Original Research

Sonographic anatomical variations of internal jugular vein and common carotid artery relationships in a South African tertiary hospital

Gouws L. Germishuys, Bojan Korda

Received: 08 Dec. 2025; Accepted: 01 June 2026; Published: 17 Aug. 2026

Copyright: © 2026. The Authors. Licensee: AOSIS.
This work is licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/).

Abstract

Background: Internal jugular vein (IJV) cannulation is widely performed, yet complication rates remain substantial, often associated with anatomical variation. Existing evidence is predominantly derived from non-African populations and frequently lacks bilateral, multi-level assessment. A clearer understanding of IJV–common carotid artery (CCA) relationships in African patients is needed to support safer vascular access.

Aim: To characterise sonographic anatomical variations of the IJV–CCA relationship across three cervical levels and both sides of the neck in adult surgical patients.

Setting: Chris Hani Baragwanath Academic Hospital, Johannesburg, South Africa.

Methods: A cross-sectional ultrasound study was conducted in 178 adults. A point-of-care ultrasound (POCUS) certified investigator performed bilateral scans at the upper thyroid cartilage, cricoid cartilage and Sedillot’s triangle. Radial IJV position, vessel diameters, depth from skin, centre-to-centre distance, degree of overlap and atypical variants were recorded.

Results: Typical IJV position was consistently more frequent on the right (upper = 84.3%, middle = 70.8%, lower = 52.8%) than on the left (66.9%, 52.8%, 16.3%). Overlap > 50% occurred less often on the right at all levels (0.7% – 34.3%) compared with the left (24.2% – 67.4%). The IJV was larger on the right at all depths, while CCA depth differed significantly between sides. Atypical variants, including absence, duplication, bifurcation or valves, were rare (2.3%). Increasing age and body mass index were associated with greater overlap and deeper vessel position.

Conclusion: Marked variability exists in IJV–CCA relationships, with the right side demonstrating more favourable anatomy for cannulation.

Contribution: This study provides the first bilateral, multi-level sonographic dataset from an African cohort.

Keywords: vascular ultrasound; regional anatomy; internal jugular vein; common carotid artery; anatomical variations.

Introduction

The internal jugular vein (IJV) is one of the preferred sites of central venous access for anaesthesiologists due to its anatomical location and characteristics.¹ Originating at the base of the sigmoid sinus, the IJV runs through the jugular foramen. It then runs parallel to the carotid artery within the carotid sheath, continuing to its most common position posterior to the sternocleidomastoid muscle and anterolateral to the common carotid artery (CCA).² It is often accessible intraoperatively and easily visualised during ultrasound-assisted central venous catheterisation.³

Complications during and after IJV access include bleeding, accidental arterial puncture, pneumothorax, malposition, thrombosis, cardiac arrhythmias and infection.⁴ Adequate training reduces complication rates,⁵ which increase with more access attempts.⁶

Point-of-care ultrasound (POCUS) gained popularity for central venous access in recent decades due to its real-time guidance capabilities, improving success rates and reducing complications.^7,8,9 The Association of Anaesthetists of Great Britain and Ireland¹ recommends ultrasound for central venous access as the standard of care.

Anatomical variations of the IJV include positional differences, absence, hypoplasia, duplication and fenestration.¹⁰ These are well-documented in various populations, including China,^11,12 Colombia,¹³ Germany,^14,15 Grenada,¹⁶ Iran,¹⁷ Italy¹⁸ and Japan.¹⁹ No study examining the African population could be identified. Anatomical variation may contribute up to 15% of complications in IJV access.²⁰ Understanding these variations is crucial for safe catheter insertion. Ultrasound aids in identifying these variations and reducing complications.^9,21,22

While extensive research exists on IJV variations, few studies have explored nor made recommendations with regard to which side of the neck is potentially a safer option for central venous access.^23,24

Objectives

This study aimed to characterise the anatomical relationships between the IJV and CCA in adult surgical patients by assessing radial position, vessel overlap, diameters and skin depth at three cervical levels on both sides of the neck. The secondary objectives included the evaluation of how patient factors correlate with anatomical variability.

Research methods and design

This was a cross-sectional descriptive analysis using ultrasound imaging done at Chris Hani Baragwanath Academic Hospital, Soweto, South Africa. Inclusion criteria included all patients aged 18 years or older presenting for elective surgery. Consecutive convenience sampling was used. Exclusion criteria included patients unable to lie supine or with a history of neck pathologies, previous neck surgeries or prior IJV access. Patients were screened at the theatre reception and recruited for the study preoperatively. Written informed consent was obtained from all individual participants involved in the study. Age, ethnicity and country of origin were noted. Patient weight was either self-reported or retrieved from the patient’s record, where available, while height and neck circumference were measured by the investigator. Body mass index (BMI) was calculated where possible.

