ROUTINE STOOL EXAMINATION

• Specimen collection

  • Clean, dry, wide-mouthed containers
  • Sealed and sent to the laboratory immediately after collection
  • Preserved specimens can usually be kept at a room temperature
  • Large gallon containers for 24-, 48-, and 72-hour stool collections for fecal fat and urobilinogen; specimens normally refrigerated throughout collection period
• Ideal containers for stool

  Have spatula or spoon
• Collecting stool specimen

  1. Carefully give instruction to the patient on how to properly collect their stool

  2. Let the feces go on the side of the toilet and use the scooper to collect a pea-sized amount
• Reasons for rejecting stool specimen

  • Specimens in unlabeled containers
  • Nonmatching labels and requisition forms
  • Specimens contaminated with urine or toilet paper
  • Containers with contaminated exteriors
  • Specimens of insufficient quantity
  • Specimens that have been improperly transported
• Routine stool examination

  • Physical analysis
  • Chemical analysis
  • Microscopic analysis
• Physical examination - Consistency

  • Degree of moisture in a stool specimen
  • Formed, semi-formed, soft, loose, or watery
• Physical examination - Color

  • The normal color of the stool is brown
  • Check the composition (could be pathologic or because of food intake)
• Physical examination - Gross abnormalities

  • Adult worms (ascaris, tapeworms), proglottids (egg laying segments of adult tapeworms), and parasitic indications (pus and mucus)
  • Samples containing adult worms (ascaris, tapeworms [thinner]) may be carefully washed through a wire screen. This process allows for the retrieval and examination of the parasites for identification purposes
• Chemical examination - Occult blood

  Fat, urobilinogen (gives stool normal color) could be tested as well, not just occult blood
• Hema-screen Guiac Slide Test Kit

  1. Hema-screen slide

  2. Hema-screen developer (<6% H2O2)
• Hema-screen Guiac Slide Test Kit - Results

  • (+) any trace of blue coloration
  • (-) no detectable blue coloration
• Presence of occult blood is a marker for cancer (colorectal cancer)
• Interference of FOBT - False-positive

  • Aspirin and anti-inflammatory medications
  • Red meat (beef or goat)
  • Horseradish
  • Raw broccoli, cauliflower, radishes, turnips
  • Melons
  • Menstrual and hemorrhoid contamination
• Interference of FOBT - False-Negative

  • Vitamin C > 250 mg/d
  • Iron supplements containing vitamin C
  • Failure to wait specified time after sample is applied to add the developer reagent
• Microscopic examination

  • To detect the presence of parasites in a stool specimen
  • It can also reveal artifact (microscopic structures that can be seen in the stool)
  • It should be performed on a fresh specimen
• Microscopic examination - Procedures

  • Direct wet preparations (most common)
  • Concentrated technique
  • Permanently stained smear
• Reporting

  • NOPS - No ova and/or parasite seen
  • NIPS - No intestinal parasite seen (if ova or parasite seen, you have to know what parasite was seen)
• Artifacts, pseudoparasites, and confusers

  • White blood cells
  • Red blood cells
  • Macrophages
  • Charcot-Leyden Crystals
  • Epithelial cells
  • Eggs of arthropods, plant nematodes, and other spurious parasites
  • Fungal spores
  • Elements of plant origin
  • Plant and animal hairs
  • Muscle fibers
  • Fat globules
• Direct fecal smear

  1. About 2 mg of stool (amount forming a low cone at the tip of an applicator stick)

  2. 0.85% sodium chloride solution (NSS)

  3. Cover with cover slip
• Direct fecal smear - Temporary stain

  • Weak iodine solution (Lugol's and D'Antoni) are temporary stain to demonstrate nuclei
  • Cytoplasm: Golden Yellow
  • Nucleus: Pale and refractile
  • Glycogen: Deep brown