Lipid-soluble pigment in plasma excreted in urine at a constant rate. Gives urine its yellow color.

If specimen is exposed to light, urobilinogen will oxidize and turn orange-brown.

Pink pigment, most evident when it deposits on urate crystals, producing a precipitate often described as brick dust.

By-product of hemoglobin catabolism and has characteristic yellow color. If significant, can give urine an amber color

If specimen is improperly stored, bilirubin will oxidize and cause the urine to turn greenish color

Used to treat UTI's gives urine a distinctive yellow-orange (orange soda pop) color. May interfere with the color interpretation on the chemical reagent strip

• Not normally included on report
• White indicates elevated Albumin
• Yellow indicates elevated Bilirubin

• Contamination from skin
• bacteria growth
• x-ray contrast media
• Precipitation of dissolved solutes
• RBCs, WBCs, epithelial cells

Alkaline urine (produces a white or beige precipitate)

Acidic urine (produces a pinkish precipitate "Brick dust")

Urine on standing becomes odorous due to bacterial conversion of urea

Produce sweet or fruity smell

Normally 94% water and 6% solutes

Quantity of solutes present in volume of urine excreted

Expressed as specific gravity or osmolality

Ratio of urine density to density of an equal volume of pure water under standard conditions. Affected by number of solute particles and molecular size

Indirect colorimetric estimation of urine density based on amount of ionic or charged solutes present. Nonionic solutes such as glucose, urea, protein, or radiographic media are not measured

Indirect method based on refractive index of light. Affected by wavelength of light used, Temperature, and concentration of solution.

Impregnated with polyelectrolyte and pH indicator at an alkaline pH. Released protons change pH of test pad. resulting in a color change.

Suspect radiographic contrast media or another large molecular weight solute

Concentration of solution expressed in terms of osmoles of solute particles per kilogram of water

275 to 900 mOsm/kg

depends on diet, fluid intake, and physical activity

275 to 300 mOsm/kg

Remains relatively constant

• Concentrating ability of kidneys
• Monitor renal disease
• Fluid and electrolyte balance
• Diagnose causes of polyuria

600 to 1800 mL/day

Inability of kidneys to change specific gravity of plasma ultrafiltrate (which is 1.010)

Excretion of greater than 3 L/day

Excretion of less than 400 mL/day

Complete lack of urine excretion

1.002 to 1.035

Density of urine / density of equal volume of pure water