Rectal stenosis is a medical condition characterized by an abnormal narrowing or constriction of the lumen of the rectum or the anal canal, the final section of the large intestine. This narrowing restricts the passage of stool, leading to a partial or complete obstruction of bowel contents. The condition affects patients of any age, including infants born with the condition and adults who develop it later in life. This reduction in the passage diameter makes normal bowel movements difficult or impossible.
Causes and Types of Rectal Stenosis
The origins of rectal stenosis fall into two primary categories: congenital (present from birth) and acquired (developing over time). Congenital rectal stenosis is generally classified as a type of anorectal malformation (ARM), involving developmental issues in the formation of the anus and rectum. In some congenital cases, the narrowing is caused by external pressure from an associated pathological condition in the presacral space, such as a teratoma or bony anomaly.
Acquired rectal stenosis in adults frequently results from the formation of scar tissue, which is less flexible than healthy tissue and restricts the canal’s diameter. The most common cause is a complication following anorectal surgery, such as an aggressive hemorrhoidectomy or fistula repair, which leads to excessive scarring. Inflammatory bowel diseases (IBD), particularly Crohn’s disease, can cause chronic inflammation that leads to strictures in the rectum. Other causes include radiation therapy for pelvic cancers, chronic infections, trauma, and the long-term use of laxatives.
Recognizing the Signs
The symptoms of rectal stenosis relate directly to the physical obstruction of the stool passage, causing a noticeable change in bowel habits. Patients most frequently report chronic or severe constipation and significant difficulty passing stool, a condition known as obstructed defecation. This difficulty often leads to straining and can cause pain during defecation, known as dyschezia.
A common sign is a change in the physical appearance of the stool, which may become thin, ribbon-like, or break apart into small pellets. Patients may also experience tenesmus, the persistent feeling of incomplete evacuation after a bowel movement. In severe cases, rectal bleeding can occur due to tears or fissures caused by the passage of hard, narrow stools.
Diagnostic Procedures
The evaluation of rectal stenosis begins with a review of the patient’s medical history and a physical examination. The physician will perform a digital rectal examination (DRE), which can often confirm the presence of stenosis by detecting a reduced anal opening or fibrous scar tissue.
If the stenosis is too painful or narrow for a thorough examination, or if the narrowing is higher in the rectum, imaging studies determine the extent and location of the condition. Contrast studies, such as a barium enema, use a contrast agent to outline the bowel on an X-ray, visualizing the narrowed segment. Cross-sectional imaging, including Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), provides detailed views of the bowel wall and surrounding structures, which is useful for ruling out external compression or malignancy.
Endoscopic procedures, such as colonoscopy or sigmoidoscopy, allow for direct visual inspection of the stenosis. A flexible tube with a camera is inserted to assess the degree of narrowing and the condition of the surrounding tissue. During endoscopy, biopsies can be collected to rule out underlying malignancy or confirm inflammatory conditions like Crohn’s disease. Endoscopic ultrasound (EUS) uses sound waves to create detailed images of the rectal wall layers, helping to determine the depth of the scar tissue.
Management and Treatment Options
Treatment for rectal stenosis is tailored to the underlying cause, the severity of the narrowing, and the symptoms experienced by the patient. For mild cases, conservative, non-surgical approaches are often the first line of treatment and can be highly effective. This primarily involves dietary modifications, such as increasing fiber intake and fluid consumption, to ensure that stools are soft and bulky.
Stool softeners and emollient laxatives are frequently recommended to facilitate the easy passage of stool. If the stricture is mild to moderate, the physician may recommend anal dilation, performed manually or with specialized medical dilators. Dilation helps to stretch the scar tissue, often preventing the need for a more invasive procedure.
When the stenosis is severe, fibrotic, or does not respond to dilation, surgical intervention becomes necessary to restore the normal diameter of the rectum. One common surgical approach is anoplasty, which involves surgically reconstructing the anal canal by removing the restrictive scar tissue. The removed tissue is replaced with a flap of healthy, pliable tissue from the surrounding area, aiming to restore the anal canal’s ability to expand during defecation.
For strictures higher in the rectum, a procedure called stricturoplasty may be performed. This involves making an incision along the length of the narrowed segment and then closing it transversely to widen the lumen. In challenging cases, such as long-segment strictures or those that recur after multiple treatments, a surgical resection and anastomosis may be required to remove the entire diseased section and reconnect the healthy ends of the bowel. If the stenosis is too severe or refractory to surgical repair, a temporary or permanent colostomy may be required to divert the waste passage and relieve the obstruction.