Chemical Properties of Stool
Analysis of the chemical properties of stool is an important diagnostic method that helps detect digestive disorders, assess intestinal microflora, and identify inflammatory processes in the gastrointestinal tract. Let’s look at the main parameters, their values, and clinical significance:
- pH (acid-base balance):
pH indicates the acidity or alkalinity of the stool environment.
• Normal: 6.5–7.5 (neutral or slightly acidic).
• Acidic reaction (pH < 6.5): suggests fermentation processes in the intestine, often seen in dysbiosis, overgrowth of opportunistic microorganisms, or incomplete carbohydrate digestion.
• Alkaline reaction (pH > 7.5): may indicate putrefactive processes, slowed peristalsis, bile stasis, or digestive disorders.
- Occult blood:
Detects hidden blood in stool, invisible to the naked eye.
• No blood: normal.
• Positive result: may indicate peptic ulcers, colitis, polyps, tumors, or mucosal injury.
Detection of occult blood requires further investigation and endoscopy.
- Stercobilin:
A pigment formed by the breakdown of bilirubin by intestinal microflora; gives stool its characteristic brown color.
• Normal: 10–20 µmol/L.
• Decrease: suggests bile flow obstruction (e.g., obstructive jaundice), liver disease, or dysbiosis.
• Increase: rare, may be associated with increased bilirubin metabolism.
- Bilirubin:
Normally absent in adult stool, as it is converted to stercobilin.
• Presence of bilirubin: indicates impaired enzymatic conversion, accelerated intestinal transit, or liver disease.
- Protein:
Should be absent in normal stool.
• Presence of protein: indicates inflammation of the intestinal mucosa (e.g., colitis, enterocolitis), mucosal damage, or intestinal infections.
- Bile acids:
Produced in the liver, involved in digestion and fat absorption.
• Normal levels: 2.0–6.0 mmol/L (depending on method).
• Increase: may indicate malabsorption in the small intestine, increased bile secretion, or liver and biliary tract disorders.
• Decrease: rare, may result from impaired bile acid synthesis.
- Acids and Ammonia:
Reflect intestinal microbial activity.
• Acids (e.g., acetic, butyric): are byproducts of carbohydrate and fat fermentation by normal microflora.
• Ammonia: forms during protein putrefaction and nitrogenous compound breakdown.
• Normal levels: vary by analytical method.
• Increase: indicates intestinal dysbiosis and enhanced putrefactive activity, often accompanied by bloating, abdominal pain, and digestive disturbances.
These indicators help doctors assess the functional state of the digestive system, detect hidden pathologies, inflammation, maldigestion, and intestinal dysbiosis — all essential for selecting effective treatment strategies.