An unidentified woman presumed to be about 35-years-old presented to the ED via EMS after sustaining 3 gunshot wounds at a nightclub. The patient was unresponsive at the scene. En route to the ED the medics were able obtain IV access. The ED was pre-notified of the patient, and 4 units of PRBCs were called for. Trauma surgery was also notified.

Primary survey revealed an unresponsive female with a patent airway, which she was unable to protect. She did have occasional spontaneous respirations. Her extremities were cool with weak pulses.

Rapid sequence intubation was performed without difficulty.

 

Initial VS: BP 112/72, HR 130, Sp02 100% on 50% FiO2

 

Secondary survey revealed 3 separate bullet wounds. The first was at the midline of the cervical spine, inferior to the base of the skull. The second was in the midline of the abdomen, inferior to the umbilicus. The third was on the left lateral anterior chest at the third intercostal space.

Blood was hung on the level 1 infuser, and a FAST exam was performed.

Sliding signs were noted to be absent on the left, however, there no ultrasound clips were saved. The left side of the chest was prepped for a chest tube as the rest of the FAST was performed.

 

Here is a subcostal view of the heart:

 

You can see that the heart appears small, hyperdynamic, and under-filled despite a normal BP initially.

 

Here is the RUQ view:

 

Appreciate the fluid stripe in Morison’s pouch.

 

Here is the LUQ view:

 

There was noted to be a large amount of free fluid surrounding the spleen, but it also looked like there was fluid above the diaphragm, consistent with a hemothorax. This image was obtained before the chest tube had been placed.

 

Here is another view of the LUQ. We wanted to show this view because an extra structure is seen that has confused some of our residents before. See below:

 

What is the extra structure?

 

It’s the stomach with gastric contents seen within.

Screen Shot 2015-05-11 at 3.42.20 PM

 

Here is a pelvic view:

 

There is no anechoic free fluid, however, everything in front of the bladder is clotted blood.

 

The sonographer bounced the transducer on the abdomen while obtaining a view of the pelvis, which makes it more obvious that this is clotted blood. See below:

 

The chest tube was placed, and there was a gush of air, however, there was no bloody output. Why is this? Is the chest tube not in the chest?

Portable CXR was obtained, which showed the chest tube was in the correct location and no sign of hemothorax.

How could the ultrasound be so wrong? Answer: mirror artifact.

 

What is Mirror Artifact?

Mirror artifact occurs when an object is displayed on both sides of a highly reflective object, e.g., the diaphragm in this case. The ultrasound beam is reflected off of the surface of the diaphragm several times, and then the signal returns. Some of the beams may take longer to return because they have to travel along a longer path; recreating the same figure twice. When this happens, one can try repositioning the patient to make the artifact go away.

 

Once stabilized, she was taken for a head CT to see the extent of the head injury before going for an exploratory laparotomy. The HCT revealed stigmata of gunshot wound with entry point in the paramedian left occipital bone, traversing the left hemisphere of the cerebellum, left cerebellar peduncle, the left lateral ventricle, and with a large fragment seen against the inner table of the left frontal bone. There was about 5 mm of midline shift.

The case was quickly discussed with neurosurgery who felt this head injury was non-survivable.

After discussion with both neurosurgery and trauma surgery about prognosis, it was decided not to take the patient for an exploratory laparotomy and to transition to comfort cares. The patient expired within the hour.

 

Bottom Line: Mirror artifact can make free fluid in the abdomen look like there is also a pleural effusion.

 

References:

Hecht C and Manson W. Physics and Image artifacts. Ma and Mateer’s Emergency Ultrasound. 3rd ed. Chicago; McGraw-Hill Education, 2014: 43-44
Hennepin Ultrasound Logo

New Post Notifications

Join our mailing list to receive email notification of new posts!

You have Successfully Subscribed!