On admission to a hospital; preparation for surgery; as part of a medical examination; or when evaluating a new pregnancy. It may be done if you have tummy or back pain, frequent or painful urination, or blood in the urine
Sample of urine (20-50 mls) in a sterile container; the first urine passed in the morning is the most valuable
This test identifies and measures some of the by-products of normal and abnormal metabolism, cells, cell fragments, and bacteria in urine. Urine is produced by the kidneys, which filter wastes out of the blood, help regulate the amount of water in the body, and conserve proteins, electrolytes, and other compounds that the body can reuse. Anything that is not needed is excreted in the urine.
Several diseases can be diagnosed in their early stages by detecting abnormalities in the urine. Abnormally high levels of glucose, protein, bilirubin, red blood cells, white blood cells, crystals, and bacteria can indicate disease. They may be present because: 1) There are elevated concentrations in the blood which spill over into urine, 2) Kidney disease has made the kidneys less effective at filtering or, 3) An infection has put bacteria and white blood cells into the urine .
A complete urinalysis consists of three distinct testing phases:
- Visual examination, which evaluates the urine's colour, clarity, and concentration;
- Chemical examination, which tests chemically for a number of substances that provide valuable information about health and disease; and
- Microscopic examination, which identifies and counts the type of cells, casts, crystals, and other components (bacteria, mucous ) that can be present in urine.
See below for details of these examinations.
Today, a routine urinalysis consists of the visual and the chemical examinations. Your urine may be examined under a microscope if there is an abnormal finding in one of the first two phases listed above or if your doctor specifically requests it.
How is the sample collected for testing?
Urine for urinalysis can be collected at any time. The first morning sample is the most valuable because it is more concentrated and more likely to yield abnormal results. Because of the potential (particularly in women) to contaminate urine with bacteria and cells from the surrounding skin, it is important to first clean the genitalia. Men should wipe the tip of the penis; women should spread the labia of the vagina and clean from front to back. As you start to urinate, let some urine fall into the toilet, then collect a sample of urine in the container provided.
A sample will only be useful for urinalysis if taken to the doctor’s surgery or laboratory for processing within a short period of time. If it will be longer than an hour between collection and transport time, then the urine should be refrigerated.
Is any test preparation needed to ensure the quality of the sample?
No advance test preparation is needed.
How is it used?
Urinalysis is used as a screening and/or diagnostic tool because it can detect different metabolic and kidney disorders. Often, substances such as protein or glucose will begin to appear in the urine before patients are aware that they may have a problem. It is used to detect urinary tract infections (UTI) and other disorders of the urinary tract. In some conditions, urinalysis also provides an easy, economical, and relatively fast test to follow patient progress, for example, if you want to know whether a condition is getting better or worse. However, a urinalysis cannot detect all disorders.
When is it requested?
A routine urinalysis may be done when you visit your doctor, when you attend the outpatient clinic or when you are admitted to the hospital. It may also be part of a routine medical examination, a new pregnancy evaluation, or preparation for planned surgery. A urinalysis will most likely be performed if you see your doctor complaining of tummy pain, back pain, painful or frequent urination, or blood in the urine. This test can also be useful in monitoring whether a condition is getting better or worse.
What does the test result mean?
Urinalysis results can have many interpretations. Abnormal findings are a warning that something may be wrong and should be looked at further. Normal urinalysis results do not mean there is no illness. Urinalysis is only one screening test that can provide a general overview of a person’s health. Your doctor must look at the urinalysis results alongside your health complaints and other information available.
How long does it take to get results for urinalysis?
Urinalysis testing is frequently carried out by dip-stick testing in the clinic and results are available immediately. If there is an abnormal finding, such as excessive protein or the presence of blood, it may be necessary to send the sample on to the laboratory for further analysis. This will take several days and depending on the tests that need to be carried out.
Is the time of day a factor when collecting a urine sample?
Because this is a general screening test, this is usually not important. However, if your doctor is looking for a specific finding, you may be asked to collect a sample at a specific time. For example the presence of glucose is better looked for in a specimen collected after a meal, low levels of protein are better detected in a concentrated specimen collected first thing in the morning.
Are there home test kits available?
Some commercial testing strips can be purchased at a pharmacy to perform part of the chemical examination, such as urine pH, urine glucose, and urine ketones but the tests are best performed by someone who is used to reading and interpreting them.
During the visual examination of the urine, the laboratory scientist may look at the urine’s colour, clarity, and concentration. Urine can be a variety of colours, most often shades of yellow, from very pale or colourless to very dark or amber.
