Urinalysis

Jennifer Lyon, M.S., M.L.I.S.Jennifer.Lyon@Vanderbilt.edu

Joanna Karpinski, M.L.I.S.Joanna.Karpinski@Vanderbilt.edu

Urinalysis

A complete urinalysis consists of three distinct testing phases:

Physical examination – Evaluates the urine's color, clarity, and concentration

Chemical examination – Tests chemically for many substances that provide valuable

information about health and disease only some of these are covered today

Microscopic examination Identifies and counts types of cells, casts, crystals, and other

components (bacteria, mucous) that can be present in urine

Additional testing: urine culture (check to see if a microorganism is growing in the urine – not covered today)

Why Is It Important?

Urine composition provides information about: The health and function of part of the body’s

waste management system State of kidney functionPossible blood abnormalities

Urine analysis can help a clinician: Identify infections and other diseases Gauge generally the body’s hydration level

Sample Clinical Questions

Is there a predictive value of acute kidney injury in ICU patients?

Is there a method for localizing the site of a urinary tract infection: upper (renal) vs. lower (bladder).

Which is the best procedure: rapid (quick-emptying) versus slow (periodically-clamped) voiding of urine through a catheter in patients with urinary retention?

What strategies to prevent urinary tract infection in the acutely ill adult population are supported by evidence

Is MRSA (methicillin-resistant staphylococcus aureus) a significant pathogen for urinary tract infections?

Physical Exam

ColorConcentrationClarity (Turbidity)

(rarely) Odor

Urine ColorThe depth of urine color is also a crude indicator of urine

concentration: A dilute urine where lots of water is being excreted: pale yellow Excretion of waste products in as little water as possible (eg., during a

fever, or first morning urine): dark yellow

Normal color range: yellow to dark amber

Some color changes may not indicate disease: Drugs and vitamins: chloroquine, iron supplements, levodopa,

nitrofurantoin, phenazopyridine, phenothiazines, phenytoin, B vitamins, warfarin…

Food: beets… Contamination: menses…

Some can indicate disease or damage: Trauma – presence of red blood cells(RBCs)-(red) Disease/disorder – presence of RBCs(red), chirrhosis(dark amber),

melanin/melanoma(black), liver disease(neon yellow)

Urine Concentration

Accurate measurement of urine concentration can be done using chemical tests called specific gravity and osmolality Measures the amount of dissolved substances in

the urine water

The specific gravity and osmolality tests will be covered in the Chemical Exam section.

Urine Clarity

Urine clarity refers to how clear the urine is Labs usually report clarity of the urine as

clear slightly cloudy cloudy turbid

“Normal” urine can be clear or cloudy Clinically unimportant substances that cause cloudiness:

mucous, sperm and prostatic fluid, cells from the skin, normal urine crystals, and contaminants (eg. body lotions/powders)

Clinically important substances that cause cloudiness: Red blood cells, white blood cells, protein, and bacteria

Chemical Exam

These tests are often done using a urine dipstick - a plastic stick that has patches of chemical indicators on it which is placed in the urine. The color changes of the patches provide the results.

specific gravity/osmolality pH protein hematuria (see also RBCs under microscopic exam) glucose ketones leukocyte esterase nitrite bilirubin and urobilinogen

Specific Gravity (urine density)

Specific gravity measures the concentration of particles in a solution (grams/ml).

Normal values under specific conditions: 1.010 to 1.025 (normal specific gravity) 1.001 after water loading More than 1.025 after water deprivation Concentrated (increased specific gravity) after ADH

administration

Specific Gravity - Abnormalities

Increased urine specific gravity may indicate: Dehydration; Water restriction Diarrhea; Vomiting; Excessive sweating Glucosuria Heart failure (related to decreased blood flow to the kidneys) Renal arterial stenosis Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Decreased urine specific gravity may indicate: Excessive fluid intake Diabetes insipidus – central or nephrogenic Renal failure (loss of ability to reabsorb water) Pyelonephritis

Urine Osmolality

Normal values are 50 to 1400 mOsm/kg 12 to 14 hour fluid restriction: greater than 850 mOsm/kg

Greater-than-normal measurements may indicate: Addison's disease (rare) Congestive heart failure Shock Syndrome of inappropriate ADH secretion

