The FAST exam is generally described as a trauma assessment (hence the acronym). But it is often used as a metanym to mean any assessment of the peritoneum for fluid. In fact when I was a resident folks would often say, “let’s FAST that gallbladder,” or “get the FAST machine so we can put that central line in.” And we didn’t have Twitter.
Anyway, here are a few cases where the “FAST” was used in a non-trauma patient to assess the peritoneum:
Cirrhotic with abdominal pain and tenderness:
who was found to have ascites, and spontaneous bacterial peritonitis
Lower abdominal pain in pregnancy:
who was found to have hemoperitoneum from a ruptured ectopic pregnancy
Diffuse abdominal tenderness in a healthy ten-year-old:
who was found to have idiopathic seromas of the peritoneum, pleura, and pericardium!
Shortness of breath and abdominal distension:
which turned out to be massive abdominal abscesses
Diffuse abdominal tenderness and distension after hysteroscopy:
which was complicated by a bowel perforation; hence fecal material throughout the peritoneum
Take home points:
- Assessment of the peritoneum greatly aids medical and surgical diagnoses
- Fluid appears black (anechoic) on ultrasound. Very difficult to tell what TYPE of fluid by appearance alone
- Your clinical assessment must guide the differential diagnosis for your ultrasound findings
Here’s a quick trick:
When the Transeptic spray bottle won’t spray, it is often because the pump has become disconnected from the plastic tubing within the bottle. Instead of trying to fish it out with forceps, just turn the whole bottle upside-down.
Disinfectant Spray Bottle Troubleshooting from Sinai EM Ultrasound on Vimeo.
I hope this takes away just one small annoyance on your next shift. Unfortunately this will leave room for another, larger annoyance to occupy the space.
Counter-intuitively, when insonating the lungs of healthy patients, we don’t “see” lung tissue. Instead we see and interpret artifacts arising from the pleural lines and the diaphragm. These artifacts change with pulmonary disease processes. In pneumonia, the airway spaces become inspissated with bacterial byproducts and consequently the sonographic appearance of lung tissue changes.
The transformation of lung tissue is termed hepatization: the lung tissue now appears similar to liver tissue.
This can be confusing in the lower lung fields, especially adjacent to the diaphragm because we use the mirror image artifact of the liver and spleen to indicate that lung tissue is normal. This mirrored, artifactual splenic or liver appearance could then be called pseudo-hepatization.
So, how do we differentiate hepatized lung versus pseudo-hepatized lung?
- Never use a single image for your diagnosis, scan through area and convince yourself (then save a representative image or clip for QA).
- Be systematic and scan down from the lung apices to the diaphragm.
- Hunt for the diaphragm and use it as a dividing line between the lung and the abdominal organs.
- Hepatized lung will often have a rim of fluid around it.
Image 1: Normal lung with visible diaphragm
Ultrasound of lung and spleen from Sinai EM Ultrasound on Vimeo.
Image 2: Normal lung with obscured diaphragm
Lung and Spleen Interface on ultrasound from Sinai EM Ultrasound on Vimeo.
Image 3: Hepatized lung at the lower lung field
So we are scanning the left thorax in a patient with shortness of breath, in an effort to assess for pleural effusion. The following video was obtained:
The operator correctly noted the presence of a pleural effusion, and a bit of lung tissue can be seen towards the left side of the screen floating in fluid. In addition, there are THREE shadows evident, each from a different source. Can you spot them?
So let’s take these one at a time, with labels:
Is the easiest one. It extends almost from the first pixel at the top of the screen down to the far field. We can’t even see the characteristic echotexture of skin or subcutaneous tissue in the near field. There’s no contact here between the transducer and skin, possibly due to:
- the probe not touching at all
- clothing or an EKG lead getting in the way
- not enough gel (the novice’s answer to everything but sometimes still true)
The most interesting one of the bunch. Probably two major factors at work here. First, this section of diaphragm is a particularly bright reflector so it can create a shadow behind it due to the sheer amount of reflection occurring. Second, the density difference between the diaphragm and pleural effusion is creating a refraction artifact, often referred to as an edge artifact. Beams of sound which were roughly parallel as they struck this interface get bent at different angles based on whether they hit the dense diaphragm or the less dense fluid. The space in between the formerly tightly spaced beams is displayed as blackness, or the absence of returning echoes.
