para lab

• Based on color:

  • Brown: Normal/Stercobilinogen
  • Black and tarry: Bleeding in upper GIT (proximal to cecum), Drugs (iron salts, bismuth salts, charcoal)
  • Red: Lower GIT bleeding/tumors, inflammatory process, Anal fissure, hemorrhoids, tumors, Undigested tomatoes or beetroot
  • Yellow or yellow green: Diarrhea
  • Clay-colored (gray-white): Biliary obstruction
  • Silvery: Carcinoma of ampulla of Vater
• Based on appearance:

  • Watery: Certain strains of Escherichia coli, Rotavirus enteritis, Cryptosporidiosis
  • Rice water: Cholera
  • Unformed with blood, mucus, and pus: Bacillary dysentery, Ulcerative Colitis, Intestinal tuberculosis, Amoebiasis, Enteritis
  • Unformed, frothy, foul-smelling, which float on water: Steatorrhea
  • Pale color stool with greasy appearance: Pancreatic deficiency due to malabsorption
• Based on odor:

  • Foul odor: Undigested protein & by excessive intake of carbohydrate
  • Sickly odor: Undigested lactose & fatty acids
• Presence of mucus in stools:

  • Translucent gelatinous material clinging to surface of stool
  • Produced by colonic mucosa in response to parasympathetic stimulation
  • Seen in severe constipation, Mucous colitis
• Presence of mucus and blood in stools:

  • Bacillary dysentery, Ulcerative Colitis, Intestinal tuberculosis, Amoebiasis, Enteritis
  • Mucus with blood clinging to stool is seen in Lower GIT malignancy, Inflammatory lesions of anal canal
• Chemical examination:

  • Occult blood
  • Excess fat excretion (malabsorption)
  • Reducing sugars
  • Stool osmotic gap
  • Urobilinogen
  • Stool pH
• Test for occult blood in stools:

  • Principle: Hemoglobin has peroxidase-like activity & releases oxygen from hydrogen peroxide
  • Causes of false-positive tests: Ingestion of peroxidase-containing foods, Drugs like aspirin
  • Causes of false-negative tests: Foods containing large amounts of vitamin C
• • Epithelial cells: Seen in inflammatory conditions of the bowel
• Microscopic examination of stool samples:

  • Findings: Leukocytes (WBCs), Red Blood Cells (RBCs), Macrophages, Epithelial cells, Bacteria, Ova/Cysts/Trophozoites of parasites, Meat/muscle fibers, Fat
  • Leukocytes (WBCs): Increased in Bacillary dysentery, Chronic ulcerative colitis, Shigellosis, Salmonella infections, Invasive E-Coli infections, etc.
  • Red Blood Cells (RBCs): Bright red stool in lower GIT bleeding, Black and tarry blood in upper GIT bleeding, Dysentery, Hemorrhoids, GIT Malignancies
  • Macrophages: Seen in Bacillary dysentery, Ulcerative colitis
• Fat:

  • Present in Malabsorption, Deficiency of pancreatic digestive enzyme, Deficiency of bile
• Microscopic examinations - Artefacts:

  • Artefacts should be identified during microscopic examination of stool samples to avoid confusion with ova & cysts of various protozoa & helminths
  • Artefacts may include yeast & fungal elements, pollen grains, plant fiber/cells, air bubbles, Charcot-Leyden crystals
• Reference ranges in stool examination:

  • Bulk: 100-200 grams/day
  • Color: Brown
  • Water: Up to 75%
  • pH: 7.0-7.5
  • Red blood cells: Absent
  • White blood cells: Few
  • Epithelial cells: Present
  • Crystals: Calcium oxalate, triple phosphate
• Stool odor: indole and skatole which are formation by bacterial formation and putrefication