Sludge v. Stones
The preferred mode of identification of gallstones
is ultrasound; stones typically are solid and cast
a shadow on ultrasound.
Some stones are too small to cast a shadow or may represent "sludge" within the gallbladder. When i see this result on ultrasound, it tells me that there may not be stones; therefore, i would only recommend surgery if the rest of the clinical picture was crystal-clear.