Which of the following is typically a sign of kidney dysfunction?

The presence of casts in urine is a significant indicator of kidney dysfunction. Casts are cylindrical structures that form in the renal tubules and can indicate different types of kidney injury depending on their composition. For instance, the presence of specific types of casts, such as red blood cell casts or white blood cell casts, can point to glomerular disease or acute tubular necrosis, respectively. This formation reflects the kidney's inability to maintain normal filtering and excretion processes and suggests underlying pathological processes affecting kidney function.

In contrast, high urine volume might suggest conditions like diabetes insipidus or uncontrolled diabetes rather than direct kidney failure. Pale urine color typically indicates good hydration and is not necessarily a sign of dysfunction. Normal glucose levels do not signify kidney issues; in fact, the kidneys are responsible for glucose reabsorption, and normal levels imply that the kidneys are functioning well in this regard.