Which of the following can cause metabolic alkalosis?

Metabolic alkalosis is a condition characterized by an increase in blood pH due to an excess of bicarbonate or a loss of hydrogen ions. Among the listed options, diuretic therapy is a well-known cause of metabolic alkalosis. This occurs because many diuretics promote the excretion of potassium and hydrogen ions in the urine, leading to a decrease in acid in the bloodstream. As hydrogen ions are removed, bicarbonate levels can rise, resulting in an elevated blood pH and the development of metabolic alkalosis.

In contrast, chronic obstructive pulmonary disease generally leads to respiratory acidosis due to CO2 retention, while severe diarrhea typically causes metabolic acidosis due to loss of bicarbonate. Respiratory failure also tends to cause an increase in CO2 levels that would lead to acidosis rather than alkalosis. Therefore, diuretic therapy stands out as being directly linked to the causes of metabolic alkalosis.