POCUS - Abdominal Flashcards
According to a 2005 meta-analysis, what is the sensitivity and specificity of eFAST for hemoperitoneum?
Sens: 79%
Spec: 99.2%
Why is eFAST not perfectly sensitive for hemoperitoneum?
A couple of reasons:
- Adhesions could cause trapping of blood in non-FAST views
- There are anatomic gutters that blood can accumulate in that are not seen on FAST
- Position of patient can cause false negatives
FAST will miss hemoperitoneum below what threshold of bleeding?
Thought to be 250 mL
It’s important to note that FAST will miss what type of abdominal trauma?
Solid-organ injury without hemoperitoneum
Describe the usual path of bleeding in the peritoneum.
- Bleeding from the spleen typically collects in the sub-phrenic space. Overflow will go down along the transverse colon to the liver (because of the ligament at the splenic flexure).
- Bleeding from the liver will collect in Morrison’s pouch and usually go down the ascending colon to the pelvis.
- Bleeding from the pelvis will typically stay in the pelvis. If there is overflow it will go first to the liver.
True or false: blood on FAST will always be anechoic.
False
It can be mildly echogenic.
About _____% of patients with cholecystitis have stones in the CBD.
15
Because of this, the decision to operate in cholecystitis should only be done after the CBD is assessed.
The gallbladder is normally ___ cm long.
7
The common bile duct is made by the fusion of the cystic duct with the _______________ duct.
common hepatic
To begin the sagittal view of the gallbladder, place the probe ______________.
in the mid-clavicular line, just below the costal margin, with the probe indicator pointed to the patient’s R shoulder
From there, you may need to fan and slide to find the gallbladder.
The gallbladder lies _________ and _________ to the R kidney.
anterior; medial
The _____________ is a landmark that connects the portal vein to the gallbladder. It can be used to help identify the gallbladder.
main lobar fissure
It is typically seen in the sagittal (longitudinal) view of the gallbladder.
The ideal patient position for finding the gallbladder is ____________.
supine (deep inspiration can help) and tilted slightly to the left
If you see stones in the gallbladder neck, you must _________________.
repeat the views with the patient in a different position (so that you can see if it is stuck)
There are three things to consider when you can’t find the gallbladder. What are they?
- Surgical absence (look for surgical clips)
- Contracted to the point of not being recognizable
- Full of stones (and thus looking like bowel artifact)
True or false: the transverse gallbladder view should be taken from the R side.
False
It can be done that way if that is the only obtainable view, but it is preferably done from the anterior aspect.
The hepatorenal space has what eponym?
Morrison’s pouch
The haustra on small bowel are called ___________.
plicae circularis
In pediatric patients, list the most frequent places blood will collect.
1) RUQ
2) Pelvis
3) Dome of the spleen
The most sensitive area for detection of free fluid in the abdomen is _______________.
the caudal tip of the liver
What are the sensitivity and specificity of the FAST exam for intraabdominal bleeding?
- Sensitivity: 66%
- Specificity: 95%
What’s the minimum amount of fluid needed for a FAST to be positive?
200 mL
Where does fluid first collect in the LUQ?
Between the spleen and diaphragm
What studies should you obtain in the gallbladder US?
- Long axis showing neck
- Short axis
- Anterior wall thickness
- CBD (w/ color if uncertain)
- Gallbladder length
The CBD is right on top of the _______________.
portal vein
True or false: the CBD has hyperechoic borders and appears bright white on both sides.
False
The portal vein appears this way.
Always look in the ___________ in the gallbladder US.
neck
Be sure to look for shadowing that may indicate a stone.
The portal vein is ___________ to the hepatic artery and CBD.
deep/posterior
This is why the CBD is “on top” of the portal vein from the transverse view.
The CBD is usually ____________ to the hepatic artery.
lateral
How many lung views do you need in an eFAST?
6 total (3 each side)
Where do you put the probe in the perihepatic view of the FAST exam?
Mid axillary line in the 8th-11th intercostal spaces with the probe marker pointed to the patient’s head
__________ capsule surrounds the liver.
Glisson’s
When doing a search for bleeding (such as the FAST) beware of ___________ that will not appear anechoic.
clotted blood
It’s rare to develop pyloric stenosis after what age?
