Abdominal CT: solid organ injuries

Types of trauma

Trauma is a leading cause of death worldwide and it has two broad classifications:

• Blunt trauma: e.g. injuries from motor vehicle accidents, falls, sports, and assaults.
• Penetrating trauma: e.g. gunshot, knife wound, or other objects that pierce the skin and cause internal injury.

Treatment of trauma

Haemodynamically unstable patients with low blood pressure and decreased organ perfusion often proceed directly to the operating room for surgical exploration of injuries without undergoing imaging studies first. However, in many cases, computed tomography (CT) imaging plays a major role in diagnosing and triaging patients who present with acute traumatic injury.

Non-operative management is preferred for many solid organ injuries. It results in similar or better long-term outcomes compared to surgery

Reading a trauma abdominal CT scan

When reading a trauma abdominal CT scan, you should follow the same basic search pattern as for non-traumatic abdominal CT.

1. Look at each organ in context. Look at each major organ but with an emphasis on examining for signs of traumatic injury in the context of the patient’s presentation.
2. Review history. Take some time to review the history and mechanism of trauma.
3. Check for external signs. Check for external signs of injury such as bruising, bleeding, or penetrating injury.
4. Ask the trauma team. Find out if the trauma team has any specific concerns based on their exam.

These points can all be extremely helpful in refining your search pattern, directing your focus to areas of concern, and making appropriate assessments about indeterminate findings.

Describing the location of the abdominal injury

To understand trauma scans, you will need to use new terminology that characterizes abdominal injuries. Let’s take a look at some of this terminology next.

Haemoperitoneum

As you begin your review of a trauma CT, one of the first things that alerts you to the presence of significant injury is blood surrounding an injured organ and spreading throughout the abdomen. Haemoperitoneum is the term for blood in the peritoneal cavity.

In the example featured next, there is a large amount of haemoperitoneum surrounding the liver and spleen. The blood has a density of 35 Hounsfield units (HU), which is much greater than simple fluid.

At first glance, haemoperitoneum might look similar to ascites, but blood will have an increased density, and you may even see denser areas within the blood indicating clot formation. Ascites generally measures less than 20 HU, whereas blood will range in density from 30–70 HU or even higher if there is active bleeding containing contrast.

Extravasation

When the bleeding is brisk, it often looks like bright, swirling jets arising from the area of injury. Active bleeding is also called active extravasation, which describes the fact that contrast-opacified blood is seen leaking from arteries or veins due to injury.

Pelvic blood

Peritoneal blood often accumulates in the pelvis because of its gravity-dependent position. Pelvic blood can be related to pelvic injury or blood from another source in the abdomen. Below you see dense blood in the pelvis related to vascular injury of the mesentery.

Retroperitoneal blood

There can also be retroperitoneal blood in the space behind the peritoneum, often related to a renal or adrenal injury. In the next example, there is blood surrounding the kidney related to renal injury and haemorrhage. The density here is 45 HU.

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Describing the progression of the injury

Whenever you find blood, all organs and vasculature must be carefully evaluated to identify the source of the bleeding and to direct the trauma team’s management. When describing injury to the solid organs, there is a range of progressive injuries including the following:

• Haematoma: accumulation of blood under the organ capsule
• Contusion: haematoma or bruising of the organ tissue
• Laceration: a cut in the organ tissue of varying thickness and depth
• Active bleeding: contrast-mixed bleeding from an injury
• Devascularization: the traumatic disruption of the organ’s blood supply

On CT imaging, haematoma are relatively vague areas of decreased enhancement, whereas lacerations are linear cut-like areas through the tissue.

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References

• Top 100 CT scan quiz. LITFL

Radiology Library: Abdominal Trauma. Solid organ injury

• Hartung MP. Abdominal Trauma: solid organ injuries
• Hartung MP. Abdominal Trauma: spleen, liver, and pancreas injury
• Hartung MP. Abdominal Trauma: renal, ureter, and adrenal injury
• Hartung MP. Abdominal Trauma: solid organ injury [case study]

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