Ultrasound Madness Flashcards
Best acoustic mirror in the body
Gas reflects almost 100% sound it hits!
LUNGS common
Trachea
Bowel gas
- Surfaces that reflect more light act as better mirrors
Refraction and it’s results
sound is refracted when it passes obliquely through an interface between 2 substances that transmit sound at different speeds
Results in duplication of structures (eg duplication of upper pole of lt kidney when scanning through spleen and perisplenic fat interface)
Speed propagation artifact.
Displacement of organ borders due to difference in speed of sound between tissue,fat, fluid
Twinkle artifact on Color Doppler
Strong reflectors with rough surface
Eg, stones, calcification
Can help detect kidney stones not visible on grey scale
Types of Modes USS
B-mode: “Brightness,” two-dimensional gray scale image with up to 256 shades of gray
M-mode: “Motion”; displays motion on the vertical axis and time on the horizontal axis
Doppler modes: Use the ultrasound frequency shift to display velocity or direction of movement
Color Doppler detects movement (flow) toward and away from the probe and displays them in different colors, usually blue and red
Power Doppler displays flow without regard to direction and is more sensitive to slower flow
Pulsed-wave Doppler (spectral Doppler): A type of quantitative Doppler that displays the velocity of moving structures (blood cells) on the vertical axis and time on the horizontal axis
Image misinterpretations: fluid pitfalls/pericardium
Free fluid vs :
- fluid in vessels
- fluid in stomach and bowels
Fat pad vs pericardial effusion:
Pericardial fat pad: almost always located anterior to the right ventricle and is not present posterior to the left ventricle.
**Pericardial fat appears as an echo free space mimicking the echocardiographic appearance of pericardial effusions
-fluid tends to collect in the dependent areas, echo free space predominantly in the posterior portion suggests» fluid
Echocardiogram
Views:
Sweep through
Long axis -10 o’clock (right shoulder)
Short axis -2 o’clock (left shoulder)
*rotate 90 degrees to alternate
- subxiphoid
- subxiphoid long axis of IVC
- parasternal (3rd-4th intercostal space)-ideal, over the mitral valve
- apical- 4chamber:10 o’clock
- 2chamber:2 o’clock - suprasternal notch-marker to right nipple and aim to apex> plane of the aortic arch is oblique proximally anterior and distally posterior.
*Lt lateral decubitus improves parasternal and apical views
When looking at vessels USS
Identify vein from artery
Check transverse and longitudinal views
Look for intraluminal thrombus/plaque mural thrombus (circumferential, other), Intimal flap
Abdominal Aorta: <3cm
Iliac arteries: <1.5cm
DO NOT confuse the spine shadow with an AAA or AA with IVC
- AAAs usually rupture into the retroperitoneal space (not the intraperitoneal space), so the actual hemorrhage is not detected with ultrasound.
Gallbladder USS
At mid-clavicular line, under Rt costal margin, cephalad and adjust to find true longitudinal view >rotate 90 for transverse
anterior gallbladder wall >3 mm is abnormal
CBD: internal diameter < than 7 mm is normal
What is the “olive sandwich” sign?
The Hepatic artery (olive) noted between long axis views of CBD and Portal Vein on USS
Normal kidney dimensions on USS
Length:9-13cm
Width-4-6cm
Depth:3-4cm
Cortical thickness >1cm
USS clues to ectopic pregnancy
- Hepatorenal recess fluid > highly suggestive
- complex extra-adnexal cyst/mass: 95% chance (if no IUP)
* an intra-adnexal cyst/mass is more likely to be a corpus luteum - tubal ring sign: 95% chance (echogenic ring surrounding enraptured ectopic)
- extrauterine yolk sac/fetal pole/fetal cardiac activity
- moderate to large free fluid in pelvis 86%likely
- ring of fire sign on coloraturas doppler: high vascularity»_space; ectopic vs corpus lute cyst
- thick echogenic endometrium
ovarian torsion USS
- enlarged (>4cm), asymmetric ovary
- peripheral follicles
- midline ovary position
- ovarian tenderness
- free pelvic fluid
- Doppler findings variable
- whirlpool sign of twisted vascular pedicle
- underlying mass/lesion
what is interstitial ectopic pregnancy?
