What is the recommended approach to managing constipation in a patient on hemodialysis, including dietary measures, safe laxatives, and medication adjustments?

Management of Constipation in Hemodialysis Patients

Start with stimulant laxatives (senna or bisacodyl 10-15 mg daily to three times daily) as first-line therapy, with a goal of one non-forced bowel movement every 1-2 days, and escalate systematically to osmotic laxatives if inadequate response occurs within 48-72 hours. 1, 2

Initial Assessment and Prevention

Before initiating treatment, rule out the following conditions:

• Fecal impaction (perform digital rectal examination if suspected) 2
• Bowel obstruction (physical exam and abdominal imaging if necessary) 1, 2
• Metabolic causes: hypercalcemia, hypokalemia, hypothyroidism, diabetes mellitus 1, 2

Discontinue non-essential constipating medications, particularly opioids if possible, anticholinergics, antacids, and calcium-containing phosphate binders if serum phosphorus is low. 1, 2 The case example in the American Journal of Kidney Diseases demonstrates how phosphate binders can worsen constipation and should be held when phosphorus levels are low. 1

Dietary and Lifestyle Modifications

• Increase fluid intake within dialysis restrictions 1, 2
• Increase dietary fiber if adequate fluid intake is maintained (target 11 g/day based on CAPD patient data showing lower constipation rates) 2, 3
• Encourage physical activity when appropriate 1, 2
• Consider adding 40g raw almonds daily as a safe, high-fiber option that improved constipation without significantly affecting potassium or phosphate levels in a 2020 clinical trial 4

Important caveat: Avoid bulk laxatives (psyllium/Metamucil) as primary therapy in hemodialysis patients, especially those with low fluid intake or limited mobility, due to risk of mechanical obstruction. 2

First-Line Pharmacologic Treatment

Initiate stimulant laxatives immediately:

• Bisacodyl 10-15 mg daily to three times daily 1, 2
• OR Senna 2-3 tablets twice to three times daily 1, 2
• Goal: One non-forced bowel movement every 1-2 days 1, 2

Stool softeners (docusate) can be added but evidence suggests stimulant laxatives alone may be sufficient. 2 The combination of senna plus docusate is commonly used but not necessarily superior to stimulants alone. 2

If no response within 48-72 hours, increase bisacodyl to 10-15 mg two to three times daily. 2

Second-Line Treatment (Add Osmotic Laxatives)

When stimulant laxatives alone are inadequate, add osmotic agents:

• Polyethylene glycol (PEG) 17g with 8 oz water once or twice daily - This is particularly effective and safe in hemodialysis patients based on a 2021 case series showing significant reduction in stimulant laxative requirements and improved spontaneous bowel movements. 2, 5
• Lactulose 30-60 mL two to four times daily 1, 2
• Magnesium hydroxide 30-60 mL daily to twice daily - USE WITH EXTREME CAUTION in hemodialysis patients due to risk of hypermagnesemia and potential toxicity 1, 2
• Magnesium citrate 8 oz daily - Avoid long-term use in any patient with renal impairment 2

The combination of stimulant and osmotic laxatives is more effective than either agent alone for rapid relief. 2

Management of Fecal Impaction

If impaction is confirmed:

1. Glycerin suppository 1, 2
2. Mineral oil retention enema 1, 2
3. Manual disimpaction following premedication with analgesic ± anxiolytic 1
4. Bisacodyl suppository (one rectally daily to twice daily) 1, 2
5. Tap water enema until clear 1

Avoid liquid paraffin in bed-bound patients due to aspiration risk. 2

Third-Line Treatment for Refractory Constipation

For Suspected Gastroparesis

Metoclopramide 10-20 mg orally four times daily 1, 2

For Opioid-Induced Constipation

Methylnaltrexone 0.15 mg/kg subcutaneously every other day (maximum once daily) - This peripherally acting μ-opioid receptor antagonist relieves opioid-induced constipation while maintaining pain control. 1, 2

Contraindications for methylnaltrexone: postoperative ileus and mechanical bowel obstruction 1, 2

Naloxegol is an alternative for chronic non-cancer pain patients. 2

For Chronic Idiopathic Constipation

• Lubiprostone (activates chloride channels to enhance intestinal fluid secretion) 2
• Linaclotide (guanylate cyclase-C receptor agonist) 2

Special Considerations for Hemodialysis Patients

Hemodialysis patients have a 3.14 times higher risk of constipation compared to peritoneal dialysis patients due to lower dietary fiber intake (5.9 g vs 11.0 g), higher use of constipating resins (49% vs 3.4%), and suppression of defecation urges during dialysis sessions (78.5% suppress urges). 3

Key medication safety issues:

• Avoid magnesium-based laxatives long-term due to accumulation risk in renal impairment 2
• Hold phosphate binders if serum phosphorus is low (e.g., <2.1 mg/dL) as they contribute to constipation 1
• Perform medication reconciliation at each transition of care to identify constipating medications and prevent prescribing cascades 1

Complementary Therapies

Acupressure at true acupressure points three times weekly during hemodialysis significantly increased defecation frequency (13.73 vs 10.06 times in 4 weeks) and improved stool consistency in a 2019 randomized controlled trial. 6

Clinical Significance

Constipation in hemodialysis patients is associated with serious outcomes: a 2025 cohort study of 35,230 hemodialysis patients found that chronic constipation requiring laxatives was associated with 15% higher composite cardiovascular events or death, 16% higher ischemic stroke, and 14% higher all-cause mortality over 5.4 years of follow-up. 7 This underscores the importance of aggressive constipation management in this population.