PHYSICAL EXAMINATION OF URINE

1. PHYSICAL EXAMINATION OF URINE CHAPTER 4

2. Learning Objectives Upon completing this chapter, the reader will be able to • List the common terminology used to report normal urine color. • Discuss the relationship of urochrome to normal urine color. • State how the presence of bilirubin, biliverdin, uroerythrin, and urobilin in a specimen may be suspected. • Discuss the significance of cloudy, red urine and clear, red urine. • Name two pathologic causes of black or brown urine.

3. Learning Objectives (cont’d) • Discuss the significance of phenazopyridine in a specimen. • State the clinical significance of urine clarity. • List the common terminology used to report clarity. • Describe the appearance and discuss the significance of amorphous phosphates and amorphous urates in freshly voided urine. • List three pathologic and four nonpathologic causes of cloudy urine. • Define specific gravity, and tell why this measurement can be significant in the routine analysis.

4. Learning Objectives (cont’d) • Describe the principles of the refractometer, reagent strip, and osmolality for determining specific gravity. • Given the concentration of glucose and protein in a specimen, calculate the correction needed to compensate for these high-molecular-weight substances in the refractometer specific gravity reading. • Name two nonpathogenic causes of abnormally high specific gravity readings using a refractometer. • Describe the advantages of measuring specific gravity using a reagent strip and osmolality. • State possible causes of abnormal urine odor.

5. Introduction • Physical examination of urine includes • Color • Clarity • Specific gravity • Results provide • Preliminary information • Correlation with other chemical and microscopic results

6. Physical Characteristics • Provides preliminary information concerning disorders such as • Glomerular bleeding • Liver disease • Inborn errors of metabolism • Urinary tract infection • Renal tubular function

7. Color • Ranges from colorless to black • Normal variations caused by • Normal metabolic functions • Physical activity • Ingested materials • Pathologic conditions • Abnormal variations caused by • Bleeding • Liver disease • Infection

8. Normal Urine Color • Common terminology • Pale yellow, yellow, dark yellow • Should be consistent within institution • Urochrome is pigment causing yellow color • Normally excreted at a constant rate • Increased in thyroid disorders and fasting • Increases when specimen sits at room temperature • Provides estimate of body hydration • Pale yellow to dark yellow can be normal

9. Normal Urine Color (cont’d) • Additional pigments uroerythrin, urobilin • Color changes in older specimens • Uroerythrin • Pink pigment • Attaches to amorphous urates formed in refrigerated specimens • Urobilin • Oxidation of normal constituent, urobilinogen • Orange-brown color in older specimens

10. Abnormal Urine Color • Many colors and causes • Often reason patient comes to the physician • Common abnormal colors • Dark yellow/amber/orange • Red/pink/brown • Brown/black • Blue/green

11. Dark Yellow/Amber/Orange • Dark yellow and amber • Normal = concentrated urine • Abnormal = bilirubin • Bilirubin indicates possible hepatitis virus present • Standard precautions • Foam • Bilirubin produces yellow foam when shaken • Normal urine produces small amount of white foam caused by protein

12. Dark Yellow/Amber/Orange (cont’d) • Photooxidation of large amounts of urobilinogen produces yellow-orange urine • No yellow foam when shaken • Photooxidation of bilirubin to biliverdin produces yellow-green urine

13. Dark Yellow/Amber/Orange (cont’d) • Phenazopyridine (pyridium) or Azo-Gantrisin for urinary tract infection produces thick orange pigment and yellow foam (no bilirubin) • Thick pigment is noticeable, obscures natural color, and interferes with reagent strips

14. Red/Pink/Brown • Blood is a common cause of red urine • Color can range from pink to brown • Pink = small amount of blood • Brown = oxidation of hemoglobin to methemoglobin • Methemoglobin • RBCs remaining in acid urine • Fresh brown specimen can indicate glomerular bleeding • Cloudy red urine = RBCs • Clear red urine = hemoglobin/myoglobin • Hemoglobin • In vivo lysis of RBCs • Patient’s plasma will also be red • Consider in vitro lysis/specimen handling

15. Red/Pink/Brown (cont’d) • Myoglobin • Breakdown of skeletal muscle • Fresh urine is often more reddish/brown • Patient’s plasma is clear • Port wine–colored urine • Oxidation of porphobilinogen to porphyrias • Nonpathogenic red urine • Menstrual contamination • Pigmented foods • Medications (rifampin, pheno-compounds) • Fresh beets • Genetically susceptible people in alkaline urine • Black raspberries in acid urine

16. Brown/Black • Additional testing for specimens that • Turn black after standing at room temperature • Test negative for blood • Melanin • Excess in malignant melanoma • Oxidation of melanogen to melanin • Homogentisic acid • Black color in alkaline urine • Alkaptonuria • Medications, levodopa, phenol derivatives, flagyl

17. Blue/Green • Urinary and intestinal bacterial infections are the pathogenic cause • Urinary: pseudomonas infection • Intestinal: infection causing increased urinary indican oxidizing to indigo blue • Catheter bags: purple color from Klebsiella, Providencia, and indican • IV phenol medications cause green • Clorets (green) medications: Robaxin, methylene blue, Elavil (blue)

