A colonic stricture is a medical condition defined by the abnormal narrowing or tightening of a segment of the large intestine, also known as the colon. This constriction occurs within the hollow passageway, or lumen, of the colon, physically reducing its internal diameter. The presence of a stricture impedes the normal movement of digested material and waste, making it difficult or impossible for stool to pass through the affected area. This narrowing can range from a partial blockage, which allows some liquid or gas to pass, to a complete obstruction, which is a medical emergency.
The Mechanism of Colonic Narrowing
The physical formation of a stricture results from the body’s response to chronic injury or inflammation in the colon wall. When the lining is repeatedly damaged, the body attempts repair through wound healing. This prolonged inflammatory cycle eventually leads to the deposition of collagen and other proteins, resulting in fibrosis, or scarring, within the intestinal wall.
This scar tissue is rigid and lacks the natural elasticity of healthy colon tissue. The accumulation of this non-flexible scar tissue causes the intestinal wall to become stiff and contract inward. This fixed narrowing, known as a fibrotic stricture, physically restricts the passage of contents. While some narrowing is initially caused by acute swelling that may respond to medication, irreversible scar tissue requires different treatment.
Underlying Causes of Stricture Formation
A variety of conditions that damage the colon lining can lead to stricture development, with chronic inflammatory diseases being the most frequent causes. Inflammatory Bowel Disease (IBD) is a significant contributor, particularly Crohn’s disease. Up to half of all Crohn’s patients may develop a stricture, as the characteristic transmural inflammation affects the full thickness of the bowel wall, leading to deep ulcerations and extensive scarring.
Diverticulitis, involving the inflammation of small pouches (diverticula), is another common cause of benign strictures. Repeated episodes of inflammation and infection cause abscess formation and eventual scar tissue buildup in the affected segment, often resulting in a localized constriction in the sigmoid colon.
Other injuries can also precipitate stricture formation. Ischemic colitis occurs when blood flow to a segment of the colon is reduced, causing tissue damage that heals into a scarred, narrowed area. Radiation therapy aimed at pelvic or abdominal cancers can cause radiation proctitis or colitis, leading to chronic inflammation and delayed scarring months after treatment. Colorectal cancer also causes strictures when the physical growth of a tumor mass invades and constricts the colon lumen.
Recognizing the Physical Signs
Symptoms of a colonic stricture arise from the impaired passage of waste through the narrowed segment. A common sign is a progressive change in bowel habits, including increasingly severe constipation or alternating episodes of constipation and diarrhea. Stool may become thin, ribbon-like, or pencil-shaped as it is squeezed through the constriction.
Abdominal pain and cramping are typical, often intensifying after meals as the digestive system attempts to push contents past the obstruction. Significant blockage causes gas and stool to back up, leading to abdominal distension, bloating, and fullness. Near or complete obstruction can cause serious symptoms like nausea and vomiting. Unexplained weight loss, anemia, and fatigue may also develop from chronic inflammation or malabsorption caused by the underlying disease.
Diagnosis and Treatment Options
Physicians use imaging and direct visualization techniques to confirm a stricture and determine its cause. Colonoscopy is often the primary diagnostic tool, allowing visual inspection of the colon lining and assessment of the narrowing. Biopsies can be taken during this procedure to differentiate between benign causes, such as inflammatory scarring, and malignant causes like cancer.
Imaging tests provide a broader view of the stricture’s characteristics, including its length and associated inflammation. A computed tomography (CT) scan visualizes the colon wall and surrounding tissues, helping identify abscesses or complications. Barium studies, such as a contrast enema, involve introducing a liquid contrast agent into the colon to highlight the stricture on an X-ray, providing a clear map of the narrowing.
Treatment is determined by the stricture’s cause and location. For strictures caused by inflammation, such as in Crohn’s disease, medications may be used to reduce swelling and improve passage. If the narrowing is fixed due to scar tissue, endoscopic balloon dilation may be attempted. This minimally invasive procedure involves passing and inflating a specialized balloon within the stricture to stretch and widen the area.
If dilation is unsuccessful, the stricture is too long, or malignancy is a concern, surgical intervention is necessary. The most common surgical approach is resection, where the affected segment of the colon is removed. The remaining healthy ends are then reconnected to restore digestive tract continuity. In certain Crohn’s-related cases, a strictureplasty may be performed to widen the bowel without removing a segment.