Peak Urinary Flow Rate: Observations in Female subjects and Comparison to Male Subjects

Abstract

Peak urinary flow rates and volume were determined with a disposable plastic device in 364 female subjects, ranging in age from 15-71 yr. Of the subjects studied 166 were considered normal, 92 were considered abnormal and 106 were pregnant. The requirement for a minimum voided volume of 100 ml resulted in a loss of data from 105 patients, leaving 259 for analysis. Normal female subjects have higher peak flow rates for a given volume voided than do male subjects of the same age. When the minimum volume of 100 ml is accepted the mean of the female population is near 26 ml/s .+-. 14. Such means are not useful clinically because of change with flow owing to volume voided. Female peak flow rates did not show deterioration of voiding with age. Women with diseases such as stress urinary incontinence and urinary infection did reveal a significant decrease in peak urinary flow rate when compared to normal female subjects by linear regression. The mean peak flow rate of this group was 20 ml/s .+-. 10. Limited observations were made in these patients after correction of stricture or treatment of urinary infection. In comparison to treated male patients, abnormal female patients who were treated did not have as much improvement in peak urinary flow rate. Obstetrical patients were observed to void at consistently higher peak flows than normal female subjects. This increase was not statistically significant when compared to normal subjects. No obstetrical patient voided a volume larger than 350 ml. Pregnancy appears to create more rapid voiding of smaller volumes than that of non-pregnant female subjects.