Predictive factors for postoperative renal function after off-clamp, non-renorrhaphy partial nephrectomy
Introduction
Partial nephrectomy has become the standard procedure for removing renal tumors. Robot-assisted partial nephrectomy (RAPN) has been established as a safe and minimally invasive procedure for tumors measuring <40 mm (1-3). Renal pedicle clamping and renorrhaphy are included in laparoscopic partial nephrectomy in most institutes. However, these operative procedures cause postoperative complications, such as renal function impairment or pseudoaneurysm, at a certain rate (4).
Preservation of estimated glomerular filtration rate (eGFR) and no chronic kidney disease (CKD) upgrading are important outcomes after RAPN (1,3,5,6). Although studies have reported eGFR preservation after on-clamp partial nephrectomy with renorrhaphy (open or laparoscopic), limited studies have reported that after off-clamp open partial nephrectomy without renorrhaphy. In particular, assessment of renal function impairment within 3 months after surgery is deficient.
We retrospectively analyzed the perioperative data of 138 patients who underwent off-clamp open partial nephrectomy without renorrhaphy. The association between perioperative renal function preservation and tumor characteristics and patient characteristics was analyzed. We present the following article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-22-321/rc).
Methods
Patients
Among 220 patients with renal tumors who underwent off-clamp, non-renorrhaphy open partial nephrectomy at our institute between 2013 and 2020, those with postoperative complications of urinoma or incomplete data were excluded. Therefore, clinical records of 138 patients were retrospectively analyzed. Our primary endpoint was to detect predictors of perioperative decline in eGFR within 3 months after off-clamp, non-renorrhaphy open partial nephrectomy. This study was conducted in accordance with the Declaration of Helsinki (revised in 2013). The study was approved by the institutional ethics board of NTT Medical Center Tokyo (No. 20-198) and individual consent for this retrospective analysis was waived.
Surgical techniques
The complexity of renal tumors was analyzed according to RENAL nephrometry scoring system (7). Briefly, (R)adius (tumor size as maximal diameter), (E)xophytic and endophytic properties, (N)earness of the tumor to the collecting system or sinus, and (L)ocation relative to the upper and lower polar lines were scored on a 1, 2 or 3-point scale. The RENAL score represents the sum of R, E, N, and L scores. All patients underwent open partial nephrectomy retroperitoneally. The renal pedicle was not secured, and renal pedicle clamping and cortical renorrhaphy were omitted. We used monopolar SOFT COAG (VIO300D, ERBE, Germany) with a normal saline drip for hemostasis. Surgical techniques have been described previously (8). In partial nephrectomy, the renal parenchyma was repeatedly separated bluntly using a spatula-shaped tip of a monopolar device, followed by soft coagulation of the separated renal parenchyma and bleeding blood vessels. To minimize blood loss, tumor resection was advanced by a millimeter unit. Resection beds were sutured with 4-0 VICRYL® when the collecting system was opened. Urine leakage was ruled out by intravenous injection of indigo carmine solution. TachoSil® was placed on the resection surface to ensure hemostasis.
Assessment of renal function and perioperative reduction in renal function
The eGFR was calculated using the equation 186 × (Creatinine/88.4)−1.154 × (Age)−0.203 × (0.742 if female). Perioperative eGFR preservation at 5 days, 1 month, and 3 months after surgery was calculated as postoperative eGFR/preoperative eGFR × 100 (%).
Statistical analysis
The Student’s t-test was used to analyze continuous variables. Univariate and multivariate regression analyses were performed to identify predictors of postoperative eGFR preservation. Statistical significance was set at P<0.05. All statistical analyses were performed using the SPSS version 24. Factors that were statistically significant (P<0.05) in the univariate analysis were included in the multivariate analysis.
