First and second year — the floor first, then every step
Across the arterial, portal venous and delayed phases: active extravasation GROWS and changes shape; a pseudoaneurysm or AV fistula stays the same size and washes out with the blood pool. The difference changes the grade, the urgency and the treatment.
Orient first
Contrast outside a vessel on one phase is not a diagnosis; its behaviour across phases is.
Active bleeding into a body cavity (peritoneum, pleura) is more urgent than bleeding contained within an organ capsule or Gerota fascia.
The sentinel clot — the highest-attenuation blood beside an organ — points to the bleeding source.
Acquire the study
Arterial and portal venous phases, with a delayed phase (about 5 min) whenever a contrast focus is seen; identical windows and slice position to compare.
The manoeuvre
Find each contrast focus on the arterial phase and measure its size and attenuation (similar to the aorta).
Find the same focus on the portal venous and delayed phases: larger with a changing shape = active extravasation; same size and following the blood pool = pseudoaneurysm or AV fistula.
AV fistula: early opacification of a draining vein on the arterial phase.
Contained versus free: within the organ, within the capsule or Gerota fascia, or into the peritoneum/pleura/retroperitoneum.
Name the likely source vessel from the anatomy (e.g. splenic lower pole branch, superior gluteal artery).
Haematoma attenuation and the sentinel clot location.
What confirms it
Behaviour across at least two phases.
What licenses you to exclude it
A single-phase study cannot separate active bleeding from a pseudoaneurysm — say so and recommend the delayed phase.
The classic misread
Calling excreted urinary contrast on a delayed phase active bleeding.
Calling a bone fragment or oral contrast extravasation.
Reporting the injury
Classification to use
AAST 2018 incorporates this distinction into the solid-organ grade (contained vascular injury versus active bleeding beyond the organ).
Measurements — and how to take them
Focus size on each phase (mm) and haematoma dimensions (cm).
What to report
Each focus: location, size, behaviour across phases, contained or free, likely source vessel; the haematoma and sentinel clot.
How to report it
CT: "A 9 mm arterial-phase contrast focus in the right pelvis enlarges and changes shape on the portal venous and delayed phases — active arterial extravasation, likely from a branch of the right superior gluteal artery, into a 7 × 5 cm extraperitoneal haematoma."
What not to report
Do not use "blush" alone; say active extravasation or contained vascular injury.
Associated injuries to look for
The organ or fracture it arises from; haemodynamic instability.
What changes management
Active extravasation → angioembolisation or surgery now; contained vascular injury → angioembolisation often, timing by stability.
Reference values
Each value carries the caveat that keeps it from being misused. Normal limits and diagnostic criteria are kept apart on purpose: a disease cut-off read as a normal range is the more dangerous mistake.
Diagnostic criteria
Haematoma · Attenuation of acute clotted blood on unenhanced CT
roughly 50–70 HU acutely, falling as the clot ages
Hyperacute unclotted blood and anaemic patients measure lower; active extravasation is diagnosed by contrast, not by HU. Do not use these figures on post-contrast images.
CT
See it on real cases
Direct links to Radiopaedia — the reference article and worked cases with their images. Each opens on Radiopaedia.