Spiral CT in Kidney: Assumption of Renal Function by Objective Evaluation of Renal Cortical Enhancement

ABSTRACT

PURPOSE: To correlate the degree of renal cortical enhancement, objectively evaluated by means of spiral CT, with the serum level of creatinine, and to determine the extent to which this degree of enhancement may be used to detect renal parenchymal disease. MATERIALS AND METHODS: Eighty patients [MF=5030; age=25 -90 (mean, 53) years] with available serum level of creatinine who underwent spiral CT between September and October 1999 were included in this study. In fifty patients the findings suggested hepatic or biliary diseases such as hepatoma, biliary cancer, or stone, while in thirty, renal diseases such as cyst, hematoma, or stone appeared to be present. Spiral CT imaging of the cortical phase was obtained at 30 -40 seconds after the injection of 120 ml of non-ionic media at a rate of 3ml/sec. The degree of renal cortical enhancement was calculated by dividing the CT attenuation number of renal cortex at the level of the renal hilum by the CT attenuation number of aorta at the same level. The degree of renal cortical enhancement was compared with the serum level of creatinine, and the degree of renal cortical enhancement in renal parenchymal disease with that of the normal group. Among eighty patients there were five with renal parenchymal disease and 75 with normal renal function. RESULTS: The ratio of the CT attenuation number of renal cortex to that of aorta at the level of the renal hilum ranged between 0.49 and 0.99 (mean, 0.79; standard deviation, 0.15), while the serum level of creatinine ranged between 0.6 and 3.2 mg/dl. There was significant correlation (coefficient of -0.346) and a statistically significant probability of 0.002 between the ratio of the CT attenuation numbers and the serum level of creati-nine. There was a significant difference (statistically significant probability of less than 0.01) between those with renal parenchymal disease and the normal group. CONCLUSION: The use of spiral CT to measure the degree of renal cortical enhancement provides not only an effective index for estimating renal functional status but also a means of differentiating between patients with renal parenchymal disease and those who are normal.