What metabolic imbalance results from the kidneys' reduced ability to filter hydrogen atoms in ARF or CRF?

In acute renal failure (ARF) and chronic renal failure (CRF), the kidneys lose their ability to adequately filter and excrete various metabolic waste products, including hydrogen ions. The accumulation of hydrogen ions in the body leads to an increased acidity of the blood, resulting in a condition known as metabolic acidosis. This is often characterized by a decrease in blood pH and a decrease in bicarbonate levels.

When the kidneys fail to maintain the appropriate acid-base balance by excreting hydrogen ions, the body cannot effectively elimnate excess acid. This fundamental dysfunction drives the development of acidosis rather than alkalosis. Therefore, referring to the condition as "good old-fashioned acidosis" is a colloquial way of identifying this metabolic disturbance that stems from the kidneys' compromised role in regulating hydrogen ion concentration.

Moreover, respiratory acidosis and respiratory alkalosis are conditions primarily associated with lung function and the balance of carbon dioxide in the blood, rather than direct kidney filtration issues. Metabolic alkalosis, similarly, would imply a high pH and an excess of bicarbonate, which would not be consistent with ARF or CRF. Thus, the correct answer accurately reflects the metabolic imbalance created by the kidneys' reduced ability to filter hydrogen ions.