While performing kidney ultrasound, we frequently visualize gall bladder (from the right lateral scan plane) and its good to be aware of some incidental findings. We previously discussed the differential diagnosis of thickened gall bladder wall. In this post, lets talk about some luminal findings.

Below is an image of solitary gall stone. The appearance is similar to that of a kidney stone – bright structure followed by an acoustic shadow. However, twinkle artifact is less common with gall stones as opposed to renal stones likely due to differences in composition. Of note, gall stones typically move with change in patient’s position (rolling stones!).

Following image demonstrates a case of multiple gall stones obtained from an asymptomatic nephrology clinic patient. They appear like a bunch of grapes with prominent shadowing.

Next scenario is gall bladder polyp. Polyps are isoechoic (to liver) or slightly hyperechoic structures growing into the lumen from gall bladder wall. They typically are immobile and do not cast a shadow.  Here is an example of a tiny polyp – image obtained using a handheld ultrasound device.

Next is gall bladder sludge, which is a very common incidental finding, especially in critically ill patients. It appears as a homogeneous isoechoic or hypoechoic material and moves slowly with change in patient’s position. One can clearly see the distinction between the particulate sludge and anechoic bile.

In general, sludge is easily identifiable even if its not possible to change patient’s position except when it is localized, thick and gives a little bit of shadowing. Below image demonstrates a solid filling inside the gall bladder that appears like a soft tissue/mass. We obtained this image from a patient with cirrhosis, and the material did not move with patient’s position. This is called tumefactive sludge (tumor-like). Tumefactive sludge is composed of a suspension of cholesterol monohydrate crystals or calcium bilirubinate granules embedded in mucus. In general, a mass has some internal flow on Doppler while sludge doesn’t though this is not always reliable. If you suspect tumefactive sludge, do not ignore and inform the patient’s primary care physician (or consulting team) because a considerable proportion of these patients can have malignancy; follow up exam is recommended in 2-4 weeks.

In the above case, radiologist reviewed CT scan/ formal ultrasound images and opined that it is more consistent with sludge. Below images demonstrate another case of tumefactive sludge. Interestingly, radiology-performed scan 2 weeks later reported normal gall bladder (= sludge disappeared; no tumor).