The value of sonography in the assessment of cholecystolithotripsy

To assess the reliability of ultrasound in measuring a minimum stone fragment burden we implanted radiolucent human gallstone fragments measuring from less than 1 mm up to 4 mm in size into the gallbladders of 12 domestic piglets. Forty-eight hours later the fragments in each animal were assessed by a qualified radiologist using two different ultrasound machines in a randomized blinded fashion. With regard to size estimation using a 5 MHz sector scanner, in two out of 12 examinations there was an overestimation of fragment size such that in a clinical setting an unneccessary repeat lithotripsy session would have been requested. A 5 MHz linear array transducer was of sufficient reliability in all size estimations not to have resulted in such a request. No gallbladder was falsely declared fragment free. There were nonshadowing fragments present in five of 12 examinations using both transducers. Clumping of small fragments less than or equal to 3 mm was present in two examinations. We recommend that a second ultrasound examination is performed when the presence of clumping is suspected and also when a fragment-free gallbladder is initially diagnosed.