JOURNAL OF ENDOUROLOGY Volume 28, Number 9, September 2014 ª Mary Ann Liebert, Inc. Pp. 1132–1137 DOI: 10.1089/end.2014.0259

Examining the Relationship Between Operative Time and Hospitalization Time in Minimally Invasive and Open Urologic Procedures M. Francesca Monn, MD, MPH, Rajat Jain, MD, Hristos Z. Kaimakliotis, MD, Chandra K. Flack, MD, Michael O. Koch, MD, and Ronald S. Boris, MD

Abstract

Objective: To explore the relationship between operative time, approach, and length of stay (LOS) in partial nephrectomy (PN), radical prostatectomy (RP), and adrenalectomy (AD). Materials and Methods: Using the National Surgical Quality Improvement Program database, we identified all PN, RP, and AD from 2010 to 2012. Non-prostate cancer RP were excluded. The primary outcome was LOS. Descriptive comparisons were drawn between open and minimally invasive surgery (MIS) for each surgery. Multiple linear regression assessed the impact of open versus MIS and operative time on LOS when controlling for confounders. Results: We identified 3760 PN (60% MIS), 12,081 RP (82% MIS), and 1684 AD (76% MIS) cases for inclusion. Differences in operative time were identified. In PN and RP, MIS mean operative time was 10 to 23 minutes longer ( p < 0.001 each); while for AD, open was 35 minutes longer ( p < 0.001). Open procedures had consistently longer median LOS ( p < 0.001 all). Results of the linear regression are given next. Conclusions: Operative time and surgical approach are directly associated with LOS, independent of complications and patient comorbidities. Introduction

S

ince the Institute of Medicine’s report on the status of the healthcare system in 2000, the role of quality indicators in the delivery of care has become increasingly significant.1 The University Health-System Consortium and National Surgical Quality Improvement Program (NSQIP), among others, includes length of stay (LOS) among its quality indicators for hospitals. LOS was initially used as a quality measure indicator in the intensive care unit setting but more recently, it has expanded into other fields of medicine2,3; however, its relevance in the surgical setting remains undefined. While others have reported the impact of patient and payer factors on LOS in the surgical setting,4 the relationships between operative time, approach, and LOS are poorly understood.2,5 For instance, Oyetunji et al. reported that while operative time and patient comorbidities were associated with an increase in post-discharge complications, the relationship between LOS and post-discharge complications was absent.2 Urologic procedures are increasingly performed using minimally invasive surgery (MIS) as an alternative to open surgery.6,7 Advantages of MIS are well documented in the literature, with decreased blood loss, less narcotic use, and

overall improvements in convalescence.8–10 In addition, studies have demonstrated surgical equivalence between many MIS and open procedures.11 Since the true impact of operative time and surgical approach (MIS vs open) on LOS has yet to be explored, we sought to evaluate whether these variables affect LOS and whether these relationships differ across various urological surgeries with established experience for both open and minimally invasive approaches. Materials and Methods Dataset and patients

NSQIP is a validated program of the American College of Surgeons that prospectively gathers 30-day postoperative outcomes for surgical patients in participating non-federal hospitals.12 Data are gathered by trained Surgical Clinical Reviewers and are audited to ensure the integrity of the data. Surgical patients are randomly chosen using an eight-day cycle to limit selection bias. NSQIP’s primary goal is quality improvement of surgical care.12 Using the 2010–2012 NSQIP data, we identified all patients undergoing partial nephrectomy (PN), radical prostatectomy (RP), and adrenalectomy (AD) from relevant Current Procedural Terminology (CPT) codes

Department of Urology, Indiana University School of Medicine, Indianapolis, Indiana.

1132

LENGTH OF STAY AND OPERATIVE TIME

1133

(PN: 50240, 50543; RP: 55840, 55842, 55845, 55866; AD: 60540, 60545, 60650). Although we initially intended to include cystectomy, it was excluded because we were unable to identify MIS using CPT codes. We excluded patients with disseminated cancer and patients undergoing prostatectomy for non-prostate cancer reasons. Outcomes and variables