Unusual or abnormal urine colours can be the result of a disease process, some drugs or foods. For example, some people produce red-coloured urine after eating beetroot. The colour is from the natural pigment of beetroot and is not a cause for worry. Red-coloured urine can also occur when blood is present in the urine, and can be an indicator of disease or damage to some part of the urinary system.
Blood can also be a contaminant that gets into the urine unintentionally during collection, such as from haemorrhoids or menstruation. Once this contaminating blood is in the urine, it will be detected during the chemical phase of a urinalysis, and your doctor will initially assume that it came from the urinary tract. The importance of blood in urine is discussed further in the chemical and microscopic examination sections.
The depth of urine colour is also a crude indicator of urine concentration:
- Pale yellow or colourless urine indicates dilute urine where lots of water is being excreted.
- Dark yellow urine indicates concentrated urine and the excretion of waste products in a smaller quantity of water, such as is seen with the first morning urine, with dehydration, and during a fever.
Urine clarity refers to how clear the urine is. Usually laboratories report the clarity of the urine using one of the following terms: clear, slightly cloudy, cloudy, or turbid. “Normal” urine can be clear or cloudy. Substances that cause cloudiness but that are not considered unhealthy include mucus, sperm and prostatic fluid, cells from the skin, normal urine crystals, and contaminants such as body lotions and powders. Other substances that can make urine cloudy, like red blood cells, white blood cells, or bacteria, indicate a condition that requires attention.
Urine colour and clarity can be a sign of what substances may be present in urine. However, confirmation of suspected substances is obtained during the chemical and microscopic examinations.
Chemical examination is usually done using test strips. These are narrow plastic strips that hold small squares of paper called test pads, arranged in a row. The test pads have chemicals impregnated into them. When a strip is briefly, but completely, dipped into urine, the test pads absorb the urine and a chemical reaction changes the colour of the pad within a few seconds or minutes.
The nurse, doctor or laboratory scientist compares the colour change for each reaction pad to a colour chart provided with the test strips to give a result for each test. Each reaction pad must be evaluated at the appropriate time for that chemical. If too little time or too much time has passed since the reaction, the laboratory scientist may get incorrect results. To reduce timing errors and eliminate variations in colour interpretation, sometimes automated instruments may be used to “read” the reaction colour of each test pad.
The degree of colour change on a test pad can also give an approximation of the amount of substance present. For example, a slight colour change in the test pad for protein may indicate a small amount of protein present in the urine whereas a deep colour change may indicate a large amount.
The most frequently performed chemical tests using reagent test strips are
- specific gravity,
- leukocyte esterase,
- bilirubin, and
Some test strips also have a test pad for ascorbic acid (vitamin C).
The first test, specific gravity, is a measure of urine concentration and is measured using a chemical test.
There are no “abnormal” specific gravity values. This test simply indicates how concentrated the urine is. Specific gravity measurements provide a comparison of the amount of substances dissolved in urine as compared to pure water. If there were no solutes present, the SG of urine would be 1.000 – the same as pure water. Since all urine have some substances dissolved, a urine SG of 1.000 is not possible. If a person drinks excessive quantities of water in a short period of time or gets an intravenous (IV) infusion of large volumes of fluid, then the urine SG may be as low as 1.002. The upper limit of the test pad, an SG of 1.035, indicates a concentrated urine.
pH is not generally a very helpful test. As with specific gravity, there are typical but not “abnormal” pH values. The kidneys play an important role in maintaining the acid-base balance of the body. Therefore, any condition that produces acids or bases in the body such as acidosis or alkalosis, or the ingestion of acidic or basic foods, can directly affect urine pH.
Diet can modify urine pH. A high-protein diet or consuming cranberries will make the urine more acidic. A vegetarian diet, a low-carbohydrate diet, or the ingestion of citrus fruits will tend to make the urine more alkaline.
Some of the substances dissolved in urine can precipitate out to form crystals when the urine is acidic, others can form crystals when the urine is basic. If crystals form while the urine is being produced in the kidneys, a kidney stone or “calculus” can develop. By modifying urine pH through diet or medications, the formation of these crystals can be reduced or eliminated.
The pH can change and become less acidic if the urine is not tested within a few hours of collection.
