Analysis of anatomical parameters of visceral vessels in fenestrated endovascular aortic repair of the abdominal aorta

Introduction

Endovascular aortic repair (EVAR) is widely used in the treatment of abdominal aortic diseases. Currently, there is no consensus on a standardized treatment strategy for patients with complex abdominal aortic diseases involving the visceral vessels. Fenestration is commonly used in clinical applications for the reconstruction of the visceral vessels, and offers certain advantages in the treatment of such diseases, making it an important focus of both clinical practice and research. However, this novel technology has several limitations. It requires a high level of technical expertise from operators, and further technical improvements, medical device innovation, and additional clinical data are needed before the technique can be used by more centers. This study aimed to investigate the main visceral arteries based on computed tomography angiography (CTA) images. The anatomical parameters derived from this cross-sectional analysis provide a theoretical basis for stent-graft design. We present this article in accordance with the STROBE reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-aw-2304/rc).

Methods

Patients

This retrospective study was conducted using archived images from patients who underwent CTA of the abdominal aorta at Xiamen Cardiovascular Hospital of Xiamen University between July 2019 and December 2024. Approximately 9,399 images were reviewed. The exclusion criteria included abdominal aortic dissection, abdominal aortic aneurysm (AAA), and significant atherosclerotic lesions involving the abdominal aorta and its branches. Images from patients who had undergone surgical or interventional procedures, or who had trauma, tumors, or infections involving the abdominal aorta and its branches were also excluded, as were poor-quality images that did not permit accurate identification of the structures due to motion artifacts or the insufficient distribution of contrast material. Additionally, patients with variant celiacomesenteric trunk anatomy and those younger than 18 years were excluded. Ultimately, a total of 479 patients (181 females, 298 males) who met the inclusion criteria were included in this study.

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of Xiamen Cardiovascular Hospital of Xiamen University (approval No. 2022-YLX-3). The requirement for written informed consent was waived due to the retrospective nature of the study and the use of anonymized data.

Computed tomography (CT) data acquisition and image processing

All examinations were performed using either a third-generation multi-detector dual-source CT system (SOMATOM Drive, Siemens Healthcare, Forchheim, Germany) with high-pitch spiral acquisition, or a 256-slice, CT system with 16 cm coverage (Revolution CT, GE Healthcare, USA). Patients were all placed in a supine position and scanned in the craniocaudal direction with the coverage extending from the abdominal aorta to the iliac artery. A nonionic iodinated contrast agent (approximately 60 mL, 350 mg iodine per milliliter) was injected at a rate of 4.5 mL/s using a power injector, followed by a 40 mL saline flush. A bolus-tracking technique was used to trigger image acquisition once the attenuation in the region of interest in the aorta reached the pre-set threshold. Axial images were reconstructed with a 512×512 pixel matrix and a slice thickness ≤1 mm. The post-processing of CTA images was performed on a dedicated workstation (DetecMicro, version 02, Boea Wisdom, Hangzhou, China) with specialized planning for fenestrated stents.

Analysis of CT data

The data analysis was performed by an experienced radiologist (Q.D. with 11 years of experience) and an experienced radiographer (T.X., with 12 years of experience), using DetecMicro (version 02). The clock positions and heights of the fenestrations were obtained via an automatic detected centerline (i.e., the line that ideally passes through the center of the aortic lumen). CTA image examination was conducted to identify the ostial centers of the visceral vessels (Figure 1A). At the same level, the angle of the origin of each vessel relative to the sagittal aortic axis (clock position), and the mutual distance between the centers of origin of the vessels were measured (Figure 1B).

Figure 1 Image processing workflow for anatomical analysis. (A) 3D volume rendering of the abdominal aorta and visceral arteries, showing automated centerline extraction (yellow line) aligned with the aortic lumen for anatomical reference. (B) Visceral artery clock positions and mutual distances were automatically measured using 3D CTA reconstruction. 3D, three-dimensional; CA, celiac artery; CRA, cranial; CTA, computed tomography angiography; LAO, left anterior oblique; LRA, left renal artery; RRA, right renal artery; SMA, superior mesenteric artery; WL, window level; WW, window width.

Statistical analysis

The statistical analysis was performed using SPSS software (version 27.0; SPSS, Chicago, IL, USA). Appropriate methods were applied for normally and non-normally distributed data, with values expressed as the mean ± standard deviation, or the median [interquartile range (IQR)], respectively. Comparisons between two groups were conducted using the unpaired Mann-Whitney test, while comparisons among three or more groups were performed using Kruskal-Wallis one-way analysis of variance followed by the post-hoc Dunn’s test. All P values were two-sided, and a P<0.05 value was considered statistically significant.

Results

Patient characteristics

A total of 479 patients, including 298 (62.2%) male patients and 181 (37.7%) female patients, were enrolled in the study. The age of the patients ranged from 20 to 94 years (median, 52 years; IQR, 41–63 years).

