Case m -  Splenic Hematoma and approach to abdominal trauma

There is high density fluid around the spleen, liver, and stomach consistent with hemoperitoneum.  There is a liner area of low attenuation bisecting the spleen indicating a splenic laceration.   Some of the surrounding hemorrhage appears constrained by the splenic capsule.  The underlying spleen looks compressed by the hematoma, confirming the subcapsular location. The remainder of the spleen enhances normally.  The liver and kidneys enhance normally.  The pancreas, duodenum, and mesentery appear normal. 

This patient has a splenic laceration, a subcapsular splenic hematoma, and generalized hemoperitoneum.  There is no extravascular high density contrast to suggest active arterial bleeding.  This injury was treated conservatively and one month later the hemoperitoneum had resolved and the subcapsular hematoma was smaller (1 and 2).  Notice that there is no longer hemorrhage around the stomach or liver.  On both these images  (1 and 2) you can clearly see that the hematoma is constrained by the splenic capsule which is seen as a thin white line.  Also, you can clearly see that the lateral margin of the spleen is compressed.  Two good indicators of  subcapsular hemorrhage are smooth contours to the collection which parallel he expected contour of the organ and displacement of the periphery of the organ by the hematoma.

Hyper-acute hemorrhage has the same density as blood in the vessels, HU of about 40.  As the blood clots the serum gets displaced and the clot becomes more hyperdense.  As the clot becomes resorbs days to weeks later, the hemorrhage becomes low attenuation (<20 HU).  Chronic hematoma's can have a complex appearance and can even have enhancing septations.

Notice that although there is high density fluid around the liver, spleen, and within the pelvis, the brightest fluid is adjacent to the spleen.  This is called the sentinel clot sign.  The brightest hemorrhage is seen adjacent to the organ which is injured; in this case the spleen.  This sign is not 100% accurate.  It is more useful for directing the surgeons attention.  If they perform an exploratory laparotomy they will evaluate the entire abdomen. 

Approach to abdominal trauma

I enjoy reading trauma CT's because it is an an opportunity to be of immediate help in the care of a critically ill patient.  Several trauma algorithms place high importance on the results of the trauma CT scan.  Where I went to medical school blunt abdominal trauma went to the OR if the patient was unstable or if the CT showed any evidence of intra-abdominal fluid or blood.  Some institutions use bedside ultrasound to evaluate for intra-abdominal fluid so patients can be triaged more rapidly.  Some surgical teams in our own hospital perform a deep peritoneal lavage whereby a trochar is placed into the abdomen and lavage with saline is performed. If there is blood in the abdomen than the patient may go to the OR.

You are not likely to miss injury to the solid intra-abdominal organs.  Fractures and lacerations of the solid organs look like focal, linear, low attenuation areas in an otherwise normally enhancing organ.  Contusions look like rounded areas of low attenuation.  A shattered organ is uniformly hypoattenuating and irregular from all the fracture lines and contusions. The liver, spleen, and kidneys, are thus straightforward to evaluate.  There are official trauma grading scores for each of these organs which are based on the size and extent of the fracture/contusion.  Some surgeons will want to know the Trauma Grade and it is important only to know where you can find the appropriate scale.  For example, in our ED this grading scale is pinned on a bulletin board next to the PACS station for easy reference.  There is no need to memorize them.  Many studies have shown that management and outcome does not correspond to the grade of the injury.

Because it is easy to be distracted by the large organs, there are are several important things to do when looking at the trauma CT.  These are discussed briefly here and examples are provided in subsequent cases.

• Look for intra-abdominal fluid or blood.  Hemorrhage in the abdomen is usually high density (HU > 40), but any fluid in the abdomen following trauma should be called hemoperitoneum except in patients with known ascites or cirrhosis, recent surgery, or recent deep peritoneal lavage.  Menstruating women may also have a trace amount of low density pelvic fluid. I n this case, there is hemorrhage in the pelvis.  The pelvic fluid is high density and is more than the normal physiologic amount.  Also, this patient is post menopausal. In many institutions hemoperitoneum alone is justification for an exploratory laparotomy. Even if you miss the real injury, finding the fluid raises suspicion for a subtle or injury and keeps the patient in a monitored environment.
• Look for evidence of active arterial bleeding.  Active bleeding will look like a region of enhancement (as bright as the artery) surrounded by hematoma.  On delayed images the extravasated contrast will diffuse into the hematoma. View the schematic.  Active arterial bleeding implies that an end-organ is at risk for ischemia/necrosis and is also a sign of impending hemodynamic collapse.  You can readily bleed all 5 liters of your blood into your pelvis.  Active arterial bleeding should prompt an angiogram or surgical exploration and is a much stronger predictor of management than the Trauma Grades mentioned above.
• Specifically look in places where injuries can be subtle.  Places where it is easy to miss an injury are in the retroperitoneal duodenum, the pancreas, in the mesentery, and in the bowel.  Stranding in the root of the mesentery indicates injury and is associated with bowel ischemia/necrosis/perforation.  Use lung windows to look for free intra-abdominal air as a result of penetrating injury or bowel rupture.
• Be present when the trauma scan is performed and take a quick look at the images.  If you see any gross abnormality then get a delayed scan.  The delayed images are useful for evaluating arterial bleeding.  They allow identification of injury to the renal collecting system by showing extravasation of contrast near the renal hilum.  Lastly, delayed scans are useful for proving that areas of abnormal enhancement within the liver or spleen are lesions such as tumor, hemangioma or FNH and not acute trauma.
• Scrutinize the spine for small fractures.  The trauma abdomen and pelvis CT is not a substitute for dedicated spine images (with a smaller FOV and increased spatial resolution) and if there is concern for a spine fracture then axial and coronal images should be obtained.  However, identifying small but stable transverse process and rib fractures will explain persistent back pain and can prevent further imaging  the next day.

Key points:

• Surgeons need to know if there are solid organ injuries.
• Surgeons need to know if there is active bleeding.
• Surgeons need to know about secondary signs of injury such as hemoperitoneum, mesenteric stranding, or extraluminal air.
• Organ fractures look like low attenuation lines through an otherwise normally enhancing organ.
• Get 2-3 minute delayed imaging for any gross abnormality.