The primary outcome of interest was LOS, defined as the days between surgery and initial discharge. Any LOS recorded as longer than 30 days was censored at 30 days, because NSQIP does not regularly report days collected beyond this. We eliminated patients whose operative times were among the shortest 5% and the longest 5% to mitigate the effects of any miscoding of operative time and to eliminate cases that were more or less complex for unknown reasons. This resulted in operative time bounded at 90 and 327 minutes. MIS was determined by CPT code (PN: 50543; RP 55866; AD 60650). Other variables in the study were age, sex, race, body mass index (BMI), history of diabetes, history of chronic obstructive pulmonary disease (COPD), history of congestive heart failure (CHF), malignancy, resident involvement in the surgery, and in-hospital postoperative complications. Complications included wound infection, dehiscence, venous thromboembolism, pneumonia, urinary tract infection, septic shock, reintubation, acute renal failure, stroke, and heart attack. Variable definitions are available from NSQIP.12 Statistical analyses

Descriptive analysis was performed by comparing MIS with open surgery for each of the procedures. Pearson’s chisquared, Student’s t-test, and the Mann–Whitney test were used as appropriate for reporting differences between the groups. For each procedure type, multiple linear regression assessed the impact of open surgery (compared with MIS) and operative time on LOS when controlling for age, sex (when appropriate), race, BMI, diabetes, COPD, CHF, malignancy, resident involvement, and in-hospital complica-

tions. From these multiple linear regressions, adjusted prediction models for LOS were generated for each procedure type based on the operative time and approach. Variables chosen for inclusion in the multiple linear regression were determined a priori as potential confounders of either LOS or operative time. A priori p < 0.05 for two-tailed tests was set as our threshold for statistical significance. All statistical analyses were performed using Stata version 12.1 (Statacorp, College Station, TX). The Indiana University Institutional Review Board granted exempt status for conducting this study. Results Partial nephrectomy

The cohort of PN patients consisted of 3760 patients, of whom 2248 (60%) were minimally invasive PN (MIPN) (Table 1). Malignant cases were slightly more likely to be performed open than by MIS ( p = 0.044), and residents were more likely to participate in open than MIS cases ( p < 0.001). Seven percent of open PN (OPN) developed an in-hospital complication versus two percent of MIPN ( p < 0.001). Although the mean operative time was 10 minutes longer for MIPN than OPN ( p < 0.001), MIPN cases had a median 2 day shorter LOS than OPN ( p < 0.001) (Table 1). Adjusting for potential confounders, open compared with MIS conferred a 1.7 day increase in LOS for PN ( p < 0.001) (Table 2). Insulindependent diabetes was independently associated with a third of a day increase in LOS. In addition, each 60 minute increase in operative time was associated with a 0.34 day increase in hospitalization regardless of operative technique ( p < 0.001) (Fig. 1a). For instance, the predicted adjusted LOS for a 120 minute MIPN was 2.5 versus 4.1 days for OPN; however, when the procedure lasted 300 minutes, the adjusted LOS was 3.5 for MIPN and 5.2 for OPN (Fig. 1a). Prostatectomy

There were 12,081 patients comprising the cohort of prostatectomy patients, 82% in whom the procedure was

Table 1. Patient Characteristics Partial nephrectomy

N Age, mean (SD) Sex (female) Race White Black Hispanic Asian Other/unknown BMI, mean (SD) Malignancy Resident involved Operative time, mean (SD) In-hospital complication LOS, median (IQR) Death in 30 days

Prostatectomy

MIS

Open

2248 58.9 (12) 969 (43)

1512 58.7 (13) 630 (42)

9893 61.8 (7) —

1672 182 95 50 249 30.2 1330 589 192 39 2 7

1145 121 82 32 132 31.0 944 563 182 102 4 11

7567 (76) 946 (10) 380 (4) 156 (2) 844 (9) 28.8 (5) 9893 2786 (28) 200 (51) 68 (0.7) 1 (1–2) 8 (0.1)

(74) (8) (4) (2) (11) (7) (59) (26) (54) (2) (2–3) (0.3)

(76) (8) (5) (2) (9) (7) (62) (37) (57) (7) (3–5) (0.7)

MIS

Adrenalectomy

Open

MIS

Open

2188 62.4 (7) —

1287 52.7 (14) 744 (58)

397 56.3 (14) 215 (54)

1472 (67) 125 (6) 57 (3) 22 (1) 512 (23) 28.8 (5) 2188 767 (35) 177 (54) 22 (1) 2 (2–3) 3 (0.1)

870 184 75 41 117 31.3 100 703 152 35 2 2

279 48 28 14 28 30.4 107 222 187 37 5 2

IQR = interquartile range; LOS = length of stay; MIS = minimally invasive surgery; SD = standard deviation.

(68) (14) (6) (3) (9) (8) (8) (55) (50) (3) (1–3) (0.2)

(70) (12) (7) (4) (7) (10) (27) (56) (61) (9) (4–7) (0.5)

1134

MONN ET AL.