Anatomy of visceral arteries based on CTA

Among the 479 patients, the distances between the main visceral arteries varied considerably. The distance between the celiac trunk and superior mesenteric artery (SMA) ranged from 7.90 to 27.90 mm, with a median distance of 15.30 mm (IQR, 13.00–17.60 mm). Normally, the renal artery arises from the abdominal aorta just below the branching of the SMA. However, in 9 patients (1.9%), the right renal artery (RRA) was slightly higher up than the SMA, and in 3 patients (0.6%), the left renal artery (LRA) was slightly higher up than the SMA. The remaining 470 (98.1%) RRAs and 476 (99.4%) LRAs were below the ostium of the SMA. The distance between the SMA and RRA ranged from 0.40 to 34.40 mm, with a median distance of 12.80 mm (IQR, 8.40–17.60 mm). The distance between the SMA and LRA ranged from 1.90 to 70.40 mm, with a median distance of 14.80 mm (IQR, 10.70–18.90 mm). Further, the RRA emerged superiorly to the LRA in 62% of the patients.

The celiac trunk, SMA, RRA, and LRA ostium originated from the aorta at mean axial angles of 29.89°±12.72°, 13.58°±10.85°, 298.52°±13.35°, and 98.94°±12.27°, respectively. The clock position of the celiac trunk ranged from 11:24 to 02:17, with a median of 00:59 (IQR, 00:42–01:17). The clock position of the SMA ranged from 10:54 to 01:48, with a median of 00:27 (IQR, 00:13–00:41). The clock position of the RRA ranged from 08:39 to 11:35, with a median of 09:55 (IQR, 09:38–10:13). The clock position of the LRA ranged from 01:48 to 04:23, with a median of 03:17 (IQR, 03:01–03:35). The anatomical parameters of the visceral arteries are summarized in Table 1.

Comparative analysis based on gender and age

Subgroup analyses were performed based on age and sex. Statistical analyses were performed after stratifying the patients into male and female subgroups, as well as into different age subgroups. All the patients were categorized into age groups: young (18–44 years), middle-aged (45–59 years), elderly (60–74 years), and old (≥75 years). The results showed that the distances between the main visceral arteries were not significantly associated with age. Meanwhile, sex was not significantly associated with the celiac trunk–SMA distance or the RRA–SMA distance (P>0.05). Conversely, the LRA–SMA distance was significantly associated with sex, with males exhibiting a higher distance.

No significant correlation was observed between the clock position of the RRA and either sex or age. The clock positions of the celiac trunk, SMA, and LRA differed significantly between women and men (P<0.01 for all). Specifically, the median clock positions were 01:01 (IQR, 00:49–01:23) in women versus 00:57 (IQR, 00:39–01:13) in men for the celiac trunk; 00:32 (IQR, 00:18–00:44) versus 00:25 (IQR, 00:10–00:38) for the SMA; and 03:25 (IQR, 03:12–03:38) versus 03:12 (IQR, 02:56–03:29) for the LRA. Moreover, a significant correlation was observed between the clock positions of the LRA, SMA, celiac trunk, and age (P<0.05). The clock position of the LRA increased progressively from the young to the elderly groups, with a significant overall difference among the age groups (P<0.05). Specifically, the young group (median: 03:10; IQR, 02:54–03:24) differed significantly from both the middle-aged (03:16; IQR, 03:01–03:36) and elderly (03:24; IQR, 03:05–03:41) groups (both P<0.05). No significant difference was observed between the middle-aged and elderly groups (P>0.05). In addition, the clock positions of the celiac trunk and SMA increased with age, although the pattern of significant differences varied by vessel. For the celiac trunk, a statistically significant increase was observed between the young and middle-aged groups [(00:54; IQR, 00:37–01:11) vs. (01:01; IQR, 00:44–01:20), P<0.05]. For the SMA, a statistically significant difference was observed between the young and elderly groups [(00:23; IQR, 00:10–00:36) vs. (00:32; IQR, 00:17–00:44), P<0.05]. No significant differences were found in the other group comparisons. The results of the subgroup analyses are shown in Table 2.

Discussion

In the early 1990s, Parodi reported endovascular repair for AAAs, opening a new era of EVAR technology (1). After decades of research and technological development, in 2024, the European Society for Vascular Surgery recommended that endovascular repair should be the preferred course of treatment for elective AAA repair for the majority of patients with suitable anatomy and a reasonable life expectancy (2). However, for complex AAAs, standard EVAR techniques cannot ensure the preservation of visceral tissue blood flow. Complex aneurysms are defined as those in which the sac extends beyond the renal arteries or presents an insufficient neck landing zone to deploy a traditional endograft (3).

The first report describing the use of fenestrated grafts was published in 1999 (4), less than a decade after Parodi’s seminal report on the use of an endograft for the repair of an AAA (1). Fenestrated endografts were introduced to enable the repair of complex aneurysms by creating fenestrations that allow blood flow into the visceral arteries. Currently, fenestrated EVAR includes custom-made devices (CMDs), in situ fenestrations, and physician-modified endografts (PMEGs). CMDs require an 8–10-week manufacturing and delivery period, which limits their clinical application. A major concern with both the in situ fenestration process and fenestrated PMEGs is the operational difficulty and steep learning curve for surgeons. No standardized consensus exists for PMEG or in situ fenestration techniques, including fenestration reinforcement, diameter reduction, preloading, and target vessel localization, all of which vary widely across centers. In situ fenestration requires a high level of surgical proficiency, and ischemia time during procedures remains a limiting factor for this technology (5). Achieving more precise and rapid localization and puncture, thereby promoting the further refinement of this technology, requires continuous advancements through relevant technological upgrades and the development of innovative equipment.