aka intramural pregnancy
Eccentric implantation of the gestational sac at the superior fundic level of the uterus. In almost all cases, there is myometrial thinning or absent myometrium around portions of the sac
clue: interstitial line sign» consists of visualizing a thin, echogenic line that extends from the central uterine cavity echo to abut the periphery of the interstitial gestational sac
What is heterotropic pregnancy ?
implantation of one or more viable embryos into uterine cavity and also ectopically
Endometrium finding after miscarriage?
normal: <5mm
thickened (retained POC): >10mm
USS uterine measurements:
uterus (L x W x D)
nulliparous: 7-9 x5 x3 cm
parous: 8-11 x 6 x 4cm
post menopausal: <6 x 2 x 2cm
endometrium
after menses 2-4mm
proliferative phase 4-8mm
secretory phase. 8-15mm
post menopause <8mm
USS bladder wall and prostate dimensions
Bladder wall thickness:
distended <3mm
collapsed <5mm
prostate
H: 2-3cm
D: 2-3cm
W: 4-5cm
Testicle normsl dimensions and volume
L: 4-5cm
W: 2-3cm
D: 2-2.5cm
Volume <15-30mls
If gallstone noted at GB neck, what examination can be done to determine wether stone is fixed (obstructive) or mobile?
Roll patient to the right and scan, stone will fall to dependent areas if mobile.
How to detect biliary dilation on USS?
Appears as an extra tube running alongside the intrahepatic portal veins (double-barrel sign) or as an extrahepatic dilated common bile duct.
Focal gallbladder wall thickening with a rounded cystic focus and echogenic reflector with comet-tail artifact. What would this suggest?
Highly specific for adenomyomatosis and is the result of cholesterol crystals within Rokitansky-Aschoff sinuses.
Adenomyomatosis is relatively common and is a hyperplastic cholesterolosis of the gallbladder wall, a benign condition.
* may be associated with gallstones
What is wall-echo-shadow (WES complex)? How is it helpful?
This consists of three arc-shaped lines followed by a shadow.
1st line»_space;echogenic - usually represents pericholecystic fat, the interface between the gallbladder wall and the liver, and the outer surface of the gallbladder wall.
2nd line»_space; hypoechoic - represents the muscular layer of the gallbladder wall.
3rd» echogenic and arises from STONES
- suggests either a large gallstone or multiple small gallstones filling the lumen of a contracted or incompletely visualised gallbladder
- *a useful finding when seen but it is not useful when absent.
When would you see floating Gall bladder stones?
This occurs when the specific gravity of bile is greater than the specific gravity of the stones and
Indicates that stones are»_space;cholesterol in nature.
Describe gallbladder sludge
consists of calcium bilirubinate granules and cholesterol crystals.
-appears as nonshadowing reflectors localizing in the dependent portion» forming a bile-sludge level
- may fill the entire GB lumen
- may form mass-like aggregates: sludge balls or tumefactive (no blood flow) sludge
- Stones may coexist
- can form echogenic bands»_space;confused with sloughed membranes
-may produce Doppler twinkle artifact
**In some cases the crystalline components of the sludge float in the nondependent portion of the GB lumen, producing multiple comet-tail artifacts **don’t confuse with stones
-biliary crystals may cause pancreatitis and this can make the detection of sludge important in patients with pancreatitis of unknown origin
Acute Cholecystitis USS signs
-Gallstones Wall thickening (≥3 mm) -Gallbladder enlargement >4 cm transverse >10 cm longitudinal Pericholecystic fluid -Impacted stone -Sonographic Murphy's sign
USS Signs of Gangrenous Cholecystitis
Pericholecystic fluid Sloughed mucosal membranes Wall disruption Wall ulceration Focal wall bulge
Porcelain Gallbladder
associated with chronic gallbladder inflammation and 95% of the cases have gallstones
USS: with extensive transmural calcification, it will appear as an echogenic arc with dense posterior shadowing
Adenomyomatosis features USS:
Thickened muscular layer
Mucosal herniations:Rokitansky-Aschoff sinuses
Comet tail artifact: cholesterol deposit in sinuses
Hepatic Hemangioma features USS
Most common benign liver neoplasm
Women > Men
- a homogeneous, hyperechoic mass that is usually less than 3cm in size.
