Abstract
Objective:
Limited data exist comparing the transabdominal and retroperitoneal approaches to open abdominal aortic aneurysm (AAA) repair, especially late mortality and laparotomy-related reinterventions and readmissions. Therefore, we compared long-term rates of mortality, reintervention, and readmission after open AAA repair via a transabdominal compared to a retroperitoneal approach.
Methods:
We identified all patients in the Vascular Quality Initiative (VQI) undergoing open AAA repair from 2003–2015. Patients with rupture or supraceliac clamp were excluded. We used the VQI linkage to Medicare to ascertain rates of long-term outcomes, including rates of AAA-related and laparotomy-related (i.e. hernia, bowel obstruction) reinterventions and readmissions. We used multivariable Cox regression to account for differences in comorbidities, aneurysm details, and operative characteristics.
Results:
We identified 1,282 patients in the VQI with linkage to Medicare data, 914 (71%) who underwent a transperitoneal approach and 368 (29%) who underwent a retroperitoneal approach. Patients who underwent a retroperitoneal approach were slightly more likely to have preoperative renal insufficiency but were otherwise similar in terms of demographics and comorbidities. They more often had a clamp above at least one renal artery (61% vs. 36%, P < .001) and underwent concomitant renal revascularization (9.5% vs. 4.3%, P < .001). Patients who underwent a transabdominal approach more often presented with symptoms (14% vs. 9.0%, P < .01) and had a femoral distal anastomosis (15% vs. 7.1%, P < .001). There was no difference in 5-year survival (62% vs. 61%, Log-Rank P = .51). However, patients who underwent a transabdominal approach experienced higher rates of repair-related reinterventions and readmissions (5-year: 42% vs. 34%, Log-Rank P < .01), even after adjusting for demographic and operative differences (HR 1.5, 95% CI: 1.1 – 1.9, P < .01).
Conclusions:
A transabdominal exposure for AAA repair is associated with higher rates of late reintervention and readmission than the retroperitoneal approach, which should be considered when possible in operative decision-making.
Table of Contents Summary:
This Vascular Quality Initiative (VQI) study of 1,282 patients retroperitoneal abdominal aortic aneurysm (AAA) repair was associated with lower rates of reintervention and readmission compared to the transabdominal approach.
Introduction
In the current endovascular era, fewer than one in five patients with abdominal aortic aneurysms (AAA) undergo repair via an open surgical approach.1–3 Despite improvements in management, open surgical repair of AAA remains associated with higher rates of perioperative mortality and morbidity compared to endovascular aortic aneurysm repair. Therefore, determining the best approach may help reduce the complications of repair.
We and others previously compared the transabdominal to the retroperitoneal approach to open AAA repair.4–7 Many surgeons prefer the transabdominal approach, given its familiarity and ease of access to the aorta as well as intraabdominal organs.8–10 While we demonstrated higher rates of hernia and intraperitoneal adhesions from non-aortic transperitoneal procedures as compared to retroperitoneal procedures, data regarding incisional approach for aortic surgery have been more mixed.11 Several small, single-center series showed higher rates of postoperative ileus and prolonged length of stay following the transabdominal approach,4, 12, 13 whereas others showed no difference in early outcomes.6, 14 We previously used two large, national databases to compare incisional approaches, and found mixed results regarding early outcomes, but neither database could assess laparotomy-related complications or late outcomes.5, 7 Our prior studies of Medicare beneficiaries demonstrated higher rates of late laparotomy-related complications including reintervention for bowel obstruction and hernia in patients undergoing open AAA repair compared to EVAR, but this study could not evaluate surgical approach.15 Therefore, we aimed to use Medicare-linked late outcomes data in conjunction with the Vascular Quality Initiative to compare late mortality, reinterventions, and reinterventions, including aneurysmrelated reintervention, laparotomy-related reintervention, and nonoperative readmission for laparotomy-related complications, following a transabdominal versus a retroperitoneal approach to open AAA repair.
Methods
The Beth Israel Deaconess Medical Center Institutional Review Board approved this study and waived informed consent due to the use of de-identified data in the Vascular Quality Initiative.
