Hysterectomy is one of the most commonly performed procedures in the United States. Each year approximately 600,000 hysterectomies are performed.1–3 Although the abdominal hysterectomy is the most common route for the procedure, approximately 22% of hysterectomies are performed vaginally and 14% are performed laparoscopically.2
Vaginal hysterectomy is the preferred route for hysterectomy for benign disease when technically feasible.4 The procedure has been shown to be safe and is associated with acceptable morbidity and mortality.4–6 In a large analysis of women who underwent vaginal hysterectomy, infectious morbidity was the most frequent complication. Perioperative mortality was rare and occurred in only 0.06% of the cohort.5 A number of factors, including age, medical comorbidities, and uterine factors, are known to influence the incidence of complications for vaginal hysterectomy.6
In addition to patient-related factors, physician characteristics including surgical volume have been demonstrated to affect outcomes for a number of procedures; those patients operated on by high-volume surgeons and at high-volume hospitals have superior outcomes.7–15 In a study of patients undergoing cardiovascular and cancer surgery, operative mortality was reduced significantly for all of the procedures examined when the surgery was performed by high-volume physicians.9 The association between volume and outcome appears to be most pronounced for high-risk cardiovascular and oncologic procedures. The correlation between increased volume and improved outcomes for more commonly performed, less complex procedures has been inconsistent.14,16 The objective of our study was to estimate the effect of surgical volume on outcomes and resource use in women undergoing vaginal hysterectomy for benign disease. In addition, we estimated the influence of both overall gynecologic surgical volume as well as vaginal surgical volume on outcomes.
MATERIALS AND METHODS
Data from the Perspective database were analyzed. Perspective is a nationwide, voluntary, fee-supported database developed to measure quality and resource use. Perspective contains inpatient data from more than 500 acute-care hospitals throughout the United States. Each participating hospital submits electronic updates quarterly. The data are audited regularly to ensure quality and integrity. Perspective collects data on patient demographics, clinical characteristics, procedures, and all billed services. Data submitted to Perspective undergo a rigorous process of quality assurance and validation.17–19 Perspective is validated and has been used in a number of outcomes studies.17,18,20 All data were deidentified and deemed exempt by the Columbia University Institutional Review Board.
Women who underwent total vaginal hysterectomy (International Classification of Diseases, 9th Revision, Clinical Modification code 68.5) between 2003 and 2007 for benign disease were analyzed. Concomitant procedures performed at the time of vaginal hysterectomy, including oophorectomy, anterior colporrhaphy, posterior colporrhaphy, and incontinence repair procedures, were recorded. Each of the following indications for surgery was examined: leiomyoma, endometriosis, abnormal bleeding, benign ovarian neoplasms, and prolapse. Patients may have had multiple indications for surgery. Patients who underwent a laparoscopically assisted procedure were excluded from analysis.
Procedure-associated complications were assessed using International Classification of Diseases, 9th Revision codes for known hysterectomy-related morbidity. Complications were classified into the following groups: 1) operative complications (bladder injury, ureteral injury, intestinal injury, vascular injury, other operative injury); 2) perioperative surgical complications (reoperation, postoperative hemorrhage, wound complication, venous thromboembolism); and 3) medical complications (cardiovascular, pulmonary, gastrointestinal, renal, infectious). Length of hospital stay was defined as the number of days from hysterectomy to discharge. Rates of transfusion and intensive care unit use were calculated. Perioperative death was defined as death during the hospitalization during which the patient underwent hysterectomy. Operative time was determined based on the total recorded operative time. We included only patients whose total operative times were recorded and were more than 30 minutes. Cost was measured based on a recorded code for patient costs. Approximately three-fourths of hospitals submit direct cost data to Premier; the remainder submit calculated costs based on hospital specific cost to charge ratios.18
Predictor variables included demographic, clinical, and hospital characteristics. Age (younger than 50, 51–65, 65 years of age or older), year of surgery (2003–2005, 2006–2007), and race (white, African American, other) were categorized for each patient. Each patient's insurance and marital status were recorded. Comorbidity was estimated using the Deyo index.21 Hospital characteristics including location (urban, rural), type (teaching, nonteaching), size (fewer than 300, 300–500, 500 beds or more), and region (midwest, northeast, south, west) were recorded.
The primary focus of our analysis was to estimate the association between surgical volume and outcome. Because not all physicians contributed patients during the entire study period, we calculated annual surgeon volume by dividing the total number of procedures performed by the number of years in which an individual surgeon performed at least one vaginal hysterectomy. Two separate volume classification systems were used. The first analysis focused on vaginal surgical volume. For this analysis, the annual number of vaginal hysterectomies each surgeon performed was determined. The second analysis focused on overall gynecologic surgical volume. For this analysis, the annual number of all gynecologic procedures performed for each surgeon was determined. For each of the two analyses (vaginal surgical volume and gynecologic surgical volume), the distribution of annual volume analyzed was determined and cut points selected to divide patients into approximately equal volume tertiles was: low, intermediate, and high.
