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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 32  |  Issue : 1  |  Page : 15-22

Using R.E.N.A.L. nephrometry and preoperative aspects and dimensions employed for anatomical classification to evaluate perioperative outcomes of renal tumors greater than 4 cm in patients who underwent minimally invasive partial nephrectomy in a single center


1 Department of Urology, E-DA Hospital, Kaohsiung, Taiwan
2 Department of Urology, E-DA Hospital; Department of Nursing; Department of Chemical Engineering and Institute of Biotechnology and Chemical Engineering; School of Medicine, College of Medicine, I-Shou University, Kaohsiung, Taiwan
3 Department of Urology, E-DA Hospital; School of Medicine, College of Medicine, I-Shou University, Kaohsiung, Taiwan
4 School of Medicine, College of Medicine, I-Shou University; Department of Urology, E-DA Cancer Hospital, Kaohsiung, Taiwan

Date of Submission06-Jun-2020
Date of Decision15-Aug-2020
Date of Acceptance12-Jan-2021
Date of Web Publication27-Mar-2021

Correspondence Address:
Victor C Lin
No. 1, Yida Road, Jiaosu Village, Yanchao District, Kaohsiung 82445
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/UROS.UROS_78_20

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  Abstract 


Purpose: The R.E.N.A.L. (radius, exophytic/endophytic tumor properties, nearness of tumor to deepest portion of collecting system or sinus, anterior/posterior descriptor, and location relative to the polar line) and preoperative aspects and dimensions used for an anatomical (PADUA) (tumor size and position, relationship with the renal sinus or the urinary collecting system, and the grade of deepness into the kidney) nephrometry scoring systems are frequently used in predicting the perioperative outcomes of nephron-sparing surgery (NSS). Minimally invasive NSS on renal masses beyond 4 cm in diameter remains challenging and may result in the significant complications. We aimed to evaluate the associations of both scoring systems with perioperative outcomes for minimally invasive NSS on renal masses larger than 4 cm in diameter. Materials and Methods: We retrospectively reviewed patients who received robot-assisted partial nephrectomy (PN) or laparoscopic PN for renal tumors larger than 4 cm in diameter in our institution between January 2008 and March 2019. Computed tomography scan and magnetic resonance imaging were the standard cross-section imaging modalities done before surgery and both R.E.N.A.L. and PADUA scores were calculated in every case accordingly. The correlation between each scoring system and the perioperative and renal functional outcomes was analyzed by logistic regression models. Results: A total of 93 cases were enrolled in this study. The mean tumor size was 6.1 ± 2.03 cm in the largest dimension. A higher R.E.N.A.L. score was significantly correlated with longer warm ischemia time (WIT) (r = 0.267, P = 0.021), prolonged hospital stays (r = 0.258, P = 0.013), and poorer renal functional outcome at 1 year (r = 0.421, P = 0.003). Meanwhile, a higher PADUA score was significantly correlated with longer operation time (r = 0.255, P = 0.014), longer WIT (r = 0.278, P = 0.016), and poorer renal function after 1 year (r = 0.615, P < 0.001). Neither scoring system correlated with estimated blood loss (P = 0.510 and 0.5466, respectively). The R.E.N.A.L. score, PADUA score, patient age, body mass index, Charlson comorbidity index, tumor size, and American Society of Anesthesiologists score were not associated with surgical complications as well. Conclusion: Both the R.E.N.A.L. and PADUA scoring systems were associated with WIT and renal functional outcomes, but the latter was more relevant. When performing minimal invasive NSS on renal masses beyond 4 cm, both systems can provide valuable risk stratification, but PADUA was found to be superior in the current study.