Table 2. Multiple Linear Regression Models Assessing the Relationship Between Operative Technique (Open vs Minimally Invasive) and Time with Length of Hospital Stay Partial nephrectomy Coefficient Age Sex (female) Race (non-white) BMI Diabetes Non-insulin Insulin COPD CHF Malignant Resident Operative timea Open surgery Complication Constant

Prostatectomy

Adrenalectomy

p-Value

Coefficient

p-Value

Coefficient

p-Value

0.02 0.20 0.24 0.01

< 0.001 0.003 0.002 0.133

0.01 — 0.28 - 0.004

< 0.001 — < 0.001 0.165

0.02 0.42 0.29 - 0.005

< 0.001 0.001 0.022 0.528

0.08 0.34 0.77 - 0.07 - 0.13 0.07 0.34 1.67 5.00 0.06

0.466 0.025 < 0.001 0.901 0.061 0.380 < 0.001 < 0.001 < 0.001 0.820

0.001 - 0.02 0.36 - 0.46 — - 0.17 0.17 1.02 6.80 0.54

0.980 0.829 0.001 0.347 — < 0.001 < 0.001 < 0.001 < 0.001 0.001

0.32 0.87 1.20 4.13 - 0.57 - 0.04 0.42 2.71 6.45 0.40

0.081 < 0.001 < 0.001 < 0.001 0.003 0.734 < 0.001 < 0.001 < 0.001 0.366

a

Operative time is in 60 minute increments BMI = body mass index; CHF = congestive heart failure; COPD = chronic obstructive pulmonary disease.

FIG. 1.

Adjusted length of stay for partial nephrectomy (a), prostatectomy (b), and adrenalectomy (c).

LENGTH OF STAY AND OPERATIVE TIME

performed using minimally invasive techniques (Table 1). Residents participated more commonly in open prostatectomies ( p < 0.001). There was no difference in incidence of inhospital complications ( p = 0.184). Mean operative time for minimally invasive RP (MIRP) was 25 minutes longer than for open ( p < 0.001); however, the LOS was one day shorter for MIRP ( p < 0.001) (Table 1). After controlling for potential confounding variables, open versus MIRP conferred a 1.02 day increase in LOS ( p < 0.001) (Table 2). Resident involvement led to a 0.2 decrease in LOS ( p < 0.001). Each additional hour of operative time was associated with a 0.17 day increase in LOS ( p < 0.001) (Fig. 1b). For example, when examining short and long duration surgeries, the predicted adjusted LOS for a 120 minute MIRP was 1.3 versus 2.4 days for open RP (ORP); while for a 300 minute MIRP, the predicted LOS was 1.9 versus 2.9 days for ORP (Fig. 1b). Adrenalectomy

Of the 1684 AD cases included, 76% were performed using minimally invasive techniques (Table 1). Fifty-seven percent of patients were women and 68% were white, with no differences noted between open and MIS. Malignant cases only accounted for 12% of the adrenalectomies, and more than half of these were managed with open surgery ( p < 0.001) (Table 1). Open cases had thrice the incidence of in-hospital complications ( p < 0.001). Open AD was 30 minutes longer on average than minimally invasive ( p < 0.001). LOS was 3 days longer in the open AD group ( p < 0.001) (Table 1). Adjusting for confounders, open AD compared with MIS AD conferred a nearly three-day increase in LOS ( p < 0.001) (Table 2). Furthermore, each 60 minute increase in operative time was associated with an adjusted additional 0.4 day increase in LOS ( p < 0.001) (Fig. 1c). Using the adjusted prediction model, a 120 minute MIS AD was associated with a predicted 2.2 day LOS versus 4.9 for open AD; whereas a 300 minute MIS AD had an LOS of 3.5 days versus 6.2 for open (Fig. 1c). Discussion

The impact of increasing operative times on LOS has been briefly described in the general surgery literature13,14; however, this relationship has not been examined among urology patients. In additionally, multiple publications have suggested that prolonged operative time may be associated with increased medical and surgical complications.2,13,15,16 Why should urologists be concerned with LOS? Beyond its association with direct patient and hospital costs, LOS is currently tracked as an outcome indicator of quality of care. A recent study suggested, however, that while LOS has significantly decreased over the past few decades, there has been a significant increase in hospital readmission rates over the same period of time.17 Furthermore, patients requiring readmission had worse overall survival compared with non-readmitted patients.17 Balancing LOS with patient safety is critical in the perioperative management of surgical patients. Predicting patients at risk for prolonged hospitalization and understanding the impact of operative time on these risks may improve discharge pathways and help stream line appropriate post-operative care. Although there was variability between the procedures, multiple factors apart from operative time were associated with significantly increased LOS for all three surgical procedures that were analyzed in our study. Age and co-

