Biliary Microlithiasis

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Biliary Microlithiasis - Rapid Patient Rotation Protocol

Technical Considerations

The gallbladder was imaged with medical ultrasound equipment by qualified sonographers.  ATL 5000 system (Philips Medical Systems) - C5-2 transducer ACUSON Sequoia™ and Sequoia 2000 (Siemens Medical Solutions) - 4C1 and 6C2 transducers.

Sequential unselected patients fasted and prepped for routine abdominal ultrasound. The voluntary Rapid Patient Rotation Protocol of the gallbladder was added to each exam. Prior to rapid rotation, the patient is held in a stationary position for a variable time or if prone subjected to a slow rocking motion within a limited arc. This may accumulate particles in one location and also facilitate migration of particles into the gallbladder from the cystic duct prior to rotation. Voluntary patient rotation is as rapid as possible to agitate the gallbladder bile causing particles to fall from the dependant wall where they can be observed in suspension “freefalling” within the bile of the gallbladder. The foci appear as discrete, echogenic structures approximately 0.5 to 2mm, which rapidly fall to the dependent gallbladder wall when agitated by rapid patient rotation. They do not shadow and are not seen on the dependent gallbladder wall when the patient is stationary, likely remaining very near or against the wall during slow rotational movements with routine ultrasound.

Detection and imaging of foci requires the transducer probe to be placed on the gallbladder the instant a patient rotation ends.  The gallbladder should fill the image frame using proper gain adjustments to visualize the foci. Cine loop is used to record particles because they disappear very quickly. To mix the particles a rapid rotation of 180 to 270 degrees appears optimal.  Foci visualized initially may migrate into the cystic duct with repeat rotations reducing the number seen.  More than one rotation may be required.

One foci in the right clinical setting is felt to be a diagnostic scan.  Foci can be seen in a few patients asymptomatic of liver, biliary or pancreatic disease.  Foci may associate with or represent a cause of certain clinical disorders different than gallstone disease.