Impaired ammonium excretion in chronic kidney disease

Urinary excretion of NH₄⁺ in patients without CKD (solid line) and patients with CKD (dashed line) at baseline and after an acid load. The plasma bicarbonate concentration fell from 27 to 22 mEq/L in patients without CKD and from 22 to 14 mEq/L in CKD following the acid load. NH₄⁺ excretion rose markedly in patients without CKD but was low at baseline and did not increase in the patients with CKD despite a greater degree of metabolic acidosis.