DDD score for renal tumor: An intuitive and comprehensive anatomical scoring system to access the outcomes of retroperitoneal laparoscopic partial nephrectomy.

Objective: To present a DDD scoring system in assessing the complexity and outcomes of retroperitoneoscopic nephron-sparing surgery for kidney tumor.

Methods: We retrospectively evaluated 232 patients who underwent retroperitoneoscopic nephron-sparing surgery between January 2013 and September 2017 for a renal tumor. Both the DDD score and RENAL score were used to classify the tumors. The DDD score consisted of the maximal tumor diameter inside the kidney, the maximal tumor depth into the medulla or collecting system and the minimal distance from the tumor to the main renal vessels.

Results: The DDD scoring systems were significantly associated with warm ischemia time (P = 0.007) and estimated blood loss (P = 0.017). There was an insignificant positive correlation between the DDD score and the operative time (P = 0.051). Meanwhile, the RENAL score had a significant correlation with the decreasing value of the estimated glomerular filtration rate. Patients with high or moderate DDD scores had a 13.6-fold or 8.4-fold risk of overall complications than those with low DDD scores, respectively (all P < 0.05). As for RENAL score, patients with moderate scores had a 2.9-fold risk of overall complications compared with patients in the low scores group (P = 0.004). In the receiver operating characteristic curve analysis, the DDD score had the greatest area under the curve for overall complications (area under the curve 0.625, P = 0.009), which was more than the RENAL score (area under the curve 0.620, P = 0.013).

Conclusions: The DDD score is an intuitive renal tumor scoring system that is more effective than the RENAL score in complexity assessment, and marginally better in prediction of the risk of overall complications of retroperitoneal laparoscopic nephron-sparing surgery.