12 weeks
True or false: use the curvilinear probe to identify pyloric stenosis.
False
Use the linear
US is actually more sensitive than ____________ in detecting pneumoperitoneum.
plain radiographs
One study showed that US can detect as little as 1 mL of air.
What locations (and patient positions!) are best for detecting free air in the abdomen?
- RUQ, curvilinear probe, patient in left-lateral decubitus position looking for air above the dome of the liver: 83%
- Epigastric area, curvilinear probe, patient supine: 81%
What should you look for in detecting pneumoperitoneum?
A lines that do not vary with respiration with distortion behind the A lines (that is, distortion where there should not be distortion such as over the liver)
What might appear like pneumoperitoneum over the RUQ?
Subcutaneous air from a PTX
Look for the peritoneal stripe. If the air signal arises from above that then it is no intraperitoneal.
What is Chalaiditi’s anomaly?
Bowel that is interposed between the liver and the diaphragm
This is important in US because it can look like pneumoperitoneum over the RUQ.
You can see ________________ in those with ascites who develop pneumoperitoneum.
bubbles in the ascites
How does ring down artifact differ in appearance from comet tail artifact?
Both appear as bright columns, but comet tail decreases in intensity the farther it gets from the probe, whereas ring down stays as a uniformly bright band.
How does emphysematous cholecystitis appear on US?
A bright white, irregular wall with ring down artifact
How does pneumobilia present?
Look for bright white streaks in the liver. These are bubbles that deflect US waves.
What things can cause portal venous gas?
NEC Umbilical vein catheterization in neonates Ischemic bowel Perforated ulcer Invasive colorectal cancer Intrasbdominal infection (appendicitis, cholecystitis, diverticulitis) Barotrauma Steroid use Post op
Compared to pneumobilia, portal venous gas will appear _____________.
more peripherally and generally smaller (like a more speckly appearance rather than large bubbles)
Otherwise, both pneumobilia and portal venous gas look like bright white bubbles in the liver with posterior ring downing.
What can appear like pneumobilia or portal venous gas?
Hepatic calcifications
What is the normal length and width of a gallbladder?
Width less than 4 cm
Length less than 8 cm (Dr. Jones says 10 cm)
What is the age-adjusted CBD diameter?
6 mm plus 1 mm for each decade of life after 60
True or false: the dot of the exclamation mark is the CBD.
False
The dot is the portal vein. The CBD will be on top of the dot.
When you find the Mickey Mouse sign of the hepatic triad, the hepatic artery is usually Mickey’s _________ ear.
L (right on the screen)
If you see a stone in the gallbladder neck, be sure to have _______________.
the patient move to R-lateral decubitus and see if the stone is mobile
What is the WES sign?
Wall echo shadow
This is when the gallbladder is so full of stones that it appears as an irregular hyperechoic line with a shadow behind it.
What are the signs of appendicitis?
- Dilated (outer wall to outer wall greater than 6 mm)
- Fluid surrounding the appendix
- Appendicolith
- Hyperemia on color flow
- Hyperechoic fat surrounding it
When scanning for the appendix, start ____________.
where it hurts
The appendix is normally anterior to the _____________.
R psoas muscle
What do you need to scan for an SBO study?
- Bowel loop diameter (greater than 2.5 cm is abnormal)
- Bowel wall thickness (greater than 4 mm)
- Clip showing no peristalsis or to-and-fro peristalsis
What is the Tanga sign?
The Tanga sign comes from a type of underwear. It shows up in a patient with severe SBO as a bikini-shaped anechoic area next to obstructed bowel.
What do you need for an intussusception study?
Two scans per quadrant (one up and down, one side to side)
True or false: the perihepatic window done in the eFAST exam is ideally supposed to be subcostal.
False
It should be intercostal and done between the 8th and 11th ribs.
What is one way to tell if an anechoic area in Morrison’s pouch is gallbladder (as opposed to blood)?
Gallbladders have a hyperechoic border while blood does not.
What hyperechoic structure may be in the hepatorenal space?
Perinephric fat
Bleeding seen on US in the hepatorenal space will usually be between what two tissue planes?
