Which organ is primarily responsible for maintaining acid-base balance in the body?

The kidneys are primarily responsible for maintaining acid-base balance by regulating the excretion of hydrogen ions (H⁺) and reabsorption of bicarbonate (HCO₃⁻). They adjust urinary pH to correct metabolic acidosis or alkalosis, preserving the body's normal blood pH (7.35–7.45). Unlike the lungs, which control CO₂ levels rapidly, the kidneys provide a slower but more precise long-term acid-base regulation. This renal function is critical in compensating for acid-base disturbances in various pathological states.

Reference: Guyton and Hall Textbook of Medical Physiology, Guyton, 14th Edition.