Disposable peak urinary flowmeter estimates lower urinary tract obstruction

Abstract

Peak urinary flow rate represents the highest flow rate achieved during a single urination and, as such, represents the patient's best effort at micturition. Peak flow rate, correlated with patient age and volume voided, effectively estimates lower urinary tract obstruction. The 63 normal and 368 abnormal male subjects urinated in privacy into a plastic sterile disposable device (the peakometer), which measured peak flow rate and volume voided. These data plus age, ultimate diagnosis and interval since last urination comprised our data base. Percentage distribution of diagnosis in this population was prostatic obstruction 47.3 per cent, stricture 19.3 per cent, normal 14.6 per cent, prostatitis 8.4 per cent, neurogenic bladder 2 per cent and miscellaneous 8.4 per cent. The average peak flow rate for normal male subjects reaches 27.6 ml. per second, which differs significantly from that for patients with prostatic obstruction--9.4 ml. per second, stricture--10.5 ml. per second, prostatitis--16.3 ml. per second and neurogenic bladder--13.9 ml. per second. The peak flow rate decreased progressively as the age of the subjects increased. We measured average decreases of 10 ml. per second peak flow for every 30 years after age 10. Peak flow rate increases as volume voided increases. Requirements of our measuring device combined with urodynamic responses caused us to select 100 ml. voided as the minimum acceptable volume. With volumes more than this any given individual may deviate plus or minus 10 per cent from the true mean peak flow depending upon volume voided. For practical purposes peak flow, age and volume must be considered to categorize voiding by peak flow rate. With these variables 2 graphs that compare peak flow, age and volume may be used to estimate voiding function for a given male patient. Comparison of peak flow rates, volume voided and voiding interval before and after surgical correction of obstruction documented significant increase in volume voided or in interval between voiding. Peak urinary flow rate measurement by this device predicted normality or abnormality with 90 to 95 per cent accuracy. Therefore, this represents a valid screening test but it does not in itself provide the diagnosis of abnormal urination.