Radiation colitis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Qasim Salau, M.B.B.S., FMCPaed [2]

Synonyms and keywords:

Overview

Radiation therapy is a common treatment modality for Abdominal and pelvic malignancy. Radiation colitis may complicate this radiotherapy. Radiation colitis tends to develop insidiously and it is often progressive.

Pathophysiology

• Occur following radiation therapy for Abdominal and pelvic malignancies .
• More common with radiation doses higher than 45Gy.
• The main site of damage is the DNA. Pathogenesis involves direct ionizing damage to the DNA resulting in inhibition mitosis. Radiation may also affect RNA, proteins and cell membranes. Oxidative injury to the DNA may also be contributory to the development of radiation colitis.
  • Injury occur few hours to days, up to three months after irradiation in acute radiation colitis. It affects rapidly dividing cells of the epithelium and mucosa crypts. This leads to cell death, recruitment and activation of polymorphonuclear (PMN) inflammatory cells, mucosal edema and damage to small blood vessels. The effect of this damage to the mucosa is fluid, electrolyte and nutrient loss. Radiation also reduces bowel motility. Acute radiation colitis is usually transient and self limiting, with regeneration of the epithelium.
  • In chronic radiation colitis, mesenchymal tissue is involved. The damage is progressive with atrophy of the mucosa, fibrosis of the intestinal wall, obliteration of small arteries, chronic ischemia, ulcers, strictures and fistula formation. This changes usually occur three months to years after radiation. Secondary colonic malignancy may occur.

Genetics

There is no specific genetic cause for radiation colitis.

Gross Pathology

Endoscopy should be gentle and with care especially in acute radiation colitis.

• The mucosa may appear erythematous or pale, is edematous, friable with or without small erosions in acute radiation colitis.
• In chronic radiation colitis, mucosa atrophy, fibrosis, obliterative arteritis, stenosis, strictures, fistula and ulcers are seen.

Microscopic Histopathology

Histopathological findings of radiation colitis may be categorized into the following

• Acute: Reduced mitosis, increased apoptosis bodies, mucin depletion, eosinophilia, presence of crypt abscesses and evidence of regeneration
• Chronic: Dilated capillaries and lymphatics, hyaline fibrosis, atypical fibroblast and endothelial cells and distortion of the crypts.

Differentiating radiation colitis from other Diseases

Symptoms of acute radiation proctitis may overlap with other causes of acute colitis, but prior history of radiation will help in distinguishing the cause. Differential diagnosis of acute radiation colitis include:

• Allergic colitis
• Chemical colitis
• NSAID induced colitis
• Ischemic colitis

Differential diagnosis of chronic radiation colitis include:

• Ischemic colitis
• Inflammatory bowel disease

Epidemiology and Demographics

The exact prevalence and incidence of radiation colitis is not certain due to different methods of definition. The incidence of acute radiation injury to the bowel is said to be about 75% to 80% of patients receiving pelvic radiotherapy, while 15% to 20% of patients receiving pelvic radiotherapy will develop chronic radiation injury to the bowel.

Age

The prevalence of radiation colitis is more among older age group (over 60 years) patients. This may be a reflection of the increase frequency of predisposing malignancy requiring radiotherapy in this age group.

Gender

Men and women are affected equally by radiation colitis.

Race

There is no racial predilection to radiation colitis.

Risk Factors

Common risk factors for developing radiation colitis include:

• Radiation dose greater than 54 Gy
• Elderly (above 60 years)
• Past radical abdominal or pelvic surgery such as radical hysterectomy and radical colectomy
• Asthenic individuals
• Smoking
• Chronic co-morbid medical diseases such as diabetes mellitus, hypertension and atherosclerosis
• Past pelvic inflammatory disease
• Collagen vascular disease
• HIV infection- Hypothesized to increase risk for radiation toxicity in the colon

