C ommonly associated with chronic kidney disease, metabolic acidosis accelerates the progression of chronic kidney disease to end-stage renal disease and leads to higher mortality. 1 Renal ammonia metabolism is a cornerstone of kidney's ability to excrete acid, and a declining ability to excrete the daily net acid load because of a failure to adapt renal ammonia excretion is an independent risk factor for the progression of chronic kidney disease toward endstage renal disease. 2 (In this article, the term "ammonia" refers to the combination of NH 3 and NH 4 þ. The term