Urinalysis chapter 5

Physical examination of the urine includes:

• color

• clarity

• specific gravity

What can the variations of color in urine be due to?

• normal metabolic function

• physical activity

• ingested materials

• pathological conditions

How should a urine specimen be examined for color?

Using a good light source look through the container against a white background

What is the yellow color in urine due to?

Urochrome

When is urochrome production dependant on?

The body’s metabolic state

When is urochrome production increased?

In thyroid conditions and/or those in a fasting state

Under normal conditions what rate is urochrome excreted at?

A constant rate

What other pigments are present in urine?

Uroerythrin and urobilin

When is uroerythrin most evident?

In refrigerated samples, it attaches to amorphous urates and gives a pink color to the sediment

When is urobilin most evident?

In old urine, it is the product of the oxygenation of urobilinogen

What causes colorless urine?

Recent fluid consumption

What causes pale urine?

• dilute random specimens

• polyuria or diabetes

What causes dark yellow urine?

• concentrated specimens (exercise or first morning)

• b complex vitamins

• dehydration

• acriflavine

• nitrofurantoin

What causes orange-yellow urine?

• phenazopyridine

• phenindione

• sulfasalazine

What causes yellow-green urine?

Bilirubin oxidized to biliverdin

What causes green urine?

• Pseudomonas infection

• asparagus

What cause blue green urine?

• amitriptyline

• methocarbamol

• clorets

• indican

• methylene blue

• phenol

• propofol

• familial hypercalcemia

• indomethacin

What causes pink/red urine?

• RBCs

• hemoglobin

• myoglobin

• beets

• rifampin

• menstral contamination

What causes port wine urine?

Porphyrins

What causes red-brown urine?

• myoglobin

• Oxidized RBCs

What causes brown/black urine?

• homogentisic acid

• malignant melanoma

• phenol derivatives

• argyrol

• methyldopa

• metronidazole

• chloroquine

• methocarbamol

• fava beans, rhubarb, aloe

What happens to samples containing bilirubin when shaken?

Yellow foam appears

What happens to normal urine when shaken?

Small amount of rapidly disappearing foam appears, with a large amount of white foam appearing with increased concentration of protein

When is phenazopyridine given?

To treat urinary tract infections, gives orange-yellow color to urine.

What happens to RBCs left in acidic urine for several hours?

Turn brown due to oxidation of hemoglobin to methemoglobin.

Fresh urine with this color indicated glomerular bleeding

What happens to urine clarity if hemoglobin and myoglobin are present?

Specimen is red and clear. Urine containing intact RBCs is cloudy

How are myoglobin and hemoglobin -urina distigusted?

By examination of plasma

What color should the plasma be to indicate hemoglobinuria?

Red due to in vivo breakdown of RBCs

What color is the plasma in myoglobinuria?

Clear as myoglobin is cleared more rapidly from the plasma

The port wine color of urine results from the oxidation of?

Porphobilinogen to porphyrins

What condition produces homogentisic acid and black urine?

alkaptonuria, caused by an error in metabolism that prevents the full breakdown of phenylalanine

What is familial benign hypercalcemia also called?

blue diaper syndrome

What is the clarity for normal fresh urine?

Clear, might be cloudy in alkaline urine

What are some nonpathological causes of turbidity in urine?

• mucus and squamous epithelial cells

• standing or refrigerated specimens

• semen

• radiographic contrast

What are some pathological causes of turbidity in urine?

• RBCs

• WBCs

• bacteria

• yeast

• trichomonads

• abnormal crystals

• lymph fluid

• lipids

What does hyposthenuric mean?

Urine with a specific gravity lower than 1.010

What does hypersthenuric mean?

Urine with a specific gravity higher than 1.010

At what specific gravity are specimens probably not urine?

lower than 1.002

What is specific gravity defined as?

The density of a solution compared with the density of a similar volume of distilled water

What is the only method of routine urinalysis that required correcting?

The refractometer

How does refractometry determine the concentration of dissolved particles?

By measuring the refractive index

What is the refractive index?

A comparison of velocity of light in air with the velocity of light in a solution

What is the advantage of using a refractometer?

Only a small volume of sample is needed

What methods are used to determine specific gravity?

• refractometry

• osmolality

• reagent strip

What two substances must a refractometer reading be corrected for?

glucose and protein

What can cause abnormality high specific gravities?

• injected radiographic contrast

• dextran and other high molecular weigh IV fluids

Osmolality is affected by?

the number of particles present

An osmole is defined as?

One gram molecular weigh of a substance divided by the number of particles into which it dissolves

In the clinical lab what is the unit of measurement for osmolality?

milliosmole (mOsm)

What colligative properties does solute dissolved in solute change?

• lower freezing point

• higher boiling point

• increased osmotic pressure

• lower vapor pressure

What is a colligative properity?

A property that is mathematically related to the number of particles in the solution

What do reagent strips for specific gravity measure?

the dissociation constant (pKa) of a polyelectrolyte in an alkaline medium

How does the polyelectrolyte work?

It ions and releases a proportional of hydrogen ions to ions in the solution. The resulting ph changes is indicated by bromothymol blue

What happens to the odor of urine as it stands?

Ammonia smell increases

What causes a foul oder?

Bacteria

What causes a fruity odor in urine?

Diabetic ketones