How does refeeding cause constipation and what are the management strategies?

Refeeding-Related Constipation: Mechanisms and Management

Refeeding causes constipation primarily through intestinal dysmotility that occurs when nutrition is reintroduced after a period of starvation or malnutrition, requiring a gradual reintroduction of nutrition with adequate hydration and early implementation of preventive measures to manage this complication. 1

Pathophysiological Mechanisms

Refeeding-related constipation occurs through several mechanisms:

• Gut Microbiota Alterations: Starvation and subsequent refeeding cause significant changes in gut microbiota composition, with imbalances characterized by reduction in beneficial bacteria and overgrowth of potentially harmful bacteria, directly impacting colonic motility and stool consistency 1, 2

• Fluid and Electrolyte Shifts: Reintroduction of carbohydrates leads to insulin release, causing sodium and fluid retention, which reduces intestinal water content, leading to harder stools 1

• Colonic Transit Changes: Studies have shown that patients with severe malnutrition (such as those with anorexia nervosa) often have slow colonic transit initially during refeeding, which typically normalizes after approximately 3 weeks of adequate nutritional intake 3

• Metabolic Derangements: The classic biochemical feature of refeeding syndrome is hypophosphatemia, but it may also feature abnormal sodium and fluid balance, changes in glucose, protein, and fat metabolism, thiamine deficiency, hypokalaemia, and hypomagnesaemia 4

Management Strategy

Prevention

1. Gradual Nutrition Reintroduction:

   • Start with low caloric intake (5-10 kcal/kg/day) in severely malnourished patients 4, 1
   • Slowly increase energy intake over 4-7 days until full nutritional requirements are reached 4
   • Avoid aggressive refeeding which increases risk of constipation and other refeeding complications 1

2. Electrolyte Monitoring and Replacement:

   • Monitor and supplement key electrolytes before and during refeeding 4:
     • Potassium (2-4 mmol/kg/day)
     • Phosphate (0.3-0.6 mmol/kg/day)
     • Magnesium (0.2 mmol/kg IV or 0.4 mmol/kg orally)
   • Closely monitor electrolytes during the first few days of refeeding 1, 5

3. Vitamin Supplementation:

   • Supply vitamin B1 (thiamine) 200-300 mg daily before and during nutritional repletion 4
   • Provide a balanced micronutrient mixture 4

Treatment of Established Constipation

1. Dietary Modifications:

   • Consider fiber-containing feeds which can help with refeeding-related constipation 1
   • Maintain adequate protein intake (at least 1g/kg actual body weight/day) 1
   • Ensure adequate hydration alongside nutritional repletion 1

2. Medication Management:

   • Start with fiber supplementation and/or an inexpensive osmotic agent (polyethylene glycol, milk of magnesia) 4
   • If needed, supplement with a stimulant laxative (e.g., bisacodyl or glycerol suppositories), preferably administered 30 minutes after a meal to synergize with the gastrocolonic response 4
   • Avoid antimotility agents which may worsen constipation 1

3. Monitoring and Adjustments:

   • Monitor bowel movements carefully during refeeding 1
   • Consider implementing breaks in feeding (4-8 hours) to allow normalization of gut function 1
   • Monitor volume of circulation, fluid balance, heart rate and rhythm, as well as clinical status closely 4

Special Considerations

• Risk Assessment: Patients with prolonged starvation (>10 days) and weight loss exceeding 15% are at higher risk for refeeding-related constipation 1

• Timing of Resolution: Colonic transit typically normalizes after approximately 3 weeks of adequate nutritional intake in patients with severe malnutrition 3

• Growth Hormone Treatment: May aggravate hypophosphatemia and potentially worsen refeeding complications including constipation 5

By understanding the mechanisms of refeeding-related constipation and implementing appropriate preventive and management strategies, clinicians can minimize this complication and improve patient outcomes during nutritional rehabilitation.