Fenestrated grafts are individually customized devices, designed based on precise CT-based planning of the visceral artery locations. The deployment of fenestrated grafts must be equally precise and is more complex than that of standard endografts. Although off-the-shelf fenestrated stent grafts are available overseas, the anatomical variability of abdominal aortic branches has consistently been a key factor limiting their indications (5). Mazzaccaro et al. (6) confirmed the anatomic homogeneity of the origins of both the celiac artery and the SMA. The results of the present study are consistent with these findings. In this analysis of 479 patients, the longitudinal position of the celiac trunk arose 7.9–27.9 mm distal to the SMA. Compared with a lower ostial location (10th percentile), a higher ostial location (90th percentile) was associated with a distance difference of only 8 mm (11.6 vs. 19.6 mm), indicating the relatively predictable locations of the celiac trunk and SMA. This finding provides a critical anchor point for presetting the fenestrations on the aortic component. However, in their analysis, Mazzaccaro et al. concluded that the main limitation to the manufacture of an off-the-shelf device for the thoracoabdominal aortic region is the large anatomic variability of the renal vessels. As Mendes Bernardo et al. (5) noted, the anatomy of the renal-mesenteric arteries can limit vessel incorporation with any type of endovascular technique.

Although previous research has reported anatomical data on abdominal aortic branches, most studies have focused on anatomical variations, aiming to prevent iatrogenic injuries during surgery (7). Sultanov et al. reported a rare combination of a duplicated inferior vena cava, a high-positioned aortic bifurcation, and transposed iliac arteries in a patient with right renal aplasia who underwent kidney transplantation (8). Such reports underscore the clinical importance of recognizing aberrant anatomy. However, research on the normative positional anatomy of visceral arteries in patients without overt variations is limited.

This study analyzed anatomical parameters of the visceral arteries based on CTA findings from 479 patients at a single center, aiming to provide evidence for the development of devices for abdominal aortic and visceral artery reconstruction in the Chinese population. The distance between the origins of the SMA and the RRA ranged from 0.4 to 34.4 mm, while that between the SMA and the LRA ranged from 1.9 to 70.4 mm, indicating substantial interindividual anatomical variability. The study revealed a high degree of interindividual variability in the location of the LRA origin. The gender difference in the distance between the LRA and the ostium of the SMA was statistically significant, with the ostium position being lower in males than in females. Although the distance between the LRA and SMA exhibits considerable interindividual variation, when we focused on the “most common” range of anatomical parameters, the longitudinal distances from the SMA to the RRA and LRA fell within narrow common ranges in the majority of patients. Specifically, in 80% of the study population, the SMA–RRA distance was between 4.5 and 22.0 mm, and the SMA–LRA distance was between 7.0 and 23.4 mm, revealing a relatively stable distribution pattern.

In terms of clock position, the circumferential locations of the celiac trunk, SMA, RRA, and LRA varied by approximately 30° (one hour) in 80% of the study population, revealing a relatively consistent spatial distribution pattern.

Limitations

Several limitations of this study should be acknowledged. First, as a single-center, retrospective study, it is subject to inherent selection bias and potential unmeasured confounding. Thus, the generalizability of our findings to other populations or settings may be limited. Second, due to the retrospective nature of this study, which primarily involved outpatients, detailed anthropometric data—including height, weight, and body mass index (BMI)—were not consistently recorded in the medical records. Consequently, we were unable to perform body-type subgroup analyses (e.g., asthenic, hypersthenic, hyposthenic, and sthenic), or adjust for these variables as potential confounders. The absence of these parameters represents a significant limitation, as body habitus may influence the anatomical relationships and clinical outcomes examined in this study. Notwithstanding these limitations, this study provides valuable normative data on visceral arteries. Future prospective studies with standardized data collection, including comprehensive anthropometric measurements, are warranted to validate our findings and further elucidate the clinical implications of anatomical changes.

Conclusions

Based on our findings, we hypothesized that, in the general population, the anatomical variability of visceral arteries—specifically their mutual distances and angles of origin relative to the sagittal aortic axis—can be characterized within defined parameters, such that 80% of individuals exhibit a predictable and potentially standardizable vascular anatomy. This study provides essential anatomical evidence supporting the development of off-the-shelf fenestrated stent grafts tailored to the Chinese population, highlighting their significant clinical translational potential.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-aw-2304/rc

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-aw-2304/dss

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-aw-2304/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of Xiamen Cardiovascular Hospital of Xiamen University (approval No. 2022-YLX-3). The requirement for written informed consent was waived due to the retrospective nature of the study and the anonymized data collection.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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