Implications of computer tomography measurement in the management of renal tumours

BACKGROUND: To compare radiographic measurement and pathological measurement of renal tumours to see if there was a significant difference between the two as this may have implications in the management. METHODS: We retrospectively analyzed CT measurements of 106 consecutive patients who underwent either radical or nephron sparing surgery in our institution and compared this to the actual measurement of the surgical specimen. The largest axial measurement was compared as this is the primary consideration before offering either treatment modality. RESULTS: The mean age of the patients was 64 years (range 31–92). There were 76 males and 30 females. The median tumour size was 70 mm (range 16–175) on CT and 65 mm (range 15–90) on pathological measurement. 25 patients had a CT size ≤ 40 mm. CT tended to overestimate the size of tumours in 41 patients, underestimate in 45 and agree with surgical size in 20 patients. Statistically there was no significant difference between the two measurements (p = 0.7, Wilcoxon sign ranked test). When subdivided into tumours less than 40 mm (p = 0.7) and more than 40 mm (p = 0.09) again there was no statistically significant difference between the two measurements. However in 5(5%) patients who were not offered nephron sparing surgery based on CT findings (size > 40 mm) the pathological size was ≤ 40 mm (p = < 0.001, Fishers Exact test). Pathologically the tumours were classified as renal cell carcinoma (n = 98), angiomyolipoma (3), and oncocytoma (5). CONCLUSION: CT measurement of renal tumour size correlates well with the actual size of the tumour. However CT does tend to overestimate the size in a small number of patients which may have a bearing on the modality of treatment offered.