A stool sample is a diagnostic tool used to analyze fecal matter. It provides insights into a person’s internal health without requiring invasive procedures. Stool tests can detect signs of infection, inflammation, or other diseases within the gastrointestinal system.
Infectious Agents
Stool samples identify infectious microorganisms that cause gastrointestinal illnesses, including bacteria, viruses, and parasites. For bacterial infections, tests detect common culprits such as Salmonella, certain strains of E. coli, and Clostridioides difficile (C. diff). Detecting these bacteria helps diagnose conditions like food poisoning or antibiotic-associated diarrhea.
Viral infections, such as norovirus and rotavirus, are also detectable through stool analysis. These viruses frequently cause gastroenteritis, especially in children. Analyzing stool for viral genetic material or antigens confirms the specific viral agent.
Parasitic infections are another category, with organisms like Giardia, Cryptosporidium, and various amoebas being identifiable. Microscopic examination of stool samples reveals the presence of parasite eggs or larvae. Detecting these agents guides treatment and prevents further illness spread.
Indicators of Digestive Health
Beyond infections, stool samples reveal markers related to digestive function and inflammation. One marker is occult blood, or hidden blood. Its presence indicates bleeding in the digestive tract, potentially stemming from polyps, ulcers, hemorrhoids, diverticulosis, or inflammatory bowel disease. Detecting occult blood is an early sign that may prompt further investigation, such as a colonoscopy.
Excess fat in stool, called steatorrhea, signals issues with nutrient absorption. This can manifest as pale, bulky, greasy, or foul-smelling stools. Steatorrhea often points to problems with the pancreas not producing enough digestive enzymes, as seen in exocrine pancreatic insufficiency, or conditions like celiac disease that affect the small intestine’s ability to absorb fats.
Markers of inflammation, such as calprotectin and lactoferrin, are also measured in stool samples. These proteins are released by white blood cells in the presence of intestinal inflammation. Elevated levels can suggest inflammatory bowel diseases (IBD) like Crohn’s disease or ulcerative colitis, helping differentiate them from other conditions like irritable bowel syndrome (IBS).
Insights into Gut Microbiome
Stool samples offer a snapshot of the gut microbiome, the complex community of microorganisms living in the intestines. This includes various bacteria, fungi, and viruses that influence human health. Analyzing the DNA from these microbes provides information about the diversity and balance of the gut’s microbial ecosystem.
An imbalanced microbiome, termed dysbiosis, can be identified through changes in the types and quantities of these microbes. While not a diagnostic test for specific diseases, microbiome analysis can indicate potential links to chronic conditions. This assessment differs from pathogen detection by focusing on the overall microbial community rather than specific disease-causing agents.
Screening for Specific Conditions
Stool samples play a role in screening for certain non-infectious conditions, particularly colorectal cancer. The Fecal Immunochemical Test (FIT) is a common screening method that detects hidden blood in stool. This test specifically identifies human blood from the lower intestines, which can be an early indicator of polyps or cancer.
Stool DNA tests represent another screening approach for colorectal cancer. These tests look for altered DNA and microscopic blood that cells shed from polyps or cancerous tumors into the stool. Both FIT and stool DNA tests are non-invasive options that can help detect colorectal cancer at an early stage, when treatment is often more effective.