Chemical Properties of Stool

Analysis of chemical properties of stool is an important diagnostic method that helps identify digestive disorders, intestinal microflora state, and inflammatory processes in the gastrointestinal tract. Below are the main parameters, their values, and clinical significance:

• pH (acid-base balance):
  pH reflects the acidity or alkalinity of the stool environment.
  • Normal: 6.5–7.5 (neutral or mildly acidic reaction).
  • Acidic reaction (pH < 6.5): indicates predominance of fermentation processes in the intestine, often seen in dysbiosis, overgrowth of conditionally pathogenic microorganisms, and incomplete carbohydrate digestion.
  • Alkaline reaction (pH > 7.5): may indicate putrefactive processes, slowed peristalsis, bile stasis, or digestive disorders.
• Occult blood:
  Detects blood in stool not visible to the naked eye.
  • Absent: normal.
  • Positive result: may indicate ulcers, colitis, polyps, tumors, or mucosal injuries in the intestine.
  Detection requires further examination and endoscopy.
• Stercobilin:
  A pigment formed by bacterial breakdown of bilirubin, giving stool its characteristic brown color.
  • Normal: 10–20 µmol/L.
  • Decreased stercobilin: indicates bile outflow obstruction (e.g., obstructive jaundice), liver disease, or dysbiosis.
  • Increased: rare, may be linked to intensified bilirubin metabolism.
• Bilirubin:
  Normally absent in adult stool as it is converted to stercobilin.
  • Presence: indicates impaired enzymatic conversion of bilirubin, accelerated intestinal transit, or liver disease.
• Protein:
  Normally absent in stool.
  • Presence: indicates inflammatory processes of intestinal mucosa (e.g., colitis, enterocolitis), mucosal damage, or intestinal infections.
• Bile acids:
  Produced in the liver; participate in digestion and fat absorption.
  • Normal levels: 2.0–6.0 mmol/L (depending on method).
  • Elevated levels: suggest impaired absorption in the small intestine, increased bile secretion, or liver and biliary diseases.
  • Decreased levels: rare, may indicate disrupted bile acid synthesis.
• Acids and ammonia:
  Reflect intestinal microbiological activity.
  • Acids (e.g., acetic, butyric): products of carbohydrate and fat fermentation by normal microflora.
  • Ammonia: formed from protein putrefaction and nitrogenous compound breakdown.
  • Normal levels: vary by test method.
  • Elevated levels: indicate microflora imbalance, enhanced putrefactive processes, often accompanied by bloating, pain, and digestive disturbances.

These parameters combined enable physicians to assess digestive system function, identify hidden pathologies, digestion disorders, inflammation, and intestinal dysbiosis, which is crucial for selecting appropriate treatment.