How accurate is helical CT volumetric assessment in renal tumors?

The aim of this study was to evaluate the accuracy of tumor size measurement on CT studies of renal tumors. Sixteen patients with tumors of the kidneys were imaged by helical CT prior to surgery. Assessment of tumor volume was made by two radiologists on the CT images with the summation of area method, then compared with the resected specimen water displacement volume. Intra- and interobserver agreement for CT measurements were also assessed. There were substantial differences between the CT volume measurement compared with the tumor post-operative volume (mean of differences 30.05+/-91.6, 95%CI: 31.45-91.55). The inter- and intraobservation agreements for tumor measurement by CT was found to be satisfactory (ANOVA: p < 0.0001; t-test: p < 0.05). The CT volumetric measurement by area summation is a method with good inter- and intraexamination reproducibility but not an accurate technique for tumor volume assessment.