Glissson’s capsule (around the liver) and Gerota’s fascia (tissue around the perinephric fat)
Bleeding beneath Gerota’s fascia is a sign of retroperitoneal bleed.
How will liver hematoma appear?
As a hyperechoic area within the liver
Review the technical landmarks for the perisplenic window.
L posterior axillary line between the 8th and 11th ribs in a coronal view tilted slightly obliquely
Because the spleen is so much smaller than the liver, you need to angle your probe _____________ to obtain the splenorenal fossa.
posteriorly (toward the spine)
If you angle too anteriorly in the splenic window, you will see the ______________.
stomach (this can look like hemothorax or blood in the splenorenal fossa)
Subcapsular hematomas of the spleen appear ___________.
as hypo- or hyperechoic collections contained within a capsule on the spleen
What might appear like a perisplenic fluid collection but is not?
Liver
If someone has hepatomegaly, their liver may touch the spleen and appear like a subcapsular hematoma. You can use color flow to determine if it is the liver (which will have pulsating vessels) or a hematoma (which will not).
The spleen and liver should always appear ____________.
homogeneous
If you notice areas that appear hyperechoic then you should be concerned for parenchymal injury.
In a male patient, pelvic bleeding usually shows up ___________ to the prostate and seminal vesicles.
superior
If you don’t know if an anechoic structure is free fluid or a contained cavity like the bladder, lumen of bowel, or a cyst, then check for what features at the borders?
- A luminal wall
- The shape of the fluid: rounded edges are likely a lumen; triangular edges are likely free fluid
A gallbladder tip that is folded onto itself is called a ____________.
Phrygian cap
How can you tell the difference between a septation and a Phrygian cap?
Phrygian cap will cause change in the outer contour of the GB wall.
A gallbladder fold near the neck is called what?
A junctional fold
Gallbladder sludge is isoechoic to what?
The liver
What features of a gallbladder polyp make it high risk for malignancy?
Size greater than 6 mm in a person older than 50 years
Diffuse gallbladder wall thickening can be due to what non-biliary causes?
- Cirrhosis
- Edema
- Adenomyomatosis (think this if irregularity is present)
The CBD should be measured how?
Inner wall to inner wall
In what patients is a CBD of 1 cm normal?
Post-cholecystectomy
What percent of people with symptomatic cholelithiasis or cholecystitis have CBD stones?
18%
Review Jacob Avila’s approach to GB.
He uses the intercostal view. Hee advises starting at the level of the xiphoid and then fanning transverse 7 cm.
If this doesn’t work, then try the subcostal or transhepatic windows. Held inspiration and LLD positioning can help.
The appendix is usually bound by what borders?
Lateral: iliac crest
Medial: internal iliac artery
Posterior: psoas muscle
Much of the time, the appendix is directly anterior to ___________.
the iliac artery
The major criteria for diagnosing appendicitis are ____________.
non-compressible and > 6 mm (3 + 3 is normal)
True or false: the cutoff for SBO intestine width is 3 cm.
False
2.5 cm
Free fluid around an SBO is the ___________ sign.
Tanga
The most high-yield area for SBO scanning is the ______________.
lateral lower quadrants (dependent areas where fluid is likely to be)
Describe the EPSS of the bowel.
It essentially looks like the A lines of the lungs. Normally, the peritoneal stripe should be vague and irregular. If it looks like a clean, linear, bright white stripe then it is concerning for pneumoperitoneum.
Robert Jones advises that you use the ____________ technique for scanning for SBO.
lawnmover (scanning up and down across the whole abdomen)
Review the five signs of SBO.
Dilated small intestine (> 2.5 mm)
Peritoneal free fluid (Tanga sign)
Decreased peristalsis or to-and-fro peristalsis
Bowel wall edema (>4 mm)
Transition point
True or false: US has nearly 100% sensitivity and specificity for intussusception.
True
Intussusception has what two signs?
Pseudokidney (long axis)
Target sign (short axis)
What ultrasound finding is a contraindication to air enema?
Large volume free fluid in the peritoneum (concerning for perforation)
How does inflammatory fat appear on US?
Hyperechoic (sometimes seen around the appendix)
Where does portal gas accumulate? Where does biliary gas occur?
Portal = Peripheral
Bile = central