Results
Patient characteristics are described in Table 1. There were 92 (66.7%) male patients and 46 (33.3%) female patients. The median age and tumor size were 63 years [interquartile range (IQR), 14.5 years] and 28 mm (IQR, 21.5 mm), respectively. Among the tumors, 41 (29.7%) were ≥50% exophytic, 62 (44.9%) were <50% exophytic, and 35 (25.4%) were entirely endophytic. The median nephrometry score was 7 (IQR, 2).
Table 1
Variables | Data (n=138) |
---|---|
Sex (%) | |
Male | 92 (66.7) |
Female | 46 (33.3) |
Median age, years (IQR) | 63 (14.5) |
Median BMI (IQR) | 23.4 (5.12) |
No. tumor laterality (%) | |
Right | 69 (50.0) |
Left | 69 (50.0) |
Median tumor size, mm (IQR) | 28 (21.5) |
Median RENAL nephrometry score (IQR) | 7 (2.0) |
Exophytic/Endophytic properties (%) | |
≥50% exophytic | 41 (29.7) |
<50% exophytic | 62 (44.9) |
Entirely endophytic | 35 (25.4) |
Location relative to the polar lines (%) | |
Entirely above the upper or below the lower polar line | 46 (33.3) |
Lesion crosses polar line | 64 (46.4) |
>50% of mass is across polar line or mass crosses the axial renal midline or mass is entirely between the polar lines | 28 (20.3) |
Comorbidity, n (%) | |
Hypertension | 54 (39.1) |
Diabetes mellitus | 22 (15.9) |
Dyslipidemia | 17 (12.3) |
BMI, body mass index; The RENAL nephrometry score was the sum of the sectional scores (R, E, N, and L); IQR, interquartile range.
The surgical results are described in Table 2. The median operation time was 122.5 min (IQR, 44.5 min). The median estimated blood loss was 155 mL (IQR, 247.5 mL). There were no cases of conversion to nephrectomy or consequential renal hilum clamping. The mean eGFR preservation at 5 days, 1 month, and 3 months after surgery was 95.3%, 91.0%, and 90.7%, respectively. The relationship between age and perioperative eGFR decline is shown in Figure 1. Statistically significant reduction in eGFR was detected only in patients over 80 years old (Figure 1).
Table 2
Variables | Data |
---|---|
Median operative time, min (IQR) | 122.5 (44.5) |
Median volume of estimated blood loss, mL (IQR) | 155 (247.5) |
No. additional resections | 0 |
No. conversion to nephrectomy | 0 |
Intraoperative blood transfusion | 0 |
Postoperative blood transfusion | 0 |
Pathology, n (%) | |
Clear cell RCC | 92 (66.7) |
Papillary RCC | 13 (9.4) |
Chromophobe RCC | 10 (7.2) |
Angiomyolipoma | 17 (12.3) |
Oncocytoma | 2 (1.4) |
Others | 4 (2.9) |
Mean eGFR preservation, % (SD) | |
Five days after surgery | 95.3 (14.9) |
One month after surgery | 91.0 (11.5) |
Three months after surgery | 90.7 (16.3) |
eGFR, estimated glomerular filtration ratio; RCC, renal cell carcinoma; IQR, interquartile range.
Tumor size, R, N, RENAL score, and estimated blood loss were predictors of perioperative decline in eGFR 5 days after surgery. Multivariate analysis revealed that estimated blood loss was an independent predictor of perioperative decline in eGFR 5 days after surgery [odds ratio (OR): 0.97; 95% confidence interval (CI): 0.96, 0.98; P<0.001] (Table 3).
