What is the best course of treatment for a 10-month-old infant with a one-week history of diarrhea?

Management of One-Week Diarrhea in a 10-Month-Old Infant

Oral rehydration therapy (ORS) with commercially available reduced-osmolarity solutions is the cornerstone of treatment, combined with immediate resumption of age-appropriate feeding after rehydration is achieved. 1, 2

Immediate Assessment

Clinically evaluate the infant's hydration status using these specific signs 1:

• Mild dehydration (3-5% deficit): Thirst, slightly decreased skin turgor, normal mental status
• Moderate dehydration (6-9% deficit): Delayed capillary refill (>2 seconds), absent tears, dry mucous membranes, sunken eyes, decreased urine output 1, 3
• Severe dehydration (≥10% deficit): Shock signs, altered mental status, poor perfusion—this is a medical emergency requiring immediate IV access 1

Weigh the infant to establish baseline and calculate fluid deficit 1. At 10 months with one-week duration, most cases will be mild-to-moderate dehydration from viral gastroenteritis 4.

Rehydration Phase

For mild dehydration (most likely scenario):

• Administer 50 mL/kg of ORS containing 50-90 mEq/L sodium over 2-4 hours 1
• Use small, frequent volumes initially (one teaspoon every 1-2 minutes) using a syringe or medicine dropper, gradually increasing as tolerated 1, 3
• This approach succeeds in >90% of cases, even with vomiting 4, 5

For moderate dehydration:

• Increase ORS volume to 100 mL/kg over 2-4 hours using the same technique 1, 2

For severe dehydration:

• Initiate IV boluses of 20 mL/kg normal saline or Ringer's lactate immediately until perfusion normalizes, then transition to oral therapy 1

Ongoing Loss Replacement

Throughout treatment, replace each watery stool with 10 mL/kg of ORS and each vomiting episode with 2 mL/kg 1, 2. This is critical since losses continue during the rehydration phase.

Feeding Strategy

Immediately after achieving rehydration (typically 2-4 hours), resume normal feeding—do not delay: 1, 2

• If breastfed: Continue nursing on demand throughout the entire illness, including during rehydration 1, 2
• If formula-fed: Offer full-strength, lactose-containing formula immediately after rehydration 1
• Lactose-free formulas are acceptable but not necessary—lactose-containing formulas work well under supervision 1
• Early refeeding shortens diarrhea duration and improves nutritional outcomes 3, 5

The outdated practice of prolonged dietary restriction ("therapeutic starvation") worsens outcomes and should be avoided 1.

What NOT to Do

Avoid these common pitfalls:

• Do not use "clear liquids" like cola, juice, or sports drinks—these contain inadequate sodium (2-3 mEq/L vs. required 50-90 mEq/L) and excessive sugar, which worsens osmotic diarrhea 1
• Do not give antimotility agents (loperamide) to any child under 18 years—they are contraindicated and potentially dangerous 2
• Do not prescribe antibiotics for uncomplicated watery diarrhea without bloody stools, high fever, or signs of sepsis—this promotes resistance without benefit 2
• Do not delay feeding while awaiting test results or "resting the gut" 2

Diagnostic Testing

Stool cultures and laboratory work are NOT indicated for typical acute watery diarrhea in an immunocompetent 10-month-old 1, 2. Testing is reserved only for:

• Bloody diarrhea (dysentery) 1
• Signs of sepsis or severe systemic illness 2
• Immunocompromised status 2

ORS Product Selection

Use commercially available premixed ORS products rather than homemade solutions to ensure proper concentration 1, 5. U.S. formulations now contain appropriate lower sodium concentrations (45-75 mEq/L) compared to older WHO-ORS 1. Examples include Pedialyte or Infalyte, both proven equally effective 6.

When to Escalate Care

Refer immediately if 1, 2:

• Severe dehydration or shock develops
• Oral rehydration fails after appropriate trial
• Bloody stools appear
• Mental status changes occur
• Persistent high fever with toxic appearance

The one-week duration suggests viral etiology (likely rotavirus or norovirus), which is self-limiting with proper hydration management 4. Most infants recover fully with ORS and continued feeding within days of initiating appropriate therapy 4, 5.