What is Infrarenal Ectasia?
Infrarenal ectasia is a mild dilatation of the abdominal aorta below the renal arteries, defined as a diameter between 2.0 and 3.0 cm, representing less than 50% increase from the normal aortic diameter. 1
Definition and Diagnostic Criteria
The term "ectasia" specifically applies to arterial dilatations that are less than 50% of the expected normal diameter, distinguishing it from a true aneurysm which requires at least 50% increase in diameter. 1
- The normal infrarenal abdominal aorta measures up to 2 cm in anteroposterior diameter 1
- Ectatic range: 2.0-3.0 cm in diameter 1
- Aneurysmal threshold: ≥3.0 cm in diameter 1, 2
- These thresholds are approximately 10% smaller in women than in men 1
Clinical Significance and Natural History
Infrarenal ectatic aortas expand very slowly, do not rupture, and rarely progress to meet criteria for operative repair. 3
- Median expansion rate is approximately 0.65 mm/year 4
- However, 19% of ectatic aortas can progress to become aneurysmal (>3.0 cm) within 2 years of follow-up 4
- No ruptures have been documented in purely ectatic aortas (2.0-2.9 cm diameter) 3
- The risk profile differs substantially from true aneurysms, with no identified risk factors specifically linked to ectasia development 3
Surveillance Recommendations
For infrarenal aortic ectasia measuring 2.6-2.9 cm, repeat ultrasound imaging should be performed every 5 years. 1, 3
- Ultrasound is the preferred imaging modality due to its non-invasive nature, lack of radiation exposure, and cost-effectiveness 1, 2
- Once the diameter reaches 3.0-3.4 cm (transitioning to small aneurysm), surveillance intervals should shorten to every 3 years 1, 2
- If ectasia progresses to 4.5-5.4 cm, surveillance should increase to every 6 months 1
Common Pitfalls to Avoid
Do not confuse ectasia with aneurysm—the distinction at 3.0 cm is critical for determining surveillance intervals and patient counseling about rupture risk. 1
- Using a fixed 3.0 cm cutoff for all patients may lead to underdiagnosis in women, where a ratio-based definition (>1.2 times suprarenal diameter or >1.5 times normal) may be more appropriate 1
- Ensure consistent measurement technique using anteroposterior diameter perpendicular to the longitudinal axis of the aorta 1
- Ectatic aortas can cause a pulsatile abdominal mass on examination, mimicking an aneurysm clinically, making imaging confirmation essential 1