Disease: Urinalysis
(Urine Test)

What is a urinalysis?

A urinalysis is simply an analysis of the urine. It is a very common test that can be performed in many healthcare settings including doctors' offices, urgent care facilities, laboratories, and hospitals.

It is performed by collecting a urine sample from the patient in a specimen cup. Usually only small amounts (30-60 ml's) may be required for urinalysis testing. The sample can be either analyzed in the medical clinic or sent to a laboratory to perform the tests. Urinalysis is abbreviated UA.

Urine can be evaluated by its physical appearance (color, cloudiness, odor, clarity), or macroscopic analysis. It can be also analyzed based on its chemical and molecular properties or microscopic assessment.

Urinalysis is ordered by doctors for a number of reasons, as follows:

  • Routine medical evaluation: general yearly screening, assessment before surgery (pre-operative assessment), admission to hospital, screening for kidney disease, diabetes mellitus, hypertension (high blood pressure), liver disease, etc.
  • Assessing particular symptoms: abdominal pain, painful urination, flank pain, fever, blood in the urine, or other urinary symptoms.
  • Diagnosing medical conditions: urinary tract infection, kidney infection, kidney stones, uncontrolled diabetes (high blood sugars), kidney impairment, muscle breakdown (rhabdomyolysis), protein in urine, kidney inflammation (glomerulonephritis).
  • Monitoring disease progression and response to therapy: diabetes related kidney disease, kidney impairment, lupus related kidney disease, blood pressure related kidney disease, kidney infection, protein in urine, blood in urine.

What can urinalysis results show?

Urinalysis can disclose evidence of diseases, even some that have not caused significant signs or symptoms. Therefore, a urinalysis is commonly a part of routine health screening.

 Urinalysis is commonly used to diagnose a urinary tract or kidney infection, to evaluate causes of kidney failure, to screen for progression of some chronic conditions such as diabetes mellitus and high blood pressure (hypertension).

It also may be used in combination with other tests to diagnose some diseases. Additional tests and clinical assessment are often required to further investigate findings of urinalysis and ultimately diagnose the causes or specific features of underlying problems. For example, urine infection is generally diagnosed based on results of urinalysis. However, urine culture is often ordered as a follow-up test to identify the bacteria that may be causing the infection. Other examples include kidney stones, inflammation or the kidneys (glomerulonephritis), or muscle breakdown (rhabdomyolysis).

Who is involved in the interpretation of urinalysis?

Interpretation of urinalysis is generally based on reviewing all the components of the test and correlating it with the clinical signs and symptoms of the patient and the physical examination. The results are reviewed and interpreted by the doctor who ordered the test.

What does urinalysis involve?

Urinalysis is done by collecting a urine sample from a patient. The optimal sample tends to be an early morning urine sample because it is frequently the most concentrated urine produced in the day. Typically, no fasting is required before the collection of urine sample and routine medications can be taken before the test, unless otherwise instructed by the ordering physician.

Methods of collection are slightly different for female and male patient.

  • For females, the patient is asked to clean the area around the urethra with a special cleansing wipe, by spreading the labia of the external genitals and cleaning from front to back (toward the anus).
  • For men, the tip of the penis may be wiped with a cleansing pad prior to collection.
  • The urine is then collected in a clean urine specimen cup while the patient is urinating. It is best to avoid collecting the initial stream of urine. After the initial part of urine is disposed of in the toilet, then the urine is collected in the urine container provided. Once about 30 to 60 ml (roughly 3 to 5 tablespoons) are collected in the container for testing, the remainder of the urine may be voided in the toilet again. This is called the clean catch or the midstream urine collection.

The collected urine sample should be taken to the laboratory for analysis, typically within one hour of collection. If transportation to the lab could take more than one hour, then the sample may be refrigerated.

In some patients who are unable to void spontaneously or those who are not able to follow instructions other methods may be used, such as placing a catheter (a small rubber tube) through the outside opening to the bladder (urethra) to collect the sample directly from the bladder.

What are the pros and cons of dip sticks?

The main advantage of dipsticks is that they are convenient, easy to interpret, and cost-effective. They can be analyzed within minutes of urine collection in the doctor's office or in the emergency room to provide valuable information.

However, what can be learned from a dipstick is limited by the design of the dipstick. The main disadvantage is that the information may not be very accurate, as the test is time-sensitive. It also provides limited information about the urine, as it is qualitative test and not a quantitative test (for example, it does not give a precise measure of the quantity of abnormality). Therefore, normal and abnormal values are not reported as part of urinalysis results.

What is microscopic urinalysis?

