Abstract
Background
Chronic kidney disease (CKD) has been identified as an independent predictor of poorer long-term prognosis after endovascular aneurysm repair (EVAR) for complex abdominal aortic aneurysm (AAA). However, its impact on short-term perioperative outcomes is conflicting, which can be important for preoperative risk stratification. This study aimed to evaluate the 30-day outcomes of patients with CKD following non-ruptured complex EVAR in a national registry.
Methods
Patients who had EVAR for complex AAA were identified in ACS-NSQIP targeted database from 2012-2022. Complex AAA included juxtarenal, suprarenal, or pararenal proximal extent, Type IV thoracoabdominal aneurysm, and/or aneurysms treated with Zenith Fenestrated endograft. Exclusion criteria included age<18 years, ruptured AAA, acute intraoperative conversion to open, emergency presentation, and dialysis. Multivariable logistic regression was used to compare 30-day postoperative outcomes of CKD and non-CKD patients, where demographics, baseline characteristics, aneurysm diameter, distant aneurysm extent, anesthesia, and concomitant procedures were adjusted.
Results
There were 695 (39.33%) and 1072 (60.67%) patients with and without CKD, respectively, who underwent EVAR for complex AAA. Patients with and without CKD have comparable 30-day mortality (aOR = 1.165, 95 CI = 0.646-2.099, P = 0.61). However, CKD patients had a higher risk of renal complications (aOR = 2.647, 95 CI = 1.399-5.009, P < 0.01) including higher progressive renal insufficiency (aOR = 3.707, 95 CI = 1.329-10.338, P = 0.01) and acute renal failure requiring renal replacement therapy (aOR = 2.533, 95 CI = 1.139-5.633, P = 0.02). All other 30-day outcomes were comparable between CKD and non-CKD patients.
Conclusion
Patients with CKD had similar 30-day mortality and morbidity rates but a higher risk of postoperative renal complications. Therefore, meticulous preoperative planning and postoperative management, which may include optimal hydration, appropriate contrast use, and close renal function monitoring, are essential for patients with CKD after complex EVAR.
Introduction
Abdominal aortic aneurysm (AAA) is a prevalent condition that impacts roughly 3% of the U.S. population.1,2 Endovascular aneurysm repair (EVAR) has emerged as the predominant treatment modality for AAA since it was introduced in 1996.3–6 Compared to traditional open surgical repair, EVAR is often preferred for high-risk patients due to its reduced risk of complications after surgery.6,7
For infrarenal AAA, EVAR is the treatment of choice for over 80% of the patients.8–10 However, traditional EVAR is not suitable for complex AAA, which involves the visceral branches in the upper abdominal aorta, because traditional EVAR cannot provide adequate proximal sealing.10,11 Complex AAA represents a significant concern, as they constitute approximately 20% of all AAA cases (Crawford et al, 1986; Ultee et al, 2017). However, recent advancements in EVAR techniques, including fenestrated, branched, and chimney stents, have broadened the scope of EVAR to include patients with complex proximal neck anatomy. 12
Chronic kidney disease (CKD) has been positively linked to the development of AAA. 13 Previous research has confirmed that CKD correlates with worse postoperative outcomes in patients undergoing infrarenal EVAR. 14 In cases of EVAR for complex AAA, CKD has been identified as an independent predictor of poorer long-term prognosis.15,16 However, its impact on short-term perioperative outcomes is conflicting.15,17 This is a crucial consideration for preoperative risk stratification in CKD patients. Consequently, this study aimed to evaluate the 30-day outcomes of patients with CKD following non-ruptured complex EVAR in a national registry.
Methods
Patient Population
The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) targeted EVAR database from 2012-2022 was used in this retrospective cohort study. Patients with complex AAA who underwent EVAR were identified, where complex AAA included juxtarenal, suprarenal, pararenal proximal extent, Type IV thoracoabdominal aneurysm, or aneurysms treated with the Zenith Fenestrated endograft (Cook Medical, Bloomington, Ind). 10 Patients with age less than 18 years, ruptured AAA, acute intraoperative conversion to open, and emergency presentation were excluded. CKD was defined as an estimated glomerular filtration rate (eGFR) less than 60 mL/min/1.73 m2. Patients under dialysis were excluded. Patients with and without CKD were stratified into the two study cohorts.