Study Population and Medicare Linkage
We performed a retrospective cohort study using the Society for Vascular Surgery Vascular Quality Initiative (SVS-VQI), a national clinical registry established as a collaboration between regional quality groups to improve patient care through the prospective collection of clinical data. The SVS-VQI is an Agency for Healthcare Research and Quality (AHRQ) Patient Safety Association with restrictions and protections on the use of patient, procedure, and outcome information for research and quality improvement purposes. More information about the VQI can be found at www.vascularqualityinitiative.org.
While the VQI-SVS provides excellent clinical and anatomic granularity, including operative variables and early outcomes, long-term data are limited, and had previously not been collected beyond one-year follow-up. Therefore, we indirectly linked patient information between the VQI and Medicare claims data using patient International Classification of Disease, version 9, (ICD-9) code, date of surgery, date of birth, gender, first three digits of billing zip code, and surgeon National Provider Identifier number, as previously described.16 We identified all patients undergoing open repair of an abdominal aortic aneurysm with successful Medicare linkage between 2003 and 2015 who also had exposure recorded in the VQI. We excluded patients presenting with rupture (n = 301) and those who had a supraceliac clamp (n = 118), as these patients would be expected to have more bowel-related complications that may not be related to the surgical exposure.
Variables
Demographics, comorbid conditions, operative details, and in-hospital postoperative outcomes were identified for all patients. We used a single preoperative creatinine value to estimate the glomerular filtration rate (GFR) for each patient using the Modification of Diet in Renal Disease Study equation, which accounts for patient sex and race.17 We defined renal insufficiency as an estimated GFR < 30 mL/min/1.73m2 or current dialysis, and preoperative anemia as hemoglobin < 10 g/dL. Prior aneurysm repair included open or endovascular repair of any aortic aneurysm, and prior AAA repair was noted separately. The VQI defined aortic diameter as the maximum total aortic diameter within the diseased segment being treated. Symptomatic patients were those presenting with symptoms but without rupture, as defined by the VQI. Concomitant procedures included thrombectomy, renal bypass, infrainguinal bypass, or other intraabdominal procedures.
Outcomes
We captured early- and long-term mortality using linkage between the VQI and the Social Security Death Index. We defined early postoperative mortality as any 30-day or inhospital mortality. The VQI records all other postoperative outcomes as in-hospital events, including renal complications (defined by the VQI as a creatinine elevation of at least 0.5 mg/dL or new dialysis), wound complications (including any superficial skin infection or separation), intestinal ischemia, and reoperation. Additionally, we collected hospital lengths of stay for each patient. Time-to-event variables added to the VQI dataset from Medicare for successfully linked patients included: survival, aneurysm rupture, and readmission and reintervention. Readmission and reintervention included aneurysm-related reintervention, laparotomy-related reintervention, and nonoperative readmission for laparotomy-related complications, such as bowel obstructions and hernias. We listed the ICD-9 procedure and diagnosis codes used to categorize aneurysm- and laparotomy-related complications in Supplemental Table I.
Statistical Analysis
We present categorical variables as percentages. All continuous variables were nonnormally distributed and thus presented as median (interquartile range [IQR]). We assessed differences between cohorts using the Fisher’s exact test for categorical variables and the Wilcoxon Rank Sum test for continuous variables, where appropriate. Kaplan-Meier survival estimates and Cox hazards regression modeling compared late outcomes including reintervention, readmission, and survival. Purposeful selection was used to identify covariates for inclusion in the models, which allows for inclusion of select covariates identified on univariate analysis with P < .1 as well as clinically relevant factors shown to be predictive of adverse events in previous studies.18 All variables used in the multivariable models had < 5% missing data. Due to limitations in the Data Use Agreement with the Centers for Medicare and Medicaid Services, no data counts < 11 or percentages < 3% could be identified to protect patients’ identity; therefore, numbers at risk for Kaplan-Meier survival estimates are limited to numbers at risk at 1-year and 5-year. Standard error was < 0.1 at each year for each group and each graph. We used two-sided statistical tests, and a P-value of less than 0.05 was considered significant. Statistical analysis was conducted using STATA version 15 (StataCorp LP, College Station, TX).
