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 Results provide
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 Methemoglobin
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 Melanin
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 (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 to 1.025
Below 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 for each gram of protein present
Subtract 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 – (protein) = – (glucose) = 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 ± 0.001
9% sucrose should read ± 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
Aromatic
Normal
Foul, ammonia-like
Bacterial decomposition, urinary tract infection
Fruity, sweet
Ketones (diabetes mellitus, starvation, vomiting)
Maple syrup
Maple syrup urine disease
Mousy
Phenylketonuria
Rancid
Tyrosinemia
Sweaty feet
Isovaleric acidemia
Cabbage
Methionine malabsorption
Bleach
Contamination