Perioperative Morbidity of Open Versus Minimally Invasive Partial Nephrectomy: A Contemporary Analysis of the National Surgical Quality Improvement Program

Introduction

Partial nephrectomy (PN) has become the preferred operative technique in the surgical management of small renal masses, given evidence supporting similar oncologic efficacy with a reduction in chronic kidney disease when compared with radical nephrectomy (RN). ^{1 –3} In recent years, there has been a shift to minimally invasive PN (MIPN), which offers the potential benefits of improved perioperative outcomes and faster recovery compared with open PN (OPN). ^{4 –11} Since the introduction and dissemination of robotic technology, the utilization of MIPN has surpassed OPN as the most common approach for PN. ^{12 –15}

However, contemporary data assessing the perioperative morbidity of OPN and MIPN are limited. Early reports describing improved perioperative outcomes with MIPN were largely limited to single institution cohorts with small sample sizes. ^{4 –8} Subsequent studies reporting on population-based cohorts were performed before the dissemination of robot-assisted techniques for MIPN, and may not reflect contemporary practice patterns or patient poulations. ^{9 –11}

In this study, we, therefore, examined the perioperative morbidity and mortality of OPN and MIPN in a contemporary, population-based cohort using the National Surgical Quality Improvement Program (NSQIP). We hypothesized that MIPN is associated with decreased perioperative morbidity compared with OPN, and sought to both comprehensively characterize its perioperative morbidity profile as well as the timing of postoperative complications, hospital readmission, and reoperation.

Methods

Results

A total of 13,658 patients underwent PN, including 4,640 (34%) patients who underwent OPN and 9,018 (66%) patients who underwent MIPN. Baseline demographics, stratified by surgical approach, are summarized in Table 1. Median age at surgery was 60 (IQR 51, 68) years, and 59% of patients were male. There were statistically significant differences in several baseline characteristics between groups, including lower ASA class and decreased prevalence of diabetes, chronic obstructive pulmonary disease, hypertension, and renal failure among patients undergoing MIPN (Table 1). Median operative time was slightly longer among patients undergoing MIPN compared with OPN (183 vs 174 minutes; p < 0.0001), and the rate of discharge to a skilled nursing facility was higher in the OPN group (3.3% vs 1.4%; p < 0.0001).

Perioperative outcomes are summarized in Table 2. Overall, 30-day complications occurred in 6.7% of patients. The most common complication categories were infectious (2.3%), surgical site infection/wound (1.7%), and respiratory (1.7%). Compared with OPN, MIPN was associated with significantly lower rates of any 30-day complication (4.9% vs 10.1%; p < 0.0001), with statistically significantly lower rates of each complication category, except pulmonary embolism, suggesting that there is a global decrease in morbidity rather than a particular type of complication. Furthermore, compared with patients undergoing OPN, those who underwent MIPN had statistically significantly lower rates of perioperative blood transfusion (3.8% vs 12.5%; p < 0.0001), prolonged hospitalization (5.6% vs 23.4%; p < 0.0001), hospital readmission (4.4% vs 7.8%; p < 0.0001), reoperation (1.8% vs 3.2%; p < 0.0001), and 30-day mortality (0.3% vs 0.6%, p = 0.001).

We further evaluated the associations of surgical approach with perioperative outcomes in multivariable analyses (Table 3). After adjusting for patient features, MIPN remained independently associated with reduced risks of 30-day complications (OR 0.46; p < 0.0001), perioperative blood transfusion (OR 0.27; p < 0.0001), prolonged hospitalization (OR 0.19, p < 0.0001), readmission (OR 0.59; p < 0.0001), and reoperation (OR 0.57; p < 0.0001). MIPN was associated with a reduced risk of 30-day mortality that did not reach statistical significance (OR 0.62; p = 0.10).

As an exploratory analysis, we evaluated the timing of post-operative complications, hospital readmission, and reoperation, stratified by surgical approach. Reinforcing the bivariate analyses in Table 2, MIPN was associated with improved survival free of any complication (p < 0.0001), cardiac complications (p < 0.0001), DVT/PE (p = 0.03), UTI/sepsis (p < 0.0001), respiratory complications (p < 0.0001), renal failure (p < 0.0001), neurologic complications (p = 0.0006), and surgical site infection (SSI)/sound complications (p < 0.0001) (Figs. 1 and 2a–i). More importantly, Kaplan–Meier figures illustrate that the occurrence of 30-day complications is predominantly early—that is, within the first 10 days postoperatively (Fig. 1). Similarly, predominantly early timing was apparent for cardiac, respiratory, renal, and neurologic complications, whereas thromboembolic complications, UTI/sepsis, and SSI/wound complications occurred consistently throughout the first 30 days after surgery (Fig. 2a–i). Hospital readmissions and reoperation likewise appeared to occur consistently throughout the 30-day postoperative period (Figs. 3 and 4).

