Radiotherapy is a highly effective treatment often used for cancers located in the pelvis, such as prostate, cervical, rectal, and bladder malignancies. While radiation precisely targets and destroys cancer cells, it can also unintentionally affect the healthy tissues of the gastrointestinal tract that lie within the treatment field. This unintended exposure can lead to side effects that manifest long after the primary cancer treatment has concluded. This article focuses on the chronic, long-term bowel problems that can emerge months or even years following the completion of pelvic radiation therapy.
Understanding Chronic Bowel Injury After Radiotherapy
The long-term damage to the bowel is medically defined based on the affected location, referred to as Chronic Radiation Proctitis when the rectum is involved, or Chronic Radiation Enteritis when the small intestine is affected. This condition is fundamentally different from the acute symptoms experienced during or immediately after treatment, which are typically temporary inflammation of the mucosal lining. Chronic injury is an indolent, progressive disease resulting from permanent structural changes within the bowel wall. The primary mechanism involves damage to the tiny blood vessels supplying the tissue, a process known as obliterative endarteritis.
This vascular damage gradually diminishes blood flow, leading to chronic low-grade ischemia, or lack of oxygen, in the affected area. Over time, the body attempts to repair this damage by producing excessive scar tissue, a process called fibrosis. This fibrosis causes the bowel wall to become thick, stiff, and less flexible, permanently impairing its ability to function normally. The chronic injury can begin to manifest anywhere from three months to several decades after the radiation course is completed, often presenting as a progressive worsening of bowel habits.
Specific Long-Term Gastrointestinal Symptoms
When the rectum is affected (proctitis), the most common symptom is chronic rectal bleeding, which arises from fragile, abnormal blood vessels called telangiectasias that form on the damaged mucosal surface. Patients frequently experience tenesmus, which is the persistent, painful feeling of needing to pass stool even when the rectum is empty, along with an urgent need to defecate. Diarrhea, sometimes mixed with mucus, and fecal incontinence are also common due to the rectum’s reduced capacity and elasticity caused by fibrosis.
When the small intestine is the primary site of injury (enteritis), symptoms often relate to malabsorption and obstruction. Chronic inflammation and fibrosis can cause narrowing of the intestinal lumen, leading to strictures that result in colicky abdominal pain and partial bowel obstructions. Malabsorption can occur because the damaged small bowel cannot properly absorb nutrients, which may manifest as chronic diarrhea or weight loss. In more advanced cases, severe tissue damage can lead to the formation of fistulas, which are abnormal connections between the bowel and other organs, such as the bladder or vagina.
Diagnostic Procedures and Medical Evaluation
The evaluation process begins with a thorough review of the patient’s history, including the previous cancer diagnosis, the type and dose of radiation received, and a detailed description of the onset and nature of the current bowel symptoms. A central goal of the medical evaluation is to rule out a recurrence of the original cancer, which can present with similar symptoms like bleeding or obstruction. Blood work may be used to check for anemia resulting from chronic blood loss or nutritional deficiencies linked to malabsorption.
Imaging studies, such as computed tomography (CT) or magnetic resonance imaging (MRI), are often employed to visualize the structure of the bowel and surrounding tissues. These scans help assess for complications like strictures, fistulas, or signs of bowel obstruction, and are particularly useful for detecting any suspicious masses that could indicate recurrent malignancy. Endoscopy, typically a flexible sigmoidoscopy or colonoscopy, allows a physician to directly view the characteristic mucosal changes. During this procedure, the bowel lining may appear pale, fragile, and contain the tell-tale clusters of telangiectasias.
While endoscopy confirms the visual signs of injury, biopsies are generally approached with caution because the damaged, fibrotic tissue is prone to poor healing and potential perforation. A biopsy may be necessary in specific instances where a mass or ulcer is present, in order to distinguish between radiation damage and a cancerous lesion. Specialized tests, such as hydrogen breath tests, may also be used to detect small intestinal bacterial overgrowth, which is a common complication contributing to chronic diarrhea and malabsorption in radiation enteritis.
Comprehensive Management and Treatment Options
Treatment for chronic radiation-induced bowel problems is often multifaceted, focusing on managing symptoms and healing the damaged tissue. The initial approach involves dietary and lifestyle adjustments, such as maintaining good hydration and adopting a low-residue diet to reduce the bulk and frequency of stools. Identifying and avoiding specific irritants, including caffeine, high-fat foods, and dairy products if lactose intolerance is present, can significantly mitigate symptoms. A physician may also recommend specific nutritional supplements to correct deficiencies caused by chronic malabsorption.
Medical treatments are primarily aimed at symptom control and may include oral medications like anti-diarrheal agents, such as loperamide, to slow bowel transit and reduce urgency. For diarrhea caused by impaired bile acid absorption, known as bile acid malabsorption, medications like cholestyramine can bind the bile acids and reduce their irritating effect on the colon. Topical treatments, such as sucralfate or corticosteroid enemas, are often prescribed for proctitis to directly coat and protect the inflamed rectal lining, promoting healing and reducing bleeding.
When chronic rectal bleeding persists, procedural interventions are often necessary, with Argon Plasma Coagulation (APC) being the most common and effective endoscopic technique. APC uses a beam of argon gas and electrical current to coagulate and seal the fragile telangiectasias, controlling the hemorrhage and often requiring multiple treatment sessions. For patients with severe, non-healing ulcers or damage that is refractory to other treatments, Hyperbaric Oxygen Therapy (HBOT) may be considered, as it delivers high-concentration oxygen to promote the growth of new blood vessels and tissue healing in ischemic areas. Surgery is reserved as a last resort, typically for serious complications like complete bowel obstruction caused by a stricture, or for complex fistulas that have not responded to other therapy.