When patients have hypokalemia, they often exhibit paradoxical aciduria, which is a typical manifestation of hypokalemia. In hyperkalemia, however, there is paradoxical alkaline urine. When serum potassium ions decrease, the renal tubular epithelium reduces its potassium excretion function and instead increases hydrogen excretion, leading to increased reabsorption of sodium and bicarbonate. This results in metabolic alkalosis, causing an increase in plasma bicarbonate, unlike typical alkalosis where alkaline urine is excreted. However, in the case of hypokalemia, acidic urine is excreted, hence it is called paradoxical aciduria.