Is ultrasonography a reliable method for evaluation of fragment clearance after biliary ESWL? A prospective, blinded study of two independent ultrasound units.

Ultrasound is the preceding method for evaluation of fragmentation and subsequent fragment clearance from the gallbladder. Considering the methodological shortcomings of ultrasonography, this study was therefore designed to investigate the degree of conformity between two independent ultrasound units. In our protocol patients were evaluated for fragments two weeks and three, six, nine and twelve months after ESWL. A restricted number of experienced sonographers in two independent ultrasound units examined the patient without knowledge of the other unit's findings. A total of 62 examinations have been carried out so far. Complete or sufficient conformity with a difference in size of 0-3mm was achieved in 24 examinations. Seven examinations revealed differences of 4-13 mm. In 31 cases the diagnosis of a stone-free gallbladder has been made, but only in 25 cases this could be confirmed by the other ultrasound unit. In six examinations a small fragment of less than 5mm was found by the respective other sonographer. We conclude that the diagnoses of a stone-free gallbladder after ESWL should be reconsidered by a second independent and experienced sonographer.