Final answer:
Low urine specific gravity can suggest diabetes insipidus, as it indicates the kidneys' reduced ability to concentrate urine. While diabetes mellitus also results in high urine output, the specific gravity is typically higher due to glucose. Further testing such as urine osmolality is needed for confirmation.
Step-by-step explanation:
Diabetes insipidus is characterized by low urine specific gravity due to the kidneys' inability to concentrate urine. The condition leads to the excretion of large volumes of dilute urine. Measuring urine specific gravity can be done with a urinometer, and accurate readings depend on temperature adjustments. A low urine specific gravity suggests a decrease in solute concentration, which can be indicative of conditions like diabetes insipidus, wherein there's a defect in water reabsorption by the kidneys. When fluid intake is restricted, and if the specific gravity remains low (<1.020), it reflects the kidneys' diminished capability to concentrate urine, supporting a potential diagnosis of diabetes insipidus.
In contrast, diabetes mellitus can also produce large urine volumes, but the specific gravity tends to be higher due to the presence of glucose in the urine. Therefore, specific gravity can be an initial indicator to differentiate between diabetes mellitus and diabetes insipidus, though confirmation typically requires further testing, such as urine osmolality tests.