Accuracy of Surgeon-performed Ultrasound in Detecting Gallstones - a Validation Study

Enrolment of patients:

Three hundred patients, with an acute or elective referral to the radiology department at Stockholm South General Hospital, Sweden, for any diagnostic abdominal US examination, including both patients admitted to in-hospital care and out-patients, were prospectively enrolled between October 2011 and November 2012. Eligible patients were identified in the radiology department by a study surgeon and informed consent was obtained. Six US educated surgeons participated in the enrolment of patients. Exclusion criteria were age <18 years or inability to communicate with the examiner. Referrals concerning metastases of the liver or contrast-enhanced examinations were considered not suitable for the study and were also excluded. The surgeons examined patients consecutively if time was available, but mostly they didn't have time to examine every patient referred per day, hence a certain prioritisation between referrals was done.

Data collection:

Enrolled patients received one US examination by the study surgeon as well as the standard US examination by the on-duty radiologist. In a majority of cases the two examinations were performed consecutively and the time interval between the surgeon-performed US and radiologist-performed US never exceeded 24 hours. The surgeon's examination took place either before or right after the radiologist's examination. The examining surgeon and radiologist were blinded to each other's findings. The surgeon's US examination followed a standardised protocol, which included a full abdominal scan, regardless of the nature of the referral. The presence of gallstones was marked as a 'yes' (positive finding, regardless of number or size) or 'no' (negative finding) by the surgeon. In cases where a full abdominal scan could not be performed, due to urgent patient management, a focused examination based on the referral as well as a right upper quadrant (RUQ) scan was advised. The on-duty radiologist performed a standard care US focusing on the individual referrals. The radiologist's statement was collected from the patient's medical record and transferred to the study protocol by a separate radiologist, who was also blinded to the surgeon's examination. Among the radiologists the major part of the scans was done by US specialised radiologists with several years of training (56% US specialists, 73% specialists in radiology).

The surgeons used a portable US machine of the model LOGIQ e with a convex (1.6-4.6 MHz) or linear (5-13 MHz) transducer, GE Healthcare, WuXi, China. All scans were saved on a separate hard drive, which was kept together with the study protocol. The radiologists used Philips iU22 with a convex C5-1 or a linear L12-5 transducer.