Table 3
Variables | Univariate analysis | Multivariate analysis | |||||
---|---|---|---|---|---|---|---|
Unstandardized regression coefficient B (95% CI) | Standardized regression coefficient β | P value | Unstandardized regression coefficient B (95% CI) | Standardized regression coefficient β | P value | ||
Age | −0.128 (−0.332, 0.077) | −0.105 | 0.219 | ||||
BMI | −0.470 (−1.054, 0.114) | −0.136 | 0.114 | ||||
Tumour size | −0.218 (−0.356, −0.081) | −0.261 | 0.02* | ||||
Preoperative eGFR | −0.127 (−0.273, 0.018) | −0.147 | 0.073 | ||||
R | −6.417 (−11.209, −1.625) | −0.221 | 0.009* | ||||
E | −0.926 (−2.487, 4.339) | −0.046 | 0.592 | ||||
N† | −3.752 (−6.615, −0.89) | −0.217 | 0.011 | ||||
L | −2.435 (−5.923, 1.054) | −0.118 | 0.17 | ||||
RENAL score† | −1.819 (−3.276, −0.362) | −0.207 | 0.015* | −1.151 (−2.557, 0.254) | −0.131 | 0.108 | |
Operative time | −0.055 (−0.132, 0.023) | −0.118 | 0.168 | ||||
eBlood loss† | −0.024 (−0.033, −0.014) | −0.377 | <0.001* | −0.022 (−0.032, −0.012) | −0.348 | 0.000* | |
HTN | −3.198 (−8.356, 1.96) | −0.105 | 0.222 | ||||
DM | −4.427 (−11.301, 2.446) | −0.109 | 0.205 | ||||
DL | −1.052 (−8.751, 6.647) | −0.023 | 0.787 |
†, these factors were put into the multivariate regression analysis; *, P value <0.05 was considered statistically significant. eGFR, estimated glomerular filtration rate; BMI, body mass index; eBlood loss, estimated blood loss; R, radius; E, exophytic and endophytic properties; N, nearness of the tumor to the collecting system or sinus; L, location relative to the upper and lower polar lines; (R, E, N, and L were scored according to RENAL nephrometry scoring system); HTN, hypertension; DM, diabetes mellitus; DL, dyslipidemia; CI, confidence interval.
Tumor size, R, RENAL score, estimated blood loss, and preoperative eGFR were predictors of perioperative decline in eGFR 1 month after surgery. Multivariate analysis revealed that preoperative eGFR and estimated blood loss were independent predictors of perioperative decline in eGFR 1 month after surgery (OR: 0.86; 95% CI: 0.77, 0.95; P=0.007; and OR: 0.98; 95% CI: 0.97, 0.99; P<0.001, respectively) (Table 4).
Table 4
Variables | Univariate analysis | Multivariate analysis | |||||
---|---|---|---|---|---|---|---|
Unstandardized regression coefficient B (95% CI) | Standardized regression coefficient β | P value | Unstandardized regression coefficient B (95% CI) | Standardized regression coefficient β | P value | ||
Age | −0.118 (−0.275, 0.039) | −0.127 | 0.140 | ||||
Sex | 1.08 (−3.08, 5.239) | 0.044 | 0.608 | ||||
BMI | −0.167 (−0.618, 0.285) | −0.063 | 0.467 | ||||
Tumour size | −0.182 (−0.287, −0.077) | −0.283 | 0.001* | ||||
Preoperative eGFR† | −0.137 (−0.248, −0.027) | −0.056 | 0.015 | −0.149 (−0.257, −0.042) | −0.225 | 0.007* | |
R | −5.612 (−9.276, −1.948) | −0.252 | 0.003 | ||||
E† | 0.441 (−2.204, 3.085) | 0.028 | 0.742 | ||||
N | −2.187 (−4.425, 0.052) | −0.164 | 0.055 | ||||
L | −1.597 (−4.302, 1.107) | −0.1 | 0.245 | ||||
RENAL score† | −1.277 (−2.404, −0.15) | −0.189 | 0.027* | −0.57 (−1.679, 0.539) | −0.085 | 0.311 | |
Operative time | −0.045 (−0.105, 0.015) | −0.126 | 0.144 | ||||
eBlood loss† | −0.015 (−0.023, −0.007) | −0.306 | 0.000 | −0.015 (−0.023, −0.007) | −0.311 | 0.000* | |
HTN | −2.576 (−6.567, 1.415) | −0.109 | 0.204 | ||||
DM | −1.976 (−7.393, 3.442) | −0.062 | 0.472 | ||||
DL | −2.421 (−8.496, 3.653) | −0.068 | 0.432 |
†, these factors were put into the multivariate regression analysis; *, P value <0.05 was considered statistically significant. eGFR, estimated glomerular filtration rate; BMI, body mass index; eBlood loss, estimated blood loss; R, radius; E, exophytic and endophytic properties; N, nearness of the tumor to the collecting system or sinus; L, location relative to the upper and lower polar lines; (R, E, N, and L were scored according to RENAL nephrometry scoring system); HTN, hypertension; DM, diabetes mellitus; DL, dyslipidemia; CI, confidence interval.
