Urinalysis





Definition

A urinalysis is a group of manual and/or automated qualitative and semi-quantitative tests performed on a urine sample. A routine urinalysis usually includes the following tests: color, transparency, specific gravity, pH, protein, glucose, ketones, blood, bilirubin, nitrite, urobilinogen, and leukocyte esterase. Some laboratories include a microscopic examination of urinary sediment with all routine urinalysis tests. If not, it is customary to perform the microscopic exam, if transparency, glucose, protein, blood, nitrite, or leukocyte esterase is abnormal.


Purpose

Routine urinalyses are performed for several reasons:

  • general health screening to detect renal and metabolic diseases
  • diagnosis of diseases or disorders of the kidneys or urinary tract
  • monitoring of patients with diabetes

In addition, quantitative urinalysis tests may be performed to help diagnose many specific disorders, such as endocrine diseases, bladder cancer, osteoporosis, and porphyrias (a group of disorders caused by chemical imbalance). Quantitative analysis often requires the use of a timed urine sample. The urinary microalbumin test measures the rate of albumin excretion in the urine using laboratory tests. This test is used to monitor the kidney function of persons with diabetes mellitus. In diabetics, the excretion of greater than 200 μg/mL albumin is predictive of impending kidney disease.

Precautions

Voided specimens

All patients should avoid intense athletic training or heavy physical work before the test, as these activities may cause small amounts of blood to appear in the urine. Many urinary constituents are labile, and samples should be tested within one hour of collection or refrigerated. Samples may be stored at 36–46°F (2–8°C) for up to 24 hours for chemical urinalysis tests; however, the microscopic examination should be performed within four hours of collection, if possible. To minimize sample contamination, women who require a urinalysis during menstruation should insert a fresh tampon before providing a urine sample.

Over two dozen drugs are known to interfere with various chemical urinalysis tests. These include:

  • ascorbic acid
  • chlorpromazine
  • L-dopa
  • nitrofurantoin (Macrodantin, Furadantin)
  • penicillin
  • phenazopyridine (Pyridium)
  • rifampin (Rifadin)
  • tolbutamide

The preservatives that are used to prevent loss of glucose and cells may affect biochemical test results. The use of preservatives should be avoided whenever possible in urine tests.


Description

Routine urinalysis consists of three testing groups: physical characteristics, biochemical tests, and microscopic evaluation.


Physical tests

The physical tests measure the color, transparency (clarity), and specific gravity of a urine sample. In some cases, the volume (daily output) may be measured. Color and transparency are determined from visual observation of the sample.

COLOR. Normal urine is straw yellow to amber in color. Abnormal colors include bright yellow, brown, black (gray), red, and green. These pigments may result from medications, dietary sources, or diseases. For example, red urine may be caused by blood or hemoglobin, beets, medications, and some porphyrias. Black-gray urine may result from melanin (melanoma) or homogentisic acid (alkaptonuria, a result of a metabolic disorder). Bright yellow urine may be caused by bilirubin (a bile pigment). Green urine may be caused by biliverdin or certain medications. Orange urine may be caused by some medications or excessive urobilinogen (chemical relatives of urobilinogen). Brown urine may be caused by excessive amounts of prophobilin or urobilin (a chemical produced in the intestines).

TRANSPARENCY. Normal urine is transparent. Turbid (cloudy) urine may be caused by either normal or abnormal processes. Normal conditions giving rise to turbid urine include precipitation of crystals, mucus, or vaginal discharge. Abnormal causes of turbidity include the presence of blood cells, yeast, and bacteria.

SPECIFIC GRAVITY. The specific gravity of urine is a measure of the concentration of dissolved solutes (substances in a solution), and it reflects the ability of the kidneys to concentrate the urine (conserve water). Specific gravity is usually measured by determining the refractive index of a urine sample (refractometry) or by chemical analysis. Specific gravity varies with fluid and solute intake. It will be increased (above 1.035) in persons with diabetes mellitus and persons taking large amounts of medication. It will also be increased after radiologic studies of the kidney owing to the excretion of x ray contrast dye. Consistently low specific gravity (1.003 or less) is seen in persons with diabetes insipidus. In renal (kidney) failure, the specific gravity remains equal to that of blood plasma (1.008–1.010) regardless of changes in the patient's salt and water intake. Urine volume below 400 mL per day is considered oliguria (low urine production), and may occur in persons who are dehydrated and those with some kidney diseases. A volume in excess of 2 liters (slightly more than 2 quarts) per day is considered polyuria (excessive urine production); it is common in persons with diabetes mellitus and diabetes insipidus.