Results
Baseline and Operative Characteristics
We identified 1,282 patients who underwent open AAA repair with successful linkage to Medicare data, of which 914 (71%) had a transabdominal approach and 368 (29%) a retroperitoneal approach (Table I). Those who had a retroperitoneal approach had higher rates of renal insufficiency (44% vs. 38%), but other demographics and comorbidities were similar.
Table I.
Baseline characteristics of patients undergoing transabdominal versus retroperitoneal open AAA repair.
| % or Median (IQR) | Transabdominal N = 914 (71%) |
Retroperitoneal N = 368 (29%) |
P-Value |
|---|---|---|---|
| Age | 73 (70 – 78) | 74 (70 – 79) | .11 |
| Female Sex | 31% | 36% | .15 |
| White Race | 95% | 95% | .78 |
| BMI | 26.0 (23.5 – 29.4) | 26.1 (23.2 – 29.3) | .86 |
| Comorbidities | |||
| Coronary Artery Disease | 26% | 30% | .13 |
| Prior CABG/PCI | 31% | 40% | .09 |
| Hypertension | 84% | 86% | .40 |
| COPD | 35% | 36% | .61 |
| Smoker | 89% | 90% | .92 |
| Renal Insufficiency | 38% | 44% | .04 |
| Anemia | 5.7% | 5.7% | 1.0 |
| Diabetes | 17% | 17% | .94 |
IQR = Interquartile Range; BMI = Body Mass Index; CABG = Coronary Artery Bypass Graft; PCI = Percutaneous Coronary Intervention; COPD = Chronic Obstructive Pulmonary Disease
While aneurysm diameter was similar between approaches, those with a transabdominal approach more often presented with symptoms (14% vs. 9.0%, P < .01) (Table II). Patients who had a transabdominal approach also more often had anastomoses to the femoral artery (15% vs. 7.1%, P < .001), likely due to higher rates of concomitant iliac artery aneurysms (28% vs. 17%, P < .001). Conversely, patients with a retroperitoneal approach more often had complex proximal aortic disease, with higher rates of suprarenal clamp (61% vs. 36%, P < .001) and concomitant renal procedures (9.5% vs. 4.3%, P < .001), and longer operative time (234 vs. 217 minutes, P = .03).
Table II.
Anatomic and operative characteristics of patients undergoing transabdominal versus retroperitoneal open AAA repair.
| % or Median (IQR) | Transabdominal N = 914 (71%) |
Retroperitoneal N = 368 (29%) |
P-Value |
|---|---|---|---|
| Symptomatic | 14% | 9.0% | < .01 |
| Aneurysm Diameter, cm | 5.7 (5.3–6.5) | 5.7 (5.2–6.5) | .51 |
| Proximal Clamp – Suprarenal | 36% | 61% | < .001 |
| Distal Anastomosis – Femoral | 15% | 7.1% | < .001 |
| Concomitant Iliac Aneurysm | 28% | 17% | < .001 |
| Concomitant Renal Procedure | 4.3% | 9.5% | < .001 |
| Renal/Visceral Ischemia, minutes | 0 (0–24) | 20 (0–34) | < .001 |
| Operative Time, minutes | 217 (171–287) | 234 (186–300) | .03 |
IQR = Interquartile Range
Outcomes
Early 30-day and in-hospital mortality was equivalent regardless of approach, with mortality of 4.7% with the transabdominal and 3.8% with the retroperitoneal approach (P = .29) (Table III). Other postoperative complications, including bowel ischemia, renal complications, wound complications, and reoperation also occurred at similar rates after the transabdominal and retroperitoneal approach. Five-year survival was 62% with the transabdominal and 61% with the retroperitoneal approach (Log-Rank P = .51). However, repair-related reintervention and readmission was higher in patients undergoing a transabdominal approach (5-year: 42% vs. 34%, Log-Rank P < .01) (Figure 1), driven primarily by higher rates of abdominal wall reoperations (13% vs. 6.1%, P < .01) (Figure 2). Even after adjusting for sex, age, symptom status, and anatomic differences, the transabdominal approach was associated with a 50% higher rate of late reintervention and readmission (Hazard Ratio 1.5, 95% Confidence Interval 1.1 – 1.9, P < .01).