Preoperative Factors
Demographics of Patients With and Without CKD Who Underwent EVAR for Complex AAA.
Abbreviations: AAA, abdominal aortic aneurysm; CKD, chronic kidney disease; EVAR, endovascular aneurysm repair.
Comparing the Baseline Characteristics of Patients With and Without CKD Who Underwent EVAR for Complex AAA.
Abbreviations: AAA, abdominal aortic aneurysm; AKI, acute kidney injury; ASA, American society of anesthesiology; BMI, body mass index; BUN, blood urea nitrogen; CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; CKD, chronic kidney disease; DM, diabetes mellitus; eGFR, estimated glomerular filtration rate; EVAR, endovascular aneurysm repair; INR, international normalized ratio; NA, not applicable; PT, prothrombin time, PTT, partial thromboplastin time; WBC, white blood cells.
Aneurysm Diameter, Indication for Surgery, Proximal and Distant Aneurysm Extent, Anesthesia, and Concomitant Procedures in Patients With and Without CKD Who Underwent EVAR for Complex AAA.
Abbreviations: AAA, abdominal aortic aneurysm; CKD, chronic kidney disease; EVAR, endovascular aneurysm repair; MAC, monitored anesthesia care; SMA, superior mesenteric artery.
Postoperative Outcomes
Thirty-Day Perioperative Outcomes of Patients With and Without CKD Who Underwent EVAR for Complex AAA.
Abbreviations: AAA, abdominal aortic aneurysm; aOR, adjusted odds ratio; CKD, chronic kidney diseases; CI, confidence interval; EVAR, endovascular aneurysm repair; LOS, length of stay; NA, not applicable; SD, standard deviation; VTE, venous thromboembolism.
The major morbidities were defined as composite outcomes. Cardiac complications included myocardial infarction (MI) and cardiac arrest that require cardio-pulmonary resuscitation. Pulmonary complications included pneumonia, unplanned reintubation, and prolonged mechanical ventilation > over 48 hours. Renal complications were defined as progressive renal insufficiency (serum creatinine rise by > 2 mg/dL compared to the preoperative value) and acute renal failure requiring renal replacement therapy. Wound complications included wound dehiscence, superficial and deep surgical site infections, as well as organ space infections.
Statistical Analysis
Fisher’s exact test was used to compare the preoperative factors between patients with and without CKD. Binary postoperative outcomes were compared by multivariable logistic regression adjusting for all preoperative factors that had adequate differences (P < 0.1 as in the Fisher’s exact tests). Adjusted odds ratios (aORs) and 95% confidence intervals (CI) were reported. Continuous variables were compared using generalized linear models (GLM) while adjusting for all preoperative factors.
All statistical analyses were performed using SAS (version 9.4). A P-value <0.05 was considered statistically significant. The ACS-NSQIP data was accessed from The George Washington University and all statistical analyses were performed within the institute. The authors had full access to the ACS-NSQIP dataset and took full responsibility for the accuracy of the analyses performed. Since this study is retrospective and used the de-identified ACS-NSQIP dataset, it was exempted from the Institutional Review Board (IRB) review at The George Washington University.
Results
There were 695 (39.33%) and 1072 (60.67%) patients with and without CKD, respectively, who underwent EVAR for complex AAA. Among the CKD patients, 67 (9.64%) had severe/end-stage CKD (eGFR <30 mL/min/1.73 m2) while 628 (90.36%) had moderate CKD.
