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Chapter 42

Chapter 42. Urinalysis. Urine Formation. Urine forms in kidneys and leaves body through urethra The urinary system >>. Urine Formation. How body excretes water and gets rid of waste Waste can become toxic if not removed Two kidneys eliminate soluble waste products of metabolism

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Chapter 42

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  1. Chapter 42 Urinalysis

  2. Urine Formation • Urine forms in kidneys and leaves body through urethra The urinary system >>

  3. Urine Formation • How body excretes water and gets rid of waste • Waste can become toxic if not removed • Two kidneys eliminate soluble waste products of metabolism • Click here for an animation

  4. Urine Formation • Filtration • Glomerulus filters waste products, salts, and excess fluid from blood • Tubule concentrates filtered material • Nephron • Combination of glomerulus and tubule • One million nephrons in each kidney

  5. Urine Formation • Filtration • Substances filtered out from body • Water • Ammonia • Electrolytes • Glucose

  6. Urine Formation • Filtration • Substances filtered out from body • Amino acids • Creatinine • Urea • Diabetes diagnosis • Routine urinalysis testing

  7. Urine Formation • Reabsorption • About 180 liters of filtrate produced daily • Only 1–2 liters of urine eliminated • Much filtrate reabsorbed into body • Blood cells and most proteins stay in blood • Concentration of glucose in blood below 180 mg/dl will be reabsorbed • Glucose is a threshold substance

  8. Urine Formation • Secretion • Substances not already filtered are secreted into urine through distal convoluted tubule • Hydrogen and ammonium ions may be secreted into urine in exchange of sodium

  9. Urine Composition • After passing through kidney, urine is 96% water and 4% dissolved substances (urea, salt, sulfates, phosphates)

  10. Urine Composition • Abnormal constituents of urine • WBC • Fat • Glucose • Casts • Bile • Hemoglobin and RBC

  11. Urine Composition • Changes in urine production • Amount of urine excreted can rise or fall • Urine color can change • Urine appearance can vary

  12. Urine Composition • Changes in urine production • Urine odor can change • Cells can be present in urine • Chemical constituents in urine can change • Urine concentration (specific gravity) may vary

  13. Safety • Standard precautions • Transmission-based precautions • Biohazard precautions • Proper disposal of urine

  14. Quality Control • Regulatory agencies • Written testing protocols • Maintained testing records • Recalibration of instruments

  15. Quality Control • Documentation of daily control testing must be kept at least 3 years • Commercially available urine control samples • Run positive and negative controls each day on all tests

  16. CLIA 88 • Appropriate training in methodology of test being performed • Understanding of urine testing quality control procedures • Proficiency in the use of instrumentation; being able to troubleshoot problems

  17. CLIA 88 • Knowledge of stability and proper storage of reagents • Awareness of factors that influence test results • Knowledge of how to verify test results • CLIA categorizes microscopic exam as a PPMP

  18. Urine Containers • Types • Nonsterile containers for cultures • 24 hour collection containers with added preservatives

  19. Urine Containers • Label container immediately after specimen collection • Patient’s name, age, gender, identifying number • Date and time of collection • Physician’s name • Label the cup, not the lid

  20. Urine Collection • Giving patient instructions

  21. Urine Collection • Click to play the video

  22. Urine Collection • Urine specimen types • Random (spot) specimen • Obtained at any time • Most common • If concentrated specimen preferred, first specimen of day is most concentrated

  23. Urine Collection • Urine specimen types • Fasting/timed specimens • Used when physician wants to measure substance without interference from food intake • Length of fast varies • Give patient written directions • Use regular urinalysis container

  24. Urine Collection • Urine specimen types • 24-hour specimen • Circadian rhythm and intake of food and water determine concentration of substances at different times during day/night • Requested when quantitative tests for different substances are desired • Expressed in units per 24 hours • Use of preservatives and refrigeration • Sometimes use 2-hour or 12-hour collection instead

  25. Urine Collection • Urine specimen types • Catheterized specimen • Insert sterile tube directly into bladder through urethra • Not contaminated • Can cause infection if not done correctly • Use only when other methods are contraindicated or show repeated positive testing for bacteria

  26. Urine Collection • Collection methods • Random collection • Clean-catch method; midstream collection • Catheterized

  27. Examination of Urine • Best when fresh, even still warm • Test within 30 minutes, or refrigerate

  28. Routine Urinalysis Procedure • Physical examination of urine • Assess volume of urine specimen, making sure specimen is sufficient for testing • Note any unusual urine odor • Measure specific gravity of specimen

  29. Routine Urinalysis Procedure • Physical examination of urine • Observe and record color and transparency of specimen

  30. Measuring Specific Gravity • Urinometer • Measures specific gravity • Reading the meniscus • Take temperature of urine into account

  31. Measuring Specific Gravity • Refractometer • Most common tool for measuring specific gravity of liquids • Measures refractive index of urine • Reads about 0.002 below that of true specific gravity • Needs 1 drop of urine • Easy to use but more expensive

  32. Routine Urinalysis Procedure • Chemical examination of urine • Use of multistix reagent strips with color-coded chart • Chemical testing available on urine reagent test strips • See Table 42-3

  33. Routine Urinalysis Procedure • Chemical examination of urine • Reagent test strip quality control • Automated urine analyzers >>

  34. Routine Urinalysis Procedure • Microscopic examination of urine sediment • Classified as PPMP • Sediment is forced to the bottom of centrifuged tube • Helps determine kidney disease, disorders of urinary tract, and systemic disease • Need fresh urine • Use of urine color atlas • Use of urine stains

  35. Preparing for Microscopic Examination • Centrifuge 10–15 mL of urine • Pour off supernatant urine • Resuspend sediment by tapping • Stain (optional) >> • Put drop of sediment on slide

  36. RBC WBC Renal epithelial cells Bacteria Yeast Parasites Sperm Artifacts Squamous epithelial cells Urine Sediment Cells and Microorganisms

  37. Crystals in Urine Sediment • Require little attention • Form as urine specimens stand • Uric acid, cystine, and sulfa drug crystals can indicate disease states

  38. Casts in Urine Sediment • Important to note • Formed when protein accumulates and precipitates in kidney tubules • Appearance of casts • Hyaline cast most common kind seen • Granular casts and cellular casts also seen • Takes an experienced eye to identify

  39. Urinalysis Report • Include patient’s name, type of specimen, collection method, ordering provider, MA name, date and time of collection, date and time of testing, findings

  40. Drug Screening • Becoming more common for employment • Test itself is CLIA waived, but detailed protocols must be followed • Chain of custody

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