Age, tumor size, R, N, estimated blood loss, and preoperative eGFR were predictors of perioperative decline in eGFR 3 months after surgery. Multivariate analysis revealed that age, preoperative eGFR, and estimated blood loss were independent predictors of perioperative decline in eGFR 3 months after surgery (OR: 0.64; 95% CI: 0.54, 0.81; P<0.001, OR: 0.72; 95% CI: 0.61, 0.85; P<0.001; and OR: 0.98; 95% CI: 0.97, 0.99; P=0.007, respectively) (Table 5).
Table 5
Variables | Univariate analysis | Multivariate analysis | |||||
---|---|---|---|---|---|---|---|
Unstandardized regression coefficient B (95% CI) | Standardized regression coefficient β | P value | Unstandardized regression coefficient B (95% CI) | Standardized regression coefficient β | P value | ||
Age† | −0.228 (−0.449, 0.008) | −0.173 | 0.043* | −0.435 (−0.661, −0.21) | −0.329 | 0.000* | |
Sex | −1.981 (−7.853, 3.89) | −0.057 | 0.506 | ||||
BMI | −0.073 (−0.727, 0.580) | −0.019 | 0.824 | ||||
Tumour size | −0.182 (−0.334, −0.03) | −0.199 | 0.019* | ||||
Preoperative eGFR† | −0.185 (−0.342, −0.028) | −0.196 | 0.021 | −0.319 (−0.482, −0.156) | −0.338 | 0.000* | |
R | −6.019 (−11.274, −0.764) | −0.191 | 0.025* | ||||
E | 0.706 (−3.014, 4.426) | 0.032 | 0.708 | ||||
N | −3.058 (−6.21, 0.094) | −0.162 | 0.057 | ||||
L | −1.474 (−5.292, 2.344) | −0.065 | 0.446 | ||||
RENAL score† | −1.472 (−3.075, −0.13) | −0.154 | 0.071 | −0.957 (−2.511, 0.597) | −0.100 | 0.225 | |
Operative time | 0.01 (−0.075, 0.095) | 0.02 | 0.817 | ||||
eBlood loss† | −0.014 (−0.025, −0.003) | −0.206 | 0.015* | −0.015 (−0.026, 0.004) | −0.223 | 0.007* | |
HTN | −3.94 (−9.549, 1.67) | −0.118 | 0.167 | ||||
DM | −4.882 (−12.368, 2.604) | −0.11 | 0.199 | ||||
DL | −1.584 (−9.969, 6.8) | −0.032 | 0.709 |
†, these factors were put into the multivariate regression analysis; *, P value <0.05 was considered statistically significant. eGFR, estimated glomerular filtration rate; BMI, body mass index; eBlood loss, estimated blood loss; R, radius; E, exophytic and endophytic properties; N, nearness of the tumor to the collecting system or sinus; L, location relative to the upper and lower polar lines; (R, E, N, and L were scored according to RENAL nephrometry scoring system); HTN, hypertension; DM, diabetes mellitus; DL, dyslipidemia; CI, confidence interval.