Table 1 shows the demographics of patients with and without CKD who underwent EVAR for complex AAA. Compared to non-CKD patients, those with CKD were more likely to be female (27.91% vs 19.87%, P < 0.01), have age over 75 years (75-85 years, 45.04% vs 36.19%, P < 0.01; over 85 years, 20.00% vs 8.40%, P < 0.01). In contrast, CKD patients were less likely to have age less than 75 years (65-75 years, 29.35% vs 38.71%, P < 0.01; 55-65 years, 5.04% vs 14.83%, P < 0.01; less than 55 years, 0.58% vs 1.87%, P = 0.02).
Table 2 summarizes the baseline characteristics of patients with and without CKD who underwent EVAR for complex AAA. Patients with CKD were more likely to have partially dependent functional status (3.88% vs 1.96%, P = 0.02), congestive heart failure (CHF; 5.32% vs 2.71%, P = 0.01), hypertension (86.91% vs 79.01%, P < 0.01), acute kidney injury (AKI; 1.44% vs 0.00%, P < 0.01), bleeding disorders (16.55% vs 11.75%, P < 0.01), anemia (hematocrit <37%; 34.53% vs 16.98%, P < 0.01), thrombocytopenia (platelet<150 000 counts/mL; 18.42% vs 12.97%, P < 0.01), azotemia (blood urea nitrogen >23 mg/dL; 52.23% vs 9.33%, P < 0.01), American Society of Anesthesiology (ASA) score of 4 or 5 (42.73% vs 32.37%, P < 0.01), and prior abdominal surgery (31.51% vs 25.65%, P = 0.01). In contrast, CKD patients were less likely to be smokers (27.63% vs 37.78%, P < 0.01).
Table 3 shows the aneurysm diameter, indication for surgery, proximal and distant aneurysm extent, anesthesia, and concomitant procedures in patients with and without CKD who underwent EVAR for complex AAA. Patients with CKD were more likely to have aneurysm less than 4 cm (3.02% vs 5.13%, P = 0.04).
Table 4 summarizes the 30-day perioperative outcomes of patients with and without CKD who underwent EVAR for complex AAA. Patients with and without CKD have comparable 30-day mortality (3.60% vs 2.43%, aOR 1.165, 95 CI 0.646-2.099, P = 0.61). However, CKD patients had a higher risk of renal complications (4.75% vs 1.87%, aOR 2.647, 95 CI 1.399-5.009, P < 0.01) including higher progressive renal insufficiency (2.30% vs 0.75%, aOR 3.707, 95 CI 1.329-10.338, P = 0.01) and acute renal failure requiring renal replacement therapy (2.59% vs 1.12%, aOR 2.533, 95 CI 1.139-5.633, P = 0.02). Other organ system complications, including cardiac complications (3.31% vs 2.24%, aOR 1.196, 95 CI 0.646-2.213, P = 0.57), stroke (1.15% vs 0.37%, aOR 3.219, 95 CI 0.947-10.941, P = 0.06), and pulmonary complications (4.17% vs 3.08%, aOR 1.038, 95 CI 0.593-1.817, P = 0.9), were comparable between CKD and non-CKD patients. In addition, other 30-day outcomes, including sepsis, VTE, bleeding requiring transfusion, wound complications, lower extremity ischemia, ischemic colitis, postoperative ruptured aneurysm, unplanned reoperation, and 30-day readmission did not differ between patients with and without CKD. Moreover, operation time and LOS were comparable between CKD and non-CKD patients.
Discussion
This study examined the 30-day outcomes of patients with and without CKD who underwent EVAR for complex AAA. Patients with CKD were found to have a 2.65 times higher risk of postoperative renal complications. However, all other 30-day outcomes, including postoperative mortality and morbidity, were comparable between CKD and non-CKD patients.
