Abdominal Ultrasound
Abdominal Ultrasound tests systematic survey technique and the ability to separate true pathology from normal variants in the liver, biliary tree, kidneys, pancreas and aorta. Most items hinge on a measurement plus one supporting sign.
Core rules
- Liver: portal vein walls are echogenic because of fibrous sheaths; hepatic vein walls are thin and anechoic. Portal flow is hepatopetal, hepatic vein flow triphasic toward the IVC.
- Gallbladder: normal wall ≤3 mm, no pericholecystic fluid, negative sonographic Murphy sign. Common duct ≤6 mm, up to 10 mm after cholecystectomy or in the elderly (about 1 mm per decade over 60).
- Kidney: length 9–12 cm; cortex hypoechoic relative to liver or spleen. Grade hydronephrosis by calyceal and pelvic dilation plus cortical thinning.
- Aorta: measure outer-to-outer AP diameter; ≥3 cm is aneurysmal, and 5–5.5 cm prompts urgent surgical referral.
- FAST looks for anechoic free fluid in Morison's pouch, the splenorenal recess and the pelvis.
Worked example
A patient has right upper quadrant pain. The gallbladder wall is 4 mm with pericholecystic fluid and a positive sonographic Murphy sign, and the duct measures 8 mm with no stone seen. This meets the sonographic criteria for acute cholecystitis even without a visualized stone; thickening alone is nonspecific and also occurs with ascites, cirrhosis, hypoalbuminemia and heart failure, so it is the combination that counts. A stone in the neck may be the obstructing culprit; if none is found, acalculous disease is the working diagnosis.
Traps that cost marks
A shadowing structure in the porta hepatis is not automatically a duct stone - it may be a calcified portal structure or a surgical clip. Do not measure the aorta inner-to-inner. Do not diagnose fatty liver from one image; compare hepatorenal echogenicity.