Imaging of small bowel disease to diagnose the various manifestations of radiation enteropathy is challenging. Conventional X-rays may be difficult to interpret. Therefore, computerized tomography or magnetic resonance enterography, capsule endoscopy, or balloon-assisted enteroscopy is preferred—depending on availability, local expertise, and the suspected pre-procedure diagnosis.
Telangiectasias are not seen on cross-sectional imaging but can be seen with capsule endoscopy (which should not be ordered if stricture is suspected unless a patency capsule has been tried). Single or double balloon enteroscopy (specialized endoscopes intended for reaching the mid and distal ileum), which has been used to treat strictures or telangiectasia in healthy tissues,29 can be difficult or impossible in post-XRT patients because adhesions may limit progress of the scope to the area of interest, and forceful advancement of the scope increases the risk of perforation.
Small bowel telangiectasias can cause chronic occult blood loss, which often requires iron supplementation; acute bleeding may require blood transfusion and hospitalization. Of note, choosing an iron formulation that is well tolerated is critical to avoid (additional) unpleasant GI tract adverse effects. We typically recommend elemental iron with Vitamin C to augment absorption or ferrous gluconate; some patients will require intravenous iron infusion.
Surgery may be advisable to address complications such as fistulous tracts, complex strictures, or bowel obstruction; how-ever, operating on radiated abdominal tissues and ischemic bowel is associated with high morbidity and mortality.4,25,28,30 The surgeon may encounter dense adhesions that make an otherwise “simple” surgery problematic.
For example, it may be difficult to access the desired region and determine the borders of healthy tissue; wide excisions are, thus, often performed, which may result in small bowel failure (ie, short gut syndrome) and a mortality rate in excess of 30%.31 In addition, the ischemic post-XRT tissues may not heal well even if the intended surgery is completed; indeed, anastomotic leaks, failures, and infections are not uncommon. Moreover, another 30% will have other postoperative complications, 40% to 60% may require more than one laparotomy, and 50% of those who recover from the initial surgery will develop recurrence of the fistulous tract or stricture.4,25,28,30
No drug therapy has proven effective for prevention or mechanistically-driven treatment of XRT-induced small bowel injury. Hyperbaric oxygen therapy may be the most promising medical treatment, with early response in 53% of cases and long-term response of 66% to 73% for global symptomatic relief.32 It has been used successfully for treatment of pain, diarrhea, malabsorption, and hemorrhage from mucosal ulcerations, stenosis, and fistulous tracts. When available, it should be considered as a potential therapeutic intervention.
Colon
Injury to the colon is seen in 10% to 20% of patients following XRT for prostate, bladder, cervical, or uterine cancer.33 The maximum tolerated dose of the colon is slightly higher than for the small intestine.34 The rectosigmoid area is the area most commonly implicated, but depending on the field of radiation, injury can be more extensive/proximal.
Acute XRT injury of the colon produces acute mucosal necrosis, which may manifest as bowel dysmotility, diarrhea, cramps, tenesmus, or hematochezia. Sigmoidoscopy or colonoscopy will show mucosal edema, erosions, and ulcerations with a purplish/red discoloration. A barium enema will show spasm of the affected area with so-called “thumbprinting,” which indicates mucosal edema. The onset of symptoms is generally within 3 weeks of XRT initiation; symptoms are self-limited in most cases. Management is centered on symptom relief; loperamide and Lomotil are first-line agents for diarrheal symptoms.
Chronic XRT-related colopathy is the result of chronic tissue ischemia and fibrosis. This may lead to dysmotility resulting in abnormal bowel habits (ranging from constipation to diarrhea) or sigmoid stenosis/stricture resulting in an inability to evacuate the bowel. For the latter, it is important to note that fiber supplementation may not be optimal, since increasing the fecal caliber makes it more difficult to pass through the stenotic, colonic segment.
Emollients such as small doses of mineral oil will not increase the fecal caliber, but will soften fecal matter so that it can be passed with greater ease. MiraLAX may be effective, as well, but can increase the sense of urgency and contribute to incontinence in some. Lactulose can be effective, but it causes excessive gassiness/bloating that may result in abdominal pain and episodes of incontinence.
Bleeding from telangiectasias is another chronic complication of XRT-related colonic injury. Argon plasma coagulation (APC) via flexible sigmoidoscopy or colonoscopy is typically the primary therapeutic approach, reported to have a success rate of up to 90% in healthy tissues.33,35 Even with endoscopic treatment, as mentioned earlier in the context of small bowel XRT-related telangiectasias, iron supplementation is often needed to replete stores, and choice of iron agent is important.
Furthermore, it is essential to recognize that repeat endoscopic sessions may be needed to fully treat telangiectasias, and recrudescence of bleeding months or years later should raise suspicion for recurrent telangiectasia formation (and need for repeat treatment). As with other organs, there may be a role for hyperbaric oxygen, even in difficult-to-treat cases.36,37
Colonic fibrosis/stenosis and fistulous tract formation, as in the small bowel, are also seen in this population of patients. Endoscopic dilation can be considered, and stenting may be reasonable for short and/or distal strictures. Surgical approaches for fistulous tracts and strictures can be high-risk and associated with poor outcomes, mostly because of the underlying chronic tissue ischemia and fibrosis,4,8,27,30,34 as discussed in the small bowel section.