Frequency distributions between categorical variables were compared using chi square test, whereas continuous variables were compared with one-way analysis of variance. To account for clustering within a given surgeon's panel of patients, we used generalized estimating equations.22 Generalized estimating equation logistic regression analysis was performed to determine independent predictors of complications and mortality. Individual generalized estimating equation analyses were performed for each of the complications of interest and for mortality. Length of stay, operative time, and cost were estimated with linear regression models using ordinary least squares. Outcomes are reported as adjusted odds ratios. All analyses were performed with SAS 9.2.
A total of 77,109 patients operated on by 6,195 gynecologic surgeons were identified. The low-volume vaginal surgery group included 25,666 patients operated on by 4,980 surgeons who performed fewer than 5.4 vaginal procedures annually, whereas the high-volume vaginal surgery cohort consisted of 25,684 patients treated by 310 surgeons who performed more than 13 vaginal procedures annually. When stratified by total gynecologic surgery volume, the low-volume tertile was made up of 4,282 surgeons who performed fewer than 29.5 gynecologic surgeries per year, whereas the high-volume cohort included 567 surgeons who performed more than 54.4 procedures annually (Table 1).
Compared with patients treated by low-volume vaginal surgeons, those women operated on by high-volume vaginal surgeons were younger, more often white, were less likely to have Medicare, were more often married, more frequently resided in the western United States, and had fewer medical comorbidities (P<.001 for all). Patients treated by high-volume vaginal surgeons more frequently resided in rural areas and were more likely to be operated on by smaller, nonteaching hospitals (P<.001 for all). High-volume vaginal surgeons were more likely to perform concomitant oophorectomies and antiincontinence procedures at the time of hysterectomy but less likely to perform anterior or posterior colporrhaphy (P<.001 for all). Similar trends were noted when the analysis was stratified by gynecologic surgical volume.
Table 2 displays the unadjusted and adjusted estimates of morbidity and mortality. Operative injuries occurred in 2.5% of patients treated by low-volume vaginal surgeons compared with 1.7% of those operated on by high-volume vaginal surgeons (P<.001). After adjustment for the effects of other demographic variables and concomitant procedures, patients operated on by high-volume vaginal surgeons were 31% (odds ratio [OR] 0.69; 95% confidence interval [CI] 0.59–0.80) less likely to experience an operative injury. Similarly, perioperative complications were reduced by 19% (OR 0.81; 95% CI 0.72–0.92), medical complications decreased by 24% (OR 0.76; 95% CI 0.67–0.86), intensive care unit admission reduced by 46% (OR 0.56; 95% CI 0.43–0.73), and the transfusion rate decreased by 28% (OR 0.72; 95% CI 0.61–0.85) in patients treated by high-volume vaginal surgeons.
The mean length of stay was 1.94 days in patients treated by low-volume surgeons compared with 1.67 days for women of high-volume surgeons (P<.001). The rate of readmission was increased by 24% (OR 1.24; 95% CI 1.04–1.47) among high-volume vaginal surgeons. No differences in perioperative mortality were identified (P=.56). Similar trends were noted for the analysis of morbidity and mortality when volume was stratified by total gynecologic surgery volume.
Table 3 displays mean operative times based on volume. Operative times were highest for low-volume surgeons and decreased incrementally with volume (P<.001). In a multivariable linear regression model, operative times were 6.95 minutes (parameter estimate, −6.95; 95% CI −8.36 to −5.55) lower for high- compared with low-volume vaginal surgeons and 4.18 minutes (parameter estimate, −4.18; 95% CI −5.58 to −2.77) lower for high- compared with low-volume gynecologic surgeons.
The mean cost for vaginal hysterectomy performed by a low-volume vaginal surgeon was $5,246.79 compared with $4,550.14 when performed by a high-volume vaginal surgeon (P<.001) (Table 3). Similarly, cost for vaginal hysterectomy was $5,087.99 for low-volume gynecologic surgeons compared with $4,645 for high-volume gynecologic surgeons (P<.001). In a multivariable linear regression model accounting for other clinical characteristics and concomitant procedures, the cost of vaginal hysterectomy was reduced by $609 (parameter estimate, −609.5; 95% CI −664.86 to −554.21) when performed by a high-volume vaginal surgeon. In contrast, there was no association between gynecologic procedure volume and cost of vaginal hysterectomy.
Our findings suggest that morbidity and resource use are lower in patients undergoing vaginal hysterectomy when the procedure is performed by a high-volume surgeon. The reduction in resource use appears to be specific to vaginal surgical volume. That is, although high vaginal surgical volume was associated with lower resource use, overall gynecologic surgical volume had no apparent effect on resource use.
