In advanced CKD the falling GFR causes water and sodium retention → hypervolemia, which presents with pulmonary edema (orthopnea, nocturnal cough), pleural effusions and pedal edema. Treatment is salt restriction and loop diuretics.

• Volume depletion would cause dizziness/postural hypotension, not orthopnea.
• Pneumonia (fever, sputum) and PE (acute dyspnea, pleuritic pain) do not fit a nocturnal positional cough.