Keywords: Minimally invasive partial nephrectomy, R.E.N.A.L. nephrometry and preoperative aspects and dimensions used for an anatomical classification, renal tumor beyond 4 cm


How to cite this article:
Mai HC, Wu CH, Lin YY, Kuo WW, Lee YH, Li RC, Wu RC, Lin VC. Using R.E.N.A.L. nephrometry and preoperative aspects and dimensions employed for anatomical classification to evaluate perioperative outcomes of renal tumors greater than 4 cm in patients who underwent minimally invasive partial nephrectomy in a single center. Urol Sci 2021;32:15-22

How to cite this URL:
Mai HC, Wu CH, Lin YY, Kuo WW, Lee YH, Li RC, Wu RC, Lin VC. Using R.E.N.A.L. nephrometry and preoperative aspects and dimensions employed for anatomical classification to evaluate perioperative outcomes of renal tumors greater than 4 cm in patients who underwent minimally invasive partial nephrectomy in a single center. Urol Sci [serial online] 2021 [cited 2021 Apr 19];32:15-22. Available from: https://www.e-urol-sci.com/text.asp?2021/32/1/15/312435




  Introduction Top


Renal cell carcinoma (RCC) is a deadly urological cancer, with an average 5-year survival rate of only 71%, compared with 78% for urothelial carcinoma of the bladder (excluding carcinoma in situ) and 99% for prostate adenocarcinoma.[1] The incidence of RCC is about 12/100,000 population per year,[1] with its highest prevalence in patients between 50 and 70 years old.[2] Its incidence has recently increased to about 3%–4% per year,[3] likely because the wider coverage of health insurance among the general population allows for detection during health check-ups or evaluations for abdominal problems.[4] Aside from incidental renal masses, the number of early-stage cases has also increased, and these are suitable for nephron-sparing surgery (NSS). The National Comprehensive Cancer Network guidelines in the USA recommend partial nephrectomy (PN) for the management of clinical T1a malignant renal tumors.[5] In certain situations, PN is an alternative treatment for renal tumors larger than 4 cm for patients with a solitary kidney or at risk for renal insufficiency. For T1a tumors, the morbidities of radical nephrectomy and PN are generally equivalent. The utilization of PN has gradually increased over the past years.[6] With growing experience, reports have suggested that PN can potentially be done for larger and more complex tumors.[7],[8],[9]

Nephrometry scoring systems are used to describe the anatomic features of renal masses and could be useful for providing objective findings regarding the surgical complexity of PN. The R.E.N.A.L. (radius, exophytic/endophytic tumor properties, nearness of tumor to the deepest portion of collecting system or sinus, anterior/posterior descriptor, and location relative to the polar line),[10] and preoperative aspects and dimensions used for an anatomical (PADUA) (tumor size and position, relationship with the renal sinus or the urinary collecting system (UCS), and the grade of deepness into the kidney) scores have gained wide popularity and have been proven to be significantly related to surgical outcomes.[11] Based on comparable oncological outcomes and concerns of renal function preservation, many surgeons are promoting elective PN as a surgical option for renal tumors larger than 4 cm.

A previous study has shown that the R.E.N.A.L. and PADUA scores are comparable measures of renal tumor complexity.[12] PN for larger tumors will likely introduce significant morbidity; the only difference is the complication experienced. Morbidities such as urinomas and pseudoaneurysms can also develop and may require further intervention. Furthermore, a study by Schiavina et al.[13] reported a slightly higher accuracy in the estimation of prolonged warm ischemia time (WIT) and high-grade postoperative complications by the PADUA score, but this was not statistically significant.

Due to the high morbidity of patients with complex renal tumors, the evaluation of the complication risk is essential. A previous study has assessed the size of renal tumors of patients that underwent PN.[14] So far, routinely performing PN is still controversial and challenging in renal tumors larger than 4 cm; it remains unclear which scoring system is more reliable to predict the perioperative and renal functional outcomes. This study aimed to evaluate the associations of these scoring systems with perioperative outcomes for minimally invasive NSS on renal masses larger than 4 cm.


