Computerized tomography of the kidney: tissue-plasma ratio of contrast enhancement with bolus injection and renal function.

Computerized tomography can be used not only for morphological studies but for physiological ones as well. Using computerized tomography, we were able to observe changes in renal parenchymal flow rates, with the aorta and renal parenchyma as regions of interest. There were 62 studies performed on 48 patients with and without known renal disease. The change in the tissue-plasma ratio with the use of contrast medium in 124 renal units correlated well with the renal function observed on excretory urography. The 14 patients subjected to renal ischemia during surgery underwent computerized tomography before and after the operation. The change in the tissue-plasma ratio of those kidneys operated upon was decreased significantly postoperatively compared to values found for the nonischemic contralateral kidneys. The results were reproducible and suggest that computerized tomography can be used as a method of evaluating the renal function per unit of parenchymal volume.