous cells.
  • biopsy, which involves removing a small tissue sample from your intestine so that it can be tested in a laboratory

A doctor may use a contrast chemical that you take orally or intravenously to help provide a detailed image of your digestive organs.

Read more about ulcerative colitis diagnosis.

Infectious colitis treatment usually depends on your symptoms and underlying cause. For example, antibiotics like metronidazole may be an option if you have a mild to moderate Clostridium difficile infection.

If the infection is serious, your doctor may prescribe oral vancomycin and add intravenous metronidazole if complications arise.

In the case of ulcerative colitis, treatment may include

Sometimes, people may undergo colectomy, a procedure that involves removing parts of the colon. It can be an option if medications do not work or you experience uncontrollable bleeding or side effects from medications.

Read more about ulcerative colitis treatment.

Infectious colitis and ulcerative colitis are conditions that cause diarrhea, tenesmus, and blood in the stool.

You may have a higher chance of developing infectious colitis if you get a bacterial or viral infection. It can also affect people with STIs.

Ulcerative colitis is more likely to develop if you have a family history of the condition.

Visit our dedicated IBD hub for more resources on UC.