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Blood background subtraction renography in acute renal failure.

Summary 
 
Serial computer assisted blood background subtraction renograms have been performed in 8 patients with acute renal failure. 
 
 
 
One patient showed an initial tracing identical to that from a case with a bilateral nephrectomy; in 2 patients initial tracings were indistinguishable from those of cases of advanced chronic parenchymal renal disease; however all 3 patients made a complete recovery. 
 
 
 
In 3 patients symmetrical continuously rising renograms were obtained as previously reported in acute renal failue. 
 
 
 
In 2 patients asymmetrical renograms were obtained which could have been interpreted as indicating obstructive uropathy. 
 
 
 
Renography in acute renal failure must be interpreted with extreme caution. 
 
 
 
We are grateful to Professor A. Polak and Dr H. A. Lee for their advice.