Laparoscopic partial nephrectomy-does tumor profile influence the operative performance?

Methods: Patients undergoing laparoscopic partial nephrectomy in our institution were recruited for this study. The tumor profi le was evaluated by a senior radiologist from cross sectional imaging (computed tomography or magnetic resonance imaging). Tumor characerestics was defi ned by assessing tumor size, tumor location and RENAL score. The operative performance was evaluated in terms of warm ischemia time, blood loss, operation duration and any signifi cant operative complications. Statistical inference was drawn.


Introduction
Partial nephrectomy is a well established procedure for management of renal masses, where suf icient renal parenchyma can be preserved after complete removal of the kidney tumor [1]. In expert hands, laparoscopic partial nephrectomy has shown comparable oncological outcome and acceptable renal salvage to open partial nephrectomy, with the added advantage of superior morbidity pro ile [2]. Successful performance of laparoscopic partial nephrectomy not only depends on operator skills but also the characterestics of the tumor concerned. Several assessment tools have been proposed in recent literature to help de ine the tumor pro ile [3][4][5]. Our aim was to assess the in luence of these tumor characterestics on our operative performance of laparoscopic partial nephrectomy.

Methods
All patients undergoing laparoscopic partial nephrectomy between January 2010 and June 2012 were included in this analysis. All patients were evaluated in detail including presenting complaints, clinical parameters, blood and renal pro ile. All patients underwent detailed imaging preoperatively-Computed tomography urogram (CTU) or Magnetic resonance urogram (MRU, if creatinine>1.4 mg/dl). The tumor pro ile was assessed by a single senior radiologist using standardized criteria [3][4][5]. The parameters included were tumor size, tumor location, tumor depth. RENAL nephrometry score was assessed from points assigned for Tumor radius, Exophytic/ endophytic properties, Nearness to the collecting system, Anterior/posterior location and Location relative to polar lines. The technique of partial nephrectomy was as follows-after colonic mobilisation along the line of Toldt, the dissection was continued along a plane between the Gerotas fascia and the renal capsule all around except the area around the tumor. A cuff of peritumoral fat was preserved. The renal pedicle was then mobilized and the renal artery and vein was clamped en masse using Satinsky clamp applied through an umbiliucal port. The line of resection was point mapped using hook electrocautery keeping a generous margin from the tumor edge. Tumor excision was carried out along this mark using cold scissors. The renal bed was fulgurated using spatula and electrocautery followed by single layer full thickness suturing using No 1 polyglactin. Even in cases of caliceal disruption, single layer full thickness parenchymal renorrhaphy was undertaken without separate calicorrhaphy. No loseal or surgical bolster was applied on the remnant renal bed. The operative pro ile was recorded in detail. The parameters recorded included warm ischemia time, blood loss, operation duration and any signi icant intraoperative or postoperative complications. Statistical analysis was carried out using T test, Wilcoxon rank sum test and One way Annova test. A p value <0.05 was remarked as statistically signi icant.

Results
37 patients were included in this analysis. The demographic and tumor pro ile is highlighted in tables 1,2. The mean±standard deviation RENAL score was 6.56±1.52. One patient experienced signi icant bleeding after Satinsky clamp release that was managed by additional suturing. One patient required blood transfusion in postoperative period. In seven patients caliceal disruptions during tumor excision were obvious and despite omitting separate calicorrhaphy, none of them experienced any urine leak or prolonged drainage postprocedure. One patient underwent simultaneous laparoscopic partial nephrectomy for solitary right upper pole metastasis in solitary kidney and laparoscopic segmentectomy for solitary segment VII liver metastasis. Postsurgery he suffered from hepatocellular failure and on ifth postoperative day he died. No other major intraoperative or postoperative events were encountered in this patient cohort. The in luence of tumor pro ile on operative parameters is depicted in tables 3,4 and igure 1. Statistically signi icant associations were observed between tumor location and RENAL score and warm ischemia time and operation duration. Procedural blood loss was not signi icantly associated with tumor location but with RENAL score. Tumor size had no correlation with operative pro ile.

Discussion
Widespread usage of cross-sectional imaging in modern medicine has resulted in a rising incidence in the detection of small renal masses. These patients are both asymptomatic and active and prefer surgeries with limited morbidity. Hence there is an increasing demand for performing partial nephrectomy through laaroscopic approach. Surgeons are also more versed with laparoscopic techniques presently and keen to offer challenging surgeries through minimally invasive approach in   suitable patients. Hence there is a global increase in performing laparoscopic partial nephrectomy and the parameters that may in luence the outcome of this surgery need to be de ined. The focus of our study was to identify these factors. Preoperative identi ication of unfavorable tumor characterestics will help the surgical team in their preoperative preparartions and necessary steps may be taken to effectively ward of adverse intraoperative happenings. Warm ischemia time, blood loss and procedural complications are important parameters to gauge the procedural complexity for laparoscopic partial nephrectomy. All our procedures were performed obeying the same principle and our operative parameters were comparable to the published literature [6,7]. Recently few scoring systems have emerged to quantitate the tumor characterestics in a standardised pattern [8,9]. In our study we included the RENAL nephrometry score to de ine tumor pro ile and assessed the reproducibility of this scoring system. RENAL score had signi icant correlation with warm ischemia time, blood loss and operation duration. Surgeries were more complex in tumors with higher RENAL scores (>7). This was similar to results from other centers published in literature. Additional inferences from our analysis were-tumors located on the left had more preferable operative pro ile than right sided tumors, tumors located in the lower pole recorded the lowest warm ischemia time followed by upper polar tumors. Mid polar tumors were the most complex to handle. Hew et al. [9], also reported similar observations in their analysis where mid polar tumors were associated with maximum complications. Additionally, in our study posteriorly located tumors had longer warm ischemia and operative duration than anteriorly located tumors (Tables 5,6).
This may be explained by the time taken for suturing the remnant renal bed. Our operator was right handed and the different axis of suturing for different tumor locations could be responsible for the differences observed in operative pro ile with different tumor locations. In comparison to warm ischemia time and operation duration, blood loss had less signi icant correlation with tumor pro ile. Although some authors have assessed PADUA scoring and C-index for predicting tumor characterestics, such scoring parameters were not assessed   in this study due to complexity of calculation [9,10]. All scoring assessments were done by a single radiologist and all procedures were performed by a single surgeon pro icient in laparoscopic exercises. This eliminated the possibility of bias due to interradiologist or intersurgeon differences. In our study tumor characterestics signi icantly correlated with the complexity of operative performance and meaningful conclusions could be generated. However larger prospective studies including more subjects may be needed to validate these results.

Conclusion
Tumor location (sidedness, polar location, anterior/posterior location) signi icantly in luences the operative performance of laparoscopic partial nephrectomy. Tumor size has no correlation with the operative pro ile. Additionally, RENAL nephrometry score can accurately predict the operative performance and a more complex procedure may be anticipated with a higher RENAL score.