Table III.
Early and late outcomes following open AAA repair.
| % or Median (IQR) | Transabdominal N = 914 (71%) |
Retroperitoneal N = 368 (29%) |
P-Value |
|---|---|---|---|
| Postoperative Outcomes a | |||
| Mortality | 4.7% | 3.8% | .29 |
| Bowel Ischemia | 2.5% | < 3.0% | .84 |
| Renal Complications | 17% | 17% | 1.0 |
| Wound Complications | 2.9% | < 3.0% | .85 |
| Lower Extremity Ischemia | 1.5% | < 3.0% | .63 |
| Reoperation | 7.7% | 7.6% | .54 |
| Length of Stay, days | 7 (6–9) | 7 (6–10) | .59 |
| 5-Year Late Outcomes | |||
| Survival | 62% | 61% | .51 |
| Reintervention/Readmission | 42% | 34% | < .01 |
| Abdominal Wall Repair | 13% | 6.1% | < .01 |
IQR = Interquartile Range
All postoperative outcomes are in-hospital outcomes, with the exception of mortality, which is mortality within 30-days or if before leaving the hospital.
Figure 1.
Patients undergoing open AAA repair via a transabdominal approach have higher rates of reintervention and readmission for AAA-related and laparotomy-related complications (bowel obstructions, hernias) than patients who undergo retroperitoneal repair.
Figure 2.
Patients undergoing open AAA repair via a transabdominal approach have higher rates of abdominal wall reoperations (i.e. hernia repairs) compared to those undergoing a retroperitoneal approach.
Discussion
We used detailed clinical and anatomic data from the Vascular Quality Initiative linked to administrative data from Medicare to identify late reinterventions and readmissions following open abdominal aortic aneurysm repair amongst a subset of Medicare beneficiaries. We found that, despite having more complex proximal aortic anatomy with longer operations and more concomitant renal interventions, those patients who underwent a retroperitoneal approach to AAA repair, as opposed to a transabdominal approach, experienced fewer reinterventions and readmissions in follow-up, driven primarily by lower rates of abdominal wall reinterventions.
The chosen approach to open AAA repair depends on several patient- and surgeonrelated factors. While the retroperitoneal approach allows for more extensive access to the visceral aorta and may be preferred in patients with a hostile abdomen, the transabdominal approach allows access to the intraabdominal organs and may be more familiar for some surgeons. We see that these patient factors do affect decision-making in this series, with more suprarenal clamps and renal revascularizations among those with the retroperitoneal exposure, and more distal femoral artery anastomoses in those with the transabdominal exposure. While we could not adjust for a history of prior abdominal operations, other anatomic factors, including extent of disease and symptom status, were controlled for in the multivariable analysis to reduce the effect of surgeon selection bias. Despite this, there remains an association between transabdominal access and late reinterventions and readmissions.
Several small series previously compared the transabdominal to the retroperitoneal approach to open AAA repair, but these looked almost exclusively at perioperative outcomes. In a few of these studies, the retroperitoneal approach was associated with shorter postoperative ileus and more rapid diet advancement,4, 9, 12, 13 but others found no differences between approaches.6 Furthermore, the majority of data comes from before the advent of the endovascular era, and contemporary surgeons may be less experienced with both open approaches as fewer open repairs are done each year.19
We previously evaluated the impact of surgical approach in more recent years using two large, national databases: the targeted vascular module of the National Surgical Quality Improvement Program (NSQIP) and the Vascular Quality Initiative.5, 7 Within the NSQIP, we identified higher rates of wound dehiscence with the transabdominal approach, but higher rates of postoperative reintubation in patients with a retroperitoneal approach.5 In our prior study using VQI data without linkage to Medicare, we could only evaluate early in-hospital outcomes and late survival.