A sample size calculation was performed based on the two-sample proportions test (Pearson’s chi-squared test) using Stata 18. The reference values were drawn from Maecken et al.,¹⁴ which had the largest sample size of the comparable studies identified: the proportions of IJV overlap with the CCA on the right (46.4%) and left (34.8%) sides served as p1 and p2, respectively. A minimum detectable difference of 15% between proportions was specified, with a two-sided significance level of 5% (α = 0.05) and 80% power (β = 0.20). This yielded a total representative sample size of 356 (178 per group).

Ultrasound examinations were standardised and performed by a POCUS-certified clinician using a GE LOGIQe ultrasound machine (GE, United States) with a 6 MHz – 14 MHz, linear probe. The same investigator performed all the scans to minimise inter-operator variability. Examinations were performed using the probe in vascular mode with the frequency set to 10 MHz. Patients were positioned supine with their heads in the neutral position. The transducer was applied to the skin with the probe marker facing the patient’s right, with the face of the probe at 45° to the sagittal axis at three levels: Sedillot’s triangle (above the clavicle) (lower), cricoid cartilage (middle) and the upper border of the thyroid cartilage (upper). This was intended to simulate procedural instrumentation while minimising increased overlap from head rotation.¹⁴ The CCA was positioned in the centre of the screen, and probe pressure on skin was kept as low as possible. If the IJV was not visible, patients were asked to perform a Valsalva manoeuvre. The IJV was identified by compressibility, but pulse wave doppler was used if the investigator was uncertain. Images were labelled and saved for later measurement and assessment.

Forty-four measurements were recorded for each patient apart from their anthropometric data. This included six sets of measurements, at each of the craniocaudal positions on both the left and the right sides, namely: IJV diameter, CCA diameter, IJV distance from skin, CCA distance from skin, distance between IJV and CCA centres, degree of overlap of the vessels (0%, < 50%, > 50%), radial relationship of the IJV to the CCA and the presence of atypical vessel variants. Internal jugular vein size is highly variable, and an amorphous shape makes measuring IJV size difficult without the usage of advanced software. The deepest vertical pool was used to determine IJV size, as this parameter is directly applicable to vascular access safety and the avoidance of posterior wall puncture. The distance from the skin to both vessels was measured as the distance to the superficial vessel wall of the main vessel body, which is also relevant for vascular access.

Radial relationship of the IJV to CCA was recorded using a clock-dial system (Figure 1). Each sector that the IJV was present in was marked and recorded. Typical position was defined as positions 1–4 on the left side of the neck and 8–11 on the right side of the neck.¹⁴ These positions were chosen to increase the typical group of patients who were likely to have an uncomplicated central venous access as there is no or minimal overlap of the IJV and CCA in these positions, as well as no posterior IJV segments.

FIGURE 1: Clock-dial mapping of internal jugular vein position relative to the common carotid artery.

Statistics

Microsoft Excel (Microsoft Corporation, Redmond, Washington, United States) was used for data aggregation, while statistical analysis was conducted using Stata version 16 (StataCorp LLC, College Station, Texas, United States). Radial heatmaps, which display the percentage incidence of IJV positions relative to the CCA across clock-dial sectors, were generated using RStudio version 1.4 (RStudio, PBC, Boston, Massachusetts, United States).

Normality of the continuous data was evaluated using the Shapiro–Wilk test. As the distributions of 26 out of 30 measured variables significantly deviated from normality, non-parametric tests were utilised. Differences in vessel overlap between the left and right sides were assessed using the chi-squared test and Cramér’s V, while the Wilcoxon signed-rank tests were employed to compare IJV and CCA measurements between sides.

Spearman’s rank correlation (ρ) was calculated to determine the associations between patient characteristics (BMI, neck circumference, age, weight and height) and both the ratios and absolute differences of right and left vessel measurements.

The Kruskal-Wallis equality-of-populations rank test was applied to compare median values of the three categories of overlap at the lower, mid and upper levels for all continuous predictors for the total group and for female and male patients separately.

A significance level was set at a p-value < 0.05 for all analyses.

Ethical considerations

Ethical clearance to conduct this study was obtained from University of the Witwatersrand and Human Research Ethics Committee (No. M240120).

Results

Recruitment included 178 patients presenting to the Chris Hani Baragwanath Academic Hospital theatre complex for elective surgery; no patients met exclusion criteria. The patient characteristics are depicted in Table 1.

Internal jugular vein positional variations

These findings are presented in Figure 2. Figure 3 illustrates the incidence of the radial positional relationships around the CCA. The IJV was more frequently located in the typical position at the superior levels compared to the inferior levels. In addition, the typical position was consistently observed more often on the right side of the neck than on the left.