1135

morbidities are known to be associated with increased length of hospitalization,18 and our findings support this. While a recent large study suggested a small increase in LOS associated with obesity in surgical patients (0.025 days), we did not observe this in our cohort, which might be reflective of the number of patients we examined and the small difference in LOS identified in the study.19 Interestingly, while resident involvement in PN and AD had no specific impact on LOS, it decreased LOS by 0.2 days for prostatectomy. Previous studies have suggested similar findings with regard to the impact of resident involvement in surgical cases.20 Although explanations for these findings remain elusive, potentially resident involvement may be a surrogate for an academic or a high volume surgical center where discharge pathways may be better established. Among the adrenal surgeries, malignant pathology was surprisingly associated with a decreased LOS while open surgery conferred a 2.7 day increase in hospital stay. Although these findings appear discordant, recognizing that 87% of benign cases were performed using MIS technique, it is reasonable to assume that the likelihood of an open approach for a malignant tumor greatly influenced our findings. There are many established variables in anticipating prolonged operative time, such as surgical skill, learning curve, tumor complexity, and patient comorbidity. All of these likely contribute somewhat to our observed relationship of operative time to LOS. Despite this, a few studies have examined the actual relationship between these two statistics in urologic procedures. In vascular surgery, Tan et al. examined patients undergoing femoral popliteal bypass surgery and found that longer operative times were associated with both increased LOS and increased risk of developing perioperative surgical site infections after controlling for patient comorbidities.21 Similarly, in colectomy populations, multiple studies have reported that prolonged operative times are associated with increased hospital stay.2,14 In our study, a single hour increase in operative time was associated with an increase in adjusted LOS from 0.2 to 0.4 days. Whether these increases have relevant clinical impact remains unknown. Regardless of these, our findings demonstrate that, at least when comparing extreme differences in operative times across all three procedures, the impact on length stay is consistently demonstrated and economic implications should be anticipated. It should be noted that the relationship which we report here is an association and should not be considered causative. The impact of the surgical technique on hospital LOS has been heavily debated. Our data demonstrated that depending on the procedure, an open compared with an MIS approach was associated with a one- to three-day increase in LOS, independent of operative time and patient confounders. For MIPN compared with OPN, data suggest shorter hospitalization times and complication rates at the expense of increased hospital charges.6,16 The relationship between LOS and MIS for RP is less clear, with large, population-based studies demonstrating an overall increase in LOS for open RP.5,22 However, comparisons between LOS after MIRP and ORP from individual high volume institutions and surgeons have reported no difference in hospitalization times.23,24 Since we found that ORP performed with shorter operative times had similar LOS outcomes to MIRP with longer operative times, perhaps the difference in findings published from high volume institutions which report no difference in LOS are dependent on individual surgeons’ comfort levels and

1136

skill with their respective techniques. Research on the proposed benefits of minimally invasive AD is not definitive, partially due to the large proportion of malignant cases being performed using an open approach making the compared groups unequal; however, MIS has now become the preferred approach for benign adrenal disease, in part because of its associated shorter hospitalization time.25,26 These reported shortened lengths of stay associated with MIS correspond with our findings that for the majority of cases, MIS is associated with a shorter LOS. Despite these observations, it is notable that once an MIS reaches longer operative times, the predicted adjusted LOS was no better than for a shorter open surgery, most strikingly for PN and RP as shown in Figure 1a and b. Consistently across procedures, we found that operative time demonstrated a positive association with LOS, with each hour increase in operative time resulting in approximately a 0.4 day increase in LOS independent of operative technique and postoperative complications. Increasing LOS is associated with patient comorbidities, postoperative complications, operative time, and operative approach. Experienced open surgeons with shorter operative times can expect similar LOS to longer minimally invasive surgeries, and the slope of impact of time on hospital stay appears relatively independent of surgical approach. These findings underscore the importance of intraoperative efficiency, either open or minimally invasive, in order to both improve postoperative duration of hospitalization and minimize overall complication rates.2,13,15,16 There are multiple limitations to the study, the majority of which are associated with the dataset itself. Although NSQIP is a well-validated, rigorous clinical database, there is an inherent selection bias in that the patients in the database are representative only of hospitals which self-selected to participate in the program and, thus, might not be generalizable to all patients and hospitals. Furthermore, despite data audits, there is the potential for coding errors in the dataset, which may have impacted our findings. We eliminated 10% of the operative time data in order to minimize the impact of potential miscoding or aberrant cases; however, this could have altered our findings as well. A sensitivity analysis was performed when only eliminating the shortest and longest 1% of cases in order to evaluate the effect of the decision with no difference found in the significance of the primary results. NSQIP does not include TNM staging or pathologic data, so we are unable to account for tumor severity or operative complexity, which certainly makes an impact on operative time. We were also unable to distinguish between roboticassisted and pure laparoscopic procedures for the MIS category. In addition, NSQIP does not account for hospital and surgical volume or post-surgical care pathways that have been associated with LOS in previous literature.27,28 Despite these limitations, this study provides a unique insight into the relationship between operative time and LOS for common urologic surgeries. Conclusions

