Are all gallstones visible on CT?
No. Only radiodense gall stones are seen on CT. Ultrasound is more sensitive and specific for stone detection, especially in the hands of an experienced user.
In all cases of gallstones, what else should we look for?
Apart from inflammation of the gallbladder (cholecystitis), always looks out for stones that drop down into cystic duct and/or common bile duct and could cause secondary upstream biliary tract dilatation.
Diffusely thickened gallbladder wall with mild pericholecystic free fluid. Submucosal hyperenhancement. Multiple approximately 3 mm sized calcified calculi seen. A larger rounded calculus with peripheral egg shell calcification is seen in the neck of gall bladder. A thickened fold is seen in the fundal region. There is secondary altered perfusion in segment IV of liver with areas of suspicious subsegmental filling defects in portal venous branches - possibly chronic portal venous thrombosis.