Biochemical tests

Biochemical testing of urine is performed using dry reagent strips, often called dipsticks. A urine dipstick consists of a white plastic strip with absorbent microfiber cellulose pads attached to it. Each pad contains the dried reagents needed for a specific test. The person performing the test dips the strip into the urine, lets it sit for a specified amount of time, and compares the color change to a standard chart.

Additional tests are available for measuring the levels of bilirubin, protein, glucose, ketones, and urobilinogen in urine. In general, these individual tests provide greater sensitivity; they therefore permit detection of a lower concentration of the respective substance. A brief description of the most commonly used dry reagent strip tests follows.

pH: A combination of pH indicators (methyl red and bromthymol blue) react with hydrogen ions (H + ) to produce a color change over a pH range of 5.0 to 8.5. pH measurements are useful in determining metabolic or respiratory disturbances in acid-base balance. For example, kidney disease often results in retention of H + (reduced acid excretion). pH varies with a person's diet, tending to be acidic in people who eat meat but more alkaline in vegetarians. pH testing is also useful for the classification of urine crystals.

Protein: Based upon a phenomenon called the "protein error of indicators," this test uses a pH indicator, such as tetrabromphenol blue, that changes color (at constant pH) when albumin is present in the urine. Albumin is important in determining the presence of glomerular damage. The glomerulus is the network of capillaries in the kidneys that filters low molecular weight solutes such as urea, glucose, and salts, but normally prevents passage of protein or cells from blood into filtrate. Albuminuria occurs when the glomerular membrane is damaged, a condition called glomerulonephritis.

Glucose (sugar): The glucose test is used to monitor persons with diabetes. When blood glucose levels rise above 160 mg/dL, the glucose will be detected in urine. Consequently, glycosuria (glucose in the urine) may be the first indicator that diabetes or another hyperglycemic condition is present. The glucose test may be used to screen newborns for galactosuria and other disorders of carbohydrate metabolism that cause urinary excretion of a sugar other than glucose.

Ketones: Ketones are compounds resulting from the breakdown of fatty acids in the body. These ketones are produced in excess in disorders of carbohydrate metabolism, especially Type 1 diabetes mellitus. In diabetes, excess ketoacids in the blood may cause life-threatening acidosis and coma. These ketoacids and their salts spill into the urine, causing ketonuria. Ketones are also found in the urine in several other conditions, including fever; pregnancy; glycogen storage diseases; and weight loss produced by a carbohydrate-restricted diet.

Blood: Red cells and hemoglobin may enter the urine from the kidney or lower urinary tract. Testing for blood in the urine detects abnormal levels of either red cells or hemoglobin, which may be caused by excessive red cell destruction, glomerular disease, kidney or urinary tract infection, malignancy, or urinary tract injury.

Bilirubin: Bilirubin is a breakdown product of hemoglobin. Most of the bilirubin produced in humans is conjugated by the liver and excreted into the bile, but a very small amount of conjugated bilirubin is reabsorbed and reaches the general circulation to be excreted in the urine. The normal level of urinary bilirubin is below the detection limit of the test. Bilirubin in the urine is derived from the liver, and a positive test indicates hepatic disease or hepatobiliary obstruction.

Specific gravity: Specific gravity is a measure of the ability of the kidneys to concentrate urine by conserving water.

Nitrite: Some disease bacteria, including the lactose-positive Enterobactericeae, Staphylococcus, Proteus, Salmonella, and Pseudomonas are able to reduce nitrate in urine to nitrite. A positive test for nitrite indicates bacteruria, or the presence of bacteria in the urine.

Urobilinogen: Urobilinogen is a substance formed in the gastrointestinal tract by the bacterial reduction of conjugated bilirubin. Increased urinary urobilinogen occurs in prehepatic jaundice (hemolytic anemia), hepatitis, and other forms of hepatic necrosis that impair the circulation of blood in the liver and surrounding organs. The urobilinogen test is helpful in differentiating these conditions from obstructive jaundice, which results in decreased production of urobilinogen.