CKD is strongly implicated in the development of AAA due to various mechanisms. 13 Patients with CKD share well-known risk factors for AAA formation, exhibit increased atherosclerosis and calcium deposits that can contribute to aneurysmal degeneration,18,19 and have elevated blood potassium and urea levels, which can increase the risk of AAA rupture. 20
Previous studies have indicated that CKD is linked to worse long-term mortality in AAA patients following repair.15,16 However, there is inconsistency in findings regarding the impact of CKD on short-term postoperative outcomes after EVAR. In a single institutional study, Dossabhoy et al 15 reported that preoperative CKD status did not influence the 30-day outcomes after EVAR for complex AAA. Conversely, a multi-centered study by Li et al 17 identified preoperative CKD as an independent predictor of 30-day mortality and morbidity following complex EVAR. Therefore, this study aimed to provide further insights into this topic utilizing the ACS-NSQIP targeted database. ACS-NSQIP is nationally recognized and validated as a database for the quality control of surgical outcomes. Its substantial sample size and the granularity provided by targeted databases make ACS-NSQIP a valuable resource for investigating the outcomes of CKD patients undergoing EVAR for complex AAA. This can assist in preoperative risk stratification for CKD patients undergoing complex EVAR and help the postoperative management of these patients.
This study discovered that patients with CKD had higher risks of 30-day renal complications after EVAR for complex AAA, including progressive renal insufficiency and acute renal failure requiring renal replacement therapy. Patients with preexisting CKD are inherently more vulnerable to renal injury, and the stress of a major surgical procedure like EVAR can exacerbate this susceptibility. These renal complications can arise from the use of contrast agents during EVAR, potentially leading to contrast-induced nephropathy. Furthermore, perioperative hemodynamic fluctuations can worsen renal perfusion and thus function in CKD patients. This increased risk underscores the need for meticulous preoperative planning and postoperative management. Strategies such as optimizing hydration, minimizing the use of contrast, and closely monitoring renal function postoperatively are essential. Interestingly, this study did not find a significant association between preoperative CKD and 30-day mortality or other morbidities after EVAR for complex AAA, which aligned with Dossabhoy et al. 15 ’s findings, although their study had a smaller cohort. However, it is important to note that CKD patients have been documented to have poorer long-term survival, highlighting the importance of ongoing follow-up and care.15,16 In addition, the clinical focus on managing renal complications in CKD patients after EVAR might have improved outcomes. Prompt interventions for renal complications could have mitigated the potential adverse effects on short-term prognosis. Also, the study cohort included patients who underwent elective complex EVAR, which may inherently involve a selection bias favoring those with better overall health profiles despite CKD.
This study must acknowledge several limitations. First, the ACS-NSQIP database only includes a 30-day postoperative follow-up, which limits our ability to evaluate long-term outcomes in patients with CKD following EVAR for complex AAA. This constraint could lead to an underestimation of mortality and morbidity rates after EVAR. Moreover, factors that may influence renal function during complex EVAR, such as fluoroscopic time and renal protection strategies like the amount of contrast media used or hydration protocols, are not recorded in the ACS-NSQIP database. Additionally, it would be ideal to stratify CKD patients based on their staging. However, the limited sample size of 67 patients with severe/end-stage CKD in this study did not provide sufficient statistical power to conduct a subgroup analysis. Additionally, there is potential for selection bias due to the specific hospitals participating in the ACS-NSQIP program, which may affect the generalizability of the findings.
In conclusion, this study investigated the effect of preoperative CKD status on the 30-day outcomes of patients undergoing EVAR for complex AAA. The findings revealed that patients with CKD had similar 30-day mortality and morbidity rates but a higher risk of postoperative renal complications, including progressive renal insufficiency and acute renal failure necessitating renal replacement therapy. Therefore, meticulous preoperative planning and vigilant postoperative management, including optimal hydration, appropriate contrast use, and close renal function monitoring, are essential for patients with CKD after complex EVAR.
Footnotes
Acknowledgments
The authors acknowledge Dr Richard Amdur, PhD, for giving statistical support for this project.
Author Contributions
Conceptualization: R.L.; methodology: R.L.; formal analysis: R.L.; investigation: R.L.; resources: R.L., A.S., B.N.; data curation: R.L.; writing (original draft): R.L.; writing (review & editing): R.L., A.S., B.N.; Supervision, A.S., B.N.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.
