What can indicate renal impairment in a patient?

Low creatinine clearance is a critical indicator of renal impairment. Creatinine clearance is a measure of how effectively the kidneys can filter waste products from the blood. When kidney function declines, the ability to excrete creatinine diminishes, resulting in lower clearance rates. Clinicians frequently use this metric to assess renal function, and a decreased creatinine clearance suggests that the kidneys are not functioning optimally, prompting further evaluation and management of the patient's renal status.

While high potassium levels may relate to kidney dysfunction, they are more of a consequence than a direct measurement of renal impairment. Elevated sodium levels can occur due to various factors and are not specific to renal function. Similarly, high AST levels indicate liver function or damage rather than renal impairment specifically. Thus, the significance of low creatinine clearance makes it the most direct and reliable indicator of renal impairment among the choices provided.