V. Physical Examination of Urine

What causes the normal yellow color of urine?

• It is derived from the pigmented substance called Urochrome

  • Increase urochrome production can result from thyroid disease or fasting urine sample

• Urobilin also adds minimally to the normal yellow color

  • This is formed from the oxidation of urobilinogen as urine stands

  • In unpreserved urine, the color deepens to orange-brown

How does Uroerythrin affect urine?

• Adds slight pink pigment, especially following refrigeration as the pigment attaches to the precipitated amorphous urates

What is the Clinical Significance of Colorless/Pale Yellow urine?

• Could be from Random Specimen

• May indicate diabetes insipidus or diabetes mellitus with increased urine excretion

What is the Clinical Significance of Dark Yellow urine?

• Concentrated specimen from First Morning sample or due to strenuous exercise

• Caused by dehydration such as from fever or burns

• A concentrated urine will also exhibit high specific gravity

What is the Clinical Significance of Intense Yellow/Amber/Orange urine?

• Pyridium (phenazopyridine) - UTI medication

  • Thick orange urine will mask chemical and microscopic analysis

• Bilirubin (i.e., bilirubinemia) due to liver problems such as hepatitis, biliary obstruction

  • Increased bilirubin in the blood will cause bilirubin in the urine

  • This will present as yellow foam when urine is shaken due to the presence of CONJUGATED BILIRUBIN

What is the Clinical Significance of Red/Pink urine?

• Blood due to glomerular bleeding

• Hemoglobin, erythrocytes

• Myoglobin (muscle trauma)

• Porphyrins

What is the Clinical Significance of Green/Blue urine?

• Medications and dyes such as amitriptyline, indican, phenols

• Infections causes by Pseudomonas species

What is the Clinical Significance of Brown/Black urine?

• Denatured Hemoglobin, melanin, homogentistic acid

What are the terms used to describe the Clarity of urine?

• Clear

• Hazy

• Slightly cloudy

• Cloudy

• Turbid

• Milky

• Bloody

What is the Clinical Significance of Clear urine?

• Normal urine with no formed elements

What is the Clinical Significance of Hazy/Slightly Cloudy urine?

• May have low numbers of formed elements

What is the Clinical Significance of Cloudy Urine?

• If in acidic urine, this may be due to:

  • Amorphous urates (with slight pink color)

  • Calcium Oxalate crystals

  • Uric acid crystals

• If in alkaline urine, this may be due to amorphous phosphates and carbonates

What is the Clinical Significance of Turbid urine?

• Indicate presence of large numbers of formed elements

Although not usually used in routine analysis, what odor types may be clinically significant?

• Ammonia Odor → indicate presence of bacteria as urea is metabolized into ammonia

• Strong Odor → indicate bacterial infection

• Sweet or fruit odor → indicate Ketone bodies due to diabetic ketosis

• Maple syrup odor → maple syrup urine disease

• Various odors may indicate difference foods ingested

What is Specific Gravity?

• Density of a substance compared with the density of a similar volume of deionized water at a similar temperature and is influenced by the number of particles dissolved and by particle size

Why is Specific Gravity measurement important?

• It determines the kidney’s ability to reabsorb essential chemicals and water from the glomerular filtrate since reabsorption is usually the first renal function to become impaired

• SG is also useful in detecting dehydration and antidiuretic hormone abnormalities

What is a Refractometer used for?

• To measure SG by via refractive index

• It compares the velocity of light in air to the velocity of light in a solution

• This method uses a small volume of urine and does not require temperature corrections

What is the SG of the plasma filtrate entering the glomerulus?

SG of about 1.010

What is the normal SG range for random urine?

It can range from 1.002 to 1.035

What is the clinical significance of Isosthenuric urine?

• When urine SG is fixed at 1.010

• This indicates loss of concentrating and diluting ability of the kidney

• Hyposthenuric vs Hypersthenuric

What is the Clinical Significance of Low Specific Gravity?

• This indicates loss of the kidney’s ability to concentrate urine

• May also be caused by disease such as Diabetes insipidus, glomerulonephritis, and pyelonephritis

• Can also be found normally if the person has a large fluid intake

What is the Clinical Significance of High Specific gravity?

• This may be due to Adrenal insufficiency, diabetes mellitus, hepatic disease, congestive heart failure, or dehydration

  • Dehydration due to vomiting, diarrhea, low fluid intake, or strenuous exercise

• Interference from X-ray contrast media may result in SG of >1.035