Kidney failure may be asymptomatic. As kidney function decreases, the symptoms are related to the inability to regulate water and electrolyte balances, to clear waste products from the body, and to promote red blood cell production.
Lethargy, weakness, shortness of breath, and generalized swelling may also occur. Metabolic acidosis, or increased acidity of the body due to the inability to manufacture bicarbonate, will alter enzyme and oxygen metabolism, causing organ failure. Inability to excrete potassium and rising potassium levels in the serum (hyperkalemia) is associated with fatal heart rhythm disturbances (arrhythmias) including ventricular tachycardia and ventricular fibrillation.
Rising urea levels in the blood (uremia) can affect the function of a variety of organs ranging from the brain with alteration of thinking, to inflammation of the heart lining (pericarditis), to decreased muscle function because of low calcium levels (hypocalcemia).
Weakness may be due to anemia, a decreased red blood cell count, because lower levels of erythropoietin produced by failing kidneys do not adequately stimulate the bone marrow. A decrease in red cells equals a decrease in oxygen carrying capacity of the blood, resulting in decreased oxygen delivery to cells for them to do work; therefore, the body tires quickly.
With less oxygen, cells more readily use anaerobic metabolism leading to increased amounts of acid production that cannot be addressed by the already failing kidneys.
As waste products build in the blood, loss of appetite, lethargy, and fatigue become apparent.