That’s a rib shadow. Did you know that ribs grow back if you remove them?
This young healthy woman presented in her first trimester of pregnancy with lower abdominal pain and vaginal bleeding. She had diffuse abdominal tenderness and was mildly tachycardic with a normal blood pressure. After IV access was established, labs and blood bank sample were sent, and the following ultrasound of the right upper quadrant was obtained:
So there’s a bit of free fluid in Morison’s pouch. Can we make it more evident for the kids in the back row? The next image was taken with the patient in Trendelenberg position:
That made a pretty big difference.
In this sagittal view of the uterus the bladder is visible to the screen right; there is free fluid in the pelvis just to the left of this, and it can be seen to move with probe pressure on the lower abdomen.
Thus a diagnosis of ruptured ectopic pregnancy was strongly suspected, and the patient underwent emergency laparoscopy with the obstetrics service.
Check out our pelvic ultrasound and FAST tutorials for more details on performing these assessments.
This patient presented with diffuse abdominal pain, tachycardia, and peritonitis on physical examination. A FAST exam was performed to assess for free intraperitoneal fluid, and the following view of was obtained transversely in the pelvis.
First, just look at the still image and make your best guess. Then press play:
Did the large anechoic structure in the near field look like the bladder? Or was it the anechoic area in the far field? The operator was thrown off a bit by the complex echoes within the anterior structure. Remember the bladder is going to conform to the shape of the pelvis as it enlarges, so it will take on a characteristic square/trapezoidal shape in transverse orientation. But for the same reasons free fluid will take the same shape. Through the sweep from cranial to caudal you’ll notice two fluid collections; the anterior one seemed to have much more internal echo and debris. Don’t assume that’s the peritoneal fluid- urine can also look that way.
This was the sample obtained when a Foley catheter was inserted into the bladder:
This definitely looked (and smelled) better sonographically.
Here is the longitudinal (sagittal) view through the pelvis:
As usual, the sagittal view gives a better overview of the anatomy of the pelvis. When using the transverse view of the pelvis, you can miss small amounts of pelvic fluid more easily, confuse fluid collections for the bladder, and make incorrect assumptions. Just more support for the sonographic dogma of imaging everything in two planes.
CT scan confirmed free intraperitoneal fluid but no free air or other signs of bowel perforation. The hemoglobin was stable through several assessments. The patient had an obvious urinary tract infection and renal failure on laboratory evaluation. Thus the fluid was thought to be new onset of ascites in the setting of urosepsis and mult-organ dysfunction.
- Always image anatomy in at least two planes, and fan through anything that isn’t moving.
- Rethink assumptions when the anatomy doesn’t look as it should. For example, an oddly-shaped or highly echoic bladder may not be bladder at all, or it might just be an abnormal bladder.
- ALWAYS clean the machine and put it back where you found it when you are done.
I had to throw that in there, sorry.
Patient with history of hypertension presents periumbilical abdominal pain radiating to the back. Minimal abdominal tenderness, no rebound or guarding, though a pulsatile mass is felt.
The following ultrasound is obtained:
As the title suggests, the patient was diagnosed with an abdominal aortic aneurysm and vascular surgery was consulted.
We’re experimenting a bit with the GMEP.org system. It’s a great educational collaborative run by the folks who brought you Life in the Fast Lane. Worth checking out.
As you may know, we have a Vimeo channel with a growing video archive as well. Our goal is to make this site and its content as helpful and accessible a possible, so please let us know how we can improve!