- sharp/smooth margins
- round/slightly lobulated
- some> hyperechoic periphery with isoechoic center “reverse-target”
*blood flow is generally too slow to be detected with Doppler techniques.
> >
Focal Nodular Hyperplasia clues on USS
- isoechoic or nearly isoechoic to liver (cellular makeup similar to liver» hepatocytes, Kuppfer cells, biliary structures
- spoke-wheel pattern of internal vascularity is better displayed on color or power Doppler than on CT or MRI.
Biliary Harmatomas
Rare/benign
-consists of abundant fibrocollagenous tissue containing disorganized bile ducts
- typically <5mm
- usually solid, nonshadowing, homogeneous, and either hyperechoic or less commonly hypoechoic
- may produce comet-tail artifacts
** multiplicity and size of these lesions should suggest the diagnosis
Hepatic Target lesions
What is it?
Differentials?
an echogenic or isoechoic center with a hypoechoic halo
- Thin halos»_space; dilated peritumoral sinusoids or compressed liver parenchyma,
- Thick halos» proliferating tumor
DDX:
Common
METASTASES! *usually multiple
Hepatocellular cancer
Uncommon Lymphoma Focal nodular hyperplasia Pyogenic abscess Fungal microabscess Adenoma
**mets can have a variety of appearances
Various USS features of Hepatic Metastasis
Hepatocellular Carcinoma (HCC) features:
-5th most common malignancy worlwide
Features are variable: solitary, multifocal, diffuse and infiltrating (eg hepatic vasculature)
One typical pattern» large dominanting lesion with scattered small satellite lesions
Liver abscess USS features and DDX:
- appear as complex fluid collections with mixed echogenicity, thick walled cystic lesions or as cysts with fluid-fluid levels
- may mimic solid hepatic mass
- presence of through transmission»_space; clue to liquefied nature of mass.
- gas» highly reflective regions with shadowing and ring down artefacts
- may calcify
DDX: hematoma, hemorrhagic cysts, necrotic or hemorrhagic tumor
**fungal abscess: typically not larger than 1cm, target sign
Hepatic steatosis:
- marked discrepancy between hyper echoic liver and less echogenic kidney
- liver more hyper echoic than pancreas (normally pancreas is more echogenic)
- finer echotexture of liver parenchyma (increased concentrations of tiny reflectors (fatty infiltrates))
-can be patchy/geographic
**spared parenchyma usually in front of right portal vein or portal bifurcation or around gallbladder»_space; appears hypo echoic **focal fatty sparing
How common are liver infarcts?
Uncommon due to dual arterial and portal blood supply
Even in setting of total portal vein thrombosis
Usually occur only in advanced underlying vascular disease of liver
Portal venous gas on USS
Small, individual, bright, intraluminal reflectors that move with the portal blood flow are seen on gray scale
** may be confused with pneumobilia, gas-containing abscesses, or calcifications on sonography and is more easily recognized on CT
Bile ducts and surrounding structure anatomy
Dilated intrahepatic ducts suggest Biliary obstruction
What are some features?
Dilated intrahepatic ducts can be distinguished from portal veins by:
- their tortuosity
- wall irregularity,
- presence of increased through transmission
- a stellate configuration centrally
- lack of Doppler signal
- if ducts more than 40% of the diameter of adjacent portal vein,
- peripheral ducts more than 2mm in diameter
- Confusion»_space; in setting of portal hypertension when hepatic arterial flow increases to compensate for decreased portal venous flow
What is Caroli’s disease
multifocal saccular dilatation of the intrahepatic bile ducts with sparing of the extrahepatic ducts
-Central dot sign
Commonly associated with:
- hepatic fibrosis»_space; which leads to portal HTN and variceal bleeding
- cystic kidney disease
Identify Bakers Cyst (popliteal cyst) on USS
well-defined cyst with a ‘neck’ at its deepest extent, extending into the space between the semimembranosus tendon and the medial head of the gastrocnemius
- at posteromedial knee
- looks like a “speech bubble”
-may be simple appearing or contain internal echoes, internal septations, thick irregular walls, nodular synovial proliferation, and loose bodies