Both operative time and surgical approach are directly associated with increased LOS, independent of in-hospital complication rates. Improved understanding of the relationships between operative approach, operative time, and length of hospital stay will enable better procedure-specific benchmarks and quality indicators for surgical patients.

MONN ET AL. Acknowledgments

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 here; they have not verified and are not responsible for the statistical validity of the data analysis or the conclusions derived by the authors. Disclosure Statement

No competing financial interests exist for any of the authors. References

1. Institute of Medicine. ‘‘To Err Is Human: Building a Safer Health System.’’ Washington, DC: National Academy Press, 2000. Available from: www.iom.edu/Reports/1999/ to-err-is-human-building-a-safer-health-system.aspx Accessed September 4, 2013. 2. Oyetunji TA, Turner PL, Onguti SK, Ehanire ID, Dorsett FO, Fullum TM, et al. Predictors of postdischarge complications: Role of in-hospital length of stay. Am J Surg 2013;205:71–76. 3. Rotter T, Kinsman L, James E, Machotta A, Gothe H, Willis J, et al. Clinical pathways: Effects on professional practice, patient outcomes, length of stay and hospital costs. Cochrane Syst Rev 2010:CD006632. 4. Brasel KJ, Lim HJ, Nirula R, Weigelt JA. Length of stay: An appropriate quality measure? Arch Surg 2007;142:461– 465; discussion 5–6. 5. Liu JJ, Maxwell BG, Panousis P, Chung BI. Perioperative outcomes for laparoscopic and robotic compared with open prostatectomy using the National Surgical Quality Improvement Program (NSQIP) database. Urology 2013;82: 579–583. 6. Ghani KR, Sukumar S, Sammon JD, Rogers CG, Trinh QD, Menon M. Practice patterns and outcomes for open and minimally invasive partial nephrectomy since the introduction of robotic partial nephrectomy: Results from the nationwide inpatient sample. J Urol 2014;191:907–913. 7. Stitzenberg KB, Wong YN, Nielsen ME, Egleston BL, Uzzo RG. Trends in radical prostatectomy: Centralization, robotics, and access to urologic cancer care. Cancer 2012; 118:54–62. 8. Yu HY, Hevelone ND, Lipsitz SR, Kowalczyk KJ, Hu JC. Use, costs and comparative effectiveness of robotic assisted, laparoscopic and open urological surgery. J Urol 2012;187:1392–1398. 9. Salman M, Bell T, Martin J, Bhuva K, Grim R, Ahuja V. Use, cost, complications, and mortality of robotic versus nonrobotic general surgery procedures based on a nationwide database. Am Surg 2013;79:553–560. 10. Tosoian JJ, Loeb S. Radical retropubic prostatectomy: Comparison of the open and robotic approaches for treatment of prostate cancer. Rev Urol 2012;14:20–27. 11. Vora AA, Marchalik D, Kowalczyk KJ, Nissim H, Bandi G, McGeagh KG, et al. Robotic-assisted prostatectomy and open radical retropubic prostatectomy for locally-advanced prostate cancer: Multi-institution comparison of oncologic outcomes. Prostate Int 2013;1:31–36. 12. ACS-NSQIP. National Surgical Quality Improvement Project. American College of Surgeons; 2002 [updated 2013; cited 2014 January]; Available from: http://site.acsnsqip.org/ 13. Procter LD, Davenport DL, Bernard AC, Zwischenberger JB. General surgical operative duration is associated with increased risk-adjusted infectious complication rates and

LENGTH OF STAY AND OPERATIVE TIME

14. 15.

16.

17.

18.

19.

20. 21.