FIGURE 2: Bar graph showing frequency of anatomically typical internal jugular vein positions by level and side.

FIGURE 3: Radial heat map showing internal jugular vein position relative to the common carotid artery across cervical levels.

Anatomical variants

A small subset of patients demonstrated atypical IJV variants. Medially positioned IJVs were observed in two patients (1.12%) on the right and eight patients (4.49%) on the left. Internal jugular vein valves were identified in four cases (2.25%) on the right and three cases (1.69%) on the left. Additionally, one patient (0.56%) had an absent IJV on the right. Duplication was observed in two cases (1.12%) on the right, while bifurcation was noted in one case (0.56%) on the left.

Vessel overlap

Overlap frequencies are summarised in Figure 4. There was significantly greater overlap of the IJV and CCA at inferior levels compared to superior levels, as well as on the left side of the neck compared to the right (chi²[4] = 20.95, p < 0.001). There was a strong correlation between overlap on the right and patient age and BMI (chi²[2] = 7.92, p = 0.021), especially at the lower levels of measurement. In contrast, overlap on the left increased in female patients in advancing age, predominantly at the middle (chi²[2] = 7.91, p = 0.019) and upper levels (chi²[2] = 7.73, p = 0.021) of measurement.

FIGURE 4: Incidence of internal jugular vein–common carotid artery overlap categories at three cervical levels.

Depth and distance measurements

Depth and distance measurements are summarised in Table 2. For the IJV, significant right-to-left differences were observed in vessel diameter at all depths, whereas no significant differences were found in the distance from the skin. For the CCA, significant differences between the right and left sides were detected for both diameter (at the lower and middle levels) and distance from the skin (at the lower and upper levels). In addition, the IJV–CCA centre-to-centre distances differed significantly between the sides at all measured depths. Differences in gender are summarised in Appendix 1 Table 1-A1. While IJV and CCA diameters are broadly similar across sexes, female patients tend to have slightly more right-sided IJV dominance and more superficial CCA positioning, particularly at middle and upper levels.

Associations with body mass index and age

A weak to moderate association was observed between higher BMI and an increased depth of the IJV from the skin on the left side compared to the right, at both the middle (ρ = –0.17, p = 0.046) and lower levels (ρ = −0.17, p = 0.047). Similarly, higher BMI showed a weak positive correlation with the depth of the CCA from the skin on the right side at the lower level (ρ = –0.18, p = 0.035). Furthermore, increasing age demonstrated a weak to moderate positive correlation with left sided IJV depth at the upper level when compared to the right (ρ = –0.19, p = 0.011). These findings suggest that higher BMI and older age may be associated with deeper vascular structures, particularly on the left.

Discussion

The principal study finding was that the IJV appeared more frequently in the typical anatomical configuration on the right side of the neck, with reduced overlap with the CCA across the upper, middle and lower positions. This observation aligns with previous research emphasising the importance of IJV anatomy in central venous catheterisation.

This study’s left versus right sided typical prevalence at the level of the cricoid cartilage (52.81% vs 70.79%) is comparable to the findings of Lin (66.4% vs 69.3%)¹¹ and Maecken (67.3% vs 76.1%).¹⁴ However, at the level of Sedillot’s triangle, this study’s incidence of left versus right typical anatomy (16.29% vs 52.81%) was significantly lower than in the studies conducted by Lim (81.8% vs 88.6%),²³ Umaña (58.9% vs 73.3%),¹³ Benter (93% vs 93%)¹⁵ and Shoja (98.2% vs 98.2%).¹⁷ Inconsistent definitions of typical anatomy and differing measurement methodologies likely underlie the wide disparity in reported observations. This disparity could also be explained by population variations. Using a clock-dial classification system permits direct left-versus-right comparison between studies. At the cricoid level, the present study recorded typical anatomy in 52.81% (left) and 70.79% (right) of cases, consistent with the findings of Maecken (67.3% and 76.1%, respectively).¹⁴

This study’s findings further support previous evidence by Gordon,²⁴ Lichtenstein²⁵ and Lim²³ that the right IJV tends to be larger in diameter than the left. The observation of greater overlap on the left also supports previous evidence by Lin¹¹ and Qin.¹² The observation that overlap increased with increasing age is supported by the studies by Troianos²⁶ and Umana,¹³ but is contrasted in the study by Shoja,¹⁷ which found decreasing overlap with increasing age.

The anatomical advantages of right sided IJV access, including larger vessel diameter, reduced overlap and more typical anterolateral position, may reduce the risk of complications such as posterior wall puncture, inadvertent arterial injury and catheter misdirection.^4,5 The lower anatomical variability on the right side may explain the higher success rates associated with right-sided central venous access noted by Sulek²⁷ and Gordon.²⁴ While this study did not directly measure clinical outcomes, these anatomical findings may provide a rationale for why right-sided access lowers complications associated with central venous cannulation.

