Radiation proctitis overview

# Overview
Radiation proctitis is inflammation and damage to the lower parts of the colon after exposure to x-rays or other ionizing radiation as a part of radiation therapy. Radiation proctitis most commonly occurs after treatment for cancers such as cervical cancer, prostate cancer, and colon cancer. Radiation proctitis involves the lower intestine, primarily the sigmoid colon and the rectum.The rectum is at risk of injury during pelvic irradiation because of its fixed position and close proximity to target organs. In 1897, Walsh was the first to discover the association between X-ray (radiation) and the damaging effect on GIT tract in a person working with the radiation energy.He further reported the improvement in the symptoms if exposure being shielded by the lead. In 1942, the early and late intestinal effect of radiotherapy was first described by Warren and Friedman. Based on the duration of symptoms, Radiation proctitis may be classified as either acute or chronic. The exact pathogenesis of radiation proctitis is not fully understood however it is thought that acute radiation proctitis is due to direct damage of the lining (epithelium) of the colon.Chronic radiation proctitis occurs in part because of damage to the blood vessels which supply the colon and results in full-thickness ischemia and fibrotic changes and ultimately the colon is therefore deprived of oxygen and necessary nutrients. Radiation proctitis must be differentiated from infectious colitis, inflammatory bowel disease, ischemic colitis, medication-associated colitis, chemical colitis, and allergic colitis. The reported incidence of any transient acute radiation proctitis is thought to range from 50% to 100%. The incidence of chronic radiation proctitis is estimated to be 2000-20,000 in every 100,000 radiations. Common complications of radiation proctitis include intestinal obstruction due to stricture, fecal incontinence due to overflow and fistula formation due to concomitant injury to nearby organs. The laboratory findings in a patient with acute radiation proctitis can be within reference range however, in case of chronic injury anemia, elevated white blood cell, deranged LFTs and electrolyte abnormalities can be seen.

# Historical Perspective
X- Ray was first discovered by Wilhelm Roentgen, in 1895. In 1897, Walsh was the first to discover the association between X-ray (radiation) and the damaging effect on GIT tract in a person working with the radiation energy.He further reported the improvement in the symptoms if exposure being shielded by the lead. In 1942, the early and late intestinal effect of radiotherapy was first described by Warren and Friedman.

# Classification
Based on the duration of symptoms, Radiation proctitis may be classified as either acute or chronic.

# Pathophysiology
The exact pathogenesis of radiation proctitis is not fully understood however it is thought that acute radiation proctitis is due to direct damage of the lining (epithelium) of the colon.Chronic radiation proctitis occurs in part because of damage to the blood vessels which supply the colon and results in full-thickness ischemia and fibrotic changes and ultimately the colon is therefore deprived of oxygen and necessary nutrients.

# Causes
Common causes in the development of Radiation proctitis include include dose of radiation, area of the radiation and mode of delivery of the radiation.

# Differentiating radiation proctitis from Other Diseases
Radiation proctitis must be differentiated from infectious colitis, inflammatory bowel disease, ischemic colitis, medication-associated colitis, chemical colitis, and allergic colitis.

# Epidemiology and Demographics
The reported incidence of any transient acute radiation proctitis is thought to range from 50% to 100%. The incidence of chronic radiation proctitis is estimated to be 2000-20,000 in every 100,000 radiations.

# Risk Factors
Common risk factors in the development of Radiation proctitis include include dose of radiation, area of the radiation and mode of delivery of the radiation.

# Screening
There is insufficient evidence to recommend routine screening for radiation proctitis however recent studies shows that the impairment of the rectum's ability to heal may predispose other organs, exposed to the radiation, at high risk of malignant transformation so It has been suggested that patients exposed to higher doses of radiation may need to be more closely screened for other malignancies but further studies need to be conducted before definitive recommendations can be made. The risk of second cancer after irradiation, although probably small, needs nevertheless to be carefully monitored.

# Natural History, Complications, and Prognosis

## Natural History
The symptoms and extent of radiation proctitis are variable and usually develop insidiously. The symptoms depend on the dose and duration of the radiation and how sensitive the bowel is to radiation.

## Complications
Common complications of radiation proctitis include intestinal obstruction due to stricture, fecal incontinence due to overflow and fistula formation due to concomitant injury to nearby organs.

## Prognosis
The prognosis of radiation colitis varies with the sub-type, severity, duration and responsiveness to treatment.

# Diagnosis

## Diagnostic study of choice
There is no definitive diagnostic study of choice for radiation proctitis. Diagnosis of radiation proctitis is primarily clinical; it is based on history, physical examination and endoscopic findings.

## History and Symptoms
The most common symptoms of Radiation proctitis include mild diarrhea, tenesmus, fecal urgency and mucus discharge. Less common symptoms of radiation proctitis include abdominal pain,constipation,severe diarrhea and rectal bleeding.

## Physical Examination
Patients with radiation proctitis may appear pale and dehydrated. Some patients may appear fatigued and in distress, associated with abdominal pain.

## Laboratory Findings
The laboratory findings in a patient with acute radiation proctitis can be within reference range however, in case of chronic injury anemia, elevated white blood cell, deranged LFTs and electrolyte abnormalities can be seen.

## Imaging Findings
Barium studies can be done in patients who have obstructive symptoms or those suspected of having fistulas.

## Other Diagnostic Studies
Other diagnostic studies such as colonoscopy, tissue biopsy and histological analysis can help with the diagnosis of radiation proctitis.

# Treatment

## Medical Therapy
Acute radiation proctitis is a self limiting condition and treated conservatively however in 20% of cases undergoing external beam radiation will require short interruptions in their treatment to improve symptoms.In case of chronic radiation proctitis treatment usually depends upon the severity and pattern of the symptoms.

## Surgery
Surgery is not the first-line treatment option for patients with radiation proctitis.However it is usually reserved as a last resort for patients with refractory symptoms and complications.

## Prevention
Primary prevention of radiation proctitis can be done by the modifications of radiation techniques and doses or by use of prophylactic adjunct medical and surgical therapies.