Method for detecting a progressive renal disorder superimposed on a preexisting progressive renal disorder.

We describe a patient with declining renal function due to polycystic kidney disease, who then insidiously develops bilateral renal artery stenosis. The major clue which led to the discovery of the bilateral renal artery stenosis was the finding of an unexpected increase in the rate of loss of renal function. This assessment was based on analysis of the slope of a plot of the reciprocal of the patient's serum creatinine concentration vs. time (reciprocal creatinine plot). The rationale for the use of the reciprocal creatinine plot to detect a progressive renal disorder superimposed upon a preexisting progressive renal disorder, is discussed.