A large body of evidence supports the association between surgical volume and perioperative outcomes for a variety of surgical procedures.7–13 In a study of over 470,000 patients undergoing high-risk cardiovascular or oncologic surgery, Birkmeyer et al9 noted that the OR for operative death was higher for low-volume surgeons for all of the procedures studied and ranged from 1.24 for lung resection to 3.61 for pancreatectomy. The literature correlating volume and outcome for gynecologic surgery is limited.14–16,23–30 In a study of women undergoing abdominal hysterectomy for leiomyoma, morbidity was reduced when the procedure was performed at a high-volume center.14 Among women undergoing pubovaginal sling procedures for incontinence, Anger et al16 noted no difference in the rates of complications or repeat antiincontinence procedures. Our findings suggest that volume is an important determinant of outcome in women who undergo vaginal hysterectomy. Operative complications, perioperative surgical complications, medical complications, transfusion, and intensive care unit use were all lower when the procedure was performed by a high-volume surgeon.
Despite the significance of our results, our findings of reduced morbidity for vaginal hysterectomy were clinically modest. To place our data into context, a meta-analysis examining the effect of volume on mortality suggested that only 10 patients undergoing esophagectomy for esophageal cancer would need to be moved from a low-volume to high-volume facility to prevent one volume-associated perioperative death.11 Because perioperative mortality is rare among women undergoing vaginal hysterectomy, we noted no volume-based differences in mortality in our cohort.4,5
Perhaps the most important finding from our work is that resource use was lower when vaginal hysterectomy was performed by high-volume vaginal surgeons. The etiology of the cost savings achieved by high-volume vaginal surgeons is likely multifactorial. We demonstrated decreased operative times and shorter lengths of stay when the procedure was performed by high-volume surgeons. Our data were notable in that high vaginal surgery volume was associated with decreased cost but overall gynecologic surgery volume had no apparent effect on cost. These findings suggest that specific proficiency in vaginal surgery is required to reduce resource use. The effect of volume on resource use is particularly important given the rising rate of healthcare expenditures as well as efforts underway to control costs.31
Although volume clearly influences outcomes for patients undergoing vaginal hysterectomy, what underlies this effect is more difficult to explain. Although the “practice makes perfect” analogy for surgery is intuitively logical, volume is a surrogate for the complex process of care a patient receives.11,32 In addition to technical proficiency and intraoperative decision-making, surgeon volume likely affects preoperative evaluation, operative planning, and postoperative management.32–35 Any or all of these factors may have contributed to our findings.
We recognize several limitations of our study. Using administrative data, it is impossible to perform complete risk adjustment and account for all confounding factors.36 Although we developed rigorous models to account for surgeon-level clustering and adjusted for comorbidities, undoubtedly unmeasured factors also affected the analysis. We adjusted for surgical indication, but it is impossible to gauge the “difficulty” of the procedures performed. Like with any study of claims data, the primary purpose of the data is for billing. It is difficult to distinguish preexisting conditions from medical complications. Our analysis of cost was meant to provide an estimate of acute hospital charges. We did not comprehensively examine costs for preoperative evaluation, postoperative care, readmission, or charges for rehabilitation or skilled nursing. Finally, we focused our analysis on the influence of surgeon and not hospital volume on outcomes. A priori we hypothesized that because vaginal hysterectomy is a commonly performed procedure typically associated with a short postoperative hospital course, surgeon characteristics would play a more influential role in determining outcome than hospital factors. In addition, prior work has confirmed that observed associations between hospital volume and operative mortality are largely mediated by surgeon volume.9
The disparate outcomes we identified are likely to become more pronounced. As the overall hysterectomy rate declines and the use of laparoscopic and robotic techniques for hysterectomy increases, resident training in vaginal surgery will likely decline.1,2 Strategies proposed to overcome volume-based disparities in care usually focus on either regionalization of care or improvement in quality for patients treated by low-volume providers. Given that regionalization of care for a common procedure like vaginal hysterectomy is not feasible, efforts to improve the outcomes of patients treated by low-volume surgeons are clearly needed. To enhance surgical competency, more gynecology residents are now undertaking advanced training in pelvic surgery and urogynecology. Some have argued that surgeons must perform a certain number of procedures to maintain those privileges. Finally, public reporting of outcomes and pay-for-performance programs have now been examined for a number of procedures to enhance quality.37,38
In conclusion, surgical volume is an important influence on outcomes for women undergoing vaginal hysterectomy. Perioperative morbidity is reduced in women operated on by high-volume surgeons. Furthermore, resource use is lower in patients treated by surgeons who perform a high number of vaginal surgical procedures. Further work is needed to determine the factors that influence these volume-based disparities and to design strategies to optimize the outcomes of women undergoing vaginal surgery by low-volume providers.
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