Chronic active colitis
This article was last reviewed and updated on April 26, 2018.
by Shaheed Hakim, MD FRCPC
Chronic active colitis is a condition where the tissue that lines the inside of the colon is damaged by cells from the immune system.
This diagnosis can only be made after a sample of tissue from the colon is examined under the microscope.
The most common causes for chronic active colitis are inflammatory bowel disease and medications.
The normal colon
The colon is a part of the gastrointestinal tract which also includes the mouth, esophagus, stomach, small bowel, and anus. The colon is a long hollow tube that starts at the small bowel and ends at the anal canal. The colon is divided into sections which include the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.
The functions of the colon are to absorb water from the food that we eat and to move waste out of the body.
The colon is made up of four layers of tissue:
Mucosa - The mucosa is the tissue that lines the inside surface of the colon. The mucosa includes epithelial cells that form structures called glands. The glands are surrounded and supported by a tissue called lamina propria.
Submucosa - The submucosa sits directly below the mucosa. It contains many thick blood vessels and lymphatic channels.
Muscularis propria - The muscularis propria is a thick bundle of muscle. The muscles in the muscularis propria help move digested food and waste along the colon.
Subserosal adipose tissue - This is a layer of fat that sits directly below the muscularis propria. The subserosal adipose tissue is near the outside surface of the colon.
Serosa - The serosa is a thin layer of tissue that covers the subserosal adipose tissue and the outside of the colon.
Inflammation in the colon
Inflammation in the colon can damage the epithelial cells and prevent the colon from functioning normally. Pathologists call the early stage of damage caused by inflammation active colitis. If the damage continues over a longer period of time, pathologists describe the changes as chronic colitis. When both stages are seen at the same time, pathologists describe the changes as chronic active colitis.
This damage can result in symptoms such as diarrhea (with or without blood), abdominal pain and fever. If you experience these symptoms, your doctor my suggest examining the inside of your colon in a procedure called a colonoscopy. During the colonoscopy, your doctor may take small samples of tissue in a procedure called a biopsy.
The biopsies are usually taken from the last segment of the small intestine (ileum) and then thoroughly throughout the colon, in order for your pathologist to accurately determine the cause of the symptoms.
Treatment for chronic active colitis is based on both the grade (see below) and cause. Common causes for chronic active colitis include inflammatory bowel disease, medications (particularly NSAIDs), resolving infection, and diverticular disease. An accurate cause is determined by thorough sampling of the intestines, a detailed endoscopy report, and clinical history.
How does a pathologist make this diagnosis?
When examined under the microscope, the colon with chronic active colitis can show an increased number of immune cells called plasma cells and irregularly shaped glands.
Another type of immune cell called a neutrophil is often seen close to the damaged glands. Neutrophils and the damage they cause are the active part of the disease.
The active part of the disease can be divided into three grades:
Mild colitis - Neutrophils were are seen inside the glands. Pathologists call this cryptitis.
Moderate colitis - The glands are clogged with neutrophils. Pathologists call this a crypt abscess.
Severe colitis - Many crypt abscesses are seen and the epithelial cells on the inner surface of the colon have been lost. pathologists call the loss of epithelial cells an erosion or ulcer.
Dysplasia in chronic active colitis
Dysplasia is an abnormal pattern of growth that is initially non-cancerous (benign) but can turn into cancer over time. Long term inflammation (chronic colitis) can eventually lead to dysplasia.
The earliest change is referred to as low-grade dysplasia. In some cases, the cells become even more abnormal and progress to high-grade dysplasia. With high grade dysplasia, the cells look similar to cancer cells but are only found in the epithelium.
Why is this important? Your pathologist will carefully examine the tissue to look for any evidence of dysplasia. Most cases of chronic active colitis do not show any evidence of dysplasia.