Constipation and Prostate Cancer Treatment: Causes and Management

Constipation can happen during prostate cancer treatment, though it’s usually linked to certain medicines (like opioids for pain or anti‑nausea drugs) rather than radiation itself. ^[1] Opioid pain medicines commonly cause constipation, and proactive prevention with fluids, fiber, movement, and stimulant laxatives is often needed. ^[2] External beam radiation to the prostate more often causes loose stools or diarrhea than constipation, but bowel habits can vary by person. ^[3]

Why constipation happens

• Pain medicines (opioids): These slow bowel movement and often cause hard, infrequent stools. Preventive laxatives are usually required when opioids are used for more than a few days. ^[2] Advice typically includes hydration, fiber as tolerated, physical activity, and a stimulant laxative such as senna, sometimes with a stool softener. ^[4]

• Anti‑nausea medicines and some chemotherapy: These can contribute to constipation in some people receiving cancer treatment. ^[1]

• Diet, fluid intake, and reduced activity: Low fiber intake, dehydration, and less movement can worsen constipation during treatment. ^[5]

• Radiation therapy effects: Pelvic radiation commonly leads to gas, bloating, urgency, mucus discharge, or diarrhea rather than constipation, but bowel changes vary and need tailored management. ^[3] During prostate radiation, care teams may guide diet to limit bloating and help you empty your bowels before sessions for comfort and accuracy. ^{[6] [7]}

First‑line self‑care

• Fluids and fiber: Aim for at least 8 glasses of liquids daily if you can, and include fruits, vegetables, whole grains, and prunes or prune juice to add fiber. ^[5] Adjust fiber if you’re receiving radiation and have bloating or loose stools, following your team’s guidance. ^[3]

• Gentle activity: Daily walks or light exercise can stimulate bowel motility. ^[5]

• Regular bathroom routine: Try going at the same time each day and don’t ignore the urge to pass stool. ^[8]

Safe over‑the‑counter options

• Stimulant laxatives (senna): Often recommended preventively with opioids to keep bowels moving. ^[2] These stimulate the bowel to help you have a movement. ^[9]

• Osmotic laxatives (polyethylene glycol/MiraLAX): Draw water into the bowel to ease passage; useful if fiber and stimulants are not enough. ^[9]

• Stool softeners (docusate/Colace): Make stools softer and easier to pass, often used with a stimulant. ^[9]

• Avoid rectal suppositories and enemas unless your clinician approves: These are generally not advised for constipation management in many cancer treatment contexts due to potential rectal irritation. ^[9]

When to call your care team

• No bowel movement or passing gas for 2–3 days, or persistent hard stools or straining. ^[10] Your team can adjust your plan, including prescriptions or diet guidance.

• New rectal pain, bleeding, or sudden change in bowel patterns during radiation, as plans may need adjustment and specific supportive care. ^[3]

Tips tailored to radiation therapy

• Limit bloating before treatment: Following diet guidelines to reduce gas helps keep the bowel out of the radiation field and may lessen side effects. ^[7] Keeping these diet measures through the course of radiation is often helpful. ^[6]

• Timing bowel movements: Trying to pass stool within an hour before radiation sessions can improve comfort and treatment accuracy. ^[6]

Professional support

• Dietitian input: A clinical dietitian can tailor fiber and fluid strategies, especially if you’re balancing constipation with bloating or episodes of loose stools. ^[9]

• Team monitoring: During therapy, your clinical team will track side effects and may suggest diet changes or medications to reduce bowel symptoms. ^[3]

Bottom line

• Constipation is relatively common during prostate cancer care mainly due to pain and anti‑nausea medicines, and sometimes chemotherapy. ^[1] Proactive steps hydration, fiber, movement, and appropriate laxatives are typically effective, and stimulant laxatives with or without stool softeners are often needed when opioids are used for more than a few days. ^[2] Radiation to the prostate more often causes loose stools and bowel urgency, but bowel routines, diet guidance, and symptom‑targeted medications can help you stay comfortable. ^{[3] [6]}