The Physical Examination of Urine

urine samples

The physical examination of urine consist of the determination of urine color, clarity or transparency, and specific gravity. Examination of these characteristics provides initial information concerning disorders such as glomerular bleeding, liver disease, inborn error of metabolism, and urinary tract infection.

COLOR
The urine color ranges from almost colorless to black. These variations may be due to ingested materials, physical activity, normal metabolic functions, or pathologic conditions. Common reporting of normal urine color may vary slightly among laboratories, it includes straw, pale yellow, light yellow, yellow, dark yellow and amber.

The yellow color of urine is due largely to the presence of a pigment called urochrome. Uroerythrin (pink color) and urobilin (orange-brown color) pigments are also present in urine but in smaller quantities and contribute little to the color of normal, fresh urine. Because urochrome is excreted at a continuous and steady rate, the intensity of the yellow color in a fresh urine specimen gives a rough assessment of urine concentration. A dilute urine will be pale yellow and a concentrated sample will be dark yellow.

Colors like straw, pale yellow, yellow, dark yellow and amber will not always signify normal urine, it can be pathologic too. Orange, yellow-green, yellow-brown, green, blue-green, pink, red, brown, black are some of the colors of pathologic or abnormal urine samples.

TRANSPARENCY
Color and transparency or clarity are routinely checked at the same time by visibly examining the mixed urine specimen, that is placed in a clear container, in front of a light source. Common description of urine color includes clear, hazy, cloudy, turbid,and milky.

Fresh voided normal urine is typically clear and transparent, especially if it is midstream clean-catch specimen. Nonpathologic or normal causes of urine turbidity is maybe due to any of the following: squamous epithelial cells; mucus; amorphous urates, phosphates, or carbonates; fecal contamination; semen or spermatozoa; radiographic contrast media; talcum powder; or vaginal creams.

Pathologic or abnormal causes of urine turbidity is maybe due to any of the following: red blood cells, white blood cells, bacteria, yeast, non-squamous epithelial cells, abnormal crystals, lymph fluids, or lipids.

SPECIFIC GRAVITY
It is an assessment of the kidney’s ability to reabsorb vital chemicals and water. It aids in the assessment of renal tubular function. Normal random urine samples may range from 1.003 to 1.035, depending on the patient’s  amount of hydration.  Most random samples  fall between 1.015 and 1.025.

Tags: clarity, color, physical examination of urine, specific gravity

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