  Materials and Methods Top


Our study was reviewed and approved by the E-DA hospital institutional review board (the approval number: EMRP -109-086). Patient informed consent was waived by the IRB. We retrospectively reviewed patients who underwent robot-assisted partial nephrectomy (RAPN) via the Da Vinci Xi system (IS 4000) or laparoscopic partial nephrectomy (LPN) for renal tumors larger than 4 cm from January 2008 to March 2019 at our institution. Computer tomography scan (CT scan) and magnetic resonance imaging (MRI) were the standard cross-section imaging modalities done before surgery, and the R.E.N.A.L. and PADUA scores were reviewed in each case accordingly. Demographic and clinical data were obtained from the medical records. We excluded patients with incomplete outcome data (preoperative tumor score, perioperative outcome, complication, and follow-up data) from the final analytical cohort. R.E.N.A.L. nephrometry is based on its criteria, with the score ranging from 4 to 12. The complexity of renal masses according to R.E.N.A.L. score can be classified as either low (4–6), moderate (7–9), or high (10–12).[10] In the PADUA classification, tumors are scored by assessing their size alongside their anatomical features; stratified PADUA complexity is defined as either low (6–7), moderate (8–9), or high (10 or greater).[11]

A single dedicated surgical team performed the LPN and RAPN surgeries. The surgeons are experienced in both laparoscopic and robotic techniques. If the tumor was located posteriorly, a retroperitoneal approach was taken, and only LPN could be performed due to small working space. If the tumor was located anteriorly or was larger than 7 cm, a transperitoneal approach was taken, leading to either LPN or RAPN.

Renal function was estimated using the estimated glomerular filtration rate (eGFR) with the modification of diet in renal disease equation. The eGFR 1 day before surgery was used as the baseline renal function. Early postoperative renal function was measured on the next day of surgery. Late renal function measurements were made 3, 6, and 12 months postoperatively. Patient comorbidity was calculated with the Charlson comorbidity index. The World Health Organization adult categories for body mass index (BMI) were used.[15]

We used a scoring system to quantitatively evaluate the perioperative outcomes of NSS (operative time, estimated blood loss, WIT, hospital stay, and renal function changes) and measured the correlation between nephrometry scores and these outcomes. Complications and management interventions done within 30 days were recorded and graded according to the Clavien–Dindo classification (minor complications: 1–2 and major complications: 3–5).[16] We also tried to assess the prediction of complications.[16]

Statistical analysis

Continuous variables are presented as their mean and standard deviation, whereas categorical variables are presented as numbers and proportions. The Student's t-test was used to test for differences in age and changes in eGFR, whereas the Mann–Whitney U test was used to test for differences in Charlson comorbidity index scores between the complexity groups for each respective nephrometry score. The Spearman rank correlation coefficient was determined between the two continuously coded nephrometry scores and quantitative perioperative outcomes. Logistic regression models for R.E.N.A.L. score, PADUA score, age, BMI, Charlson comorbidity index, tumor size, and American Society of Anesthesiologists (ASA) score were used to determine the predictive incidence of complications. Statistical analyses were performed using the SPSS software v24.0 (IBM Corporation, Armonk, NY, USA).


  Results Top


A total of 93 cases were enrolled in this study, including 34 (36.5%) male patients. Of these, 75 (81.4%) received LPN and 18 (18.6%) underwent RAPN. Demographic data and the operative and perioperative tumor complexity according to the two scoring systems are illustrated in [Table 1]. There were no confounding differences in age or Charlson comorbidity score between the complexity groups for each nephrometry score. The mean age was 54 years. The average Charlson comorbidity index was 3.3 ± 1.41. The mean BMI was 25.6 ± 4.07 kg/m2. The mean ASA score was 2.3 ± 0.53.
Table 1: Patient, operative, and tumor characteristics

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The mean tumor size was 6.1 ± 2.03 cm. The mean baseline eGFR preoperatively, 1 day postoperatively, and 1 year postoperatively were 70.73 ± 14.05, 64.75 ± 17.75, and 69.25 ± 15.87, respectively. The average change of eGFR after 1 year was found to be − 1.48 mL/min/1.73 m2. [Table 2] lists the distribution of cases across the classifications of both PADUA and R.E.N.A.L. scoring systems. According to the R.E.N.A.L. score, 70 (75%) cases were categorized as of high complexity, whereas 1 (1%) was classified as of under low complexity. Using the PADUA classification, 22 (23.6%) cases were of high complexity, while 12 (%) were of low complexity. There were 22 (23.6%) cases classified as high complexity in both scoring systems. On the other hand, 47 (50.5%) were defined as high complexity according to the R.E.N.A.L. score, but were considered of intermediate complexity according to the PADUA score.
Table 2: Distribution of the 93 patients in the three groups of preoperative aspects and dimensions used for an anatomical and radius, exophytic/endophytic tumor properties, nearness of tumor to deepest portion of collecting system or sinus, anterior/posterior descriptor, location relative to the polar line scoring systems