Few prior studies have been able to compare late reinterventions and readmissions by surgical approach. These late complications are important to understand, as the consequences of late complications (reoperation, readmissions) are often greater than the early complications (slow return of bowel function, a few extra hospital days). We previously showed higher rates of laparotomy-related complications after open AAA repair compared to EVAR, which is not unexpected given the lack of entry into the abdominal cavity with EVAR.15, 20 We also showed that the transabdominal approach to non-aortic surgery results in higher rates of laparotomyrelated complications compared to retroperitoneal procedures. Therefore, it follows that the transabdominal approach to open AAA repair would lead to more intraabdominal adhesions and abdominal wall hernias than the retroperitoneal approach. However, many competing factors impact the decision to pursue a transabdominal versus a retroperitoneal approach, only one of which is the higher rates of late reinterventions and readmissions that we identified in this series. Given changes in open training across vascular surgery, some surgeons may have especially limited exposure to the retroperitoneal approach to AAA repair, as compared to the transabdominal approach.2 Ultimately, surgeons will likely achieve better outcomes using the approach they are most comfortable with, which may mean performing a transabdominal repair.
These data must be interpreted in the context of the study design. Clinical registries often have incomplete data and limited variable definitions and, in particular, the VQI contains only limited long-term follow-up information. We hoped to address this issue using the linkage to Medicare administrative data; however, this too is subject to errors in coding and incomplete capture of relevant events. Furthermore, we only have long-term data on certain coded outcomes from Medicare at this time, without access to Medicare data for linked patients in its entirety. Given limitations from the Data Use Agreement with Medicare, events occurring in < 3% of any one group could not be identified as such, as specific complications occurring in a number of patients cannot be documented. Several potentially confounding variables cannot be accounted for due to limitations in the dataset, including history of prior abdominal operations, complexity of anatomy including renal anatomy, or type of closure (interrupted versus continuous). Additionally, surgeon volume cannot be recorded as we only have access for this study to the subset of Medicare patients with VQI-linkage. Of note, we suspect that a significant history of prior abdominal operations would encourage most surgeons to consider a retroperitoneal approach, therefore biasing our results towards the null. However, despite this, we still found that those with a transabdominal operation had higher rates of late reinterventions and readmissions.
Conclusions
The transabdominal approach to AAA repair is associated with higher rates of late reintervention and readmission than the retroperitoneal approach, driven primarily by higher rates of abdominal wall reinterventions. While many factors likely contribute to the decision to use a transabdominal versus a retroperitoneal approach to open AAA repair, surgeons and patients should be aware of the higher risk of late reinterventions and readmissions when making decisions.
Supplementary Material
Table IV.
Multivariable model evaluating preoperative factors associated with late reintervention or readmission.
| Hazard Ratio | 95% Confidence Interval | P-Value | |
|---|---|---|---|
| Transabdominal | 1.4 | 1.1 – 1.7 | < .01 |
| Female Sex | 0.96 | 0.8 – 1.2 | .76 |
| Age, by decade | 1.1 | 0.9 – 1.3 | .25 |
| Symptomatic | 1.2 | 0.9 – 1.6 | .28 |
| Concomitant Renal Procedure | 1.1 | 0.7 – 1.8 | .57 |
Also adjusts for coronary artery disease, body mass index, suprarenal proximal clamp, and femoral distal extent.
Article Highlights.
Type of research:
Multicenter retrospective review of prospectively collected Vascular Quality Initiative (VQI) data.
Key Finding:
In 1,282 patients undergoing open abdominal aortic aneurysm (AAA) repair, the 5-year rate of repair-related reinterventions and readmissions was higher following the transabdominal compared to the retroperitoneal approach (42% vs. 34%, Log-Rank P < .01), even on multivariable analysis (HR 1.5, P < .01).
Take Home Message:
Repair-related reinterventions and readmissions are lower following retroperitoneal compared to transabdominal open AAA repair.
Acknowledgments
SD, SZ, and TO were supported by the Harvard-Longwood Research Training in Vascular Surgery NIH T32 Grant 5T32HL007734-22.
Footnotes
Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Presented at the 44th Annual Meeting of the New England Society for Vascular Surgery, Boston, MA, Sept. 8–10, 2017.
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