What is the recommended polyethylene glycol (PEG) disimpaction dose for a child with fecal impaction?

Polyethylene Glycol Disimpaction Dose in Pediatrics

For fecal disimpaction in children, administer PEG 3350 at 1.0 to 1.5 g/kg/day for 3 to 6 consecutive days, with the higher doses (1.0-1.5 g/kg/day) achieving significantly superior disimpaction rates (95%) compared to lower doses (55%). 1

Evidence-Based Dosing Protocol

Standard Disimpaction Regimen

• Administer PEG 3350 at 1.5 g/kg/day for 4 consecutive days before any planned procedure, with a clear liquid diet on the fourth day 2, 3
• For acute fecal impaction treatment, use 1.0 to 1.5 g/kg/day for 3 days minimum, as these doses achieve 95% disimpaction success versus only 55% with lower doses (0.25-0.5 g/kg/day) 1
• Median time to complete disimpaction is 6 days (range 3-7 days) when using age-appropriate dosing: 4 sachets/day for ages 2-4 years, 6 sachets/day for ages 5-11 years 4

High-Dose Intensive Protocol (Severe Impaction)

• For severe fecal impaction with palpable fecaloma, use 6-8 sachets (approximately 2-3 g/kg/day) on days 1-2, then reduce to 2-6 sachets on day 3, which produces median stool output of 2.2 liters over 7 days 5
• Children begin defecating within 10-12 hours and reach maximum stool volume (approximately 1 liter/day) by day 2 6
• This intensive regimen achieves 92% disimpaction success without requiring invasive interventions like enemas or hospitalization 4

Critical Safety Monitoring Requirements

Hydration Surveillance (Non-Negotiable)

• Monitor clinical hydration status every 1-2 hours during preparation, specifically assessing capillary refill time, skin turgor, mucous membrane moisture, mental status, perfusion quality, and respiratory pattern 2, 3
• Measure baseline body weight and monitor daily: 3-5% weight loss = mild dehydration, 6-9% = moderate dehydration, ≥10% = severe dehydration requiring immediate IV rehydration 2, 3
• Track urine output, urine specific gravity, and ensure adequate oral fluid intake throughout the preparation period 3

Immediate IV Rehydration Triggers

• Initiate isotonic IV fluids (lactated Ringer's or normal saline) immediately if any of the following occur: severe dehydration (≥10% fluid deficit) with shock or near-shock, altered mental status, inability to tolerate oral fluids, persistent vomiting, or serum sodium abnormalities 2, 3

Electrolyte Monitoring

• Check serum electrolytes when clinical signs suggest abnormalities, particularly serum sodium (watch for <135 or >145 mmol/L), serum potassium (hypokalemia common with PEG), BUN, creatinine, and hematocrit 3

Comparative Efficacy and Safety

PEG vs. Enemas

• PEG 1.5 g/kg/day for 6 days achieves 68% disimpaction success, comparable to enemas (80%, P=0.28), but causes more fecal incontinence and watery stools while avoiding the behavioral distress associated with enemas 7
• Both treatments normalize colonic transit time equally (P=0.85), making them equivalent first-line options 7

PEG vs. Sodium Phosphate (Critical Safety Distinction)

• PEG 3350 causes significantly fewer mucosal lesions (2.3%) compared to sodium phosphate (24.5%), making it the definitively safer choice 2, 8
• Sodium phosphate preparations are absolutely contraindicated in children under 12 years due to risk of severe electrolyte disturbances, hyperphosphatemia, hypocalcemia, hypernatremia, and acute kidney injury 2, 8

Adverse Effects and Management

Expected Side Effects

• Common adverse effects include nausea (5%), vomiting (5%), bloating (18%), cramping (5%), and diarrhea (13%), with bloating and diarrhea more prevalent at higher doses (1.0-1.5 g/kg/day) but not clinically prohibitive 1
• No clinically significant electrolyte changes occur with PEG 3350 at disimpaction doses 1

Tolerance Optimization

• To reduce nausea and vomiting, do not allow children to drink ad libitum from a cup or bottle; instead, use controlled administration with motivation techniques (e.g., making it a "race" to drink the laxatives) 6, 3

High-Risk Populations Requiring Dose Adjustment

• Consider additional bowel purgatives or extended preparation time (beyond standard 3-4 days) in children with: prior inadequate bowel preparation, history of chronic constipation, prior colon resection, diabetes mellitus, spinal cord injury, or use of constipating medications (especially opioids) 2, 8, 3

Maintenance After Disimpaction

• After successful disimpaction, reduce PEG 3350 to 1 sachet daily (approximately 0.4 g/kg/day) as maintenance therapy, titrating every 3 days based on stool frequency and consistency to achieve 1-2 soft stools per day 6, 9
• PEG 3350 is significantly more effective than lactulose for preventing reimpaction (0% vs. 23% reimpaction rate, P=0.011) and maintains efficacy over 6 months without loss of effect 4, 9

Common Pitfalls to Avoid

• Do not rely solely on sunken fontanelle or absence of tears to assess dehydration; these are less reliable than capillary refill, skin turgor, and perfusion 3
• Do not ignore early signs of dehydration, as progression to severe dehydration constitutes a medical emergency 3
• Do not use adjunctive agents (simethicone, prokinetics, spasmolytics, probiotics) routinely, as they are not recommended and provide no additional benefit 2, 8
• Never use sodium phosphate preparations in children under 12 years, regardless of clinical scenario 2, 8