Introduction

Advent of modern imaging methods has facilitated early diagnosis of renal mass, this has paved way for an increased number of nephron-sparing surgeries being performed [1]. Robotic-assisted partial nephrectomy (RAPN) has the advantage of minimizing the morbidity along with preserving renal function, while achieving complete tumor resection [2]. Numerous modifications of surgical techniques for RAPN has been suggested to achieve the “trifecta” which comprises of minimizing surgical complications, achieving negative surgical margins and maximizing preservation of normal renal parenchyma [3]. The technique of reconstruction of the parenchyma can potentially impact the preservation of healthy parenchyma and prevention of surgical complications [3,4,5]. Four proposed methods of parenchymal reconstruction in partial nephrectomy are: (1) single-layer outer cortical renorraphy (SLOCR) [6, 7], (2) single inner-layer renorraphy (SLIR) with early unclamping [8], (3) double-layer renorraphy (DLR) [2] and (4) sutureless with coagulation of the bed. [9] The renorraphy methods can a have an influence on post-operative surgical complications like hemorrhage, renal artery pseudoaneurysm (RAP) and urine leak [7, 10]. It can also have a possible impact on warm ischemia time, preservation of parenchyma and long-term renal functions [7, 10]. The results of the studies which have dealt with renorraphy methods are contradictory and further evidence is required to determine the ideal methods of reconstruction [7, 8]. William et al. in their study has suggested that collecting system repair can be safely omitted with single-layer sliding clip renorraphy [7]. In another study, Bahler et al. has suggested that inner-layer renorraphy alone is safe and elimination of the cortical renorraphy will increase parenchymal preservation [8]. In this study, we are comparing our outcomes of SLOCR to DLR and its influence on post-operative renal function and complications.

Materials and methods

The retrospective analysis of patients who underwent RAPN was performed. Data extraction was performed after obtaining approval from institutional review board. All patients with a small renal mass who underwent RAPN were included in the study.

Surgical technique

RAPN was performed using a da vinci Si system (Intuitive Surgical, Sunnyvale, CA, USA). The patients were placed in lateral position, after insufflation of pneumoperitoneum, three robotic ports, camera port and two assistant ports were placed. Additional port was placed on right side for liver retraction. The colon was reflected, renal vessels were isolated, mobilization of the kidney and tumor dissection was performed. Bulldog clamps (Scanlan International Inc., MN USA) were placed on vessels and tumor excision was performed. In SLOCR group monopolar cauterization of the base and the small arterial branches were done. In cases were collecting system were opened it was selectively repaired using 4.0 Stratafix (Ethicon Inc., NJ, USA) and this was followed by sliding clip cortical renorraphy using 0 Vicryl on a CT-1 needle (Ethicon, NJ, USA) (Fig. 1). In DLR initial inner-layer continuous closure of the parenchyma was performed using 4.0 Stratafix followed by cortical renorraphy (Fig. 2). Subsequently bull dog clamps were released and hemostasis attained.

Fig. 1
figure 1

Outer cortical renorrhaphy

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Fig. 2
figure 2

Inner layer cortical renorrhaphy

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Data analysis

Preoperative parameters considered were age, sex, body mass index (BMI), estimated glomerular filtration by MDRD formula (eGFR), comorbidities, renal nephrometry score, distance from the collecting system, size of the tumor and hilar location. Renal nephrometry score was categorized into low, intermediate and high risk. Intraoperative factors assessed include warm ischemia time, renorraphy time, blood loss and operative duration [11]. Post-operative hospital stay, complications like symptomatic RAP, hemorrhage, urine leak and reduction eGFR were measured.

Statistical methods

Data were coded and recorded in MS Excel spreadsheet program. SPSS v23 (IBM Corp.) was used for data analysis. Descriptive statistics were elaborated in the form of means/standard deviations and medians/inter quartile ranges for continuous variables. For categorical variables it was described in frequencies and percentages. Group comparisons for continuously distributed data were made using independent sample ‘t’ test when comparing two groups. If data were found to be non-normally distributed, appropriate non-parametric tests in the form of Wilcoxon test were used. Chi-squared test was used for group comparisons for categorical data. In case the expected frequency in the contingency tables was found to be < 5 for > 25% of the cells, Fisher’s exact test was used instead. Linear correlation between two continuous variables were explored using Pearson’s correlation in a normally distributed data and Spearman correlation non-normally distributed data. Propensity score matching was performed using the nearest neighbour technique with variables age, gender, BMI, size, depth, hilar location and pathological stage. Statistical significance was kept at P < 0.05.