Lower-than-normal measurements may indicate: Aldosteronism (very rare) Diabetes insipidus (rare) Excess fluid intake Renal tubular necrosis Severe pyelonephritis

pH (acidity/alkalinity of the urine )

The normal values range from 4.6 to 8.0. A high urine pH (alkaline urine) may indicate:

Gastric suction Renal failure Renal tubular acidosis Urinary tract infection Vomiting

A low urine pH (acidic urine) may indicate: Chronic obstructive pulmonary disease Diabetic ketoacidosis Diarrhea Starvation

The drugs acetazolamide, potassium citrate, or sodium bicarbonate can increase pH; Ammonium chloride, chlorothiazide diuretics, and methenamine mandelate can decrease urine pH

Proteinuria (protein in the urine)

For a spot check by dipstick: the normal values are approximately 0 to 8 mg/dl.

For a 24-hour test: the normal value is less than 150mg per 24 hours.

An abnormal value (high value) usually indicates a kidney disorder/disease

Proteinuria: Mild(<0.5g/day), moderate (.05-4g/day), severe (>4g/day)

Other conditions that can also produce proteinuria include

Blood diseases involving lysis (destruction) of red blood cells Inflammation Cancer Injury of the urinary tract (bladder, prostate, or urethra) Preeclampsia

Glucosuria

Glucose should not be detectable in the urine

Diabetes (via high blood sugar) is the most common cause of glucosuria

Other causes include renal glycosuria (decrease or absence of the kidneys’ ability to absorb glucose), hormonal disorders, liver disease, some medications, and pregnancy

Hematuria

Normal: Only an occasional RBC (1-4/high power field; 1000 per millimeter of urine)

The urinary dipstick for blood measures intact RBCs, free hemoglobin, and myoglobin

False-positive results in women from contamination with menstrual blood

More detail provided in the microscopic exam portion of this presentation)

Ketones

Ketones (beta-hydroxybutyric acid, acetoacetic acid, and acetone) are intermediate products of fat metabolism and are present in starvation and diabetes

Normal: negative test result

Classification of acetone presence in the urine Small - < 20 mg/dL Moderate - 30-40 mg/dL Large - > 80 mg/dL

Ketonuria: presence of ketones in urine

Ketone Abnormalities

A positive test may indicate: Metabolic abnormalities, including uncontrolled

diabetes or glycogen storage disease Abnormal nutritional conditions, including starvation,

fasting, anorexia, high protein or low carbohydrate diets

Protracted vomiting, (eg. hyperemesis gravidarum) Disorders of increased metabolism, including

hyperthyroidism, fever, acute or severe illness, burns, pregnancy, lactation or post-surgical condition

Some drugs

Leukocyte Esterase Leukocyte esterase is an enzyme present in most white blood cells

(WBCs)

A few white blood cells is normal in urine (see microscopic examination) and this test is negative

When the number of WBCs in urine increases significantly, test will become positive

WBC count in urine is high = Inflammation/infection in the kidney or urinary tract

Common cause for WBCs in urine (leukocyturia): bacterial infection, eg. a bladder infection

Source of contamination: vaginal secretions

Nitrite

Test is used to detect a bacterial urinary tract infections (UTI) because many bacteria convert nitrate to nitrite

Normally, the urinary tract and urine are sterile Thus, no nitrites would be found

A negative test does not rule out a UTI Not all bacteria are capable of converting nitrate to

nitrite

Bilirubin

Bilirubin (a degradation product of hemoglobin) is not present in the urine of normal, healthy individuals

Increased bilirubin in the urine means that the bile ducts are obstructed

Causes include biliary strictures cirrhosis gallstones in the biliary tract hepatitis with associated biliary obstruction surgical trauma affecting the biliary tract tumors of the liver or gall bladder

Urobilirubin

Urobilinogen (a degradation product of bilirubin) is normally present in urine in low concentrations – source of color

High concentrations can be due to Hemolytic processes Hepatocellular disease

Absence may be due to Complete biliary obstruction Broad-spectrum antibiotics

Normal levels are usually too low (<0.4mg/dl) to be detectable with the urine dipstick method

Microscopic Exam

Part of the urinalysis is the examination of some urine with a microscope

Cells, crystals, and other substances are counted and reported either as the number observed “per low power field” (LPF) or “per high power field” (HPF)

Some entities are estimated as “few,” “moderate,” or “many,” such as epitheial cells, bacteria, and crystals