22.

23.

24.

length of hospital stay. J Am Coll Surg 2010;210:60– 65.e1–e2. Scheer A, Martel G, Moloo H, Sabri E, Poulin EC, Mamazza J, et al. Laparoscopic colon surgery: Does operative time matter? Dis Colon Rectum 2009;52:1746–1752. Kim BD, Hsu WK, De Oliveira GS, Jr., Saha S, Kim JY. Operative duration as an independent risk factor for postoperative complications in single-level lumbar fusion: An analysis of 4,588 surgical cases. Spine 2014;39:510–520. Tan HJ, Wolf JS, Jr., Ye Z, Hafez KS, Miller DC. Population-level assessment of hospital-based outcomes following laparoscopic versus open partial nephrectomy during the adoption of minimally-invasive surgery. J Urol 2014;191:1231–127. Schneider EB, Hyder O, Brooke BS, Efron J, Cameron JL, Edil BH, et al. Patient readmission and mortality after colorectal surgery for colon cancer: Impact of length of stay relative to other clinical factors. J Am Coll Surg 2012;214: 390–398; discussion 8–9. Kelly M, Sharp L, Dwane F, Kelleher T, Comber H. Factors predicting hospital length-of-stay and readmission after colorectal resection: A population-based study of elective and emergency admissions. BMC Health Serv Res 2012;12:77. Mason RJ, Moroney JR, Berne TV. The cost of obesity for nonbariatric inpatient operative procedures in the United States: National cost estimates obese versus nonobese patients. Ann Surg 2013;258:541–551; discussion 51–53. Uecker J, Luftman K, Ali S, Brown C. Comparable operative times with and without surgery resident participation. J Surg Ed 2013;70:696–699. Tan TW, Kalish JA, Hamburg NM, Rybin D, Doros G, Eberhardt RT, et al. Shorter duration of femoral-popliteal bypass is associated with decreased surgical site infection and shorter hospital length of stay. J Am Coll Surg 2012; 215:512–518. Ficarra V, Novara G, Artibani W, Cestari A, Galfano A, Graefen M, et al. Retropubic, laparoscopic, and robotassisted radical prostatectomy: A systematic review and cumulative analysis of comparative studies. Eur Urol 2009; 55:1037–1063. Tomaszewski JJ, Matchett JC, Davies BJ, Jackman SV, Hrebinko RL, Nelson JB. Comparative hospital cost-analysis of open and robotic-assisted radical prostatectomy. Urology 2012;80:126–129. Nelson B, Kaufman M, Broughton G, Cookson MS, Chang SS, Herrell SD, et al. Comparison of length of hospital stay

1137

25.

26. 27.

28.

between radical retropubic prostatectomy and robotic assisted laparoscopic prostatectomy. J Urol 2007;177:929–931. Jurowich C, Fassnacht M, Kroiss M, Deutschbein T, Germer CT, Reibetanz J. Is there a role for laparoscopic adrenalectomy in patients with suspected adrenocortical carcinoma? A critical appraisal of the literature. Horm Metab Res 2013;45:130–136. Guazzoni G, Cestari A, Montorsi F, Bellinzoni P, Centemero A, Naspro R, et al. Laparoscopic treatment of adrenal diseases: 10 years on. BJU Int 2004;93:221–227. Wilt TJ, Shamliyan TA, Taylor BC, MacDonald R, Kane RL. Association between hospital and surgeon radical prostatectomy volume and patient outcomes: A systematic review. J Urol 2008;180:820–828; discussion 8–9. Yao SL, Lu-Yao G. Population-based study of relationships between hospital volume of prostatectomies, patient outcomes, and length of hospital stay. J Natl Cancer Inst 1999;91:1950–1956.

Address correspondence to: M. Francesca Monn, MD, MPH Department of Urology Indiana University School of Medicine Indiana Cancer Pavilion 535 N Barnhill Drive Suite 150 Indianapolis, IN 46202 E-mail: [email protected]

Abbreviations Used AD ¼ adrenalectomy BMI ¼ body mass index CHF ¼ congestive heart failure COPD ¼ chronic obstructive pulmonary disease CPT ¼ Current Procedural Terminology LOS ¼ length of stay MIPN ¼ minimally invasive PN MIRP ¼ minimally invasive RP MIS ¼ minimally invasive surgery NSQIP ¼ National Surgical Quality Improvement Program OPN ¼ open partial nephrectomy ORP ¼ open radical prostatectomy PN ¼ partial nephrectomy RP ¼ radical prostatectomy