The usefulness of agent emission imaging - high mechanical index ultrasound mode in the diagnosis of urolithiasis: A prospective preliminary study

PURPOSE: We aimed to determine the feasibility and effectiveness of agent emission imaging - high mechanical index (AEI-High MI) mode ultrasonography (US) compared with gray-scale and color Doppler US, alone or in combination, for the diagnosis of urolithiasis with reference to unenhanced computed tomography (CT). METHODS: This prospective study included 72 consecutive patients (40 males, 32 females; mean age, 45.9±14.7 years) referred by the department of urology for acute or elective symptoms of urolithiasis and confirmed to have urinary calculi on unenhanced abdominal CT, between January 2015 and June 2015. Gray-scale, color Doppler, and AEI-High MI US were performed by two radiologists to determine the effectiveness of these methods in the diagnosis of urinary stones and to compare them with the reference modality. RESULTS: A total of 189 calculi were detected on CT examination. Gray-scale US had a sensitivity of 66.1% and positive predictive value (PPV) of 88.7% for detecting calculi, while twinkling artifact of color Doppler had a sensitivity of 70.4% and PPV of 94.3%. The scintillation artifact of AEI-High MI mode had a sensitivity of 75.1% and PPV of 95.9%. When all ultrasound-based modalities were combined, the sensitivity and PPV rose to 83.1% and 88.2%, respectively. When calculi were grouped according to their size ( 10 mm), AEI-High MI mode had a higher sensitivity (60%) compared with gray-scale (32.5%) and color Doppler (41.3%) for calculi < 5 mm. CONCLUSION: AEI-High MI mode had a higher sensitivity compared with gray-scale and color Doppler for the detection of calculi smaller than 5 mm, but it did not make a significant contribution to detection of larger calculi. The combined use of gray-scale US with AEI-High MI mode could increase the detection rate of calculi smaller than 5 mm and provide a method for verification of suspected calculi on gray-scale US.