From the Guidelines
The primary purpose of a stool routine examination in the diagnosis of diarrheal disease is to identify the underlying cause of the illness, such as bacterial, viral, or parasitic infections, and guide treatment decisions. According to the 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea 1, stool testing should be performed for various pathogens, including Salmonella, Shigella, Campylobacter, Yersinia, C. difficile, and STEC, in people with diarrhea accompanied by fever, bloody or mucoid stools, severe abdominal cramping or tenderness, or signs of sepsis.
The stool routine examination should include:
- Macroscopic examination: Observe color, consistency, presence of blood or mucus
- Microscopic examination: Look for white blood cells, red blood cells, ova, and parasites
- Fecal occult blood test: To detect hidden blood
- Culture and sensitivity: If bacterial infection is suspected, as recommended by the guidelines 1
- Testing for specific pathogens, such as Vibrio species, in people with exposure to salty or brackish waters, consumption of raw or undercooked shellfish, or travel to cholera-endemic regions within 3 days prior to onset of diarrhea 1
This examination helps identify the cause of diarrhea and guides treatment, with the presence of white blood cells suggesting inflammatory or invasive pathogens, ova and parasites indicating parasitic infection, and positive culture helping identify specific bacterial pathogens and their antibiotic sensitivities 1. It is essential to perform this examination on a fresh stool sample, ideally within 30 minutes of collection, and use proper protective equipment when handling stool samples to prevent infection. Prompt analysis and reporting are crucial for timely patient management.
In specific cases, such as immunocompromised individuals or possible outbreaks of diarrheal illness, a broader set of bacterial, viral, and parasitic agents should be considered, and selection of agents for testing should be based on a combination of host and epidemiologic risk factors, ideally in coordination with public health authorities 1.
From the Research
Purpose of Stool Routine Examination
The purpose of a stool routine examination in the diagnosis of diarrhoea disease is to:
- Identify the presence of blood, mucus, and parasites in the stool 2
- Determine the pH of the stool and examine for red and white blood cells, parasites, and stool fat 2
- Help distinguish between patients infected with different pathogens, such as Shigella and Entamoeba histolytica 2
- Detect parasites or their ova, and identify the type of parasite present, such as Giardia lamblia or Entamoeba histolytica 3
Diagnostic Value
Stool examination is most useful in:
- Establishing a diagnosis of dysentery 2
- Distinguishing between patients infected with Shigella and Entamoeba histolytica 2
- Identifying parasitic causes of diarrhoea, such as Giardia lamblia and Entamoeba histolytica 3
- Characterizing chronic diarrhoea as osmotic or secretory 4
Limitations
Stool examination has limited usefulness in: