Kidney function tests

Kidney function tests

Definition

Kidney function tests is a collective term for a mixture of individual tests and procedures that can be done to evaluate how all right the kidneys are functioning.

Purpose

The kidneys, the body's natural filtration system, accomplish many central functions, including removing metabolic waste products from the bloodstream, regulating the body's sea balance, and maintain the pH (acidity/alkalinity) of the body's fluids. Approximately one and a half quarts of blood per minute are circulated through the kidneys, where on earth waste chemicals are filter out and eliminated from the body (along near excess water) in the form of urine. Kidney function test help to determine if the kidneys are performing their tasks satisfactorily.

Precautions

A complete history should be taken prior to kidney function tests to assess the tolerant's food and drug intake. A wide miscellany of prescription and over-the-counter medications can affect blood and urine kidney function trial results, as can some food and beverages.

Description

Many conditions can affect the ability of the kidneys to carry-out their fundamental functions. Some lead to a swift (acute) decline in kidney function; others lead to a gradual (chronic) decline in function. Both result in a build-up of toxic refuse substances in the blood. A number of clinical laboratory test that measure the level of substances normally regulated by the kidneys can give support to determine the cause and extent of kidney dysfunction. These test are done on urine samples, as capably as on blood samples.

Urine tests

There are a mixture of urine tests that assess kidney function. A simple, inexpensive screening theory test, called a routine urinalysis, is regularly the first test administered if kidney problems are suspected. A small, by chance collected urine sample is examined physically for things similar to color, odor, appearance, and concentration (specific gravity); chemically for substances such a protein, glucose, and pH (acidity/ alkalinity); and microscopically for the presence of cellular elements (red blood cells, white blood cell, and epithelial cells), bacteria, crystals, and cast (structures formed by the deposit of protein, cells, and other substances within the kidneys' tubules). If results indicate a possibility of disease or impaired kidney function, one or more of the following optional tests is usually perform to more specifically diagnose the cause and the even of decline in kidney function.

• Creatinine clearance test. This interview evaluates how efficiently the kidneys clear a substance call creatinine from the blood. Creatinine, a waste product of muscle enthusiasm metabolism, is produced at a constant rate that is proportional to the muscle mass of the individual. Because the body does not recycle it, adjectives of the creatinine filtered by the kidneys contained by a given amount of time is excreted in the urine, making creatinine clearance a massively specific measurement of kidney function.The trial is performed on a timed urine specimen--a cumulative preview collected over a two to twenty-four hour period. Determination of the blood creatinine stratum is also required to calculate the urine clearance.


• Urea clearance check. Urea is a waste product explicitly created by protein metabolism and excreted in the urine. The urea clearance test requires a blood preview to measure the amount of urea within the bloodstream and two urine specimens, collected one hour apart, to determine the amount of urea that is filter, or cleared, by the kidneys into the urine.


• Urine osmolality test. Urine osmolality is a breadth of the number of dissolved particles within urine. It is a more precise measurement than specific gravity for evaluating the qualifications of the kidneys to concentrate or dilute the urine. Kidneys that are functioning normally will excrete more dampen into the urine as fluid intake is increased, diluting the urine. If fluid intake is decreased, the kidneys excrete smaller number water and the urine become more concentrated. The test may be done on a urine preview collected first thing contained by the morning, on multiple timed samples, or on a cumulative taster collected over a twenty-four hour period. The long-suffering will typically be prescribed a high-protein diet for several days before the audition and asked to drink no fluids the night until that time the test.


• Urine protein assessment. Healthy kidneys filter all proteins from the bloodstream and later reabsorb them, allowing no protein, or only slight amounts of protein, into the urine. The annoying presence of significant amounts of protein in the urine, then, is an celebrated indicator of kidney disease. A positive screening test for protein (included in a routine urinalysis) on a chance urine sample is usually followed-up near a test on a 24-hour urine token that more precisely measures the quantity of protein.

Blood tests

There are also several blood tests that can aid in evaluating kidney function. These include:

• Blood urea nitrogen test (BUN). Urea is a by-product of protein metabolism. This spend product is formed in the liver, consequently filtered from the blood and excreted contained by the urine by the kidneys. The BUN test measures the amount of nitrogen contained in the urea. High BUN level can indicate kidney dysfunction, but because blood urea nitrogen is also affected by protein intake and liver function, the check is usually done in conjunction near a blood creatinine, a more specific indicator of kidney function.