Leukocytes: The presence of white blood cells in the urine usually signifies a urinary tract infection, such as cystitis, or renal disease, such as pyelonephritis or glomerulonephritis.


Microscopic examination

A urine sample may contain cells that originated in the blood, the kidney, or the lower urinary tract. Microscopic examination of urinary sediment can provide valuable clues regarding many diseases and disorders involving these systems.

The presence of bacteria or yeast and white blood cells helps to distinguish between a urinary tract infection and a contaminated urine sample. White blood cells are not seen if the sample has been contaminated. The presence of cellular casts (casts containing RBCs, WBCs, or epithelial cells) identifies the kidneys, rather than the lower urinary tract, as the source of such cells. Cellular casts and renal epithelial (kidney lining) cells are signs of kidney disease.

The microscopic examination also identifies both normal and abnormal crystals in the sediment. Abnormal crystals are those formed as a result of an abnormal metabolic process and are always clinically significant. Normal crystals are formed from normal metabolic processes; however, they may lead to the formation of renal calculi, or kidney stones.


Preparation

A urine sample is collected in an unused disposable plastic cup with a tight-fitting lid. A randomly voided sample is suitable for routine urinalysis, although the urine that is first voided in the morning is preferable because it is the most concentrated. The best sample for analysis is collected in a sterile container after the external genitalia have been cleansed using the midstream void (clean-catch) method. This sample may be cultured if the laboratory findings indicate bacteruria.

To collect a sample using the clean-catch method:

  • Females should use a clean cotton ball moistened with lukewarm water (or antiseptic wipes provided with collection kits) to cleanse the external genital area before collecting a urine sample. To prevent contamination with menstrual blood, vaginal discharge, or germs from the external genitalia, they should release some urine before beginning to collect the sample.
  • Males should use a piece of clean cotton moistened with lukewarm water or antiseptic wipes to cleanse the head of the penis and the urethral meatus (opening). Uncircumcised males should draw back the foreskin. After the area has been thoroughly cleansed, they should use the midstream void method to collect the sample.
  • For infants, a parent or health care worker should cleanse the baby's outer genitalia and surrounding skin. A sterile collection bag should be attached to the child's genital area and left in place until he or she has urinated. It is important to not touch the inside of the bag, and to remove it as soon as a specimen has been obtained.

Urine samples can also be obtained via bladder catheterization, a procedure used to collect uncontaminated urine when the patient cannot void. A catheter is a thin flexible tube that a health care professional inserts through the urethra into the bladder to allow urine to flow out. To minimize the risk of infecting the patient's bladder with bacteria, many clinicians use a Robinson catheter, which is a plain rubber or latex tube that is removed as soon as the specimen is collected. If urine for culture is to be collected from an indwelling catheter, it should be aspirated (removed by suction) from the line using a syringe and not removed from the bag in order to avoid contamination.

Suprapubic bladder aspiration is a collection technique sometimes used to obtain urine from infants younger than six months or urine directly from the bladder for culture. The doctor withdraws urine from the bladder into a syringe through a needle inserted through the skin.


Aftercare

The patient may return to normal activities after collecting the sample and may start taking any medications that were discontinued before the test.

Risks

There are no risks associated with voided specimens. The risk of bladder infection from catheterization with a Robinson catheter is about 3%.


Normal results

Normal urine is a clear straw-colored liquid, but may also be slightly hazy. It has a slight odor, and some laboratories will note strong or atypical odors on the urinalysis report. A normal urine specimen may contain some normal crystals as well as squamous or transitional epithelial cells from the bladder, lower urinary tract, or vagina. Urine may contain transparent (hyaline) casts, especially if it was collected after vigorous exercise . The presence of hyaline casts may be a sign of kidney disease, however, when the cause cannot be attributed to exercise, running, or medications. Normal urine contains a small amount of urobilinogen, and may contain a few RBCs and WBCs. Normal urine does not contain detectable amounts of glucose or other sugars, protein, ketones, bilirubin, bacteria, yeast cells, or trichomonads. Normal values used in many laboratories are given below:

