The client with head trauma is admitted following a motor vehicle accident. The nurse notes \(5000 \mathrm{ml}\) of dilute urinary output within 3 hours of admission. Which finding would support a diagnosis of diabetes insipidus? A. Decreased red blood cell count B. Low specific gravity of urine C. Increase blood urea nitrogen D. Increased serum creatinine level

Diabetes insipidus is a condition characterized by the production of a large amount of dilute urine, which eventually leads to dehydration. It is caused by either inadequate production or an insufficient response to the hormone vasopressin, which regulates the balance of water in the body. Understanding this will help us discern which symptoms are indicative of diabetes insipidus.

A. Decreased red blood cell count: A decreased red blood cell count is not directly related to diabetes insipidus and would not support a diagnosis of this condition. B. Low specific gravity of urine: Specific gravity of urine is a measurement of the concentration of solutes in urine. A low specific gravity indicates dilute urine, which is characteristic of diabetes insipidus. Therefore, this option would support a diagnosis of diabetes insipidus. C. Increase blood urea nitrogen: Increased blood urea nitrogen is associated with kidney dysfunction and dehydration, which could also be a result of diabetes insipidus. However, it is a less specific marker than low specific gravity of urine. D. Increased serum creatinine level: Serum creatinine is also a marker of kidney function, but an increase in its levels is not specific for diabetes insipidus.

Based on our analysis, the correct option is B. Low specific gravity of urine, as it directly indicates dilute urine, which is an essential characteristic of diabetes insipidus.