Careful medical management of acute renal failure is critically important to prevent serious complications. In some instances, it may obviate or delay the need for dialysis. History taking, physical examination, and laboratory assessment usually establish the cause from among the many possibilities--from prerenal (eg, hypotension) to postrenal (obstruction of the urinary tract). Derangement of urinary output, hyperkalemia, hyperphosphatemia, hypermagnesemia, metabolic acidosis, anemia, and bleeding are common and treatable disorders found in these patients. The patient's primary care physician can and should be involved with the delivery of appropriate care.