Chapter 30 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 Click here for an animation

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

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

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

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

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

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

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

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

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

Safety Standard precautions Transmission-based precautions Biohazard precautions Proper disposal of urine

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

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

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

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

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

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

Urine Collection Giving patient instructions

Urine Collection Click to play the video

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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