A person is suspected of having chronic renal failure. To assess kidney function, urea clearance is measured and found to be very low.

A person is suspected of having chronic renal failure. To assess kidney function, urea clearance is measured and found to be very low. Explain what a very low urea clearance indicates for this patient. Compare that with the effect of chronic renal failure on the tendency for the blood K+ level to be higher than normal and the blood Na+ level to be lower than normal