How should I evaluate and manage a child presenting with foul‑smelling, greasy diarrhea?

Evaluation and Management of Malodorous Pediatric Diarrhea

Foul-smelling, greasy diarrhea in a child most commonly indicates fat malabsorption from a parasitic infection (Giardia), celiac disease, or pancreatic insufficiency; your immediate priority is to assess hydration status and initiate oral rehydration therapy while obtaining stool studies for ova and parasites, bacterial culture, and fat content. 1

Initial Clinical Assessment

Evaluate dehydration severity using the following reliable physical findings:

• Capillary refill time is the single most reliable predictor of dehydration severity 1
• Assess skin turgor by pinching the abdominal skin; tenting indicates moderate-to-severe dehydration 1, 2
• Examine mucous membranes for dryness and assess mental status for lethargy 1, 2
• Obtain an accurate body weight immediately to calculate fluid deficit and monitor response 1, 2

Classify dehydration severity:

• Mild (3–5% deficit): increased thirst, slightly dry mucous membranes 1, 2
• Moderate (6–9% deficit): loss of skin turgor with skin tenting, dry mucous membranes 1, 2
• Severe (≥10% deficit): severe lethargy or altered consciousness, prolonged skin tenting >2 seconds, cool poorly perfused extremities, rapid deep breathing indicating acidosis 1, 2

Common pitfall: Do not rely solely on sunken fontanelle or absent tears; these are less reliable than capillary refill, skin turgor, and perfusion status. 1

Immediate Rehydration Protocol

Mild Dehydration (3–5% deficit)

• Administer 50 mL/kg of oral rehydration solution (ORS) containing 50–90 mEq/L sodium over 2–4 hours 1, 2
• Begin with very small volumes (5 mL, approximately one teaspoon) using a spoon, syringe, or medicine dropper, then increase gradually as tolerated 1

Moderate Dehydration (6–9% deficit)

• Administer 100 mL/kg of ORS over 2–4 hours using the same small-volume technique 1, 2
• If oral intake is not tolerated despite small volumes, consider nasogastric administration at 15 mL/kg/hour 1

Severe Dehydration (≥10% deficit)

• This is a medical emergency requiring immediate intravenous rehydration 1, 2
• Administer 20 mL/kg boluses of Ringer's lactate or normal saline IV immediately until pulse, perfusion, and mental status normalize 1, 2
• Once circulation is restored, transition to ORS for the remaining deficit 1

Reassess hydration status after 2–4 hours of rehydration therapy to determine whether additional fluid replacement is needed. 1

Ongoing Loss Replacement

• Replace each watery stool with 10 mL/kg of ORS (approximately 120 mL per stool for a 12-kg child) 1, 3
• Replace each vomiting episode with 2 mL/kg of ORS (approximately 24 mL per episode for a 12-kg child) 1, 3

Nutritional Management During Illness

• Continue breastfeeding without interruption throughout the entire episode 1, 3, 2
• Resume age-appropriate diet immediately upon rehydration, including starches, cereals, yogurt, fruits, and vegetables 1, 3
• Avoid foods high in simple sugars and fats during the acute phase, as they can worsen stool output 1, 3
• For formula-fed infants, resume full-strength formula immediately after rehydration; consider lactose-free or lactose-reduced formula if severe diarrhea recurs upon reintroduction 1, 2

Critical point: Do not impose "bowel rest" or delay feeding—there is no justification for withholding food, and early feeding promotes intestinal recovery. 1

Diagnostic Evaluation for Malodorous, Greasy Diarrhea

The foul-smelling, greasy character suggests fat malabsorption. Obtain the following studies:

• Stool for ova and parasites (three separate specimens) to detect Giardia lamblia, the most common parasitic cause of malabsorptive diarrhea 1
• Stool bacterial culture if fever, bloody diarrhea, or illness >5 days is present 1, 3
• Stool fat content (qualitative or quantitative) to confirm steatorrhea
• Consider celiac serologies (tissue transglutaminase IgA with total IgA) if diarrhea persists beyond 5–7 days or if there is failure to thrive
• Consider sweat chloride test if there is a history of recurrent respiratory infections or poor growth, suggesting cystic fibrosis

Antibiotic Therapy

Antibiotics are NOT routinely indicated for acute gastroenteritis. 1, 3

Reserve antibiotics for:

• Dysentery (bloody diarrhea) 1, 3
• High fever with systemic toxicity 1, 3
• Watery diarrhea persisting >5 days 1, 3
• Positive stool culture for a treatable pathogen (e.g., Shigella, Campylobacter, Salmonella) 1, 3
• Confirmed Giardia infection: treat with metronidazole or nitazoxanide

If Giardia is suspected clinically (foul-smelling, greasy diarrhea lasting >5 days), empiric treatment with metronidazole or nitazoxanide is reasonable while awaiting stool studies.

Medications to Avoid

• Antimotility drugs (loperamide) are absolutely contraindicated in all children <18 years due to risks of respiratory depression and serious cardiac adverse reactions 1, 3
• Do not use cola drinks, soft drinks, or fruit juices for rehydration; they contain inadequate sodium and excessive osmolality that worsens diarrhea 1, 3

Indications for Urgent Medical Evaluation

Instruct caregivers to return immediately if any of the following develop:

• Severe lethargy or altered consciousness 1, 3
• Many watery stools continuing despite rehydration 1
• Fever 1
• Bloody diarrhea 1, 3
• Intractable vomiting preventing fluid intake 1, 3
• High stool output (>10 mL/kg/hour) 1, 3
• Decreased urine output (fewer than three wet diapers in 24 hours) 1
• Sunken eyes or increased thirst after initial rehydration 1

Expected Clinical Course

• Most viral gastroenteritis resolves within 3–5 days with appropriate fluid replacement and continued feeding 1
• Giardia infection typically causes prolonged diarrhea (7–14 days) with malodorous, greasy stools; symptoms improve within 3–5 days of starting antiparasitic therapy
• Persistence of diarrhea beyond day 5 warrants stool culture and consideration of parasitic or bacterial etiology 1, 3

Common Pitfalls to Avoid

• Do not allow a thirsty child to drink large volumes of ORS ad libitum; this worsens vomiting. Use the small-volume technique (5 mL every 1–2 minutes). 3
• Do not use homemade salt-sugar solutions; commercially prepared ORS ensures proper electrolyte composition. 1
• Do not withhold food or impose "bowel rest"; this delays nutritional recovery and has no evidence base. 1
• Do not routinely order laboratory tests for mild-to-moderate dehydration without specific clinical indications. 1