What are the differential diagnoses for a pediatric patient presenting with blood‑stained or mucus‑laden diarrhea (dysentery)?

Differential Diagnoses for Pediatric Dysentery

The most common bacterial causes of bloody or mucoid diarrhea in children are Shigella, Salmonella, Campylobacter, and Shiga toxin-producing E. coli (STEC), with Shigella being the classic dysentery pathogen that warrants empiric antibiotics. 1, 2

Primary Bacterial Pathogens

Most Common Invasive Bacteria

• Shigella species remain the prototypical dysentery pathogen worldwide and are the most likely to present with visible blood and mucus in stool, though only 70% of Shigella cases actually demonstrate fecal leukocytes. 1, 3, 2
• Salmonella species frequently cause bloody diarrhea with fever and abdominal pain, though they may present with less mucus than Shigella. 1, 2
• Campylobacter jejuni is a leading cause of bacterial dysentery in industrialized countries, typically presenting with fever, cramping abdominal pain, and bloody stools. 1, 2
• STEC (Shiga toxin-producing E. coli), particularly O157:H7 and non-O157 serotypes, cause severe abdominal pain with grossly bloody stools but characteristically present with minimal or no fever at the time of presentation—this is a critical distinguishing feature. 1, 4

Less Common but Important Bacterial Causes

• Yersinia enterocolitica should be suspected in school-aged children with persistent right lower quadrant abdominal pain mimicking appendicitis (mesenteric adenitis), especially with fever and exposure to raw or undercooked pork products. 1
• Non-cholera Vibrio species (not V. cholerae) can cause dysentery in children with exposure to salty or brackish waters or consumption of raw/undercooked shellfish. 1, 2
• Plesiomonas shigelloides is an uncommon cause that should be considered based on epidemiologic clues such as travel or water exposure. 1, 2
• Aeromonas species may cause dysentery in specific epidemiologic contexts. 2

Parasitic Causes

• Entamoeba histolytica is the primary parasitic cause of dysentery and must be strongly considered in children from developing countries, particularly rural or periurban areas, or with recent international travel. 1, 2
• Balantidium coli is a rare ciliated protozoan that can cause bloody diarrhea. 1
• Schistosoma mansoni should be considered in children with appropriate travel or exposure history to endemic areas. 2
• Cryptosporidium species occasionally present with bloody diarrhea, though watery diarrhea is more typical. 5

Viral Pathogens (Less Typical for True Dysentery)

• Rotavirus and Adenovirus are the most common viral causes of pediatric diarrhea but rarely cause true dysentery with visible blood; when blood is present, it is typically occult rather than grossly visible. 3, 5
• Viral pathogens accounted for only 16% of cases with fecal leukocytes in one study, compared to 36% for invasive bacterial pathogens. 3

Other Bacterial Considerations

• Clostridium difficile can cause bloody diarrhea in children with recent antibiotic exposure, though bloody stools are not an expected manifestation and should prompt consideration of other pathogens. 1, 2
• Cytomegalovirus (CMV) should be considered in immunocompromised children with persistent bloody diarrhea. 2

Critical Diagnostic Approach

When to Suspect Specific Pathogens

• Dysentery with high fever and systemic toxicity: Think Shigella, Salmonella, or Campylobacter. 1, 6
• Severe abdominal pain with bloody stools but minimal fever: STEC is the primary concern due to risk of hemolytic uremic syndrome—never give antibiotics empirically in this scenario. 1, 6, 4
• Right lower quadrant pain mimicking appendicitis: Yersinia enterocolitica, especially in school-aged children. 1
• Recent international travel with fever ≥38.5°C: Empiric antibiotics are indicated while awaiting cultures. 6
• Infants <3 months with bloody diarrhea: Empiric third-generation cephalosporin is indicated after obtaining blood and stool cultures. 6

Important Diagnostic Pitfalls

• The absence of fecal leukocytes does NOT rule out invasive bacterial pathogens: Only 36% of Salmonella-Shigella-Campylobacter cases and 70% of Shigella cases demonstrate fecal leukocytes. 3
• Occult blood testing has poor specificity: 39% of rotavirus cases and even 13% of controls tested positive for occult blood. 3
• Dysentery (visible blood/mucus) has poor sensitivity for Shigella: Only 11% of microbiologically confirmed Shigella cases presented with classic dysentery in one Kenyan study. 7
• Concurrent infections are common: 33.8% of children with acute diarrhea had two or more pathogens detected simultaneously, particularly in children under 2 years. 5

Testing Strategy

• Obtain stool culture for Salmonella, Shigella, Campylobacter, and Yersinia in all children with visible blood in stool. 1
• Test specifically for STEC O157 by culture on sorbitol-MacConkey agar and detect non-O157 STEC by Shiga toxin or genomic assays—this is critical because antibiotic treatment increases risk of hemolytic uremic syndrome. 1
• Obtain blood cultures in infants <3 months, children with signs of sepsis, or when enteric fever is suspected. 1
• Examine fresh stool for E. histolytica trophozoites in children from endemic areas or with appropriate travel history. 8
• Consider broader parasitic testing (Cryptosporidium, Giardia) in immunocompromised children or those with persistent symptoms. 1

Empiric Antibiotic Decision Algorithm

Do NOT give empiric antibiotics in most cases of pediatric bloody diarrhea while awaiting test results. 6

DO give empiric antibiotics in these specific scenarios:

• Infants <3 months with suspected bacterial etiology (use third-generation cephalosporin). 6
• Classic bacillary dysentery syndrome with high fever, systemic toxicity, and bloody mucoid stools (presumed Shigella—use azithromycin or third-generation cephalosporin). 8, 6
• Recent international travelers with fever ≥38.5°C and/or signs of sepsis. 6
• Immunocompromised children with severe illness and bloody diarrhea. 6

Critical caveat: If STEC is suspected (severe abdominal pain, grossly bloody stools, minimal fever), withhold antibiotics even if the child appears ill, as treatment increases the risk of hemolytic uremic syndrome. 1, 6, 4