  • Glucose: negative (quantitative less than 130 mg/day or 30 mg/dL).
  • Bilirubin: negative (quantitative less than 0.02 mg/dL).
  • Ketones: negative (quantitative 0.5–3.0 mg/dL).
  • pH: 5.0–8.0.
  • Protein: negative (quantitative 15–150 mg/day, less than 10 mg/dL).
  • Blood: negative.
  • Nitrite: negative.
  • Specific gravity: 1.015–1.025.
  • Urobilinogen: 0–2 Ehrlich units (quantitative 0.3–1.0 Ehrlich units).
  • Leukocyte esterase: negative.
  • Red blood cells: 0–2 per high power field.
  • White blood cells: 0–5 per high power field (0–10 per high power field for some standardized systems).

Resources

BOOKS

Chernecky, Cynthia C, and Barbara J. Berger. Laboratory Tests and Diagnostic Procedures , 3rd ed. Philadelphia, PA: W. B. Saunders Company, 2001.

Henry, J.B. Clinical Diagnosis and Management by Laboratory Methods , 20th ed. Philadelphia, PA: W.B. Saunders Company, 2001.

Kee, Joyce LeFever. Handbook of Laboratory and Diagnostic Tests , 4th ed. Upper Saddle River, NJ: Prentice Hall, 2001.

Wallach, Jacques. Interpretation of Diagnostic Tests , 7th ed. Philadelphia, PA: Lippincott Williams & Wilkens, 2000.

ORGANIZATIONS

American Association of Kidney Patients. 100 S. Ashley Drive, Suite 280, Tampa, FL 33260. (800) 749-2257. http://www.aakp.org .

American Kidney Fund. 6110 Executive Blvd., Suite 1010, Rockville, MD 20852. (301) 881-3052. http://www.akfinc.org .

American Medical Technologists. 710 Higgins Road, Park Ridge, IL 60068-5765. (847) 823-5169. http://www.amt1.com .

American Society for Clinical Pathology (ASCP). 2100 West Harrison Street, Chicago, Il 60612-3798. (312) 738-1336. http://www.ascp.org .

National Kidney and Urologic Diseases Information Clearinghouse. 3 Information Way, Bethesda, MD 20892-3580.

OTHER

National Institutes of Health. http://www.nlm.nih.gov/medlineplus/encyclopedia.html [cited April 4, 2003].


Victoria E. DeMoranville Mark A. Best



User Contributions:

Amira Anwar
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Feb 28, 2006 @ 11:11 am
i think this article is good, but i search about articles illustrating the urine acidity and the normal components of urine such as (chlorides, uric acids, ammonia, amino acids etc...); their normal values & the practical method of their determination.
thanks

Amira Anwar
gareth calvert
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Aug 3, 2006 @ 8:20 pm
very informative. explains what my lecturer didn't!
thanks
heidi
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Nov 13, 2007 @ 5:17 pm
loved it thanks to all they wanted to write more thanks to all
Jimmy Beard
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Jan 10, 2008 @ 2:14 pm
Being just a lay person, was interested in learning what the results of my Urinalysis actually meant/tested for: browsed for it on the Net and found this site. Thanks! Told me everything I wanted/needed to know.