The microscopic urinalysis is the study of the urine sample under a microscope. It requires only a relatively inexpensive light microscope. Cells and cellular debris, bacteria, and crystals in the urine can be detected by this examination to provide further clinical clues.

How is microscopic urinalysis done?

Microscopic urinalysis is done simply pouring the urine sample into a test tube and centrifuging it (spinning it down in a machine) for a few minutes. The top liquid part (the supernatant) is discarded. The solid part left in the bottom of the test tube (the urine sediment) is mixed with the remaining drop of urine in the test tube and one drop is analyzed under a microscope.

The sediment is examined through the microscope under low-power to identify what are called casts, crystals, squamous (flat) cells, and other large objects.

Examination is then performed through the microscope at higher power to further identify any cells, bacteria and clumps of cells or debris called casts.

What kind of cells can be detected?

Epithelial (flat cells), red and white blood cells may be seen in the urine.

Sometimes cells, cellular debris, and casts are seen in the microscopic urinalysis. Epithelial cells (cells in the lining of the bladder or urethra) may suggest inflammation within the bladder, but they also may originate form the skin and could be contamination.

Casts and cellular debris originate from higher up in the urinary tract, such as in the kidneys. These are material shed from kidney cell lining due to injury or inflammation and travel down through the urinary tubes. These usually suggest an injury to the kidney from an inflammation or lack of blood flow to the kidneys. Rarely, tumor cells can be in the urine suggesting a urinary tract cancer.

What can the presence of red blood cells in the urine mean?

Red blood cells can enter the urine from the vagina in menstruation or from the trauma of bladder catheterization.

A high count of red blood cells in the urine can indicate infection, trauma, tumors, or kidney stones. If red blood cells seen under microscopy look distorted, they suggest kidney as the possible source and may arise due to kidney inflammation (glomerulonephritis). Small amounts of red blood cells in the urine are sometimes seen young healthy people and usually are not indicative of any disease.

What can the presence of white blood cells in the urine mean?

Urine is a generally thought of as a sterile body fluid, therefore, evidence of white blood cells or bacteria in the urine is considered abnormal and may suggest a urinary tract infection such as, bladder infection (cystitis), infection of kidney (pyelonephritis). White blood cells may be detected in the urine through a microscopic examination (pyuria or leukocytes in the blood). They can be seen under high power field and the number of cells are recorded (quantitative) as "rare,""few,""moderate," or "many."

White cells from the vagina or the opening of the urethra (in males, too) can contaminate a urine sample. Such contamination aside, the presence of abnormal numbers of white blood cells in the urine is significant.

Who is involved in the interpretation of urinalysis?

Interpretation of urinalysis is generally based on reviewing all the components of the test and correlating it with the clinical signs and symptoms of the patient and the physical examination. The results are reviewed and interpreted by the doctor who ordered the test.

What does urinalysis involve?

Urinalysis is done by collecting a urine sample from a patient. The optimal sample tends to be an early morning urine sample because it is frequently the most concentrated urine produced in the day. Typically, no fasting is required before the collection of urine sample and routine medications can be taken before the test, unless otherwise instructed by the ordering physician.

Methods of collection are slightly different for female and male patient.

  • For females, the patient is asked to clean the area around the urethra with a special cleansing wipe, by spreading the labia of the external genitals and cleaning from front to back (toward the anus).
  • For men, the tip of the penis may be wiped with a cleansing pad prior to collection.
  • The urine is then collected in a clean urine specimen cup while the patient is urinating. It is best to avoid collecting the initial stream of urine. After the initial part of urine is disposed of in the toilet, then the urine is collected in the urine container provided. Once about 30 to 60 ml (roughly 3 to 5 tablespoons) are collected in the container for testing, the remainder of the urine may be voided in the toilet again. This is called the clean catch or the midstream urine collection.

The collected urine sample should be taken to the laboratory for analysis, typically within one hour of collection. If transportation to the lab could take more than one hour, then the sample may be refrigerated.

In some patients who are unable to void spontaneously or those who are not able to follow instructions other methods may be used, such as placing a catheter (a small rubber tube) through the outside opening to the bladder (urethra) to collect the sample directly from the bladder.

What is macroscopic urinalysis?

Macroscopic urinalysis is the direct visual observation of the urine, noting its quantity, color, clarity or cloudiness, etc.

Normal urine is typically light yellow and clear without any cloudiness. Obvious abnormalities in the color, clarity, and cloudiness may suggest possibility of:

  • an infection (cloudy urine),
  • dehydration (dark urine color) ,
  • red blood in the urine, also referred to as hematuria (red urine color),
  • liver disease (urine the color of tea), or
  • breakdown of muscle (orange or tea colored urine).

