First and second year — the floor first, then every step
Grade the laceration and haematoma by AAST 2018 on the portal venous phase, then decide from the arterial and delayed phases whether there is a vascular injury or active bleeding — that is what moves the grade to IV or V and the patient to angiography.
Orient first
The normal spleen enhances heterogeneously ("zebra" or moiré pattern) in the arterial phase. That pattern is not injury; judge the parenchyma on the PORTAL VENOUS phase, when it should be uniform.
The 2018 AAST revision added vascular injury to the CT grade: a pseudoaneurysm or AV fistula is grade IV; active bleeding beyond the spleen into the peritoneum is grade V.
Delayed splenic rupture happens: a subcapsular haematoma or a contained vascular injury can bleed days later.
Acquire the study
Trauma CT with an ARTERIAL phase (or a split-bolus single acquisition) and a PORTAL VENOUS phase; add a DELAYED phase (about 5–10 min) whenever there is solid organ injury or free fluid of uncertain source — it separates active bleeding from a contained vascular injury and shows urine leaks.
Thin slices with CORONAL and SAGITTAL reformats; read the arterial and portal venous phases side by side.
The manoeuvre
Portal venous phase: map each low-attenuation linear or branching defect (laceration) — its depth from the capsule in cm and whether it reaches the hilum.
Subcapsular haematoma: a crescent flattening or indenting the spleen — estimate the percentage of surface area involved.
Intraparenchymal haematoma: an ovoid collection — measure its maximal diameter in cm.
Compare every focus of contrast outside the normal vessels across phases: ACTIVE EXTRAVASATION grows and changes shape from arterial to portal venous to delayed; a PSEUDOANEURYSM or arteriovenous fistula is a well-defined focus that follows the blood pool and washes out without growing.
Measure attenuation of free fluid: simple fluid about 0–20 HU, unclotted blood about 30–45 HU, clotted blood (the sentinel clot) about 45–70 HU — the highest-attenuation clot sits next to the injured organ.
Look for devascularisation: a wedge or the whole spleen not enhancing on the portal venous phase (segmental or hilar vascular injury).
Haemoperitoneum: perisplenic, left paracolic gutter and pelvis; note the sentinel clot beside the spleen.
What confirms it
A laceration or haematoma persisting on the portal venous phase; a vascular lesion defined by its behaviour across phases.
What licenses you to exclude it
An arterial-phase-only reading cannot exclude parenchymal injury (the normal heterogeneous enhancement hides it).
A normal CT does not exclude delayed rupture of a missed small injury; with a strong mechanism and left upper quadrant pain, clinical observation continues.
The classic misread
Calling arterial-phase heterogeneous enhancement a laceration.
Calling a splenic cleft (smooth, rounded, with a thin capsule line, no perisplenic blood) a laceration.
Missing a pseudoaneurysm because only the portal venous phase was read.
Reporting the injury
Classification to use
AAST Organ Injury Scale 2018 (spleen). CT criteria: I — subcapsular haematoma < 10% surface area; laceration < 1 cm depth. II — subcapsular haematoma 10–50%; intraparenchymal haematoma < 5 cm; laceration 1–3 cm. III — subcapsular haematoma > 50% or ruptured; intraparenchymal haematoma ≥ 5 cm; laceration > 3 cm. IV — any vascular injury or active bleeding confined within the splenic capsule; laceration involving segmental or hilar vessels producing > 25% devascularisation. V — any vascular injury with active bleeding extending beyond the spleen into the peritoneum; shattered spleen.
Advance one grade for multiple injuries up to grade III (per the scale). State that the 2018 revision was used.
Measurements — and how to take them
Laceration depth from the capsule, in cm (thresholds 1 and 3 cm).
Intraparenchymal haematoma maximal diameter, in cm (threshold 5 cm).
Subcapsular haematoma as an estimated percentage of the surface area (thresholds 10% and 50%).
Devascularised parenchyma as an estimated percentage (threshold 25%).
Pseudoaneurysm diameter in mm.
What to report
Laceration depth and location, haematoma type and size, the percentage of devascularised parenchyma.
Vascular injury: pseudoaneurysm / AV fistula versus active extravasation, and whether bleeding is contained within the capsule or into the peritoneum.
Volume and distribution of haemoperitoneum.
The AAST 2018 grade.
How to report it
CT: "Splenic laceration 4 cm deep extending to the hilum with a 6 mm pseudoaneurysm in the lower pole that does not grow on the delayed phase. Moderate perisplenic and pelvic haemoperitoneum. AAST 2018 grade IV splenic injury."
CT: "Active contrast extravasation from the splenic hilum growing on the portal venous and delayed phases into the left paracolic gutter — AAST 2018 grade V."
What not to report
Do not report arterial-phase splenic heterogeneity as injury.
Do not call a focus "extravasation" when it does not change between phases — that is a contained vascular injury, a different grade and a different decision.
Do not give a grade from the 1994 scale without saying so.
Associated injuries to look for
Left lower (9–11) rib fractures, left renal injury, pancreatic tail injury, left hemidiaphragm rupture.
What changes management
Any vascular injury (grade IV) — angioembolisation is usually considered in the stable patient.
Active bleeding into the peritoneum (grade V) or haemodynamic instability — theatre or emergency angiography.
Grades I–III without vascular injury in a stable patient — non-operative management is usual.
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.
Normal limits
Spleen (cleft) · Splenic cleft versus laceration
a smooth, corticated congenital cleft, usually along the superior or inferior margin; a lacerated spleen has irregular, non-corticated, often peri-splenic-haemorrhage-associated defects (AAST grade is the trauma conversation)
Axial and coronal CT/MRI (or US): a congenital cleft is a smooth, corticated notch; a laceration is irregular, non-corticated and usually accompanied by perisplenic blood — morphology, not a ratio.
A cleft does not have adjacent haematoma. Name AAST only for trauma.
report the organ, laceration depth / subcapsular extent, and ANY vascular injury (active extravasation, pseudoaneurysm, AVF, or hilar disruption). Modern AAST grades upgrade on vascular injury — a blush is not “grade III because someone remembered 3 cm”. Read the current organ table; do not invent an edition year
A blush is a vascular injury, not a “grade III because I remembered 3 cm”. Name the organ and the edition. Versioned criterion — verify against the current edition before clinical use.
CT
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.