What is the differential diagnosis and management of bloody diarrhea in a pediatric patient?

Differential Diagnosis of Bloody Diarrhea in Pediatric Patients

Bloody diarrhea in children requires immediate medical evaluation because it often indicates bacterial or parasitic infection requiring antimicrobial therapy, and oral rehydration alone is insufficient. 1

Infectious Etiologies (Most Common)

Bacterial Pathogens

• Escherichia coli O157:H7 is a critical diagnosis requiring vigilance in all cases of bloody diarrhea, as it can lead to hemolytic uremic syndrome 2, 3
• Shigella species cause dysentery with bloody, mucoid stools and require specific antimicrobial treatment 1
• Salmonella species can produce bloody diarrhea, particularly in young infants 3
• Campylobacter jejuni is a common cause of inflammatory diarrhea with blood 2
• Clostridium difficile should be considered if there is recent antibiotic exposure 2

Parasitic Infections

• Entamoeba histolytica causes amoebic dysentery with bloody stools and requires specific antiparasitic therapy 1
• Other parasites may occasionally present with bloody diarrhea depending on geographic exposure 1

Viral Pathogens

• Recent molecular testing reveals that pathogens typically associated with bloody diarrhea are detected in less than half of cases, suggesting viral etiologies may be more common than previously recognized 4

Non-Infectious Etiologies

Inflammatory Bowel Disease

• Ulcerative colitis and Crohn's disease can present with bloody diarrhea, particularly in older children and adolescents 2
• Consider if symptoms are chronic, recurrent, or associated with weight loss and extraintestinal manifestations 2

Intussusception

• Classic presentation includes "currant jelly" stools with blood and mucus 3
• More common in infants 6-36 months of age 3
• Requires urgent imaging and surgical consultation 2

Allergic Colitis

• Food protein-induced allergic proctocolitis typically occurs in infants, often related to cow's milk or soy protein 3
• Usually presents with small amounts of blood in otherwise well-appearing infants 3

Ischemic Colitis

• Rare in children but can occur in critically ill patients or those with vascular abnormalities 2

Meckel's Diverticulum

• Can cause painless rectal bleeding, though typically presents with melena rather than bloody diarrhea 3

Immediate Diagnostic Approach

The priority is rapid microbiologic investigation while simultaneously assessing and treating dehydration. 2

Essential Stool Studies

• Stool culture is mandatory for all children with bloody diarrhea to identify bacterial pathogens 3
• Specific testing for E. coli O157:H7 should be requested explicitly, as standard cultures may miss this pathogen 2, 3
• Stool microscopy for ova and parasites if parasitic infection is suspected based on travel history or exposure 1
• Fecal leukocytes or lactoferrin can help distinguish inflammatory from non-inflammatory diarrhea 3

Clinical Assessment Priorities

• Dehydration status using capillary refill time (most reliable), skin turgor, mental status, and perfusion 5
• Signs of shock including altered consciousness, cool extremities, and rapid deep breathing 5
• Recent antibiotic exposure suggesting C. difficile 2
• Travel history for endemic parasitic infections 6
• Age and appearance as young infants who appear ill may require empiric antibiotics 6

Laboratory Testing (Selective Use)

• Blood urea nitrogen and electrolytes only if severe dehydration or clinical features suggest significant metabolic derangement 3
• Complete blood count if sepsis is suspected or to assess for hemolytic uremic syndrome 2
• Avoid routine laboratory testing in mild-moderate dehydration without specific clinical indications 5

Management Principles

Immediate Rehydration

• Severe dehydration (≥10% deficit) requires immediate IV boluses of 20 mL/kg Ringer's lactate or normal saline until perfusion normalizes 7, 5
• Moderate dehydration (6-9% deficit) can often be managed with 100 mL/kg ORS over 2-4 hours, but IV therapy may be needed if oral intake fails 5
• Ongoing losses should be replaced with 10 mL/kg ORS per watery stool 7, 5

Antimicrobial Therapy Considerations

• Do NOT give empiric antibiotics for uncomplicated watery diarrhea without bloody stools 6
• Consider antibiotics when dysentery (bloody diarrhea) is present with high fever, when stool cultures confirm a treatable pathogen, or in immunocompromised patients 6
• Wait for culture results before initiating antibiotics in most cases, as inappropriate antibiotic use is common and promotes resistance 4
• Avoid antibiotics in suspected E. coli O157:H7 until confirmed, as they may increase risk of hemolytic uremic syndrome 2

Nutritional Management

• Continue breastfeeding throughout the illness without interruption 7, 6
• Resume age-appropriate diet immediately after rehydration, including starches, cereals, yogurt, fruits, and vegetables 7, 5
• Do not withhold food as there is no justification for "bowel rest" 5

Critical Contraindications

Antimotility drugs (loperamide) are absolutely contraindicated in all children <18 years of age due to risks of respiratory depression and serious cardiac adverse reactions. 7, 5, 6

• Never use loperamide in any pediatric patient with bloody diarrhea 7
• Ondansetron may be considered only for vomiting in children >4 years after adequate hydration is achieved 7

Common Pitfalls to Avoid

• Do not delay stool testing while awaiting clinical improvement, as this delays appropriate antimicrobial therapy when indicated 2
• Do not assume viral etiology without microbiologic confirmation, as bacterial pathogens require specific treatment 4
• Do not use cola drinks or soft drinks for rehydration as they contain inadequate sodium and excessive osmolality 5
• Do not rely solely on sunken fontanelle or absent tears for dehydration assessment, as capillary refill is more reliable 5

When to Hospitalize

• Severe dehydration (≥10% deficit) or signs of shock 5
• Failure of oral rehydration therapy despite proper technique 6
• Altered mental status or lethargy 6
• Stool output exceeding 10 mL/kg/hour 6
• Young infants who appear ill with clinical features of sepsis 6