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2. Lymphadenopathy as a pitfall in iliac artery aneurysm detection and surveillance.

Steven Wallace BSc AVS. Liverpool Vascular and Endovascular Service

The National Abdominal Aortic Aneurysm Screening Program (NAAASP) is active across the UK in the screening of men in their 65th year for Abdominal Aortic Aneurysm (AAA). This screening test is performed by screening technicians (STs) who are a group of professional staff specifically trained to visualise and accurately measure the abdominal aorta using ultrasound.

The scope of practice for screening technicians within NAAASP is the identification and differentiation of the abdominal aorta and the inferior vena cava from the level of the xiphisternum to the level of the aortic bifurcation with the subsequent measurement of the abdominal aorta at its widest point.(3) This assures abdominal aorta has been visualised in its entirety when concluding the investigation.

Figure 1 Aortic anatomy identifying key anatomical points for NAAASP visualisation

 

Case Study

A patient attended for AAA screening and was noted to have a normal calibre aorta measuring <3cm in both transverse and longitudinal diameter.  During the scan an enlarged left CIA, measuring 3.8cm in diameter (Figure 2 & 3) was recorded. As CIA assessment falls outside of the scope of the screening program practice, the patient was referred to the local vascular laboratory for confirmatory imaging.

Figure 2 NAAASP measurements

Figure 3 NAAASP measurements

 

On attendance to the local vascular laboratory the abdominal aorta was confirmed as normal calibre (Figure 4) and there was confirmatory ultrasound evidence of a left CIA aneurysm measuring 4cm      (Figure 5). There was, however, concern noted in the report regarding the appearances of the surrounding pelvic tissues with reference made to the patient’s history of malignancy. As a result, the findings were escalated to the medical team and an urgent CT angiogram was arranged  (Figure 6).

Figure 4 Transverse view of the abdominal aorta

Figure 5 Structure identified as the left CIA

Figure 6 CT image showing bulky, retroperitoneal lymphadenopathy (arrows)

 

The CT angiogram (Figure 6) identified extensive retroperitoneal and iliac lymphadenopathy. Iliac nodes were reported to measure 5.5-4.4cm with subsequent poor visualisation of the left CIA reported on the previous ultrasound.

Figure 7 Iliac lymph nodes (1)

 

As a result of this and further investigation the patient underwent extensive, non-surgical, treatment for prostate malignancy.

On the patients return for planned surveillance of the previously reported left CIA aneurysm, the imaging quality was noted to be significantly improved with no ultrasound evidence of pelvic masses or any hindrance to obtaining diagnostic ultrasound images of the iliac arterial system.

Figure 8 Proximal bilateral CIA post treatment for prostate malignancy

 

Figure 9 Left iliac vessel imaging post treatment for prostate malignancy

 

  • Dotted arrow – Left CIA.
  • Solid arrow – left external iliac artery.
  • Dashed arrow – left internal iliac artery

At this event, six months from the original ultrasound investigation, the left iliac was noted to be of normal calibre measuring 1cm in transverse diameter and 1.14cm in longitudinal section (Figures 8 & 9 respectively) with no evidence of any aorto-ilaic aneurysm extension or other arterial abnormality

Conclusion

The misidentification of iliac aneurysm due to lymphadenopathy is not well documented and should be considered when there is an atypical appearance in the region of the iliac vessels.

Given the anatomical location of the iliac lymph nodes (figure 7), lymphadenopathy can obscure and/or mimic enlarged iliac vessels. In circumstances when grey scale imaging is sub optimal, visualisation, patency and anatomy of the iliac vessels should be confirmed with colour Doppler.

Figure 10 Coronal (A) and Axial (B) CT images of the aortic bifurcation illustrating the normal calibre common iliac vessels (solid arrows) and surrounding lymph nodes (dashed arrows)

 

Even in the hands of an experienced operator, the subjectivity of ultrasound is illustrated in this case; however recognition of atypical appearances and the ability to direct the patient to the medical team demonstrates the importance of wider knowledge and skill sets when performing vascular ultrasound imaging.

This case highlights one of the many pitfalls of ultrasound imaging the pelvic vasculature and when access to a second modality is beneficial.

References

  1. https://www.kenhub.com/en/library/anatomy/lymphatic-vessels-and-nodes-of-the-pelvis
  2. Public Health England. 1st February 2018. Non-visualised aortas. Guidance for local AAA screening programmes in the management of non-visualised screening results. https://www.gov.uk/government/publications/aaa-secondary-ultrasound-screening
  3. Public Health England. 15th December 2014. AAA screening: clinical guidance and scope of practice for professionals involved in the provision of the ultrasound scan within the NHS Abdominal Aortic Aneurysm Screening Programme. https://www.gov.uk/government/publications/aaa-screening-clinical-guidance-and-scope-of-practice
  4. https://www.sciencedirect.com/topics/medicine-and-dentistry/external-iliac-lymph-nodes
  5. Solivetti FM, Elia F, Graceffa D, Di Carlo A. Ultrasound morphology of inguinal lymph nodes may not herald an associated pathology. J Exp Clin Cancer Res. 2012;31(1):88. Published 2012 Oct 18. doi:10.1186/1756-9966-31-88