Microscopic Exam

Things found on microscopic exam can include:

Bacteria and other microorganisms Casts Crystals Fat Mucous Red blood cells Renal tubular cells Transitional epithelial cells White blood cells (Pyuria)

RBCs

Only a few RBCs (erythrocytes) should be present in urine sediment

Normal values are less than, or equal to 4 RBC/HPF

Normal value ranges may vary slightly among different laboratories

Note: RBC/HPF = red blood cells per high power field (a microscopic exam)

RBCs - Abnormalities

Hematuria – presence of RBCs in urine

Hemoglobinuria – hemoglobin in urine Even small increases in the amount of RBCs in urine are

significant. Causes:

Numerous diseases of the kidney and urinary tract Trauma Medications Smoking Strenuous exercise

All patients with hematuria (>5 RBC/HPF) require further diagnostic workup

WBCs (Pyuria)

The number of WBCs in urine sediment is normally low (1-4 WBCs/HPF)

The presence of >5 WBC/HPF = significant pyuria

When the number is high, it indicates an infection, damage or inflammation somewhere in the urinary tract

Causes include calculous disease, strictures, neoplasm, glomerulonephropathy, or interstitial cystitis

Epithelial Cells

Epithelial cells: cells that form sheets that cover the surface of the body and line internal organs

Healthy urine shows a few normal epithelial cells and is relatively free of debris

Epithelial cells are usually reported as “few,” “moderate,” or “many” present per low power field (LPF)

In urinary tract conditions such as infections, inflammation, and malignancies, more epithelial cells are present

Microorganisms

Include bacteria, trichomonads, yeast In health, the urinary tract is sterile: No microorganisms Presence indicates infection

Microorganisms are usually reported as “few,” “moderate,” or “many” present per high power field (HPF)

Microorganisms found may be from specimen contamination: From bacteria that normally live on the skin or in vaginal

secretions (most often women) Yeast can also be present in urine and are more common

in women due to a vaginal yeast infection

Trichomonads

Trichomonads are parasites that may be found in the urine of women or men (rarely)

Often infect the vaginal canal

Their presence in urine is due to contamination during urine collection

Urinary Casts Casts – renal tubule “imprints” –

Absent in normal people, except for a few (0–5) hyaline casts per LPF.

Abnormal results include:

Hyaline casts – made of protein; caused by dehydration, exercise, diuretic meds

Granular casts -- include prominent granules; related to underlying kidney disease Fatty casts –condition of lipiduria (lipids in urine); related to nephrotic syndrome

RBC casts – result of bleeding into tubule from the glomerulus; nephrotic syndrome

WBC casts – interstitial cell kidney disease (interstitial inflammation, pyelonephritis, and parenchymal infection)

Renal tubular epithelial cell casts -- damage to the tubules; ie.renal tubular necrosis

Crystals

Urine contains many chemicals dissolved in the urine for elimination from the body.

These solutes can form crystals based on the urine pH & temperature and their concentration.

Crystals are identified by their shape, color, and urine pH.

Crystals are considered “normal” if they are from solutes that should be in urine

If they are from solutes that are not supposed to be in the urine, they are considered “abnormal.” Acidic urine: uric acid, oxalate, cystine Alkaline urine: phosphate

Quick Summary: Normal Values

Normal color varies from almost colorless to dark amber. The urine specific gravity ranges between 1.003 and

1.030 (higher numbers mean a higher concentration). The normal pH range is from 4.6 to 8.0, with an average

of 6.0. There is usually no detectable urine glucose, nitrites,

ketones, or protein. There are usually no red blood cells in urine (<4/HPF). Hemoglobin is not normally found in the urine. Bilirubin is normally not detected in the urine. There may

be a trace of urobilinogen in the urine. White blood cells (leukocytes) are not normally present

in the urine (<4/HPF).

Resources

http://www.labtestsonline.org/understanding/analytes/urinalysis/sample.html

http://kidshealth.org/parent/general/sick/labtest7_p2.html

http://www.nlm.nih.gov/medlineplus/ency/article/003579.htm

Corbett JV. Laboratory Tests and Diagnostic Procedures. 5th ed. New Jersey: Prentice-Hall, Inc., 2000.

Current Medical Diagnosis & Treatment - 44th Ed. (2005) online via Stat!-Ref