Surveillance after EVAR: is that jet a type I or type II endoleak?
A 72-year-old man attends for 6-month surveillance after endovascular repair of a 5.8 cm infrarenal aortic aneurysm. Blood pressure is 148/82 mmHg and eGFR is 42 mL/min/1.73 m². Ultrasound shows a sac diameter of 6.4 cm, up from 5.6 cm at one month. Colour Doppler demonstrates a focal jet within the sac, but you cannot decide whether it arises at the proximal graft attachment or from a lumbar vessel. Layered thrombus fills much of the sac, and bowel gas obscures part of the anterior wall. The vascular surgeon's request reads simply '? endoleak'. The patient is asymptomatic and has no abdominal pain.
1. How do you use flow characteristics and location to distinguish a type I from a type II endoleak, and what limits your confidence on ultrasound?
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Start from the classification, then test it against the image:
- Type I - flow at a graft attachment site: Ia proximal, Ib distal. The jet usually originates at the end of the graft, is often higher velocity and pulsatile, and may appear continuous with aortic or iliac flow.
- Type II - retrograde flow from a branch (lumbar, inferior mesenteric, accessory renal). It tends to sit within the sac away from the graft, is often slow and low-velocity, may be to-and-fro, and may vary with Valsalva or compression.
- Type III - fabric defect or modular disconnection, typically mid-graft. Type IV - graft porosity, a diffuse early blush that usually resolves. Type V - sac growth without a detectable leak (endotension).
Confidence is limited because ultrasound cannot reliably trace a jet to its origin. A slow type I can resemble a branch vessel, and a type II can appear anywhere in the sac. Thrombus, bowel gas and body habitus further degrade localisation. The decisive clinical clue is sac growth: an enlarging sac with any visible leak should be treated as a possible type I until proven otherwise. State the uncertainty and recommend CT angiography or contrast-enhanced ultrasound.
2. What technical adjustments would you make to detect and characterise a slow-flow endoleak?
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Optimise for low flow without creating artefact:
- Reduce the colour scale/PRF to roughly 10–20 cm/s and lower the wall filter.
- Raise colour gain until background noise just appears, then back off slightly. Excess gain will bleed colour into thrombus and mimic a leak.
- Use power Doppler as a sensitive adjunct, and a low-frequency curved array for penetration.
- Narrow the colour box and place the focus at the sac rather than at the near wall.
- Use harmonic imaging, and contrast-enhanced ultrasound if available.
- Scan the whole sac in transverse and longitudinal planes, including both attachment sites, not just the obvious jet.
- Use breath-holding and the left or right decubitus position to move bowel gas; Valsalva can augment a type II.
- Avoid heavy compression in a 6.4 cm sac.
- Measure the sac outer-to-outer and compare directly with the prior study.
Document which manoeuvres produced the flow and which did not.
3. What would you put in your report and what recommendation would you make?
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Report should be concise, quantitative and action-oriented:
- Sac diameter 6.4 cm, an increase of about 8 mm since the one-month scan.
- A focal colour jet within the sac; origin not confidently identified; cannot exclude a type I endoleak.
- Limitations: layered thrombus, obscuring bowel gas, body habitus.
- Recommend urgent CT angiography (or contrast-enhanced ultrasound if CT is contraindicated by eGFR 42) and same-day discussion with vascular surgery.
Reasoning: growth of more than 5 mm, and a sac now over 6 cm, is a failure of exclusion until proven otherwise. A type II leak is often managed conservatively, but a type I or III requires intervention. Ultrasound alone cannot make that distinction reliably, so the report should communicate suspicion and the need for cross-sectional confirmation rather than simply stating 'endoleak present'.