The protein test pad usually measures the amount of albumin in the urine. Normally there will not be detectable quantities of the protein albumin. When urine protein is levels are high, you have a condition called proteinuria; this can be an early sign of kidney disease. Albumin is smaller than most other proteins and is typically the first protein that is seen in the urine when kidney dysfunction begins to develop. Other proteins are not generally detected by the test pad but may be measured using a separate urine protein test. Other conditions that can produce proteinuria include
- Disorders that produce high amounts of proteins in the blood, such as multiple myeloma
- Infections of the urinary tract
- Conditions that destroy red blood cells
- Inflammation, malignancies (cancer), or injury of the urinary tract – for example, the bladder, prostate, or urethra
- the presence of blood in the urine perhaps due to stones which are damaging the walls of the kidney or bladder
- Vaginal secretions that get into and contaminate the urine
Glucose is not normally present in urine. When glucose is detectible, the condition is called glycosuria. It results from either
- An excessively high glucose concentration in the blood, such as may be seen with people who have uncontrolled diabetes.
- A reduction in the "kidney threshold". When blood glucose levels reach a certain concentration then the kidneys begin to excrete glucose into the urine. Sometimes the threshold concentration is reduced and glucose enters the urine sooner- at a lower blood glucose concentration.
Some other conditions that can cause glycosuria include hormonal disorders, liver disease, certain drugs, and pregnancy. When glycosuria occurs; other tests such as blood glucose are usaully performed to further indentify the specific cause.
Ketones are not normally found in the urine. They are intermediate products of fat metabolism. They can form when a person does not eat enough carbohydrates (for example, in cases of starvation or high-protein diets), or when a person’s body cannot use carbohydrates properly. When carbohydrates are not available the body metabolises fat instead to get the energy it needs to keep functioning.
Ketones in urine can give an early indication of insufficient insulin in a person who has diabetes. Severe exercise, exposure to cold, and loss of carbohydrates, such as with frequent vomiting, can also increase fat metabolism, resulting in ketonuria.
This test is used to detect haemoglobin in the urine (haemoglobinuria). Haemoglobin is a oxygen-transporting protein found inside red blood cells (RBCs). Its presence in the urine indicates blood in the urine (known as haematuria). The small number of RBCs normally present in urine (see microscopic examination) usually result in a “negative” test. However, when the number of RBCs increases, they are detected as a “positive” test result.
Even small increases in the amount of RBCs in urine can be significant. Numerous diseases of the kidney and urinary tract, as well as trauma, medications, smoking, or strenuous exercise can cause haematuria or haemoglobinuria.
This test cannot determine the severity of disease nor be used to identify where the blood is coming from. For instance, contamination of urine with blood from haemorrhoids or vaginal bleeding cannot be distinguished from a bleed in the urinary tract. This is why it is important to collect a urine specimen correctly, and for women to tell their health care provider that they are menstruating when asked to collect a urine specimen.
Sometimes a chemical test for blood in the urine is negative, but the microscopic examination shows increased numbers of RBCs. When this happens, ascorbic acid (vitamin C) many be checked because it can cause falsely low or negative test results.
Leukocytes are white blood cells (WBCs). Normally, a few white blood cells (see microscopic examination) are present in urine and this test is negative. When the number of WBCs in urine increases significantly, this screening test will become positive.
When the WBC count in urine is high, it means that there is inflammation in the urinary tract or kidneys. The most common cause for WBCs in urine (leukocyturia) is a bacterial urinary tract infection (UTI), such as bladder or kidney infection.
This test detects nitrite and is based upon the fact that many bacteria can convert nitrate to nitrite in your urine. Normally the urinary tract and urine are free of bacteria. When bacteria find their way into the urinary tract they can cause a urinary tract infection (UTI). A positive nitrite test result can indicate a UTI. However, since not all bacteria are capable of converting nitrate to nitrite you can still have a UTI despite a negative nitrite test.
Bilirubin is not present in the urine of normal, healthy individuals. Bilirubin is a waste product that is produced by the liver from the haemoglobin of RBCs that are removed from circulation. It becomes a component of bile, a fluid that is secreted into the intestines to aid in food digestion.
In certain liver diseases, such as biliary obstruction or hepatitis, bilirubin leaks back into the blood stream and is excreted in urine. The presence of bilirubin in urine is an early indicator of liver disease and can occur before clinical symptoms such as jaundice develop.
Urobilinogen is normally present in urine in low concentrations. It is formed in the intestine from bilirubin, and a portion of it is absorbed back into the bloodstream. Positive test results help detect liver diseases such as hepatitis and cirrhosis, and conditions associated with increased RBC destruction (haemolytic anaemia). When urine urobilinogen is low or absent in a patient with urine bilirubin and/or signs of liver dysfunction it can indicate the presence of hepatic or biliary obstruction.
A microscopic examination may or may not be performed as part of a routine urinalysis. It will typically be done when there are abnormal findings on the physical or chemical examination. It is performed on urine sediment – urine that has been centrifuged to concentrate the substances in it at the bottom of a tube. The fluid at the top of the tube is then discarded and the drops of fluid remaining are examined under 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). In addition, some entities, if present, are estimated as "few," "moderate," or "many," such as epithelial cells, bacteria, and crystals.
