Rectal stenosis, also known as rectal stricture, is an abnormal narrowing of the rectal passage that restricts the normal movement of stool. This constriction of the lower gastrointestinal tract lumen presents a partial or complete obstruction to the body’s natural waste elimination process. The condition is considered serious because it can lead to severe complications, including bowel obstruction and fecal impaction, requiring prompt medical intervention. Rectal stenosis can be caused by various factors, but the underlying mechanism often involves the formation of inelastic scar tissue within the rectal wall, which prevents the passage from dilating normally during defecation. A diagnosis of this condition usually means the rectal opening is so narrow that a standard medical scope cannot pass through the affected cross-section.
Common Causes and Risk Factors
The primary reason for acquired rectal narrowing is the development of non-flexible scar tissue. The most common cause of benign rectal stricture is scarring that develops following colorectal surgery, particularly after procedures like a low anterior resection for cancer or a hemorrhoidectomy. When surgeons connect two ends of the bowel after removing a diseased section, the resulting surgical connection, or anastomosis, can sometimes heal with excessive fibrosis, leading to a constricted passage. Up to 74% of all reported benign rectal strictures are formed after an anastomosis.
Inflammatory Bowel Disease (IBD) is another significant cause, accounting for approximately 20% of benign cases, with Crohn’s disease being a particular risk factor. Chronic inflammation from Crohn’s disease causes transmural damage, leading to layers of scar tissue, or fibrosis, that stiffen and narrow the rectal wall. Similarly, radiation therapy used to treat pelvic cancers, such as those of the prostate or cervix, can induce chronic inflammation in the rectum, known as radiation proctitis. This injury eventually results in the formation of tough, fibrous tissue that causes a stricture, often presenting months to years after the initial treatment.
Other less frequent causes include severe infections, trauma, and certain venereal diseases. While the majority of cases are acquired in adulthood, some individuals are born with the condition, known as congenital stenosis.
Signs and Symptoms of Rectal Stenosis
The physical narrowing of the rectum causes symptoms related to obstructed defecation, which worsen as the stricture becomes tighter. The most noticeable manifestation is progressive constipation, characterized by increasing difficulty and straining when attempting to pass stool. This chronic difficulty can evolve into obstipation, a severe form of constipation where the patient is unable to pass either stool or gas.
Many patients experience tenesmus, the sensation of incomplete bowel evacuation, making them feel like they constantly need to have a bowel movement. A characteristic sign is a change in the shape of the stool, which appears thin, narrow, or ribbon-like as it is squeezed through the constricted rectal opening. The effort required to push stool through the narrow passage can also lead to pain during bowel movements and, in some cases, bright red rectal bleeding. In severe instances, the inability to pass waste can result in fecal impaction, where a hard mass of stool becomes lodged above the stricture, creating a medical emergency.
Diagnostic Procedures and Treatment Approaches
Diagnostic Procedures
Diagnosis begins with a physical assessment, including a detailed review of the patient’s history of constipation, surgeries, or inflammatory conditions. A digital rectal examination (DRE) is the first step, where the clinician manually checks for a narrowed passage; a stricture may be defined as a narrowing that cannot accommodate a finger’s width. Imaging studies are then used to visualize the stricture’s length and severity, which may include contrast studies like a barium enema or a CT scan.
Endoscopy, specifically a colonoscopy or sigmoidoscopy, is a primary diagnostic tool, allowing direct visualization of the stricture and the surrounding tissue. During this procedure, the physician determines if the stricture is benign or if a biopsy is needed to rule out recurrent cancer. The inability to pass a standard colonoscope through the stricture confirms its presence and guides the selection of the appropriate treatment method.
Treatment Approaches
Treatment selection depends on the stricture’s cause, length, and severity. For milder, benign strictures, the first-line approach is endoscopic balloon dilation. This procedure involves inserting a specialized balloon catheter through an endoscope and inflating it within the narrowed segment to gently stretch the scar tissue. Dilation is a safe method and can often be performed on an outpatient basis, although the stricture may recur, requiring repeat sessions. Sometimes, a steroid medication like triamcinolone is injected directly into the scar tissue during dilation to help prevent the stricture from reforming.
If the stricture is long, severe, or fails to respond to multiple dilation attempts, surgical intervention becomes necessary.
Surgical Options
One common surgical approach is stricturoplasty, where incisions are made in the scar tissue to widen the passage without removing a segment of the bowel. For the most complex strictures, particularly those caused by extensive scarring or cancer, a resection may be performed. This involves surgically excising the narrowed segment and then performing an anastomosis to reconnect the healthy bowel ends. Temporary measures like placing a stent may also be used to keep the passage open, particularly in palliative care settings.