Discussion
We reported a perioperative decline in renal function during off-clamp, non-renorrhaphy open partial nephrectomy within 3 months after surgery.
The advantage of the off-clamp technique in perioperative renal function preservation is controversial. Deng et al. have reported less decrease in renal function in off-clamp surgery compared to that in on-clamp surgery (weighted mean difference: 4.81 mL/min/1.73 m2; 95% CI: 3.53–6.08; P<0.00001) (9). Meanwhile, several studies have failed to show the advantages of off-clamp surgery in eGFR preservation over clamping surgery in pneumoperitoneum settings (10-13).
As for the advantage of renorrhaphy, the non-renorrhaphy technique failed to benefit the preservation of perioperative renal function for ≥T1b renal tumors in open partial nephrectomy compared with the cold ischemia technique (14). In this study, the renal function was analyzed at 4 and 6 months after surgery. However, studies comparing single-layered and double-layered renorrhaphy have shown the benefits of single-layered renorrhaphy in eGFR preservation (4,15,16). In these analyses, eGFR was assessed between the date of discharge and 1 month postoperatively. Considering these findings, it is possible that omission of renorrhaphy preserves renal function during the early postoperative period.
The RENAL score correlates with perioperative reduction in renal function during on-clamp partial nephrectomy (17). In this study, split renal function was measured using diethylene triamine penta-acetic acid scintigraphy, which showed a significant decrease in ipsilateral renal function 6 months after surgery, with no significant change thereafter (17).
There are limited data on perioperative renal function during combined off-clamp and non-renorrhaphy partial nephrectomy. We have recently reported the surgical results of off-clamp, non-renorrhaphy open partial nephrectomy for ≥T1b renal tumors (8). The perioperative eGFR preservation at 1 month and 3 months after surgery was 88.9% and 87.3%, respectively (8). In laparoscopic or robotic surgeries, perioperative eGFR preservation was 96.9–100% for highly selected patients (18-20). In our study, the eGFR preservation at 5 days, 1 month, and 3 months after surgery was 95.3%, 91.0%, and 90.7%, respectively. We believe our report will add some knowledge on the chronological recovery of renal function after off-clamp, non-renorrhaphy partial nephrectomy.
Importantly, preoperative eGFR did not negatively affect the decline in eGFR during off-clamp, non-renorrhaphy open partial nephrectomy. Our results suggest that this surgical technique can be safely adopted for patients with impaired renal function. Estimated blood loss was a predictor of perioperative decline in eGFR during the 3-month period following surgery. We assumed that damage to the renal parenchyma by soft coagulation directly contributed to the decline in postoperative eGFR. Impairment of the potential for renal function recovery by age may also affect eGFR recovery within 3 months after surgery (21).
This study had some limitations. First, it was a retrospective study. Second, the postoperative eGFR was analyzed within 3 months following surgery.
Conclusions
We analyzed perioperative changes in renal function after off-clamp, non-renorrhaphy open partial nephrectomy until 3 months after surgery. Perioperative eGFR preservation rates at 5 days, 1 month, and 3 months after surgery were 95.3%, 91.0%, and 90.7%, respectively. Age was a predictor of decline in eGFR at 3 months after off-clamp, non-renorrhaphy open partial nephrectomy, while estimated blood loss during surgery remained a predictor of decline in eGFR throughout the 3 months after surgery. Our results suggest that off-clamp, non-renorrhaphy open partial nephrectomy can be safely adopted in patients with impaired renal function.
Acknowledgments
Funding: None.
Footnote
Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-22-321/rc
Data Sharing Statement: Available at https://tau.amegroups.com/article/view/10.21037/tau-22-321/dss
Peer Review File: Available at https://tau.amegroups.com/article/view/10.21037/tau-22-321/prf
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-22-321/coif). MK serves as an unpaid editorial board member of Translational Andrology and Urology from May 2022 to April 2024. The other authors have no conflicts of interest to declare.
Ethical Statement:
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
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