What is the primary purpose of a urinalysis?

The primary purpose of a urinalysis is to assess kidney function. This diagnostic test analyzes the physical and chemical properties of urine, which can provide valuable information about the kidneys' ability to filter waste and maintain homeostasis. By examining components such as protein, glucose, specific gravity, and other substances, healthcare providers can identify abnormalities that may indicate issues related to kidney health, such as infections, kidney stones, or diseases that affect renal function.

While other options involve important health parameters—such as blood composition or heart and respiratory efficiency—urinalysis specifically focuses on the urinary system and the vital filtering role that the kidneys play in overall body function. This makes option B the most accurate representation of the urinalysis's main purpose.