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Presentation on theme: "INTRODUCTION TO URINALYSIS"— Presentation transcript:


2 Learning Objectives Upon completing this chapter, the reader will be able to List three major organic and three major inorganic chemical constituents of urine. Describe a method for determining whether a questionable fluid is urine. Recognize normal and abnormal daily urine volumes. Describe the characteristics of the recommended urine specimen containers. Describe the correct methodology for labeling urine specimens. State four possible reasons why a laboratory would reject a urine specimen.

3 Learning Objectives (cont’d)
List 10 changes that may take place in a urine specimen that remains at room temperature for more than 2 hours. Discuss the actions of bacteria on an unpreserved urine specimen. Briefly discuss five methods for preserving urine specimens, including their advantages and disadvantages. Instruct a patient in the correct procedure for collecting the following specimens: random, first morning, 24-h timed, catheterized, midstream clean-catch, suprapubic aspiration, three-glass collection, and pediatric, and identify a diagnostic use for each collection technique. Describe the type of specimen needed for optimal results when a specific urinalysis procedure is requested.

4 History The beginning of laboratory medicine
Cavemen drawings and Egyptian hieroglyphics Color, clarity, odor, viscosity, sweetness Fifth century BC, Hippocrates wrote uroscopy book AD 1140 color charts 1694 albumin determination by “boiling” Charlatans/“pisse prophets” First medical licensure laws 17th century invention of the microscope Evaluation of sediment Part of a routine physical in 1827

5 Importance Readily available and easily collected specimen
Urine contains information, which can be obtained by inexpensive laboratory tests, to assess many metabolic functions CLSI Urinalysis definition: “the testing of urine with procedures commonly performed in an expeditious, reliable, safe, and cost-effective manner” Reasons to perform Aid disease diagnosis, screen for asymptomatic diseases, monitor disease progress and therapy effectiveness

6 Urine Formation Ultrafiltrate of plasma
Kidneys converts approximately 170,000 mL of filtered plasma Average daily urine output of 1200 mL

7 Urine Composition Normal 95% water, 5% solutes
Solute variations: diet, activity, metabolism, endocrine, body position Major organic solute is urea (protein, amino acid breakdown); makes up approximately one half of the dissolved solids Inorganic chloride, sodium, and potassium Urea and creatinine identify a fluid as urine May also contain cells, casts, crystals, mucus, and bacteria Increases indicative of disease

8 Urine Volume Determined by body’s state of hydration
Influenced by fluid intake, nonrenal fluid loss, antidiuretic hormone (ADH) variations, excretion of large amounts of dissolved solids (e.g., glucose) Usual daily volume = 1200 to 1500 mL Normal range = 600 to 2000 mL

9 Definitions Oliguria: a decrease in urine output
<1 mL/kg/h in infants <0.5 mL/kg/h in children, <400 mL/day in adults Causes: vomiting, diarrhea, perspiration, severe burns Anuria: cessation of urine flow Severe kidney damage, decreased renal blood flow Nocturia: increased urine excretion at night Normally two to three times more excretion in the day Polyuria: >2.5 L/day in adults and >2.5 to 3 mL/kg/day in children

10 Polyuria in Diabetes Mellitus versus Diabetes Insipidus
Increased volume caused by need to excrete the excess glucose not reabsorbed from the ultrafiltrate Patients exhibit polydipsia (Increased water intake) Urine appears dilute with a high specific gravity Decreased production or function of antidiuretic hormone (ADH) causing decreased reabsorption of water from ultrafiltrate Urine is dilute with low specific gravity Patients also exhibit polydipsia

11 Specimen Collection Wear gloves when working with urine
Clean, dry, leak-proof containers Disposable, wide-mouthed, and flat-bottom containers with screw caps are recommended Clear containers/at least 50 mL capacity Sterile transfer devices and containers are available Facilitates automated analysis 12 mL minimum for analysis Adhesive bags for pediatrics Large plastic containers for 24-hour specimens

