Management of Watery Stool in Newborns
The cornerstone of managing watery stool in newborns is immediate assessment of hydration status followed by oral rehydration therapy (ORS) with continued feeding—never withhold breast milk or formula for more than 4 hours. 1, 2
Immediate Assessment
Assess dehydration severity by examining the following clinical signs in order of reliability 1, 2:
- Skin turgor and capillary refill time (most predictive) 1
- Mental status (lethargy or irritability) 1
- Mucous membranes (dry vs. moist) 1
- Sunken eyes 1, 3
Weigh the infant immediately to establish baseline and monitor treatment response 1, 2
Categorize dehydration severity 1, 2:
- Mild (3-5% fluid deficit): Increased thirst, slightly dry mucous membranes
- Moderate (6-9% fluid deficit): Loss of skin turgor, skin tenting, dry mucous membranes
- Severe (≥10% fluid deficit): Lethargy/altered consciousness, prolonged skin tenting >2 seconds, cool extremities, decreased capillary refill, rapid deep breathing
Rehydration Protocol
For mild dehydration (3-5%): Administer 50 mL/kg of ORS containing 50-90 mEq/L sodium over 2-4 hours 1, 2
For moderate dehydration (6-9%): Administer 100 mL/kg of ORS over 2-4 hours 1, 2
For severe dehydration (≥10%): This is a medical emergency requiring immediate IV rehydration with 20 mL/kg boluses of Ringer's lactate or normal saline until pulse, perfusion, and mental status normalize 1, 2
Administration Technique
Give small, frequent volumes using a teaspoon, syringe, or medicine dropper—start with 5 mL every 1-2 minutes and gradually increase as tolerated 1, 4, 5. This approach is critical because allowing a thirsty infant to drink large volumes rapidly will worsen vomiting 4.
Reassess hydration status after 2-4 hours and continue rehydration if still dehydrated 1, 2
Feeding Management During Diarrhea
Continue breastfeeding on demand throughout the entire episode without interruption—breast milk reduces stool output compared to ORS alone 1, 2, 5
For formula-fed infants, immediately resume full-strength, lactose-free or lactose-reduced formula after rehydration—this reduces both stool output and duration of diarrhea by approximately 50% compared to gradual reintroduction 1, 2. When lactose-free formulas are unavailable, use full-strength lactose-containing formula under supervision 1.
Never dilute formula or delay full-strength feeding—this worsens nutritional outcomes and prolongs diarrhea 2, 6
Replace Ongoing Losses
Administer 10 mL/kg of ORS for each watery stool and 2 mL/kg for each episode of vomiting throughout both rehydration and maintenance phases 1, 2
Critical Contraindications
Antidiarrheal agents (including loperamide) are absolutely contraindicated in newborns and all children under 2 years due to risks of respiratory depression, cardiac arrest, and death 2, 4
Avoid cola drinks, plain water, or homemade solutions—these contain inadequate sodium and excessive osmolality, which worsens diarrhea 5, 6
Stool cultures are NOT needed for typical acute watery diarrhea in immunocompetent infants 1
Red Flags Requiring Immediate Return
Instruct caregivers to return immediately if the infant develops 1, 2:
- Severe lethargy or irritability
- Sunken eyes or very poor skin turgor
- Intractable vomiting preventing oral intake
- Bloody diarrhea (dysentery)
- Decreased or absent urine output
- High fever or signs of sepsis
Common Pitfalls to Avoid
Do not diagnose lactose intolerance based solely on stool pH <6.0 or reducing substances >0.5%—true lactose intolerance requires clinical worsening with lactose reintroduction 1, 2. Only 5-10% of infants develop true lactose intolerance 6.
Do not withhold feeding to "rest the gut"—early refeeding shortens the duration of diarrhea 1, 5
Do not use antibiotics unless dysentery (bloody diarrhea), high fever, or watery diarrhea lasting >5 days is present 2, 6