RDMS Abdomen flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Couinaud liver segments
- The liver is divided into eight functional segments, each with its own portal venous, hepatic arterial, and biliary branches, while hepatic veins course between the segments.
- Portal triad contents
- The portal triad consists of the main portal vein, proper hepatic artery, and common bile duct, encased in the hepatoduodenal ligament; the portal vein is the largest structure.
- Normal common bile duct diameter
- The normal common bile duct measures up to 6 mm, increases roughly 1 mm per decade after age 60, and may reach 10 mm after cholecystectomy.
- Normal adult kidney length
- Adult kidneys measure 9 to 12 cm in length; the right kidney sits lower than the left because of the liver, and renal cortex is hypoechoic to liver.
- Resistive index formula
- RI equals peak systolic velocity minus end-diastolic velocity, divided by peak systolic velocity; normal renal RI is 0.55 to 0.70, with higher values indicating increased parenchymal resistance.
- Normal portal vein flow
- Portal venous flow is continuous and hepatopetal, meaning toward the liver, gently undulating with respiration and cardiac pulsation, with mean velocity of about 15 to 30 cm per second.
- Hepatic vein waveform
- Hepatic veins show a triphasic pulsatile waveform with A, S, and D waves reflecting right atrial pressure; loss of normal pulsatility suggests hepatic parenchymal disease.
- Normal hepatic artery waveform
- The normal hepatic artery shows a low-resistance spectral waveform with continuous forward diastolic flow and a resistive index of approximately 0.55 to 0.70.
- Simple hepatic cyst criteria
- A simple cyst is anechoic, has a thin smooth wall, shows posterior acoustic enhancement, and lacks internal septations, echoes, or detectable Doppler flow.
- Gallstone sonographic features
- Gallstones appear as echogenic foci with strong posterior acoustic shadowing that move with patient position; sludge is low-level echogenic material that does not shadow.
- Fatty liver sonographic signs
- Hepatic steatosis produces increased liver echogenicity, increased hepatorenal contrast, and poor penetration of deep structures; involvement may be focal or diffuse throughout the liver.
- Hydronephrosis severity grading
- Mild hydronephrosis shows anechoic dilation of the renal pelvis; moderate adds calyceal blunting; severe shows cortical thinning with a bear-paw appearance and parenchymal loss.
- Abdominal aortic aneurysm threshold
- An infrarenal abdominal aorta is aneurysmal when its outer-to-outer anteroposterior diameter exceeds 3 cm; mural thrombus and residual lumen are measured separately.
- Renal artery stenosis criteria
- Renal artery stenosis is suggested by peak systolic velocity above 180 to 200 cm per second, a renal-to-aortic velocity ratio above 3.5, and a post-stenotic tardus-parvus waveform.
- Portal hypertension Doppler signs
- Portal hypertension may show portal vein diameter over 13 mm, mean velocity below 15 cm per second, and hepatofugal or biphasic flow, often with splenomegaly and varices.
- Normal TIPS velocity
- A normally functioning transjugular intrahepatic portosystemic shunt shows flow velocities of roughly 90 to 190 cm per second; velocities below 50 or above 200 suggest dysfunction.
- FAST exam windows
- The FAST exam evaluates four windows: perihepatic at Morison's pouch, perisplenic, pelvic at the pouch of Douglas, and subxiphoid pericardial, looking for free fluid.
- Free fluid on FAST
- Free intraperitoneal fluid appears anechoic and conforms to dependent recesses; acute hemorrhage may be echogenic, and small volumes are best detected in Morison's pouch.
- Most commonly injured solid organ
- In blunt abdominal trauma the spleen is the most frequently injured solid organ, followed by the liver; both are assessed for laceration and subcapsular hematoma.
- Subcapsular hematoma appearance
- A subcapsular hematoma is a lenticular or crescentic fluid collection between the organ capsule and parenchyma that compresses underlying tissue without extending beyond the capsule.
- Post-cholecystectomy CBD caliber
- After cholecystectomy the common bile duct may dilate up to 10 mm without obstruction; greater caliber or focal dilatation warrants evaluation for a retained stone or stricture.
- TIPS stent appearance
- A TIPS stent appears as two parallel echogenic lines within the liver connecting the portal vein to a hepatic vein; patency is confirmed with color and spectral Doppler.
- Renal transplant location
- A transplanted kidney is typically placed extraperitoneally in the iliac fossa, so the native renal fossa appears empty and the graft lies superficial to the iliac vessels.
- Post-surgical fluid collection
- Postoperative collections may be anechoic or complex with septations and debris; ultrasound guides assessment of size, location, and suitability for aspiration or drainage.
- Axial resolution definition
- Axial resolution is the ability to distinguish two reflectors along the beam path and equals half the spatial pulse length; higher frequency shortens the pulse and improves it.
- Posterior acoustic enhancement
- Posterior enhancement is increased echo amplitude behind a fluid-filled structure such as a cyst or gallbladder, because fluid attenuates sound less than surrounding soft tissue.
- Acoustic shadowing cause
- Shadowing is reduced echo amplitude behind strongly reflecting or attenuating structures such as bone, gallstones, or gas, producing a dark band deep to them.
- Aliasing on spectral Doppler
- Aliasing occurs when blood velocity exceeds the Nyquist limit, which is half the pulse repetition frequency, displayed as wrap-around of the spectral waveform; raise the scale or baseline.
- ALARA principle
- ALARA means keeping exposure As Low As Reasonably Achievable by using the lowest output power and shortest scanning time needed to obtain diagnostic information.
- Mechanical index limit
- Mechanical index estimates cavitation risk and should generally remain at or below 1.9 in abdominal imaging, while the thermal index estimates tissue heating.
- Abdominal scan patient preparation
- Patients typically fast for six to eight hours before abdominal ultrasound to distend the gallbladder and reduce bowel gas; renal artery Doppler also requires fasting.
- Endocavitary probe disinfection
- Endocavitary probes contact mucous membranes and are semicritical devices requiring high-level disinfection after each use, whereas surface probes require only low-level disinfection.