12 Specimen Labeling Information on label
Patient’s name, ID number, date, time Additional information: age, location, health-care provider’s name Place label on container, not lid Requisition form (manual or computerized) Must accompany specimen Information must match label Time of receipt is stamped on requisition Other information: type of specimen, interfering medications

13 Specimen Rejection Specimens in unlabeled containers
Nonmatching labels and requisition forms Specimens contaminated with feces or toilet paper Containers with contaminated exteriors Specimens of insufficient quantity Specimens that have been improperly transported Labs must have written policies for rejection of specimens

14 Specimen Integrity Changes in urine composition take place not only in vivo but also in vitro Test within 2 hours of collection Refrigerate or chemically preserve if testing is delayed Most problems are caused by bacterial multiplication Increased: color, turbidity, pH, nitrite, bacteria, odor Decreased: glucose, ketones, bilirubin, urobilinogen, RBCs, WBCs, casts

15 Changes in Unpreserved Urine
Analyte Change Cause Color Modified/darkened Oxidation or reduction of metabolites Clarity Decreased Bacterial growth and precipitation of amorphous material Odor Increased Bacterial multiplication causing breakdown of urea to ammonia pH Breakdown of urea to ammonia by urease-producing bacteria/loss of CO2 Glucose Glycolysis and bacterial use

16 Changes in Unpreserved Urine (cont’d)
Analyte Change Cause Ketones Decreased Volatilization and bacterial metabolism Bilirubin Exposure to light/photooxidation to biliverdin Urobilinogen Oxidation to urobilin Nitrite Increased Multiplication of nitrate-reducing bacteria RBCs, WBCs, and casts Disintegration in dilute alkaline urine Bacteria Multiplication Trichomonas Loss of motility, death

17 Specimen Preservation
Routine is refrigeration at 2°C to 8°C Decreases bacterial growth and metabolism Must return to room temperature for chemical testing Chemical preservative Ideal is bactericidal: inhibits urease and preserves formed elements Should not interfere with chemical tests Commercial transport tubes are available, but they must be compatible with tests

18 Preservatives Preservatives Advantages Disadvantages
Additional Information Refrigeration Does not interfere with chemical tests Precipitates amorphous phosphates and urates Prevents bacterial growth for 24 h2 Boric acid Prevents bacterial growth and metabolism Interferes with drug and hormone analyses Keeps pH at about 6.0 Can be used for urine culture transport Formalin (formaldehyde) Excellent sediment preservative Acts as a reducing agent, interfering with chemical tests for glucose, blood, leukocyte esterase, and copper reduction Rinse specimen container with formalin to preserve cells and casts Sodium fluoride Is a good preservative for drug analyses Inhibits reagent strip tests for glucose, blood, and leukocytes

19 Preservatives (cont’d)
Advantages Disadvantages Additional Information Commercial preservative tablets Convenient when refrigeration not possible Have controlled concentration to minimize interference Check tablet composition to determine possible effects on desired tests Urine Collection Kits4 (Becton Dickinson, Rutherford, NJ) Contains collection cup, transfer straw, C&S preservative tube or UA tube Light gray and gray C&S tube Sample stable at room temperature (RT) for 48 h; prevents bacterial growth and metabolism Do not use if urine is below minimum fill line Preservative is boric acid, sodium borate, and sodium formate Keeps pH at about 6.0

20 Types of Specimen The composition of urine depends on the patient’s metabolic state and the timing and procedure used for collection Time, length, and method of collection and the patient’s dietary and medicinal intake Patients must be instructed when special collection techniques are required

21 Random Specimen Most common type received
Routine screening for obvious abnormalities May be collected at any time Collection time must be recorded Dietary intake and physical activity may alter results Patients may have to collect an additional specimen under controlled conditions

22 First Morning Specimen
Ideal screening specimen Patient is in a basal state Use for orthostatic protein confirmation and urine pregnancy tests More concentrated than a random specimen Patient collects immediately on arising, delivers to lab within 2 hours Refrigeration is an alternative