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The type of complications and their corresponding management are listed in [Table 3]; among these, 8 minor and 9 major complications were recorded. In the cases with major complications, three cases presented with urine leakage with symptoms and were managed with double J stent placement, while 1 case had urine leakage with abscess formation and required percutaneous nephrostomy drainage. Two cases required transarterial embolization, 1 case with pseudoaneurysm with gross hematuria, and 1 case with delayed bleeding. One case had intraoperative bleeding, covered during open surgery. Another case had renal pedicle injury and required table consult with a cardiovascular surgeon for repair. Finally, there was one Clavien–Dindo grade 4 case that developed perirenal abscess with septic shock and required ICU care after percutaneous nephrostomy drainage.
Table 3: Details of type and severity of complications in 93 patients underwent nephron-sparing surgery

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[Figure 1] and [Table 4] show the quantitative NSS perioperative outcomes correlated with the two scoring systems. The R.E.N.A.L. scores showed a significant correlation with WIT (r = 0.267, P = 0.021), hospital stay (r = 0.258, P = 0.013), and renal functional outcome 1 year postoperatively (r = 0.421, P = 0.003). On the other hand, the PADUA scores showed stronger correlations with operation time (r = 0.255, P = 0.014), WIT (r = 0.278, P = 0.016), and renal function 1 year postoperatively (r = 0.615, P < 0.001). Neither of the scoring systems or other variables (patient age, BMI, Charlson comorbidity index, tumor size, and ASA score) was associated with surgical complications after univariate regression analysis [Table 5].
Figure 1: R.E.N.A.L. score and preoperative aspects and dimensions used for an anatomical score correlated with quantitative NSS perioperative outcomes, including operative time (a), estimated blood loss (b), warm ischemia time (c) hospital stay (d) and the change of estimated glomerular filtration rate (e) asterisk indicates P < 0.05, ** indicates P < 0.01

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Table 4: Spearman rank correlation coefficient of nephrometry scores and perioperative outcomes (>4 cm, n=93)

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Table 5: Univariate analysis model predicting complications (>4 cm patient) (n=93)

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  Discussion Top


Nephrometry scores have previously been used as standardized reporting systems for outcome comparison and also as a tool for surgeons to decide whether to perform NSS based on the complexity of the renal tumor.[17] To our knowledge, the current literature lacks data on renal tumors larger than 4 cm, and nephrometry scores can potentially predict the perioperative course, functional outcome, and complications. Tumor size alone is not sufficient to describe the surgical complexity of a kidney tumor.[11] We performed a comparative analysis to evaluate how the R.E.N.A.L. and PADUA nephrometry scores correlate with the complications and quantitative perioperative outcomes of NSS for renal tumors larger than 4 cm.

The R.E.N.A.L. scores correlated with hospital stay length, WIT, and renal functional outcomes. On the other hand, the PADUA scores correlated with operation time, WIT, and renal functional outcomes. The PADUA scores had a stronger correlation with renal function outcome compared with those of the R.E.N.A.L. No correlation with complications was found in this study after univariate analysis. Similar results were noted in a review by Draeger et al.[18] This may be because the scoring systems were devised to predict tumor complexity and anticipated difficulties during surgery. However, the difficulty during operation depends on many factors, such as the surgeon's experience, surgical plan, anatomy, and tumor characteristics.[19] Postoperative complications also rely on the patient's age and comorbidities. Since the PADUA score had a higher correlation with operation time and renal functional outcome after analysis, it might be the better scoring system for evaluating operation time and renal function for patients with renal tumors larger than 4 cm undergoing NSS.

