urinalysis

urinalysis, clinical examination of urine for the purpose of medical diagnosis. Urine is initially examined for such characteristics as color, odor, and specific gravity. It is routinely tested for acidity, as indicated by its pH reading, and screened for sugar, ketone bodies, proteins, and bile content. Benedict's solution, for example, may be used to test for simple sugars, a high level of which is a possible indicator of diabetes mellitus. Ketone bodies, e.g., acetone and acetoacetic acid, in the urine indicate the substitution of fats for sugar in the energy cycle and are another indication of diabetes mellitus. Abnormal levels of protein may be signs of kidney disease. A high concentration of bile in the urine is a sign of liver malfunction or blockage of the bile duct. Urine is examined microscopically to determine blood count. High levels of erythrocytes, or red blood cells, and leukocytes, or white blood cells, may be a result of bleeding and infection, respectively, in the urinary tract. Casts, crystals, and other substances, whose origins may be ascertained by determining their chemical structures, can be observed microscopically. Additional studies are performed when specific malfunctions are suspected. Clearance tests, for instance, will determine the ability of the kidneys to remove waste substances from the blood plasma per unit of time. The urine of patients with melanotic cancer will often contain melanin, a skin pigment. A diagnosis of drug addiction may be confirmed by the presence of specific chemical substances in the urine. Urinalysis is also employed to test for pregnancy. Pregnant women secrete high levels of gonadotrophic, or ovary-regulating, hormones from the placenta. A reagent containing gonadotrophic hormones is mixed with a sample of urine from the patient, and gonadotrophic antigens are added to it. Failure of the antigens to clump, or agglutinate, is positive evidence of pregnancy.

Laboratory examination of a urine sample for clinical information. Abnormal concentrations of substances normally found in urine or presence of those that are not may indicate a disorder. Colour, specific gravity, or volume changes may reveal a specific disease or injury. Significant findings include high glucose and acetone in diabetes mellitus; various nitrogen compounds, pigments, amino acids, and their metabolic products in disorders of the enzymes that act on them; uric acid in gout; and urea, albumins, and globulins in kidney disease. Hormones may be evidence of pregnancy or endocrine imbalance. Urinalysis can also detect poisons and drugs.

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A urinalysis (or "UA") is an array of tests performed on urine and one of the most common methods of medical diagnosis. A part of a urinalysis can be performed by using urine dipsticks, in which the test results can be read as color changes.

Medical urinalysis

A typical medical urinalysis usually includes:

• a description of color and appearance.
• specific gravity - normally 1.010 to 1.030. This test detects ion concentration of the urine. Small amounts of protein or ketoacidosis tend to elevate results of the specific gravity.
• pH - normally 4.8 to 7.5.
• ketone bodies - normally negative (absent)
• protein - normally negative (absent)
• urobilinogen
• bilirubin
• glucose - normally negative (absent)
• RBC number
• WBC number
• hCG - normally absent, this hormone appears in the urine of pregnant women. Home pregnancy tests commonly detect this substance.

Microscopic examination

The numbers and types of cells and/or material such as urinary casts can yield a great detail of information and may suggest a specific diagnosis.

• eosinophiluria - associated with allergic interstitial nephritis, atheroembolic disease
• RBC casts - associated with glomerulonephritis, vasculitis, malignant hypertension
• WBC casts - associated with acute interstitial nephritis, exudative glomerulonephritis, severe pyelonephritis
• (heme) granular casts - associated with acute tubular necrosis
• crystalluria -- associated with acute urate nephropathy (or "Acute uric acid nephropathy", AUAN)
• calcium oxalate - associated with ethylene glycol toxicity

See also

• uroscopy, the ancient form of this analysis
• Medical technologist

External links

• WebMD
• American Family Physician
• Interpreting urinalysis
• PediatricOnCall
• Lab Tests Online: Urinalysis