Certain medications may also change the color of urine. Very foamy urine may represent large amounts of protein in the urine (proteinuria).

What is urine dipstick chemical analysis?

Urine dipstick is a narrow plastic strip which has several squares of different colors attached to it. Each small square represents a component of the test used to interpret urinalysis. The entire strip is dipped in the urine sample and color changes in each square are noted. The color change takes place after several seconds to a few minutes from dipping the strip. If read too early or too long after the strip is dipped, the results may not be accurate.

Each color change on a particular square may indicate specific abnormalities in the urine sample caused by a certain chemical reaction. The reference for color changes is posted on the plastic bottle container of the urine test strips. This makes for easy and quick interpretation of the urinalysis results by placing the strip next to the container and comparing its color changes to the reference provided.

The squares on the dipstick represent the following components in the urine:

  • specific gravity (concentration of urine),
  • acidity of the urine (pH),
  • protein in the urine (mainly albumin),
  • glucose (sugar),
  • ketones (products of fat metabolism),
  • blood, leukocyte esterase (suggestive of white blood cells in urine),
  • nitrite (suggestive of bacteria in urine),
  • bilirubin (possible liver disease or red blood cell breakdown), and
  • urobilinogen (possible liver disease).

Presence or absence of each of these color changes on the strip provides important information for clinical decisions.

What are the pros and cons of dip sticks?

The main advantage of dipsticks is that they are convenient, easy to interpret, and cost-effective. They can be analyzed within minutes of urine collection in the doctor's office or in the emergency room to provide valuable information.

However, what can be learned from a dipstick is limited by the design of the dipstick. The main disadvantage is that the information may not be very accurate, as the test is time-sensitive. It also provides limited information about the urine, as it is qualitative test and not a quantitative test (for example, it does not give a precise measure of the quantity of abnormality). Therefore, normal and abnormal values are not reported as part of urinalysis results.

What is microscopic urinalysis?

The microscopic urinalysis is the study of the urine sample under a microscope. It requires only a relatively inexpensive light microscope. Cells and cellular debris, bacteria, and crystals in the urine can be detected by this examination to provide further clinical clues.

How is microscopic urinalysis done?

Microscopic urinalysis is done simply pouring the urine sample into a test tube and centrifuging it (spinning it down in a machine) for a few minutes. The top liquid part (the supernatant) is discarded. The solid part left in the bottom of the test tube (the urine sediment) is mixed with the remaining drop of urine in the test tube and one drop is analyzed under a microscope.

The sediment is examined through the microscope under low-power to identify what are called casts, crystals, squamous (flat) cells, and other large objects.

Examination is then performed through the microscope at higher power to further identify any cells, bacteria and clumps of cells or debris called casts.

What kind of cells can be detected?

Epithelial (flat cells), red and white blood cells may be seen in the urine.

Sometimes cells, cellular debris, and casts are seen in the microscopic urinalysis. Epithelial cells (cells in the lining of the bladder or urethra) may suggest inflammation within the bladder, but they also may originate form the skin and could be contamination.

Casts and cellular debris originate from higher up in the urinary tract, such as in the kidneys. These are material shed from kidney cell lining due to injury or inflammation and travel down through the urinary tubes. These usually suggest an injury to the kidney from an inflammation or lack of blood flow to the kidneys. Rarely, tumor cells can be in the urine suggesting a urinary tract cancer.

What can the presence of red blood cells in the urine mean?

Red blood cells can enter the urine from the vagina in menstruation or from the trauma of bladder catheterization.

A high count of red blood cells in the urine can indicate infection, trauma, tumors, or kidney stones. If red blood cells seen under microscopy look distorted, they suggest kidney as the possible source and may arise due to kidney inflammation (glomerulonephritis). Small amounts of red blood cells in the urine are sometimes seen young healthy people and usually are not indicative of any disease.

What can the presence of white blood cells in the urine mean?

Urine is a generally thought of as a sterile body fluid, therefore, evidence of white blood cells or bacteria in the urine is considered abnormal and may suggest a urinary tract infection such as, bladder infection (cystitis), infection of kidney (pyelonephritis). White blood cells may be detected in the urine through a microscopic examination (pyuria or leukocytes in the blood). They can be seen under high power field and the number of cells are recorded (quantitative) as "rare,""few,""moderate," or "many."

White cells from the vagina or the opening of the urethra (in males, too) can contaminate a urine sample. Such contamination aside, the presence of abnormal numbers of white blood cells in the urine is significant.

Source: http://www.rxlist.com

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