Radionuclide assessment of bladder outlet obstruction: A noninvasive (1-step) method for measurement of voiding time, urinary flow rates and residual urine

Radionuclide uroflowmetry was performed in 23 patients with bladder outlet obstruction and 29 controls. The parameters evaluated were voiding time, time to peak flow rate, time for 50 per cent emptying, average flow rate, peak flow rate, corrected peak flow rate [peak flow rate/(bladder volume)^0.5], ejection fraction of the bladder and post-void residual urine. There was a statistically significant difference between controls and patients with bladder outflow obstruction in each parameter: voiding time 28.2 ± 9.3 versus 49.2 ± 26.5 seconds, time to peak flow rate 13 ± 4.1 versus 19 ± 12.6 seconds, time to 50 per cent emptying 5.5 ± 2.4 versus 25.7 ± 26.9 seconds, average flow rate 9.1 ± 3.7 versus 4 ± 2.3 ml. per second, peak flow rate 19.6 ± 7.6 versus 8.8 ± 4.1 ml. per second, corrected peak flow rate 1.22 ± 0.32 versus 0.59 ± 0.22, ejection fraction 95.3 ± 3.5 versus 79.7 ± 17.6 and residual urine 13.1 ± 13.5 versus 74.1 ± 135 ml., respectively. The corrected peak flow rate showed the best separation between controls and patients with obstruction. Of the controls 93 per cent had a corrected peak flow rate of 0.87 or greater compared to only 13 per cent of the patients with obstruction. This method involves a single noninvasive procedure that enables determination of voiding parameters related to urinary volume, flow and time, and it avoids the extra determination needed to determine the residual volume.