07/02/2019
Urinalysis.
Physical characteristics of urine:
Color: Typically yellow-amber, but varies according to recent diet and the concentration of the urine. Drinking more water generally tends to reduce the concentration of urine, and therefore causes it to have a lighter color. Dark urine may indicate dehydration. Red urine indicates red blood cells within the urine, a sign of kidney damage and disease.
Smell: The smell of urine may provide health information. For example, urine of diabetics may have a sweet or fruity odor due to the presence of ketones (organic molecules of a particular structure) or glucose. Generally fresh urine has a mild smell but aged urine has a stronger odor similar to that of ammonia.
The pH of normal urine is generally in the range 5-7,5. Much of the variation occurs due to diet.
Density: Density is also known as “specific gravity.” This is the ratio of the weight of a volume of a substance compared with the weight of the same volume of distilled water. The density of normal urine ranges from 1000 to 1025
Turbidity: The turbidity of the urine sample is gauged subjectively and reported as clear, slightly cloudy, cloudy, opaque or flocculent. Normally, fresh urine is either clear or very slightly cloudy. Excess turbidity results from the presence of suspended particles in the urine, the cause of which can usually be determined by the results of the microscopic urine sediment examination. Common causes of abnormal turbidity include: increased cells, urinary tract infections or obstructions.
Chemical Composition of Urine
Protein. Normally, there is no protein in the urine or it is contained in very insignificant quantities. The presence of protein and urine is a sign of kidney disease.
Sugar in the urine of a healthy person is also absent. If its content exceeds 0.9 mmol / l, it may indicate the development of diabetes.
Bilirubin in the urine of a healthy person is absent, its presence indicates liver disease.
Ketone bodies in the urine indicate diabetes.
Urine Microscopy
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. A urinary cast is any tiny structure found in urine that consists of multiple molecules or cells bound together.
Casts form within the nephron when abnormal cells and molecules are filtered from blood, and are excreted as the bound structures in urine. Microscopy can identify casts in urine and use them to diagnose kidney diseases, by characterizing symptoms such as:
• Red blood cell casts are associated with glomerulonephritis, vasculitis, or malignant hypertension.
• White blood cell casts are associated with acute interstitial nephritis, exudative glomerulonephritis, or severe pyelonephritis.
• Epithelial cell casts are associated with toxin-induced, acute tubular necrosis, hepatitis, and cytomegalovirus.
• (Heme) granular casts are associated with acute tubular necrosis, and are often composed of proteins, especially antibodies.
• Hyaline casts are associated with dehydration; it is the most common type of cast.
• Bacterial casts are associated with urinary tract infection; the cast may be cultured in order to identify the causative organism of the cast.