After the age of 30 many structural and functional changes appear gradually in the kidney. These changes can lead to what has been referred to as nephrogeriatric giants, six conditions present in the majority of the old people: senile hypofiltration (progressive reduction in glomerular filtration), renal vascular changes (atheromatosis and dysautonomy of the renal vessels), tubular dysfunction (reduction of several functions of the renal tubules), tubular frailty (tubular susceptibility to develop necrosis, and delayed recovery), medullary hypotonicity (reduced medulla tonicity), and obstructive uropathy. These changes explain the appearance of several disorders such as renal failure, ischemic nephropathy, hypo or hyperkalemia, sodium depletion, hyponatremia, dehydration, and urosepsis in the elderly.