Focal active colitis

by Jason Wasserman MD PhD FRCPC
July 7, 2023

What does focal active colitis mean?

Focal active colitis is a pattern of tissue injury associated with inflammation in the colon. “Focal” means that the changes are only seen in parts of the tissue examined. “Active” means that the tissue injury and inflammation are ongoing or of recent onset. The changes seen in focal active colitis are usually mild and the surrounding tissue is usually normal.

What causes focal active colitis?

Causes of focal active colitis include:

• Self-limited infections of the colon (viral and bacterial)
• Medications (for example, non-steroidal anti-inflammatory drugs, mycophenolate acid, and ipilimumab)
• Early inflammatory bowel disease (ulcerative colitis and Crohn’s disease)
• Ischemia (reduced blood flow to the colon)
• Clostridium difficile infection
• Bowel preparation prior to a colonoscopy

What are the symptoms of focal active colitis?

The most common symptom of focal active colitis is diarrhea. However, many patients with focal active colitis will experience no symptoms and the condition will be discovered incidentally when a biopsy from the colon is examined for another reason.

How is focal active colitis diagnosed?

The diagnosis of focal active colitis is usually made after one or more small samples of tissue are removed from the inside of the colon during an examination called a colonoscopy. The tissue is then sent to a pathologist for examination under a microscope.

What does focal active colitis look like under the microscope?

The inside of the colon is covered by epithelial cells that connect together to form round structures called glands. In focal active colitis, specialized immune cells called neutrophils are seen within the glands. Cryptitis is a term pathologists use to describe neutrophils in-between the epithelial cells in the glands. A crypt abscess means that the neutrophils were seen within the small space in the center of the gland. Features of chronic colitis including crypt distortion and basal lymphoplasmacytosis should not be seen in focal active colitis.