Chemical Examination of Urine Part 2

• Ketones


  Intermediate products of fat metabolism
• Ketonuria


  When ketones reach the threshold level and appear in the urine
• Ketonuria


  Used in monitoring insulin dosage
• Ketone formation


  1. Inadequate carbohydrates/glucose leads to increased breakdown of fats

  2. Fatty acids converted to Acetyl-CoA

  3. Kreb's cycle overwhelmed

  4. Liver starts active ketogenesis

  5. Formation of ketone bodies

  
• Diacetic acid or Acetoacetate


  The parent ketone body
• Beta-hydroxybutyric acid


  The major ketone body in the blood
• Ketone bodies

  • Beta-hydroxybutyric acid (majority)
  • Acetoacetate (20%)
  • Acetone (smallest portion)
• Increased ketones in the blood


  Makes the blood acidic (Ketoacidosis)
• Ketone reagent strip

  Uses the Sodium Nitroprusside Reaction to detect ketones
• Reading time of Ketone Reagent Strip

  40 seconds
• Multistix is more sensitive than Chemstrip in detecting ketones
• Positive result of ketone reagent strip is PURPLE.

  
  

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  • Bilirubin
  • Ketone
  • Leukocyte Esterase
• Glycine is used to detect acetone
• Beta-hydroxybutyric acid is not detected in urine tests
• Lactose


  Color enhancer in ketone tests
• Interferences causing false negatives in Ketones

  • Improperly preserved urine (ketones are volatile)
• Interferences causing false positives in Ketones

  • Medications with free sulfhydryl groups
  • Highly pigmented urine
• Acetest


  Tablet test for ketones
• Acetest

  • Flexible
  • Detection limit: 5 mg/dL acetoacetate
  • Used in urine, serum, plasma, or whole blood
• Acetest tablet contents

  • Sodium nitroprusside (main reactive agent)
  • Disodium phosphate (buffer)
  • Glycine (detect acetone)
  • Lactose (color enhancer)
• Acetest is 10x more sensitive to acetoacetate than acetone
• Acetest does not detect beta-hydroxybutyric acid
• Older ketone tests

  • Legal's test - first test developed for ketones
  • Rothera's test - (+)purple ring at the junction in urine and ammonia
  • Gerhardt's test/Ferric chloride
  • Lange's test
  • Lieben Iodoform test
  • Hart's test - detects the beta-hydroxybutyric acid
• Hart's test


  Indirectly detects beta-hydroxybutyric acid by converting it to acetone first
• Hematuria


  Presence of intact red blood cells in urine

  Cloudy red urine

  Intact RBC
• Hemoglobinuria


  Presence of hemoglobin in urine (from RBC destruction)

  Clear red urine

  No red cells
• Myoglobinuria


  Presence of myoglobin in urine

  Clear red urine

  No red cells

  ”cola drink”

  ”black coffee” urine
• Normally, no blood in the form of hematuria, hemoglobinuria, or myoglobinuria should be detected in urine
• Clinically significant hematuria

  > 5 red blood cells per microliter of urine
• Methods to detect blood in urine

  • Assessed Physically (hematuria)
  • Chemical test for hemoglobin
  • Microscopic analysis differentiate hematuria and hemoglobinuria
• Differences between hematuria, hemoglobinuria, and myoglobinuria

  • Hematuria: Cloudy red urine, presence of intact RBCs
  • Hemoglobinuria: Clear red urine, no RBCs
  • Myoglobinuria: Clear red/brown/black urine, no RBCs
• Causes of hematuria


  • Glomerulonephritis
  • Renal calculi
  • Pyelonephritis
  • Trauma
  • S. haematobium infection
  • Exposure to toxic chemicals
  • Anticoagulant therapy
  • Tumors
• Causes of hemoglobinuria


  • Lysis of RBCs in urinary tract
  • Dilute alkaline urine
  • Transfusion reaction
  • Hemolytic anemias
  • Severe burns
  • Infections/malaria
  • RBC trauma
  • Brown recluse spider bites
  • Cholesterol-lowering statin medications
• Myoglobinuria


  • Associated with muscle destruction
• Causes of Myoglobinuria


  • Cholesterol-lowering statin medications
  • Muscular trauma/Crush syndromes
  • Convulsions
  • Muscle-wasting disease
  • Alcoholism
  • Drug abuse (e.g.heroin)
  • Strenuous exercise and menstruation
  • Extensive exertion
• S. haematobium causes hematuria because it is a blood parasite usually located in the bladder and its ovum has a terminal spine that can lacerate the bladder
• If the urine is diluted alkaline, it is hypotonic that could burst the RBC
• Statin medication are taken at night because it can cause muscle pain (rhabdomyolysis etc.)
• Blondheim's test (Myoglobinuria vs Hemoglobinuria)


  Test for the presence of myoglobin. Ammonium sulfate will precipitate the hemoglobin but not myoglobin
• Blood reagent strip

  Principle: Pseudoperoxidase activity of heme.

  (+) reaction: GREEN

  Highly sensitive but not specific