MLTS 1453 - Exam 2: Ch. 5 and 6

What does the physical examination of urine include?

• color

• clarity

• specific gravity

What can results of a physical examination of urine provide?

• preliminary information

• correlation w/ other chemical and microscopic results

What disorders can preliminary information (urine physical char.) provide?

• glomerular bleeding

• liver disease

• inborn errors of metabolism

• UTI

• renal tubular function

In Born Errors of Metabolism

large class of genetic diseases that involve a defect of a single gene that codes for an enzyme to convert a substance to be used by the body

What can urine color range from?

colorless to black

What normal variations can cause a color change in urine?

• normal metabolic functions

• physical activity

• ingested materials

• pathologic conditions

What is a normal urine color?

• pale yellow

• yellow

• dark yellow

What pigments are found in normal urine?

• urochrome

• uroerythrin

• urobilin

Urochrome

• pigment causing yellow color

• normally excreted at a constant rate

• increased in thyroid disorders and fasting

• increase when specimen sits at room temp

• provides estimate of body hydration

Uroerythrin

• pink pigment

• attaches to amorphous crates formed in refrigerated specimens (normal turbidity)

Urobilin

• oxidation of normal constituent, urobilinogen

• orange-brown color in older specimens

What are some common abnormal colors?

• dark yellow / amber / orange

• red / pink / brown

• brown / black

• blue / green

What may cause an amber color in the urine?

• bilirubin—breaks down when exposed to light1, produces yellow foam when shaken

• indicates possible hepatitis virus present

What may produce a yellow-orange urine?

• photooxidation of large amounts of urobilinogen

• no yellow foam when shaken

What may produce a yellow-green urine?

photooxidation of bilirubin to biliverdin

What drugs can cause a dark orange in urine?

• phenazopyridine (pyridium) or azo-gantrisin for UTIs—thick pigment orange (greasy / dark) and yellow foam (no bilirubin)

• thick pigment can interfere with/ reagent strips

What other drugs, other than Pyridium / AZO drug, can cause an orange-colored urine?

• azuflidine

• laxatives

• certain chemotherapy drugs

What is a common cause of red urine?

blood

What does a pink urine indicate?

small amount of blood

What does a brown urine indicate?

oxidation of Hgb to methemoglobin

What does methemoglobin in urine indicate?

• RBCs remain in acid urine

• fresh brown can indicate glomerular bleeding

What does a cloudy / clear red urine indicate?

• cloudy = RBCs

• clear = Hgb / myoglobin

Hemoglobin

• in vivo lysis of RBCs—patient’s plasma will also be red

• could be considered in vitro lysis—urine encounters something, lysing RBCs

Myoglobin

• breakdown of skeletal muscle

• fresh urine often more reddish / brown

• patient’s plasma is clear

What does a port wine-colored urine indicate?

• oxidation of porphobilinogen to Porphyrias

*NOTE: urine changes to port color upon standing

What are some nonpathogenic red urine?

• menstrual contamination

• pigmented foods

• medications (rifampin, pheno-compounds)

• fresh beets—genetically susceptible people in alkaline urine

• black raspberries in acid urine

What specimens required additional testing?

• turning black after standing at room temp.

• test neg. for blood

What may cause a brown / black urine?

• melanin

• homogentistic acid

• medications

Melanin

• excess in malignant melanoma

• oxidation of melange to melanin

Homogentisic Acid

• black color in alkaline urine

• Alkaptonuria

Alkaptonuria

• ‘In Born Error of Metabolism’ w/ phenylalanine in foods

• ‘alkali lover’ - urine becomes dark as it sits

• pH increase (alkaline)

• involves part of the phenylalanine-tyrosine pathway

What medications can cause a brown / black urine?

• levodopa

• methyldopa

• phenol derivatives

• flagyl

• furadantin

What may cause a blue / green urine?

• urinary and intestinal bacterial infections

• clorets (green)

• B vitamins and asparagus (green)

• catheter bags

• medications

If a UTI is the cause of a blue / green urine, what does it indicate?

possible pseudomonas infection

If an intestinal bacterial infection is the cause of a blue / green urine, what does it indicate?

infection causing increased urinary indican oxidizing to indigo blue

What medications can cause a blue / green urine?

• robaxin, indocin, tivorbex, elavil, diprivan (blue)

• IV phenol (green)

Clarity

• refers to the transparency or turbidity of a specimen

• one of the criteria considered in determining the necessity of performing a microscopic examination

What are some techniques to examine urine clarity?

