What is the specific gravity in prerenal renal failure?

In prerenal renal failure, the kidneys typically respond to decreased perfusion by conserving water and sodium in an attempt to maintain blood volume and blood pressure. This adaptive mechanism results in the urine becoming more concentrated.

As a result, the specific gravity of urine in prerenal failure is often greater than 1.015. A higher specific gravity indicates that the urine is concentrated, which reflects the kidneys' ability to reabsorb water effectively when faced with low blood flow. This response is a distinguishing feature of prerenal azotemia, where kidney function remains intact but is compromised due to reasons outside of the renal tissue itself, such as decreased blood volume or low blood pressure.

In contrast, conditions affecting renal function directly, like intrinsic renal failure, would lead to urine that is less concentrated, often resulting in a specific gravity less than 1.015 due to an inability to conserve water. This distinction is important for diagnosing and managing different types of renal failure.