Abdomen
Liver and biliary system
The liver is evaluated for size, echotexture, and focal lesions, with the portal vein (echogenic walls), hepatic veins (non-echogenic walls), IVC, and common bile duct identified separately. Normal gallbladder wall is under 3 mm; stones shadow, sludge layers and does not, and polyps are fixed without shadowing. A sonographic Murphy sign supports acute cholecystitis. The normal CBD is up to about 6 mm, increasing roughly 1 mm per decade after age 60. Cirrhosis shows a nodular surface, caudate hypertrophy, and secondary signs of portal hypertension such as splenomegaly and ascites.
Retroperitoneum and urinary tract
Kidneys measure about 9–12 cm with cortex hypoechoic to liver and spleen. Hydronephrosis appears as anechoic separation of the sinus; the renal sinus itself is echogenic fat. The spleen is normally under 13 cm. The abdominal aorta is measured outer wall to outer wall and is aneurysmal above 3 cm.
Pancreas and FAST
The pancreas is scanned through the liver and stomach; the head lies anterior to the IVC. FAST examines Morison's pouch, the splenorenal recess, the pelvis, and the pericardium for free fluid.
Trap: calling renal sinus fat hydronephrosis, or measuring the aorta lumen-to-lumen. Another trap is diagnosing gallstones from sludge.
Rule of thumb: CBD ≤ 6 mm plus 1 mm per decade over 60; aorta > 3 cm = aneurysm.