First and second year — the floor first, then every step
Grade the laceration and haematoma by AAST 2018, find the vascular injury across the phases, and trace every laceration to the hepatic veins, the IVC and the porta — the juxtahepatic venous injury is the one that kills.
Orient first
Lacerations follow the vascular planes; the posterior right lobe (segments VI and VII) is the commonest site in blunt trauma.
A laceration reaching the hepatic veins, the retrohepatic IVC or the porta hepatis changes the grade and the surgical approach, so the depth and the direction of every laceration matter more than its length.
Periportal low attenuation (periportal tracking) can be blood or simply fluid from aggressive resuscitation; alone it is not an injury.
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 laceration by Couinaud segment, its depth in cm and length in cm, and whether it reaches the hepatic veins, IVC or porta hepatis.
Subcapsular haematoma (percentage of surface area) and intraparenchymal haematoma (maximal diameter in cm).
Estimate parenchymal disruption as a percentage of the lobe (the threshold between grades IV and V is 75% of a lobe).
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.
Follow the hepatic veins and the retrohepatic IVC on coronal and sagittal reformats: contour irregularity, extravasation, or a laceration that meets them.
Delayed phase: a bile leak (biloma) is low attenuation and does not enhance; hepatobiliary scintigraphy or MRCP later confirms it.
Gallbladder: wall discontinuity, haemorrhage in the lumen, pericholecystic fluid.
What confirms it
A persistent low-attenuation linear or branching defect on the portal venous phase; a vascular lesion defined by its behaviour across phases.
What licenses you to exclude it
Periportal tracking alone does not indicate liver injury.
The classic misread
Calling a beam-hardening streak from ribs or the arm a laceration — it crosses anatomy and ignores vessels.
Calling periportal oedema from fluid resuscitation a liver injury.
Missing a juxtahepatic venous injury by not following the laceration to the IVC on reformats.
Reporting the injury
Classification to use
AAST Organ Injury Scale 2018 (liver). CT criteria: I — subcapsular haematoma < 10% surface area; laceration < 1 cm depth. II — subcapsular haematoma 10–50%; intraparenchymal haematoma < 10 cm; laceration 1–3 cm deep and ≤ 10 cm long. III — subcapsular haematoma > 50% or ruptured; intraparenchymal haematoma > 10 cm; laceration > 3 cm deep; any vascular injury or active bleeding contained within the liver parenchyma. IV — parenchymal disruption of 25–75% of a hepatic lobe; active bleeding extending beyond the liver parenchyma into the peritoneum. V — parenchymal disruption > 75% of a lobe; juxtahepatic venous injury (retrohepatic IVC, central major hepatic veins).
Measurements — and how to take them
Laceration depth (thresholds 1 and 3 cm) and length (threshold 10 cm), in cm.
Subcapsular haematoma as a percentage of surface area (thresholds 10% and 50%).
Parenchymal disruption as a percentage of a lobe (thresholds 25% and 75%).
What to report
Each laceration: segment(s), depth, length, relation to the hepatic veins, IVC and porta hepatis.
Haematoma type and size; parenchymal disruption as a percentage of the lobe.
Vascular injury versus active bleeding, contained or into the peritoneum; haemoperitoneum volume.
Gallbladder injury, biloma; the AAST 2018 grade.
How to report it
CT: "Laceration of segments VII and VIII, 5 cm deep, extending to within 5 mm of the right hepatic vein without venous extravasation. A 7 mm focus of contrast in segment VII that follows the blood pool and does not grow on the delayed phase is in keeping with a contained vascular injury. Moderate haemoperitoneum. AAST 2018 grade III liver injury."
What not to report
Do not report periportal tracking as liver injury.
Do not quote a grade without the vascular assessment across phases.
Associated injuries to look for
Right lower rib fractures, right haemothorax and diaphragm, right renal and adrenal injury, duodenal and pancreatic head injury.
What changes management
Active bleeding into the peritoneum, or contained vascular injury in a patient who is not stable — angioembolisation or surgery.
Juxtahepatic venous injury — the surgical team must know before laparotomy.
Biloma or bile leak on follow-up — drainage or ERCP.
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
Liver (Couinaud) · Couinaud I–VIII — how to localise a lesion
I caudate (between IVC and ligamentum venosum). II/III left lateral, left of the left hepatic vein (II superior, III inferior). IVa/IVb left medial, between middle and left hepatic veins. V/VIII right anterior, between middle and right hepatic veins (V inferior, VIII superior). VI/VII right posterior, right of the right hepatic vein (VI inferior, VII superior). The portal bifurcation is the axial superior/inferior divider. Localise to a segment, not a remembered size
Caudate is I and has its own portal and venous drainage. Do not call a lesion “right lobe” when a segment is knowable.
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.