From the Guidelines
Radiation therapy is more likely to cause diarrhea than constipation in patients, especially those undergoing pelvic or abdominal radiation treatment. The evidence from studies 1 suggests that radiation-induced intestinal injury can lead to diarrhea, with approximately 60% of patients experiencing temporary mild diarrhea during pelvic radiation treatment. The risk factors for developing radiation-induced intestinal injury include patient-related factors such as low BMI, comorbid diseases, and smoking history, as well as treatment-related factors like the volume of small bowel in the radiation field, radiation dose, and concomitant chemotherapy administration.
The pathophysiology of radiation-induced diarrhea involves damage to the intestinal mucosa, leading to malabsorption of nutrients, lactose intolerance, and altered intestinal transit time. Additionally, radiation can cause inflammation and fibrosis in the intestinal wall, leading to chronic diarrhea and other gastrointestinal symptoms. The studies 1 highlight the importance of identifying and managing radiation-induced diarrhea to improve patient outcomes and quality of life.
In terms of managing radiation-induced gastrointestinal symptoms, patients should be advised to:
- Stay well-hydrated by drinking plenty of fluids
- Increase dietary fiber intake gradually
- Maintain physical activity as tolerated
- Consider using gentle laxatives or anti-diarrheal medications as needed
- Consult their healthcare provider if symptoms persist or become severe
It is essential to note that while constipation can occur in some patients undergoing radiation therapy, the evidence suggests that diarrhea is a more common and significant side effect, particularly in those receiving pelvic or abdominal radiation treatment 1. Therefore, healthcare providers should prioritize monitoring and managing diarrhea in patients undergoing radiation therapy to minimize its impact on patient outcomes and quality of life.
From the Research
Radiation and Constipation
- Radiation therapy, particularly to the abdomen or pelvis, can cause constipation as a side effect, although it is more commonly associated with diarrhea 2.
- A study published in the Annals of Palliative Medicine found that constipation was more prevalent than diarrhea during radiation treatment and up to day 10 after radiation to the pelvis, with approximately 42% of patients experiencing constipation on day 10 post-radiation 2.
- The use of anti-emetic medications, such as serotonin (5-HT3) receptor antagonists, can also contribute to constipation in patients undergoing radiation therapy 2.
Management of Constipation
- Various agents are used to manage chronic constipation, including bulk and fiber products, lubricating agents, stimulants, and osmotic laxatives 3.
- A survey of hospice organizations found that the most commonly used preparations for the treatment of opioid-induced constipation were senna plus docusate, senna alone, docusate alone, bisacodyl, polyethylene glycol 3350, and lactulose 4.
- A randomized controlled trial found that an osmotic laxative was more effective at achieving lower rectal gas levels than a bulking laxative with probiotic in patients undergoing external beam radiation therapy for prostate cancer 5.
Radiation Therapy and Bowel Function
- A study published in the American Journal of Clinical Oncology found that patients with inflammatory bowel disease who underwent abdominal and pelvic radiation therapy experienced low toxicity, with acute grade ≥3 toxicity occurring in 11% of patients and late grade ≥3 toxicity occurring in 6% of patients 6.
- The use of intensity-modulated radiation therapy (IMRT) was associated with decreased acute toxicity compared to 3-dimensional conformal radiotherapy (3D-CRT) 6.