The wall of the large intestine, known as the colon, can sometimes become thicker than normal. This “colon thickening” is not a disease in itself but rather a physical finding often observed during medical imaging tests, such as CT scans or colonoscopies. It signals an underlying health issue within the colon that requires medical evaluation. While a normal colon wall is less than 3 millimeters thick, a measurement of 5 millimeters or more can indicate a pathological condition.
Inflammatory Bowel Conditions
Chronic inflammatory conditions frequently cause colon thickening. Inflammatory Bowel Disease (IBD) encompasses conditions like Crohn’s disease and ulcerative colitis, where the immune system mistakenly attacks the digestive tract. This ongoing inflammation leads to structural changes in the colon wall.
Crohn’s disease is characterized by transmural inflammation, affecting the entire thickness of the bowel wall. This can occur anywhere along the digestive tract but most commonly involves the end of the small intestine (ileum) and the beginning of the colon. It leads to thickening and narrowing of affected segments.
Ulcerative colitis primarily affects the colon and rectum, with inflammation limited to the innermost lining (mucosa) and submucosa. This condition presents with continuous inflammation, often starting in the rectum and extending upwards. This chronic inflammation results in measurable colon wall thickening.
Infections and Inflammation
Acute infections are another common cause of colon thickening. Various bacteria, viruses, or parasites can trigger a sudden inflammation of the colon, known as infectious colitis.
One notable bacterial infection is Clostridioides difficile (C. diff). This bacterium can overgrow in the colon, typically after antibiotic use, leading to pseudomembranous colitis. This condition causes significant and often diffuse colon wall thickening, sometimes exceeding 10 millimeters. Other common bacterial culprits include Salmonella and E. coli, often contracted through contaminated food or water. These infections induce inflammatory responses that result in colon wall thickening, which usually resolves once treated.
Diverticular Issues
Diverticular disease can also lead to colon thickening, particularly during episodes of inflammation. Diverticula are small, pouch-like protrusions that can form in the lining of the colon, commonly in the sigmoid colon. While having these pouches (diverticulosis) is common and often harmless, their inflammation or infection is termed diverticulitis.
During diverticulitis, these inflamed pouches cause localized thickening of the colon wall. Imaging often reveals segmental thickening of the bowel wall, which can be symmetric around the affected area.
Reduced Blood Flow
Insufficient blood flow to a segment of the colon can cause ischemic colitis, a condition that results in colon thickening. When the colon tissue does not receive enough oxygen and nutrients due to reduced blood supply, it becomes inflamed and damaged.
The colon is particularly susceptible to reduced blood flow compared to other parts of the digestive tract. Common factors contributing to ischemic colitis include the buildup of fatty deposits in arteries (atherosclerosis), periods of low blood pressure, or the use of certain medications. The thickening observed is due to swelling and sometimes bleeding within the colon wall.
Abnormal Growths
Abnormal tissue growths, both benign and malignant, can contribute to colon thickening. Colon polyps are growths that form on the inner lining of the colon or rectum. While many polyps are harmless, some types have the potential to develop into colon cancer over several years. Larger polyps can cause localized thickening of the colon wall.
Colon cancer, also known as colorectal carcinoma, is a serious cause of colon thickening. As a tumor grows, it infiltrates and expands the colon wall, leading to significant and often irregular thickening. When colon wall thickness exceeds 20 millimeters, it is more likely to be indicative of a malignant cause. Therefore, medical evaluation is important to distinguish between benign growths and cancerous lesions.