Urodilatin is a renal natriuretic peptide first isolated from human urine. It is derived from the same precursor as atrial natriuretic peptide in kidney tubular cells and secreted luminally. Urodilatin regulates sodium and water reabsorption in the kidney. While it is not normally found in the circulation, systemic administration of urodilatin has pharmacological effects on renal, cardiovascular, and pulmonary parameters in animals.