Jimmy
tina
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Jan 20, 2008 @ 3:15 pm
Thankyou, very helpful site, had searched many sites this one answered all my questions, keep up the good work
omorie kay
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Apr 17, 2008 @ 5:05 am
pictures of the different microscpic contents would be nicer as this brings the message more alive to the reader. what is the significant of stones in urine from a catetherised patients?
Carol
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Apr 24, 2008 @ 2:14 pm
Thank you for your interesting information. I had a urinalysis yesterday and it showed some UA bacteria, a2+, and UA Squamous Epithelials, a 10-20, as well as UA blood, a trace with slightly high UA Spec. Grav, H.1.03. I was told this was normal, yet I can't find normal values for the 1st two. Could you provide some information? Thank you. C.S.
KINETIC
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Dec 28, 2008 @ 12:12 pm
tHE WRITE UP IS WONDERFUL, PLS KEEP IT UP, KINETIC FROM NIGERIA
Emmanuel Tizah
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Mar 20, 2009 @ 5:05 am
Very informative.Precise and short.Loved it.I feel more could be detailed especially on the aspects of microscopy to include relevence of crystals such as uric acid crystals.
fare3
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Apr 10, 2009 @ 1:13 pm
thanks for your efforts......its very useful.....i hope for you to write moe and more....
fare3
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Apr 10, 2009 @ 1:13 pm
its will be more useful if you attach with it one or more case to be more informative and explained........its a suggestion.....
zygote12
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Sep 23, 2009 @ 11:23 pm
thanks for sharing. it really provides answer most especially for my analysis data.
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Mar 13, 2010 @ 5:05 am
One of the best description I ever had seen on the subject, Thanks You!
Dominique
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Jul 16, 2010 @ 11:23 pm
Could you please tell me that WBC ESTERASE 1+ means.
Thank you
Tom
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Jul 29, 2010 @ 4:16 pm
Great article. Told me more then my kidney doctor did. RCB was >60, ref range was 0-2, he did not even mention what this value means.
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Oct 6, 2010 @ 1:01 am
very informative, but I'm looking for which parameter from urine speciment that can be use to detect gastrointestinal disorder. Anyway thanks
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Oct 25, 2010 @ 3:03 am
very informative. explains what my lecturer didn't!
thanks

Read more: Urinalysis - procedure, test, blood, tube, time, infection, medication, pregnancy, cells, risk, cancer, rate, Definition, Purpose, Precautions, Description, Preparation, Aftercare

china travel
LAZAGA JANICE
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Nov 28, 2010 @ 9:21 pm
we should know the condition of our urine to remain healthy
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Jan 31, 2011 @ 12:00 am
A DETAILED CONTENT.KINDLY INCLUDE MEDICATION AND ANY REMEDY TO ENSURE HEALTHY LIVING
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Feb 16, 2011 @ 7:19 pm
Plz, kindly include the abnomal constituents that can be found in a urine sample using the combi-a strip. Also, the test to assay for ketone bodies in urine sample. Thanks.
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May 24, 2011 @ 9:09 am
my urobilinogen result is positive. please what coursed it? and how can i treat thi
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Jul 21, 2011 @ 12:00 am
Urine Examination Report's colour of Watery is normal or not ?

Urine Examination Report's colour of Straw is normal or not ?
kjohnson
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Jul 24, 2011 @ 1:01 am
Can you use old nitroglycerin tablets for nitrite testing of urine? Just wondering if this would work. I know that you can buy testing kits on-line but wondering if there is "old housewives remedy" that would work for a quick test before spending $80 at the doctor's office? As a woman, I am familiar with the pain that can be associated with UTIs & DR.'s bills.
Ikiriza Allan Katto
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Oct 11, 2011 @ 4:04 am
A well researched and resourceful data to technicians who usually carry out these investigations in the laboratories.Its an excellent information to note.
Abby
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Oct 26, 2011 @ 12:12 pm
This was really helpful in writing up observations about a urinalysis lab I had to do this year in my anatomy class--it was helpful to have specific results in the range of normal so I could elaborate more in my lab report. thanks! (ps--page cited, don't worry :))
rose amado
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Mar 1, 2012 @ 5:17 pm
what is the meaning of trace under the albumin result of the urinalysis
moiz
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Apr 27, 2012 @ 3:15 pm
what if in urine analysis pus cell is 20-25 ?

plz reply me soon

Moiz
Sabella
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May 27, 2012 @ 12:00 am
I am trying to interput symbols on my blood test. What does >1000 mean in a B12 test? The results said >1000 which was my result compared to the excepted >200- I don't know what the > means and I don't know how to read >200- what is the > and - signs mean. Everythig I try to research just says extremely low B12? But I don't know that because I don't know how to read the other symbols. Thank You very much. I have been very sick and have beenn looking for hours to find an answer. My Dr. Office is closed for 3 days so I can't call and if I have extremely low B12 (it souds like a big number) I would like to know before 3 days.
udolota
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Apr 21, 2013 @ 12:12 pm
Pls my is a question on my project research which is on attitude n practice of routine urine testing among nurses. So I dnt know how to start writing about it before but now I think I can do it with d infromation here but I still need more infor to continue. Thanks
ernie lyn preglo
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Jul 4, 2013 @ 7:19 pm
plz post also the procedure on how to take urine sample or patient who has indwelling catheter...

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