Results

Of the 181 patients who were included in analysis 114 had DLR and 67 had SLOCR. In the initial analysis, there was significant difference in size of the tumor (P < 0.001), warm ischemia time (P < 0.001), renorraphy time (P < 0.001), total operative time (P < 0.001) and symptomatic RAP rate (P < 0.001) (Table 1). To eliminate bias, 67 patients in SLOCR group were compared with similar number in the DLR group using propensity score matching. In the matched cohort it was found that warm ischemia time (P < 0.001), renorraphy time (P < 0.001) and symptomatic RAP rate (P < 0.001) were significantly less in SLOCR group (Table 2).

Table 1 Association between group and parameters
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Table 2 Association between group and parameters after propensity matching
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Discussion

Primary objective of renorraphy is to achieve hemostasis with secure closure of collecting system [10, 12, 13]. The introduction of sliding clip renorraphy in 2009 by Benway et al. has gained wide spread acceptance. This facilitates to perform the renorraphy without any parenchymal tear and allow adequate pressure for hemostasis [14]. The renorraphy techniques have been subjected to various modifications to maximize parenchymal preservation and reduce complication [13].

A standard method of reconstruction DLR were an inner-layer suturing is performed to control the vessels [2]. The inner-layer renorrhaphy could be an interrupted selective suturing of bleeding vessels and calyceal system [15]. The premise is that it provides a secure closure to preventing hemorrhagic complications and urinary leak. Outer-layer cortical renorraphy is commonly performed using an interrupted sliding Weck clip technique or by continuous sutures [14]. The drawback of this technique included inability to visualise bleeding from the base of the defect after clamp release. The inner-layer cortical renorraphy also potentially increases the rate of RAP [16,17,18]. It is postulated that repeated and failed passage of need through small arterioles can produce laceration and resultant RAP [16,17,18].

SLIR with early unclamping has been suggested by authors to obviate certain disadvantages of DLR. It is suggested that it would improve visualisation of the bleeding and allow selective control of the vessels. It is also proposed that omission of the outer cortical renorraphy may improve parenchymal preservation [8]. Bahler in a study found that renal function was affected less while performing SLIR (8%) compared to DLR (17%) [8]. Another advantage of this technique would be reduced warm ischemia due to early unclamping leading to improved long-term renal function [8]. Though SLIR has shown less reduction of renal function, the complications like RAP are still prevalent with this technique [8].

In SLOCR technique, the arterioles at the base of the defect is coagulated and pressure from cortical renorraphy helps to achieve hemostasis from opened veins. The interrupted sutures placed by sliding clip renorraphy allows secure closure without any resultant ischemia. In a study by Williams et al., omitting collecting system repair during RAPN with SLR decreased warm ischemia time without altering complication rate [7]. SLOCR has been reported in laparoscopic enucleation with high degree of success [19, 20]. Enucleation involved less aggressive resection without entry into the renal sinus obviating the need for elaborate reconstruction [19, 20]. Low incidence of symptomatic RAP (< 1%) with SLOCR is similar to what we observed in our study [7, 19, 20].

Techniques of suture less partial nephrectomy has been described by many authors. Takagi et al. showed that asymptomatic RAP diagnosed radiologically in 15% of patients and it resolved in some patients without any treatment [21]. Tanaka et al. demonstrated the complete absence of asymptomatic RAP on computed tomography after minimally invasive partial nephrectomy using clampless and sutureless techniques [9]. Total reduction of RAP in patients who did not have an inner-layer suturing in our study also strongly support this hypothesis. In a comparative study on open approach, Hidas et al. compared renal function following PN using tissue adhesive only versus PN using standard suturing technique using quantitative 99mTc-dimercaptosuccinic acid uptake by the kidney [22]. The use of tissue sealant to close the parenchymal defect demonstrated a significant advantage in terms of renal functional preservation compared with suture renorrhaphy [22]. Use of monopolar coagulation with n-Butyl cyanoacrylate had been described in clampless and sutureless laparoscopic partial nephrectomy for renal tumors with low RENAL nephrometry scores [23]. Sutureless minimally invasive partial nephrectomy has been reported by many authors with good results recently [24,25,26,27].

The complete absence of RAP in SLOCR points that inner-layer renorraphy could be the incriminating factor. Although there was significant difference in warm ischemia time and total operating time between the two groups this could not be extrapolated in change in post-operative renal function. Our study being a retrospective analysis has inherent limitations. This was a single-institution study with a small patient population. Our symptomatic RAP rates in DLIR group (9.6%) is higher 0.9–5.6% described in literature [28, 29]. Most of the DLR was performed early in our series which could have had an influence on the outcome. Finally, we did not discuss the long-term renal oncological outcomes and renal function. An ongoing trail NCT0213176 evaluating the role of renorraphy as a modifiable factor during robotic partial nephrectomy would give more accurate insight into the impact of renorraphy on complication and renal function.

Conclusion

Our study shows that inner-layer renorraphy dramatically increased the pseudoaneurysm rates. SLOCR reduced the warm ischemia time, total operating time with reduced rate of RAP. Suture less partial nephrectomy with hemostatic agents may further reduce the complications and hold great promise for the future [30].