• always mix first

• gently swirl specimen in a clear container in front of good light source

• specimen should be in a clear container

What two characteristics are routinely done at the same time for a urine specimen?

color and clarity

What terminology is used to report the clarity of a urine?

• clear

• hazy

• cloudy

• turbid

• milky

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

Describe the clarity of normal urine.

• freshly voided urine is usually clear, particularly if it is a midstream specimen

• amorphous phosphates and carbonates may cause white cloudiness in an alkaline urine specimen

• may still contain pathological constituents of clinical concern (ex. glucose or ketones)

Describe non-pathogenic turbidity in urine.

• hazy female specimens: SEC and mucus

• bacterial growth in non-preserved specimens

• refrigerated specimens w/ precipitated amorphous phosphates (white), carbonates (white), urates (pink)

• contamination: fecal, talc, semen, v-aginal creams, IV contrast media

How should amorphous crystals from refrigerated specimens be dissolved?

warm urine to room temp.

Describe pathological turbidity in urine.

• most common: RBCs, WBCs, bacteria

• non-SECs, yeast, trichomonads, abnormal crystals, lymph fluid, lipids

*NOTE: extent of turbidity should correspond to the amount of material observed in the. microscopic examination

Specific Gravity (SG)

• the density of a solution compared w/ the density of an equal volume of distilled water at the same temp.

• urine SG directly proportional to its’s dissolved solids and color

What does the evaluation of urine concentration indicate?

kidney’s ability to concentrate urine

How is the color of urine directly proportional to specific gravity?

• darker the urine = increased SG

• lighter the urine = decreased SG

Isosthenuric

SG of 1.010 (the SG of the plasma ultrafiltrate)

Hyposthenuric

SG lower than 1.010 (<1.010)

Hypersthenuric

SG higher than 1.010 (>1.010)

What is the specific gravity range for a normal random specimen?

• 1.003 to 1.035; most common 1.015 to 1.025

*NOTE: <1.002 may not be urine

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 solution

• prism determines the angle that light is passing through urine and converts angle to calibrated viewing scale

What are the advantages of a refractometer?

• temp. compensation not needed—light passes through temp.-compensating liquid; compensated b/w 15-38℃

• small specimen size: one drop

What are the disadvantages of a refractometer?

• don’t use for patients w/ X-ray dye contrast; use reagent strip for SG or osmolality

• can be falsely elevated due to glucose or protein in urine

Describe the process of using the refractometer.

• drop of urine placed on prism

• focus on light source and read scale

• wipe off prism b/w specimens

How is a refractometer calibrated?

• distilled water should be read at 1.000; adjust set screw if necessary

• 5% NaCl should read 1.022 ± 0.001

• 9% sucrose should read 1.034 ± 0.001

For large amounts of glucose or protein in urine, how is the refractometer reading corrected?

• protein = 1 g increases 0.003

• glucose = 1 g increases 0.004

Osmolality

• gives a more representative measure of renal concentrating ability

• affected only by the # of particles present

• requires osmometers

• unit: milliosmole (mOsm)

What substances are of interest pertaining to osmolality?

• sodium

• chloride

• urea

What does specific gravity of urine depend on?

• # of particles present in a solution

• density of these particles

What does automated osmometer utilize to measure osmolality?

freezing point depression

What is a reagent strip reaction based on?

change in pK_a (dissociation constant) of a polyelectrolyte in an alkaline medium

Describe indicator bromothymol-LS blue on the reagent pad.

• measures change in pH

• changes from: blue (1.000 [alkaline]), through shades of green, to yellow (1.030 [acid])

• not affected by nonionizing substances

What is the odor of fresh / older urine?

• fresh: faintly aromatic

• older: ammonia

What are some metabolic disorders that may cause an odor in urine?

• maple syrup urine disease

• ketosis (fruity)

• infection (ammonia/unpleasant)

• phenylpyruvic acid + phenylketonuria (‘mousy’)

What may cause a foul, ammonia-like odor in urine?

bacterial decomposition, UTIs

What may cause a fruity, sweet odor in urine?

ketones (diabetes mellitus, starvation, vomiting)

What may cause a mousy odor in urine?

phenylketonuria

Reagent Strips

• simple, rapid; single and multitask strips available

• specified by urinalysis instrumentation manufacturers

• consist of chemical-impregnated absorbent pads on a plastic strip—color producing

How are reactions on a reagent strip interpreted?

by comparing the color produced on the pad within the required time frame w/ a chart supplied by the manufacturer