18. Color and Clarity Procedure • Use a well-mixed specimen • View through a clear container • View against a white background • Maintain adequate room lighting • Evaluate a consistent volume of specimen • Determine color and clarity

19. Clarity • Refers to the transparency or turbidity of a specimen • Normal reporting • Clear, hazy, cloudy, turbid, milky • Visual examination • Gently swirl specimen in a clear container in front of a good light source • Automated turbidity readings are available • Fresh clean-catch urine is normally clear

20. Urine Clarity • Clear: No visible particulates, transparent • Hazy: Few particulates, print easily seen through urine • Cloudy: Many particulates, print blurred through urine • Turbid: Print cannot be seen through urine • Milky: May precipitate or be clotted

21. Nonpathogenic Turbidity • Hazy female specimens with squamous epithelial cells and mucus • Bacterial growth in nonpreserved specimens • Refrigerated specimens with precipitated amorphous phosphates (white) and urates (pink) • Contamination: fecal, talc, semen, vaginal creams, IV contrast media

22. Pathologic Turbidity • Most common: RBCs, WBCs, bacteria • Also: nonsquamous epithelial cells, yeast, abnormal crystals, lymph fluid, lipids • The extent of turbidity should correspond to the amount of material observed in the microscopic examination • Clarity is one of the criteria considered in determining the necessity of performing a microscopic examination

23. Specific Gravity (SG) • Evaluation of urine concentration • Determines if specimen is concentrated enough to provide reliable screening results • Definition: the density of a solution compared with the density of an equal volume of distilled water at the same temperature

24. Specific Gravity (SG) (cont’d) • Isosthenuric: SG of 1.010 (the SG of the plasma ultrafiltrate) • Hyposthenuric: SG lower than 1.010 • Hypersthenuric: SG higher than 1.010 • Normal random specimen range • 1.003 to 1.035; most common 1.015 to 1.025 • Below 1.003 may not be urine • Consistent low readings: further testing

25. Refractometer • Measures velocity of light in air versus velocity of light in a solution • Concentration changes the velocity and angle at which the light passes through the solution • Prism in the refractometer determines the angle that light is passing through the urine and converts angle to calibrated viewing scale

26. Refractometer (cont'd)

27. Refractometer(cont’d) • Advantages • Temperature compensation not needed • Light passes through temperature-compensating liquid • Compensated between 15°C and 38°C • Small specimen size: one or two drops

28. Glucose and Protein Corrections • Subtract 0.003 for each gram of protein present • Subtract 0.004 for each gram of glucose present • Protein or glucose concentration can be determined from the chemical reagent strip tests

29. Correction Example • A specimen containing 1 g/dL protein and 1 g/dL glucose has a specific gravity reading of 1.030 • Calculate the corrected reading 1.030 – 0.003 (protein) = 1.027 – 0.004 (glucose) = 1.023 corrected specific gravity

30. Methodology • Drop of urine placed on prism • Focus on light source, and read scale • Wipe off prism between specimens • Calibration • Distilled water should read 1.000; adjust set screw if necessary • 5% NaCl should read 1.022 ± 0.001 • 9% sucrose should read 1.034 ± 0.001

31. Clinical Correlations • Abnormally high results = >1.040 • Radiographic contrast media (IVP) • Dextran, other IV plasma expanders • Check patient’s clinical course/history • Reagent strip readings and osmometry not affected by high-molecular-weight substances • Should be used as an alternative if possible

33. Osmolality • A more representative measure of renal concentrating ability can be obtained • Specific gravity depends on the number of particles present in a solution and the density of these particles • Osmolality is affected only by the number of particles present • Substances of interest are small molecules • Sodium • Chloride • Urea

34. Osmole • 1 g molecular weight of a substance divided by the number of particles into which it dissociates (= to MW of substance) • Glu = 180 g/osm (C + H + O) • NaCl = 58.5 g/osm (Na + Cl) • The unit of measure used in the clinical laboratory is the milliosmole (mOsm)

35. Osmolarity • Osmolality of a solution can be determined by measuring a property that is mathematically related to the number of particles in the solution • Colligative property • Changes in colligative properties • Lower freezing point • Higher boiling point • Increased osmotic pressure • Lower vapor pressure

36. Measuring Osmolality • Measuring osmolality in the urinalysis laboratory requires an osmometer • Additional step in the routine urinalysis procedure • Automated osmometer utilizes freezing point depression to measure osmolality

37. Reagent Strip SG • The reagent strip reaction is based on the change in pKa (dissociation constant) of a polyelectrolyte in an alkaline medium • Releasing H ions in direct proportion to the number of ions in the solution • The more hydrogen ions released, the lower is the pH • Indicator bromothymol-LS blue on the reagent pad measures the change in pH • Indicator changes from blue (1.000 [alkaline]), through shades of green, to yellow (1.030 [acid]) • Not affected by nonionizing substances

38. Specific Gravity Dip Stick

39. Odor • Not routinely reported • Fresh urine: faintly aromatic • Older urine: ammonia • Metabolic disorders: maple syrup urine disease, ketosis (fruity), infection (ammonia/unpleasant) • Food: garlic, onions, asparagus (genetic: only certain people can smell asparagus, but all produce odor)

40. Common Causes of Urine Odor