Screening

There are no established screening guidelines for radiation colitis

Natural History, Complications and Prognosis

Natural History

The symptoms and extent of radiation colitis are variable and usually develop insidiously. The symptoms depend on the dose and duration of the radiation and the how sensitive the bowel is to radiation. In acute radiation colitis, symptoms usually starts shortly after commencement of radiation therapy and progress reaching a peak 1 to 2 weeks later. The symptoms of acute radiation colitis may not start for up to 3 months after commencement of radiation. In most cases, the symptoms of acute radiation colitis are self-limiting and resolve following termination of radiation therapy. The symptoms of chronic radiation colitis often become noticeable months to years after the completion of radiotherapy. The symptoms may occasionally follow acute radiation colitis. However, previous acute radiation colitis does not increase the risk of a patient developing chronic radiation colitis. Also, absence of acute radiation colitis, does not prevent chronic radiation colitis from occurring. injuryTreatment is required for chronic radiation colitis because resolution of the symptoms is uncommon without intervention.

Complications

Possible complications of radiation colitis include:

• Anemia
• Intestinal obstruction
• Intestinal perforation
• Fistula
• Fecal incontinence
• Strictures
• Malabsorption
• Failure to thrive
• Sepsis due to loss of the mucosal protective barrier
• Secondary malignancy (uncommon)

Prognosis

The prognosis of radiation colitis varies with the subtype, severity, duration and responsiveness to treatment.

• Acute radiation colitis is usually self-limiting, with resolution of symptoms few weeks after stopping radiotherapy.
• Chronic radiation colitis is progressive and difficult to manage. The patients may develop secondary radiation-associated malignancy which has a poor prognosis due to late diagnosis.

Diagnosis

Diagnostic Criteria

There is no definitive diagnostic criteria for radiation colitis. Diagnosis of radiation colitis is primarily clinical; it is based on history, physical examination and endoscopic findings.

Symptoms

Obtaining a complete history including dietary history is an important aspect in making a diagnosis of radiation colitis. It provides insight into the cause, and any associated underlying conditions. Radiation colitis should be suspected in any individual who presents with intestinal symptoms and has a previous history of abdominal and/ or pelvic radiotherapy. Symptoms of radiation colitis may be categorized according to duration as follows:

Acute radiation colitis

• Diarrhea
• Abdominal pain which is colicky (cramping and intermittent)
• Nausea
• Urgency
• Fecal frequency
• Tenesmus
• Mucus discharge
• Rectal bleeding

Chronic radiation colitis

• Symptoms of acute radiation colitis
• Rectal bleeding, which may be severe
• Symptoms of sepsis
• Constipation
• Abdominal pain
• Abdominal distension
• Vomiting
• Fecal vomiting especially when stricture develops

Physical Examination

Physical examination findings may reveal:

• Signs of dehydration such as lethargy, Tachycardia and Hypotension
• Abdominal tenderness which may be more prominent in lower abdominal quadrants due to involvement of the distal sigmoid colon and/ or rectum
• Fever due to dehydration or in individuals who have developed sepsis
• Pallor
• Toxic appearance in those with bowel perforation and sepsis

Laboratory Findings

Initial investigations should include hematological, biochemistry profiles and stool examination.

Hematology

• Anemia
• Leukocytosis with left shift may be seen with sepsis common, but leukopenia can be seen.

Electolytes

• Hyponatremia

Stool Examination

Stool analysis may show

• Fecal blood
• Fecal leukocytes
• Microorganism on stool culture in case of sepsis

Imaging Findings

Endoscopy is important to confirm the diagnosis of radiation colitis. However, endoscopy should be done with care due to the fragile nature of the bowel following radiation therapy. Biopsy is generally not recommended during endoscopy especially in acute radiation colitis

Endoscopy

• Features seen in acute radiation colitis on endoscopy include friable, hyperemic, edematous mucosa with/ or without ulcers that are often shallow. The features seen in acute radiation colitis are limited to the superficial parts of the colonic mucosa
• Chronic radiation colitis involves the whole of the colonic mucosa. Features include mucosal pallor, fibrosis, strictures, ulcers and telangiectasias which bleeds easily. The colonic wall is often rigid

Other Diagnostic Studies

Other diagnostic studies in radiation colitis include:

Barium enema

May show decreased peristalsis and distention of the colon, stenosis, presence of ulcers and fistulas. It is less sensitive to endoscopy

CT

CT findings include increased density and fibrosis of the pericolonic fat, fascia and colonic wall. Difficult to distinguish between radiation colitis and cancer.