The two scoring systems differ by their definition of sinus lines and the inclusion of the anatomical relationship between the tumor and the UCS or renal sinus involvement.[20] In the present study, the tumors of 50.5% of the patients were classified as of under intermediate complexity using the R.E.N.A.L. score, but had high complexity if assessed using the PADUA score [Table 2]. Renal sinus involvement is a parameter unique to the PADUA classification. Frank et al. classified tumors based on their invasion of the collecting system and or renal sinus as seen on preoperative imaging studies.[21] Renal sinus involvement is easily identified in both CT and MRI scans, allowing the anatomical relationships between tumor and UCS or renal sinus to be evaluated. The R.E.N.A.L. score only included the relationship between the tumor and both the UCS and renal sinus in a single category (N). Measuring the relative position between the tumor and the anatomical construction is more reliable than a simple evaluation of the anatomical relationship. All the other parameters are similar between the two classifications.[11] The average baseline eGFR in our patients is 70.73 mL/min/1.73 m2, 64.75 mL/min/1.73 m2 1 day after surgery, and 69.25 mL/min/1.73 m2 1 year after surgery [Table 1]. In healthy patients, eGFR declines by about 0.75 mL/min/1.73 m2 per year due to age-related changes. Aging alone can lead to nephrosclerosis and nephron loss, while comorbidities and chronic kidney disease can exacerbate this decline in renal function.[22] Mir et al. found that the decline in function after PN averages approximately 20% in the operated kidney and 10% overall for patients with two kidneys.[23] In our study, excluding 30 cases who had missing data 1 year postoperatively, the average decline in eGFR was 3.38 mL/min/1.73 m2 (4.7%, P < 0.001) after t-test analysis. This is an adequate functional outcome after NSS in renal tumors larger than 4 cm. Moreover, 17 cases of complications were recorded, including 8 minor (8.6%) and 9 major (9.6%) [Table 3]. This incidence is similar to that of the study of Kriegmair et al. (10.6%).[24]

In our study, all patients received minimally invasive PN, and all the tumors were larger than 4 cm. Patients with these characteristics were included since they were our indications for elective minimally invasive NSS. We believe that the PADUA classification might have better precision in predicting perioperative and renal functional outcomes for these patients with tumors larger than 4 cm eligible for surgery.

One limitation of this study is the small sample size and fact that it was a retrospective study. The operations were also performed by different surgeons with different levels of experience, despite belonging to the same center. Finally, renal function was only recorded as eGFR rather than as split renal functions through nuclear medicine test.

These limitations such as different surgeons, approaches (retro/transperitoneal route), and surgical techniques (laparoscopic/robotic) may introduce bias. There were five surgeons who performed minimally invasive PN, but mainly two surgeons were regularly performing these, with 68% and 26% of the patients being operated on by the first and second surgeon, respectively. Moreover, Fan et al. have concluded that the retroperitoneal approach may be faster but equally safe compared with the transperitoneal method.[25] In line with this, we routine performed a retroperitoneal approach in this study unless there is a large tumor size (>7 cm) or located anteriorly. Another prospective cohort study by Arora et al. concluded that the retroperitoneal and transperitoneal approaches to RAPN have comparable operative and perioperative outcomes, except for a shorter hospital stay with the retroperitoneal approach.[26] The different surgical techniques were assessed in a previous meta-analysis by Leow et al., and they concluded that RAPN has a superior morbidity profile compared with LPN.[27] In our study, 18.6% of the patients underwent RAPN. However, the strongest available evidence comparing the outcomes of these two modalities thus far is at level 2b.

To our knowledge, no study has focused on analyzing renal tumors larger than 4 cm and their heterogeneity. However, the population we studied is too small to perform multivariate analysis, and thus further investigation is needed to exclude these biases.


  Conclusions Top


Both the R.E.N.A.L. and PADUA scoring systems were associated with WIT and renal functional outcome, but the PADUA scoring system had stronger correlations. When performing minimally invasive NSS on renal masses larger than 4 cm, both systems can provide valuable risk stratification, but PADUA seems to be superior in the current study.

Financial support and sponsorship

Nil.

Conflicts of interest

Prof. Victor Chia-Hsiang Lin, an editorial board member at Urological Science, had no role in the peer review process of or decision to publish this article. The other authors declared that they have no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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