Red Blood Cells (RBCs)
Normally, a few RBCs are present in urine sediment. Inflammation, injury, or disease in the kidneys or elsewhere in the urinary tract, for example in the bladder or urethra, can cause RBCs to leak out of the blood vessels into the urine. RBCs can also be a contaminant due to an improper sample collection and blood from haemorrhoids or menstruation.
White Blood Cells (WBCs)
The number of WBCs in urine sediment is normally low. When the number is high, it indicates an infection or inflammation somewhere in the urinary tract. WBCs can also be a contaminant, such as those from vaginal secretions.
Normally in men and women, a few epithelial cells from the bladder (transitional epithelial cells) or from the external urethra (squamous epithelial cells) can be found in the urine sediment. Cells from the kidney (kidney cells) are less common. In urinary tract conditions such as infections, inflammation, and malignancies, more epithelial cells are present. Determining the kinds of cells present helps the doctor pinpoint where the condition is located. For example, a bladder infection may result in large numbers of transitional epithelial cells in urine sediment. Epithelial cells are usually reported as “few,” “moderate,” or “many” present per low power field (LPF).
Microorganisms (bacteria, trichomonads, yeast)
In health, the urinary tract is sterile: there will be no microorganisms seen in the urine sediment. Microorganisms are usually reported as “none,” “few,” “moderate,” or “many” present per high power field (HPF). Bacteria from the surrounding skin can enter the urinary tract at the urethra and move up to the bladder, causing a urinary tract infection (UTI). If the infection is not treated, it can eventually move to the kidneys and cause pyelonephritis. Less frequently, bacteria from a blood infection (septicaemia) may move into the urinary tract. This also results in a UTI. Special care must be taken during specimen collection, particularly in women, to prevent bacteria that normally live on the skin or in vaginal secretions from contaminating the urine. A urine culture may be performed if a UTI is suspected.
In women (and rarely in men), yeast can also be present in urine. They are most often present in women who have a vaginal yeast infection, because the urine has been contaminated with vaginal secretions during collection. If yeast are observed in urine, then tests for a yeast (fungal) infection may be performed on vaginal secretions.
Trichomonads are parasites that may be found in the urine of women or men (rarely). As with yeast, the trichomonads are actually infecting the vaginal canal and their presence is due to contamination. If these are found during a urinalysis, then follow-up testing for Trichomonas vaginalis may be performed to look for a vaginal infection.
Casts are cylindrical particles sometimes found in urine that are formed from coagulated protein secreted by kidney cells. They are formed in the long, thin, hollow tubes of the kidneys known as tubules and usually take the shape of the tubule (hence the name). Under the microscope, they often look like the shape of a “hot dog” and in healthy people they appear nearly clear. This type of cast is called a “hyaline” cast.
When a disease process is present in the kidney, other things such as RBCs or WBCs can become trapped in the protein as the cast is formed. When this happens the cast is identified by the substances inside it, for example as a red blood cell cast or white blood cell cast. Different types of casts are associated with different kidney diseases and the type of casts found in the urine may give clues as to which disorder is affecting the kidney. Some other examples of types of casts include granular casts, fatty casts, and waxy casts.
Normally, healthy people may have a few (0–5) hyaline casts per low power field (LPF). After strenuous exercise more hyaline casts may be detected. Cellular casts, such as RBC and WBC casts, indicate a kidney disorder.
Urine contains many dissolved substances (solutes) - waste chemicals that your body needs to eliminate. These solutes can form crystals, solid forms of a particular substance, in the urine if:
- the urine pH is increasingly acidic or basic;
- the concentration of issolved substances is increased; and
- the urine temperature promotes their formation
Crystals are identified by their shape, colour, and by the urine pH. They may be small, sand-like particles with no specific shape (amorphous) – or have specific shapes, such as needle-like. Some examples of crystals that can be found in the urine of healthy individuals include:
- amorphous urates
- crystalline uric acid
- calcium oxalates
- amorphous phosphates
- calcium carbonate
If the crystals are from solutes that are not normally in the urine, they are considered “abnormal.” Abnormal crystals may indicate an abnormal metabolic process. Some of these include:
When crystals form as urine is being made in the kidney, they may group together to form kidney “stones” or calculi. These stones can become lodged in the kidney itself or in the ureters – tubes that pass the urine from kidney to the bladder – causing extreme pain.
Medications, drugs, and x-ray dye can also crystallize in urine.