Disorders of the kidney are classified by both their etiology and their anatomic location along the nephron. Disorders other than those arising from tumors become evident when the kidney is unable to regulate the volume and composition of the extracellular fluids, resulting in edema and hypertension. The clinical signs cannot identify the specific segment of the nephron that is affected, since overall renal function depends on each segment functioning in sequence. The failure of one part, therefore, affects the functioning of the whole unit and makes a precise diagnosis difficult without a kidney biopsy. Knowing the location and type of abnormality is important because it may determine the prognosis or therapy.