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FIG. 1.

Survival free of any complication, stratified by surgical approach.

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FIG. 2.

(a–i) Survival free of each specific complication category, stratified by surgical approach.

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FIG. 3.

Survival free of hospital readmission, stratified by surgical approach.

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FIG. 4.

Survival free of reoperation, stratified by surgical approach.

Discussion

In this study, we utilized a large, national cohort to evaluate outcomes by surgical approach for PN. We observed that MIPN was associated with decreased risks of 30-day complications, perioperative blood transfusion, prolonged hospitalization, hospital readmission, and reoperation, even after adjusting for patient features. MIPN was associated with a similar reduction in 30-day mortality in multivariable analyses, although this did not reach statistical significance. Moreover, we characterized the timing of postoperative complications, readmissions, and reoperation, with implications for postdischarge follow-up and interventions targeted at reducing morbidity. While most complication categories occurred early, rates of hospital readmission and reoperation occurred consistently throughout the 30-day postoperative period, likely reflecting the occurrence of other complication categories that may warrant readmission and reintervention such as SSI/wound complications. These observations highlight the importance of continued vigilance and patient monitoring throughout the postdischarge period.

There is a paucity of data comparing perioperative outcomes for MIPN and OPN in contemporary clinical practice. Utilization of MIPN has increased, in large part due to the dissemination of robotic PN (RPN). Indeed, the utilization of robot-assisted techniques in renal surgery has increased from less than 2% of renal surgeries in 2006 performed with robotic assistance to almost 50% of renal surgeries in 2012 performed using the robotic platform. ¹² Furthermore, there has been a shift away from laparoscopic PN (LPN), with only 7% to 9% of PN performed using LPN. ¹²

While several studies have compared perioperative outcomes of MIPN to those of OPN, most were performed before the widespread adoption of MIPN. Early single-institutional series with relatively small sample sizes reported that MIPN was associated with increased operative time when compared with OPN, but decreased blood loss, lower opioid requirements, and shorter hospital stays. ^{4 –8} Notably, in these studies, MIPN was not associated with a statistically significant difference in complication rates compared with OPN. In a larger multicenter study involving 1800 patients undergoing PN, Gill and colleagues also reported decreased LOS and intraoperative blood loss, but an increased risk of postoperative complications with LPN. ¹⁷ Our observations of reduced rates of perioperative morbidity with MIPN contrast from such early series, and may be explained by the use of predominantly pure laparoscopic rather than robot-assisted approaches in such series. In fact, more recent multi-institutional studies comparing RPN to OPN have found OPN to be associated with more than twice the risk of postoperative complications compared with OPN. ^{18 –20}

Early population-based comparisons of MIPN and OPN were performed using surveillance, epidemiology, and end results program (SEER)-Medicare and Nationwide Inpatient Sample (NIS) data with conflicting findings. ^10,11 One study examined SEER-Medicare data from 2000 to 2007, and observed decreased pLOS for LPN compared with OPN. ¹¹ However, there were no statistically significant differences in postoperative complications or hospital readmission. Conversely, in another study that examined NIS data from 1998 to 2007, the authors reported that LPN was associated with decreased rates of perioperative complications, blood transfusion, and pLOS. ¹⁰ It is interesting that these population-based studies provided disparate findings regarding the perioperative morbidity of MIPN depending on the dataset used. This may be related to differences in ascertainment of complications using administrative claims data, or the lack of postdischarge data in the NIS, which limits captured complications to the index hospitalization. Alternatively, this may be attributed to the older study periods in these studies, which was early in the adoption period of MIPN as reflected in lower utilization rates of MIPN (28% and 6%, respectively).