23 Fasting Specimen Actually is second specimen voided, collected after the first morning specimen Does not contain metabolites from evening meal Recommended for glucose monitoring

24 24-Hour (Timed) Specimen
Carefully timed specimen will produce accurate quantitative results Good for diurnal variation solutes Catecholamines, electrolytes The patient must remain adequately hydrated during short collection period Patient must be instructed on the procedure for collecting a timed specimen Concentration of a substance in a particular period must be calculated from the urine volume produced during that time

25 24-Hour (Timed) Specimen (cont’d)
24-hour specimen must be thoroughly mixed and the volume accurately measured and recorded Multiple containers of the same collection must be combined and mixed thoroughly Additives should not interfere with the tests to be performed

26 24-Hour (Timed) Specimen (cont’d)
Required for quantitative results 24-hour specimens are needed for measuring substances with diurnal variation (results differ in a.m. and p.m.) and substances that vary with meals, activity, and body metabolism Shorter timed specimens can be used for substances with consistent levels Accurate timing is critical for accurate results

27 2-Hour Postprandial Specimen
Patient voids before eating routine meal Eats meal Collects next specimen 2 hours after finishing meal Monitors insulin therapy Results can be compared with fasting urine specimen and blood test results

28 Glucose Tolerance Specimen
Institutional option for collection with blood glucose tolerance test, not frequently done Specimens are collected at the same intervals as the blood samples Used to correlate renal threshold with patient’s ability to metabolize glucose

29 Catheterized Specimens
Sterile specimen collected from bladder with a hollow tube (catheter) Most common test is bacterial culture

30 Midstream Clean-Catch Specimen
Alternative to catheterized specimen Less traumatic method Less contaminated than routine collection Provide patient with mild cleansing material and container and instructions Do not touch or contaminate inside of container

31 Suprapubic Aspiration
Completely free of contamination for culture and cytology External introduction of needle for aspiration from the bladder Possible pediatric specimen

32 Prostatitis Specimen Collection similar to midstream clean-catch
Three-glass collection Container 1: first urine passed Container 2: midstream urine Massage prostate to obtain prostatic fluid Container 3: remaining urine and fluid Quantitative cultures on all three specimens, examine 1 and 3 microscopically for WBCs

33 Prostatitis Specimen (cont’d)
Prostatic infection = higher WBC/hpf count in specimen 3 than specimen 1; bacterial count in specimen 3 is 10 times higher than in specimen 1 Specimen 2 is a control for bladder or kidney infection Positive culture in specimen 2 invalidates positive culture in specimen 3 (cannot differentiate urinary tract infection from prostate infection)

34 Prostatitis Specimen (cont’d)
Pre- and postmassage test Specimen 1: midstream clean-catch specimen Specimen 2: postmassage specimen Prostatitis is indicated by a quantitative culture result in the second glass that is 10 times higher than specimen 1

35 Pediatric Specimens Soft, clear, plastic bags, with hypoallergenic tape applied to genital area Monitor bag frequently Clean-catch method with sterile bag can be used Cleaning for microbiology specimens Bags with tubes to a larger container are available for timed specimens

36 Drug Specimen Collection
Proper collection, labeling, and handling must be documented Chain of custody: documentation from the time of specimen collection until the time of receipt of laboratory results Free of substitution, adulteration, or dilution Standardized form always accompanies specimen Specimen must withstand legal scrutiny

37 Drug Specimen Collection (cont’d)
Points to consider Photo ID of urine donor or ID by employer No unauthorized access to specimen Witnessed versus unwitnessed collection Determined by test orderer Both specimens must be handed immediately to collector

38 Drug Specimen Collection (cont’d)
Adulteration tests Temperature taken within 4 minutes must be 32.5°C to 37.7°C Report temperatures outside of range immediately Collect another specimen ASAP Inspect urine color for anything unusual Follow laboratory instructions for labeling, packaging, and transport


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