The predictive value of helical computed tomography for collecting-system entry during nephron-sparing surgery

To assess the ability of helical computed tomography (CT) including multiplanar reformatting and volume rendering (3D CT) to predict collecting system entry at surgery, as helical CT can be used to delineate renal tumour and normal renal anatomy before nephron-sparing surgery (NSS).

Knowledge of the possibility of collecting system entry during surgery might either dissuade some surgeons from NSS in elective situations or influence the operative approach or ablative technology in cases where NSS is imperative, or prepare the surgeon for the possibility of collecting system repair. We reviewed all 3D CT (349 scans) obtained before NSS at our institution over three consecutive years. Tumour size, central tumour extension, and presence of calyceal involvement were prospectively recorded at the time of 3D rendering. Collecting system entry was analysed for these three CT variables, and for three clinical variables (tumour side, size and surgical approach) collected retrospectively from the medical records. Multivariate logistic regression was used to assess the sensitivity, specificity, and positive and negative predictive values.

Of 344 patients, 170 had collecting system entry reported at surgery. There were statistically significant associations between collecting system entry and central tumour location by CT (sensitivity 58.8%, specificity 80.5%, P < 0.001), calyceal involvement at CT (sensitivity 53.5%, specificity 78.2%, P < 0.001), and tumour size on CT of > 4 cm (sensitivity 39.4%, specificity 74.7%, P = 0.005). There were no significant associations with side or type of surgery (P > 0.83).

Helical CT is a reliable predictor of calyceal entry at surgery.