A nurse suspects a client has diabetes insipidus (DI) post-craniotomy due to high urine output. Which laboratory value should be obtained for further assessment?

In the case of suspected diabetes insipidus (DI), particularly following a craniotomy, assessing urine specific gravity is critical. DI is characterized by an inability of the kidneys to concentrate urine due to a deficiency of antidiuretic hormone (ADH) or due to an insensitivity to ADH. Consequently, the urine produced tends to be very dilute, leading to low urine specific gravity values.

By measuring urine specific gravity, the nurse can determine the concentration of the urine: lower values (typically below 1.005) would support the diagnosis of DI, indicating that the kidneys are not properly concentrating the urine. This specific test is directly relevant for assessing DI, as it provides insight into the renal response to water and solute balance.

Other laboratory values, while they may offer useful information in different contexts, are not as directly indicative of DI. For example, blood glucose levels help in diagnosing diabetes mellitus but do not provide information on urine concentration. Serum sodium levels can be affected by fluid balance but do not give direct evidence about urine concentration capabilities. A urinalysis offers general information about the urine but does not specifically assess the concentration capability of the kidneys in the context of DI. Thus, obtaining urine specific gravity is the most appropriate