Later population-based studies have supported a reduction in perioperative morbidity with minimally invasive renal surgery, suggesting improvements in perioperative endpoints with greater experience with minimally invasive techniques and a shift from LPN to RPN. ^{9,21 –23} In studies comparing minimally invasive and open renal surgery in NSQIP from 2005 to 2012, it was reported that minimally invasive renal surgery was associated with decreased 30-day morbidity, mortality, and readmission rates. ^{21 –23} Interestingly, the earliest of these studies observed increased utilization of MIPN over the period studied, with MIPN utilization increasing from 0% before 2007 to over 50% of PN by 2011. ²¹ In another study using the NIS from 2008 to 2010 comparing OPN, LPN, and RPN, the authors found that MIPN (LPN or RPN) was associated with lower risks of blood transfusion, postoperative complications, and pLOS. ⁹

The present study represents the most recent population-based data comparing the perioperative outcomes following MIPN and OPN. Indeed, two-thirds of PN in this study were performed using a minimally invasive approach. Although NSQIP does not distinguish the use of LPN from RPN, the present study reflects contemporary clinical practice in the era following dissemination of robot-assisted renal surgery.

In this study, we also examined the timing of postoperative complications (including postdischarge complications), hospital readmission, and reoperation following PN. The observation that the majority of postoperative complications occur early, likely during the index hospitalization, suggests that early complications represent events closely linked with the operative procedure. Perhaps more importantly, particularly in the current emphasis on value-based healthcare, hospital readmissions and reoperation occurred at a consistent rate throughout the first 30-days postoperatively. Accordingly, postdischarge interventions targeting reductions in these endpoints, such as postoperative outpatient follow-up, should be considered with this timing in mind.

Data examining the timing of postoperative complications following nephrectomy are sparse. In one study that investigated the timing of postoperative complications following nephrectomy (including both PN and RN), the authors reported that major complications were most likely to occur early and before discharge, whereas minor complications were more likely to occur later after discharge. ²⁴ Notably, that study did not separately examine PN, which is associated with unique complications, such urinary leak and pseudoaneurysm/arteriovenous fistula formation that may require readmission or reintervention. Indeed, in the current study, we observed that while some complication categories occurred early in the postoperative period, those likely to require readmission or reintervention, such as thromboembolic complications, UTI/sepsis, and SSI/wound complications, tended to occur throughout the 30-day postoperative period. This may explain the steady rate of hospital readmission and reoperation during the postoperative period.

The present study benefited from a large sample size, national cohort of patients from institutions participating in NSQIP, and multiple surgeons performing surgery. Accordingly, these observations may hold greater external validity for the “average” patient undergoing PN than the experience of high-volume referral institutions. In addition, NSQIP data are clinically abstracted by trained personnel in a standardized fashion and, therefore, may more accurately reflect perioperative outcomes than administrative data sources.

This study has several limitations. Most importantly, we were unable to adjust for a number of clinicopathological features that are not available in the NSQIP dataset, such as hospital or surgeon case volume, patient socioeconomic status, and preoperative functional assessment. Furthermore, NSQIP does not capture preoperative imaging or pathological features, which are necessary to adjust for anatomic complexity and case mix. This may serve as a potential source of bias as anatomically complex or pathologically advanced cases may be more likely to undergo OPN rather than MIPN. In addition, it was not possible to assess Clavien grade of postoperative complications, although additional morbidity endpoints, such as readmission, reoperation, and mortality, capture a degree of severity. Furthermore, certain complications of PN, such as urinary leak, are not specifically captured by the NSQIP database and could not be assessed. In addition, it was not possible to not distinguish LPN from RPN in NSQIP. Finally, we did not examine oncologic outcomes or endpoints beyond 30 days postoperatively, which are relevant for patient counseling and treatment selection. Despite these limitations, our study provides a comprehensive characterization of the perioperative morbidity of MIPN compared with OPN in a contemporary, national cohort, as well as characterization of the timing of postoperative complications, hospital readmission, and reoperation.

Conclusions

In this contemporary national cohort, MIPN was independently associated with reduced rates of 30-day complications, perioperative blood transfusion, prolonged hospitalization, hospital readmission, and reoperation, compared with OPN. These results suggest that MIPN techniques should be preferred when technically feasible to reduce perioperative morbidity.

Disclaimer

The American College of Surgeons National Surgical Quality Improvement Program and the hospitals participating in the ACS NSQIP are the source of the data used herein; they have not verified and are not responsible for the statistical validity of the data analysis or the conclusions derived by the authors.