Aorta and Iliac Arteries
| Vessel / Finding | Size Thresholds | Recommendation |
|---|---|---|
| AAA (infrarenal aortic aneurysm) | <3.0 cm: normal · 3.0–3.9 cm: US every 3 years · 4.0–4.9 cm: US every 12 months · 5.0–5.4 cm: US or CT every 6 months | Surgical referral: ≥5.5 cm (men) or ≥5.0 cm (women); or growth ≥1 cm/yr |
| Iliac artery aneurysm | <3.0 cm: normal · 3.0–3.5 cm: follow-up in 6 months | Surgical referral: >3.5 cm or rapidly growing |
AAA surveillance imaging type (US vs. CT) depends on body habitus and visualization — ultrasound is preferred for routine surveillance to avoid cumulative radiation. CT angiography is used for pre-operative planning.
Visceral Artery Aneurysms
| Vessel | Surveillance Threshold | Referral Threshold |
|---|---|---|
| Splenic artery | Annual surveillance if >1.5 cm | ≥2 cm; or women of childbearing age, liver transplant candidates, or portal hypertension (all have higher rupture risk) |
| Hepatic artery | Any true aneurysm | Surgical/IR referral — high rupture risk at any size |
| SMA (superior mesenteric artery) | Any true aneurysm | Surgical/IR referral |
| Renal artery | Annual surveillance if 1–1.5 cm | ≥1.5 cm; or women of childbearing age |
| Pancreaticoduodenal artery | Any | Immediate referral — high rupture risk regardless of size |
Splenic artery aneurysms are the most common visceral artery aneurysm. They carry a particularly high rupture risk in pregnant women (up to 25% mortality with rupture during pregnancy) and in the setting of portal hypertension. These patient groups should be referred for intervention even at sizes below the general 2 cm threshold.
Other Vascular Findings
| Finding | Recommendation |
|---|---|
| Penetrating aortic ulcer (PAU), asymptomatic, incidental | Annual CT surveillance; expeditious referral if symptomatic or enlarging |
| IVC dilation (>28 mm) or duplicated IVC | Echocardiography to exclude right heart failure; CT for anatomic variant documentation |
| Pelvic venous dilation in women (ovarian vein >4 mm or pelvic varicosities) | Consider pelvic congestion syndrome if symptomatic; asymptomatic → no follow-up |
Why This Matters
AAA is the most clinically consequential incidental vascular finding — it is usually asymptomatic until rupture, and rupture carries >80% mortality. Recognizing an aorta measuring 4.5 cm on a trauma CT and initiating a surveillance pathway prevents a potentially fatal outcome. For visceral aneurysms, the key principle is that small size does not equate to low risk for all vessels: hepatic, SMA, and pancreaticoduodenal artery aneurysms carry rupture risk at sizes that would be considered small for the aorta.
References
Khosa F, Krinsky G, Macari M, et al. Managing Incidental Findings on Abdominal and Pelvic CT and MRI, Part 2: White Paper of the ACR Incidental Findings Committee II on Vascular Findings. J Am Coll Radiol. 2013;10(10):789–794.
Chaer RA, Abularrage CJ, Coleman DM, et al. The Society for Vascular Surgery Clinical Practice Guidelines on the Management of Visceral Aneurysms. J Vasc Surg. 2020;72(1S):3S–39S.