What does specific gravity measure in a urine specimen?

Specific gravity in a urine specimen measures the concentration or dilution of urine. It indicates how concentrated or diluted the urine is by comparing the density of the urine to the density of water. A higher specific gravity suggests that the urine is more concentrated, meaning it has more solutes such as waste products and electrolytes relative to the amount of water. Conversely, a lower specific gravity indicates more dilute urine, which might occur in conditions where there is increased fluid intake or certain medical conditions affecting kidney function.

The other options are all different aspects of urine analysis but do not relate to the measurement of specific gravity. For instance, pH levels assess the acidity or alkalinity of urine, while color intensity reflects hydration status and the presence of substances but does not quantify concentration. The presence of bilirubin is indicative of certain liver disorders or hemolysis and is not related to the concentration of urine. Hence, the measurement of specific gravity is key to understanding the filtrative and excretory efficiency of the kidneys.