Introduction to Urinalysis

• What is urinalysis?

  Urinalysis is the testing of urine using procedures that are expeditious, reliable, accurate, safe, and cost-effective.
• How long does a manual urinalysis procedure take?

  30 minutes.
• How long does an automated urinalysis procedure take?

  6 minutes.
• What historical significance does urine analysis hold in laboratory medicine?

  Analyzing urine was the beginning of laboratory medicine.
• Where can references to the study of urine be found?

  In the drawings of cavemen and in Egyptian hieroglyphics, such as the Edwin Smith Surgical Papyrus.
• What basic observations were used to obtain diagnostic information from urine in ancient times?

  Color, turbidity, odor, volume, viscosity, and sweetness.
• Who wrote a book on "Uroscopy" in the 5th BC?

  Hippocrates.
• What significant development occurred in 1140 AD related to urinalysis?

  Color charts were developed to describe the significance of 20 different colors.
• What were "pisse prophets" as described by Thomas Bryant in 1627?

  They were individuals who made predictions about health without proper medical education.
• What did Frederik Dekker discover in 1694?

  Albuminuria (white precipitates) by boiling urine.
• What was the significance of the invention of the microscope in the 17th century?

  It allowed for the quantification of microscopic sediment in urine.
• Who introduced urinalysis as part of a doctor's routine patient examination in 1827?


  Richard Bright.
• What are the unique characteristics of urine that make it important for analysis?

  Urine is readily available, easily collected, and contains information about the body's major metabolic functions.
• What are the reasons for performing urinalysis?

  To aid in the diagnosis of disease, screen asymptomatic populations for undetected disorders, and monitor the progress of disease and effectiveness of therapy.
• What are the four parts of routine urinalysis?

  1. Specimen Evaluation (accept or reject the specimen)
  2. Physical Examination (check for physical characteristics of the urine)
  3. Chemical Examination (detect presence of different analytes)
  4. Sediment Examination (microscopic; serves as the gold standard)
• How much filtered plasma is converted to average daily urine output?

  Approximately 170,000 mL of filtered plasma is converted to 1,200 mL to 1,500 mL of average daily urine output.
• What is the composition of urine in terms of water and solutes?

  Urine is composed of 95% water and 5% solutes.
• What factors can cause variation in solute concentration in urine?

  Dietary intake, physical activity, body's metabolism, endocrine functions, and body position.
• What are the organic solutes found in urine and their significance?

  • Urea: major metabolic waste product, accounts for nearly half of total dissolved solids in urine.
  • Creatinine: product of muscular metabolism.
  • Uric acid: product of purine metabolism.
• What are the inorganic solutes found in urine?

  • Chloride: major inorganic solid dissolved in urine.
  • Sodium and potassium.
  • Other substances: hormones, vitamins, and medications.
• What are formed elements in urine and their significance?

  Increased amounts of formed elements such as cells, casts, crystals, mucus, and bacteria are often indicative of disease.
• What is the composition of urine collected for 24 hours in terms of organic components?

  • Urea: 25.0 to 35.0 g
  • Creatinine: 1.5 g
  • Uric acid: 0.4 to 1.0 g
  • Hippuric acid: 0.7 g
  • Other substances: 2.9 g
• What is the composition of urine collected for 24 hours in terms of inorganic components?

  • Sodium chloride (NaCl): 15.0 g
  • Potassium (K): 3.3 g
  • Sulfate (SO4^2-): 2.5 g
  • Phosphate (PO4^3-): 2.5 g
  • Ammonium (NH4⁺): 0.7 g
  • Magnesium (Mg²⁺): 0.1 g
  • Calcium (Ca²⁺): 0.3 g
• Why is it important to handle urine specimens correctly after collection?

  Changes in urine composition can occur in vivo and in vitro, requiring correct handling procedures.
• How soon should urine specimens be tested after collection?

  Within 2 hours.
• What should be done if a urine specimen cannot be tested within 2 hours?

  The specimen should be refrigerated or have an appropriate chemical preservative added.
• What are the most commonly used methods of specimen preservation?

  • Refrigeration (2⁰C to 8⁰C): decreases bacterial growth and metabolism.
  • Use of chemical preservatives.
• What are the requirements for urine specimen containers?

  • Clean, dry, leak-proof, disposable containers.
  • Sterile containers for culture and sensitivity.
  • Properly applied screw-top lids.
  • Wide mouth (4 to 5 cm), flat bottom.
  • Clear plastic (50 mL to 100 mL capacity).
• What information should be included on a urine specimen label?

  Patient’s name, identification number, date and time of collection, patient’s age and location, physician’s name.
• What are the common reasons for specimen rejection?

  Unlabeled containers, nonmatching labels and requisition forms, contamination, and insufficient quantity.
• What is the normal range for specific gravity in urine?

  1. 003-1.035.
• What can cause an increase in urine specific gravity?

  Increased specific gravity can occur if the patient undergoes MRI.
• What is the normal pH range for urine?

  1. 0-8.0.
• What is the normal temperature range for urine?

  32.5°C to 37.5°C.
• How does random urine differ from other specimens?

  Random urine is the most commonly received specimen because of its ease of collection and convenience.
• Why is first morning urine considered an ideal screening specimen?

  It prevents false-negative pregnancy tests and evaluates orthostatic proteinuria.
• How does a fasting specimen differ from a first morning specimen?

  A fasting specimen is the second voided specimen after a period of fasting and does not contain metabolites from food ingested before fasting.
• What is the purpose of a two-hour postprandial specimen?

  It is tested for glucose and primarily used for monitoring insulin therapy in persons with diabetes mellitus.
• What are the key points regarding urine specimen collection and analysis?

  • Urine is readily available and easily collected.
  • Changes in urine composition can occur in vivo and in vitro.
  • Specimens should be tested within 2 hours or preserved.
  • Proper labeling and handling are crucial for accurate results.
• What is the purpose of routine screening tests in urine analysis?

  To detect obvious abnormalities