• Creatinine test. This oral exam measures blood levels of creatinine, a by-product of muscle heartiness metabolism that, like urea, is filter from the blood by the kidneys and excreted into the urine. Production of creatinine depends on an individual's muscle mass, which usually fluctuates very little. With majority kidney function, then, the amount of creatinine in the blood remains relatively constant and mundane. For this reason, and because creatinine is artificial very little by liver function, an elevated blood creatinine is a more sensitive indication of impair kidney function than the BUN.


• Other blood tests. Measurement of the blood level of other elements regulated in quantity by the kidneys can also be useful contained by evaluating kidney function. These include sodium, potassium, chloride, bicarbonate, calcium, magnesium, phosphorus, protein, uric acid, and glucose.

Preparation

Patients will be given specific instructions for collection of urine sample, depending on the test to be perform. Some timed urine tests require an extended collection time of year of up to 24 hours, during which time the patient collects adjectives urine voided and transfers it to a specimen container. Refrigeration and/or preservatives are typically required to maintain the integrity of such urine specimens. Certain dietary and/or medication restrictions may be imposed for some of the blood and urine test. The patient may also be instructed to avoid exercise for a time of time before a exam.

Aftercare

If medication was discontinued prior to a urine kidney function try-out, it may be resumed once the test is completed.

Risks

Risks for these test are minimal, but may include slight bleeding from a blood-drawing site, hematoma (accumulation of blood under a puncture site), or faint or feeling light-headed after venipuncture. In decoration, suspension of medication or dietary changes imposed surrounded by preparation for some blood or urine tests may trigger side-effects surrounded by some individuals.

Normal results

Normal values for many test are determined by the patient's age and sex. Reference values can also change by laboratory, but are generally inside the ranges that follow.

Urine tests

• Creatinine clearance. For a 24-hour urine collection, normal results are 90-139 ml/min for developed males less than 40 years older, and 80-125 ml/min for adult females smaller quantity than 40 years old. For ancestors over 40, values decrease by 6.5 ml/min for respectively decade of life.


• Urea clearance. With maximum clearance, mundane is 64-99 ml/min.


• Urine osmolality. With restricted fluid intake (concentration testing), osmolality should be greater than 800 mOsm/kg of water. With increased fluid intake (dilution testing), osmolality should be smaller amount than 100 mOSm/kg in at tiniest one of the specimens collected.


• Urine protein. A 24-hour urine collection should contain no more than 150 mg of protein.

Blood tests

• Blood urea nitrogen (BUN). 8-20 mg/dl.


• Creatinine. 0.8-1.2 mg/dl for males, and 0.6-0.9 mg/dl for females.

Abnormal results

Low clearance values for creatinine and urea indicate diminished ability of the kidneys to filter these spend foolishly products from the blood and excrete them in the urine. As clearance level decrease, blood level of creatinine and urea nitrogen increase. Since it can be affected by other factor, an elevated BUN, by itself, is suggestive, but not diagnostic, for kidney dysfunction. An abnormally elevated blood creatinine, a more specific and sensitive indicator of kidney disease than the BUN, is diagnostic of impair kidney function.

Inability of the kidneys to concentrate the urine in response to restricted fluid intake, or to dilute the urine in response to increased fluid intake during osmolality testing may indicate decrease kidney function. Because the kidneys normally excrete almost no protein in the urine, its unyielding presence, in amounts that exceed the regular 24-hour urine value, usually indicates some type of kidney disease as okay.

Key Terms

Blood urea nitrogen (BUN)

The nitrogen portion of urea in the bloodstream. Urea is a lavish product of protein metabolism in the body.

Creatinine

The metabolized by-product of creatine, an organic sour that assists the body in producing muscle contractions. Creatinine is found in the bloodstream and in muscle tissue. It is removed from the blood by the kidneys and excreted in the urine.

Osmolality

A height of urine concentration that depends on the number of particles dissolved surrounded by it. Values are expressed as milliosmols per kilogram (mOsm/kg) of water.

Urea

A by-product of protein metabolism to be precise formed in the liver. Because urea contains ammonia, which is toxic to the body, it must be in the blink of an eye filtered from the blood by the kidneys and excreted surrounded by the urine.