You have now learned how to answer the focused questions in focused ultrasonography of the abdomen relevant in emergency medicine.

Free fluid is seen as anechoic (black) areas in locations where fluid is not normally found.

Free fluid often collects in specific locations in the abdomen – these include:

Perihepatic:

The original Focused Assessment with Sonography for Trauma (FAST) and the extended eFAST protocols were developed for assessment of trauma patients.

These address two concerns – pneumothorax and internal bleeding in the thorax or abdomen.

In Essential Emergency Ultrasonography we move away from the protocols towards a focused questions approach.

Ask a clinical question and answer it with all you have got – including the transducer.

We do recognise, however, that in the multi-trauma patient, the following questions your transducer can help you with are: does the patient have 1) a pneumothorax? 2) a hemothorax? 3) a hemopericardium? 4) an intraabdominal bleeding?

No. 1, 2 and 3 are covered by the previous lessons. In the following we only address no. 4 by answering the question “Is intraperitoneal free fluid visible?”

Obtain the perihepatic view.

Look for free fluid between the diaphragm and the liver (subdiaphragmatic) – remember the sweep of the transducer from anterior to posterior position to evaluate the entire area of the hepato-diaphragmal area.

Look for free fluid between the liver and the kidney (Morison’s pouch) – – remember the sweep of the transducer from anterior to posterior position to evaluate the entire area of the hepato-renal recess.

Move the probe anteriorly and caudally to look for free fluid at the anterior tip of the liver and sweep again.

Intraperitoneal fluid appears as a black anechoic (black) area.

A maximum abdominal aortic diameter of <3.5 cm makes rupture very unlikely.

In a patient with the relevant symptoms and an abdominal aortic diameter >3.5 cm, a ruptured abdominal aortic aneurism is possible.

Most ruptures (90%) do however occur at maximum abdominal aortic diameters >5 cm.

Other findings supporting a clinical suspicion of ruptured abdominal aneurism:
– Free intraperitoneal fluid on focused ultrasonography of the abdomen (this is covered later in this lesson).

Rupture into the peritoneum is only seen in 20% of patients with rupture – rupture into the retroperitoneum is much more frequent (>75% of cases), but is difficult to asses using ultrasonography.

Always find the largest diameter.

When measuring the abdominal aortic, the largest diameter should be found.

An intramural thrombus is often seen with abdominal aortic aneurisms.

Thus, it is essential to measure the entire aorta – from outer edge to outer edge.

Tips
When a mural thrombus is present, the lumen of the aorta is narrowed (and is most often irregular and not circular) – remember to measure the entire aorta not just the lumen.

Intraperitoneal fluid does not only accumulate in the rectouterine pouch.

In women ultrasonographic signs of fluid can be found in the rectouterine pouch, between the uterus and the bladder (vesicouterine pouch) or surrounding the intestines.

Notice the peritoneum (red line) as its anatomical location is important for understanding where to look for intraperitoneal fluid while scanning.

The pelvic view is one of the most difficult to interpret as a novice.

This is because of a lot of shadowing and disturbance from the surrounding structures e.g. bowel and bony structures of the pelvis.

In the image below this is especially seen as the dark areas of bony shadowing on each of the sides of the male bladder in the male pelvic view.

These areas should not be confused with intraperitoneal fluid.

Intraperitoneal fluid does not only gather in the rectovesical pouch.

In men it can be seen either in the rectovesical pouch or surrounding the the intestines, or both.

Notice the peritoneum marked as a red line as its anatomy is important for understanding where to look for intraperitoneal fluid while scanning