Noninvasive measurement of bladder muscle activity using radiofrequency ultrasound strain imaging

Lower urinary tract symptoms (LUTS) are common in elderly men. The currently standard urodynamic test for LUTS is an invasive pressure-flow study. This test is however invasive and has potential morbidity. Furthermore, it does not reveal the cause of LUTS but only provides information on one of the symptoms. Therefore we investigated the possibility to assess the function of the bladder muscle (detrusor). In an asymptomatic volunteer and a symptomatic patient population we used radiofrequency ultrasound to estimate deformation of the detrusor and related that to detrusor activity. In the asymptomatic volunteers we found an increase in axial strain at the onset of voiding. And in the symptomatic patients we found a significant positive correlation between axial strain and detrusor pressure (Spearman's coefficient: 0.52, 0.78 and 0.99 respectively, all p<;0.05). The positive correlation between detrusor strain and detrusor pressure indicates that the detrusor thickens during muscle activity. Therefore, ultrasound strain imaging could possibly be used in diagnosing lower urinary tract dysfunctions such as Bladder Outlet Obstruction and Detrusor Overactivity.