Radiation, Microscopic, Ischemic Colitis
Colitis spans a spectrum of pathologies. This chapter focuses on colitides that affect a large number of patients but may not always be appreciated. Microscopic colitis, for example, has been found to affect up to 30 % of patients over the age of 70 with
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Key Concepts • Microscopic colitis is likely an underappreciated diagnosis. Although there is no “cure,” the quality of life for a patient can be improved significantly with treatment which is typically medical and rarely surgical. • Budesonide is the only evidence-based treatment for microscopic colitis • Radiation colitis and proctitis spans a time course that ranges from acute to chronic which require different management strategies. Patients can present with problems even after 30 years of being asymptomatic. • Colorectal cancer risk is increased with pelvic radiation and patients should be screened 5 years after completion of therapy. • Surgical treatment for radiation proctitis/colitis should be individualized and based on the clinical context of the patient as morbidity and mortality rates are high postoperatively. • Ischemic colitis represents the most common cause of gastrointestinal ischemia. The clinical picture has a wide spectrum ranging from mild cases with minimal mucosal ischemia to severe cases associated with transmural necrosis. Management and investigations need to be tailored depending on the clinical scenario encountered and patients require close vigilance by the surgeon.
Radiation Colitis Introduction An understanding of radiation injury to the colon and anorectal area is important for a coloproctologist. It is estimated that approximately 50 % of treatment protocols for cancer involve the use of radiation [1]. With malignancies such as anal cancer increasing, and a higher number of cancer survivors, the colorectal surgeon will continue to
encounter post-radiation problems. The areas covered in this section consist of (1) pathogenesis, (2) prevention, (3) presentation, and (4) treatment. An important aspect to keep in mind while reading this section is the lack of high-quality evidence; an attempt has been made to provide the reader with recommendations based on the best evidence available.
Pathogenesis of Radiation Injury The two main forms of radiation delivery are external beam radiation therapy (EBRT) and brachytherapy [2]. External beam is what we encounter most and is delivered via linear accelerators which produce high-energy X-rays. The planning is typically done in three dimensions with CT (computed tomography) images. Gray (Gy) is the standard unit to indicate the amount of absorbed radiation. Fractionation refers to giving the total dose over multiple sessions—for example, 50 Gray of radiation could be given over 25 sessions with 2 Gy per session. Fractionation is done to minimize collateral tissue damage while maximizing tumor destruction. Conformal radiation refers to the use of metal plates (multileaf collimators) to bend the X-rays in order to target the tumor and minimize radiation to normal tissue. Brachytherapy refers to placement of the radiation source inside the body—i.e., beads or pellets. Radiation damage has been described through the “target cell” theory. This theory focused on the epithelium of the bowel and explained acute effects through the damage done to this l
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