A notable strength of this study is its bilateral, multi-level analysis of IJV–CCA relationships, which is uncommon in the existing literature. Most previous studies evaluated only a single level, typically the cricoid or Sedillot’s triangle. Only Hameedullah²⁸ and Qin¹² reported multi-level data, but limited their assessment to a single side of the neck. By providing bilateral, multi-level data, this study allows a comprehensive understanding of the anatomical course of the IJV and its positional evolution across the neck. This approach is novel and may help guide procedural planning and enhance safety in central venous access.

Additionally, this study contributes new data from an African population, a demographic absent in identified existing literature. Most prior data derive from Asian,^{11,12,17,19,28} European^{14,15,16,18,25,29} or North American populations^24,26,27,30 (Appendix 1 Table 2-A1). This sample reflects the South African demographic and adds to the global understanding of anatomical variability.

The influence of anthropometric variables was also notable. We found a weak to moderate association between higher BMI and increased IJV depth, particularly on the left side at lower levels, which could complicate cannulation. Older age was associated with deeper IJV positions on the left, especially in female patients. These observations underscore the importance of individualised vascular mapping prior to central venous access, particularly in older or obese patients.

These findings may have significant clinical implications in both high-risk patients and clinician training. In patients at high bleeding risk, such as those with borderline thrombocytopenia, the right IJV should be considered for central venous catheterisation, owing to its safer, more predictable anatomy and the associated lower complication rates.²⁷ For less experienced clinicians, right-sided access may offer a safer and more straightforward approach, reducing the likelihood of procedural errors, even though these recommendations are not present in current guidelines.³¹ Additional advantages include a more direct trajectory to the superior vena cava with reduced catheter misdirection, which further reinforces the preference for right-sided access, thereby complementing our primary anatomical findings.

This study has several strengths. Like most comparable studies, randomisation was achieved via consecutive convenience sampling, and the population examined was well-represented. This study used bilateral scanning at three levels and incorporated measurements of vessel diameter, skin depth, centre-to-centre distances and degrees of overlap, thus providing a multidimensional anatomical profile not noted in previous studies. A single POCUS-certified operator conducted all scans, reducing interobserver variability and enhancing internal consistency.

Nonetheless, certain limitations should be acknowledged. The study was performed at a single tertiary hospital and included only patients undergoing elective surgery. Thus, our findings may not apply to critically ill populations or those with altered haemodynamic states. Moreover, although inter-operator variability was minimised, replication by multiple operators may improve external validity in future research. Further studies may also explore how these anatomical differences influence procedural metrics, such as number of attempts, time to cannulation and complication rates.

Conclusion

This study reinforces and expands upon the established evidence that right IJV access is anatomically more predictable and potentially safer. By evaluating bilateral relationships at three neck levels, we present a comprehensive anatomical map that could inform safer practice, particularly in resource-limited settings where ultrasound may be inconsistently used. Given the variability observed, even within a single population, universal ultrasound guidance remains the only reliable safeguard against complications.

Acknowledgements

This article is based on research originally presented as a poster at the European Society for Vascular Surgery (ESVS), held in Turkey on 23 September 2025. The content has since been expanded and revised for journal publication. This republication is done with permission from the conference organisers.

The authors acknowledge Merle Werbeloff, PhD (Wits), for statistical analysis.

In this article, Microsoft Copilot was used for grammar and spelling checks. Artificial intelligence (AI) was not used for image generation, drafting text and data interpretation. All AI-assisted sections were reviewed and validated for accuracy, appropriateness and academic style. The primary author takes full responsibility for the content of the publication.

The authors declare that they have no financial or personal relationships that may have inappropriately influenced them in writing this article.

Gouws L. Germishuys: Conceptualisation, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Visualisation, Writing – original draft, Writing – review & editing. Bojan Korda: Conceptualisation, Supervision, Validation, Writing – review & editing. All authors reviewed the article, contributed to the discussion of results, approved the final version for submission and publication, and take responsibility for the integrity of its findings.

This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

The analysed data supporting the findings of this study are included within the article and its references. De-identified raw ultrasound measurement datasets generated during the study are not publicly available due to institutional data governance restrictions, but can be obtained from the corresponding author, Gouws L. Germishuys, on reasonable request. No publicly archived datasets were used in this study, and no accession codes apply. Figures derived from raw data include all overlap analyses, radial position maps and vessel measurement distributions.

The views and opinions expressed in this article are those of the authors and are the product of professional research. They do not necessarily reflect the official policy or position of any affiliated institution, funder, agency or that of the publisher. The authors are responsible for this article’s results, findings and content.

References

Appendix 1