0022-5347/78/1202-017~02.00/0 Vol. 120, August
THE JOURNAL OF UROLOGY
Printed in U.S.A.
Copyright © 1978 by The Williams & Wilkins Co.
THE NORMAL CALIBER OF THE ADULT FEMALE URETHRA DAVID T. UEHLING From the Division of Urology, University of Wisconsin Center for the Health Sciences, Madison, Wisconsin
ABSTRACT
The mean urethral caliber of 250 women undergoing cystoscopy to stage cancer of the cervix was 22F, as measured by the bougie a boule. A study of correlations between normal urethral caliber and age, weight, height, gravidity and parity of patients revealed a significant correlation with weight only. Although urodynamic studies have largely replaced static calibrations in the evaluation of voiding dysfunctions, urethral calibration with the bougie a boule may still be useful in certain conditions involving the female urethra. The normal caliber of the female urethra has been described for the pediatric age group. 1• 2 However, only a few normal values have been reported for adults. 3 To provide a normal value frame of reference urethral calibrations were done on normal women.
1. Caliber of the urethra in normal women grouped by ages Min. Max. Mean S.D. Age No. Pts. Observed (yrs.) Caliber Calibrated Observed of Mean Caliber Caliber
TABLE
20-30 30-40 40-50 50-60 60-70 70-80 80-90 Totals
MATERIALS AND METHODS
The 250 women who underwent urethral calibration as part of a urologic evaluation and clinical staging of gynecological cancer ranged from 20 to 90 years old. Most patients had stage IA or IB cervical cancer. Patients were excluded if they had a history of urinary tract infection, had any bladder symptoms, had undergone any urologic instrumentation except catheterization at the time of a delivery or had cancer that caused bladder infiltration or distortion as judged by the subsequent cystoscopy. During the study approximately as many women were excluded for these reasons as were included. Calibration was done with the Otis conical bougies (bougie a boule). After instillation of a local urethral anesthetic bougies were passed, beginning with smaller sizes. When substantial resistance to withdrawing the shoulder of the instrument was noted the urethral caliber was considered to be lF size smaller. For instance, if the 20F bougie passed satisfactorily and the 22F bougie required a stronger pull to withdraw the urethral caliber was considered to be 20F. The usual point in the urethra to offer first resistance to the bougie was approximately 1 cm. from the external meatus, although some patients seemed to have the narrowest caliber at the meatus. Mean caliber and the standard deviation of the mean were calculated for each age group. Means were compared by Student's t test. In addition to age the patient's height, .weight, gravidity and parity were considered possible factors that might affect urethral caliber. Correlation coefficients were determined between these factors and urethral caliber in an effort to find significantly linear relationships. RESULTS
The mean urethral caliber in each of the adult age groups was 22F (table 1). In addition, the 22F urethral caliber was the most common value observed. However, small and large caliber urethras were encountered in this series of supposedly normal women. When the mean ± 2 standard deviations is used to yield a range in which 95 per cent of normal values would be expected, an 18 to 28F urethral caliber might be considered within the usual range. 4 With the correlation Accepted for publication October 14, 1977.
TABLE
14 20 58 59 58 35 6 250
18 18 14 16 14 14 18 14
24 28 32 30 28 28 32 32
22.0 22.7 22.3 22.3 22.3 22.0 21.3 22.2
1.4 2.9 2.7 3.2 2.9 3.1 3.3 2.8
2. Correlations between urethral caliber and age, weight, height, gravidity and parity
Variable Age Weight Height Gravidity Parity
Correlation Coefficient -0.031 0.225 -0.032 -0.069 -0.086
p Value 0.6 0.001 0.6 0.3 0.2
coefficients the only significantly linear relationship (p < 0.05) was that between increasing patient weight and a correspondingly increasing urethral caliber (table 2). DISCUSSION
The normal values reported here generally agree with the 37 normal calibrations reported by Hole, who noted that patients with voiding symptoms did not differ from normal patients in urethral caliber. 3 Gleason and associates also have questioned the usefulness of bougie calibration because of an absence of correlation among symptoms, trabeculation, reflux, residual urine and urethral caliber. 5 Additionally, they noted a strong negative correlation between urethral caliber as measured by bougies and urethral flow rate, proposing that bougies define limits of distension rather than functional urethral diameter. A negative correlation between urethral caliber and flow rate would seem to be an argument against the continued usage of bougie calibration. However, accurate urodynamic evaluation is not accessible to all patients seeking urologic care and the use of bougies is a common part of urologic practice. The present study shows a surprisingly large range of values for urethral caliber in women without symptoms or infection. Although awareness of the normal range of urethral caliber may not be helpful in determining treatment for women with symptoms or infections it may be helpful in eliminating unnecessary operative procedures on women who are found to have a urethral caliber previously thought to be out of the normal range.
176
177 REFERENCES
EDITORIAL COY.AMEl'\TT
1. Graham, J. B., King, L. R., Kropp, K. A. and Uehling, D. T.:
Since effective urethral caliber in normal female subjects has been shown to be 9F the therapeutic use of urethral dilatation is based not on correcting a stricture to increase maximum flow but on altering the flow characteristics through the entire urethra. The final statement in this article is over-modest; awareness of normal ranges will help even those urologists addicted to urethral dilatation. Frank Hinman, Jr. Division of Urology University of California Medical Center San Francisco, California
The significance of distal urethral narrowing in young girls. J. Urol., 97: 1045, 1967. 2. Immergut, M., Culp, D. and Flocks, R. H.: The urethral caliber in normal female children. J. Urol., 97: 693, 1967. 3. Hole, R.: The caliber of the adult female urethra. Brit. J. Urol., 44: 68, 1972. 4. Siegel, S.: Nonparametric Statistics for the Behavioral Sciences. New York: McGraw-Hill Book Co., 1956. 5. Gleason, D. M., Bottaccini, M. R. and Lattimer, J. K.: What does the bougie a boule calibrate? J. Urol., 101: 114, 1969.
THE JOURNAL OF UROLOGY
Printed in U.S.A.
Copyright © 1978 by The Williams & Wilkins Co.
THE NORMAL CALIBER OF THE ADULT FEMALE URETHRA DAVID T. UEHLING From the Division of Urology, University of Wisconsin Center for the Health Sciences, Madison, Wisconsin
ABSTRACT
The mean urethral caliber of 250 women undergoing cystoscopy to stage cancer of the cervix was 22F, as measured by the bougie a boule. A study of correlations between normal urethral caliber and age, weight, height, gravidity and parity of patients revealed a significant correlation with weight only. Although urodynamic studies have largely replaced static calibrations in the evaluation of voiding dysfunctions, urethral calibration with the bougie a boule may still be useful in certain conditions involving the female urethra. The normal caliber of the female urethra has been described for the pediatric age group. 1• 2 However, only a few normal values have been reported for adults. 3 To provide a normal value frame of reference urethral calibrations were done on normal women.
1. Caliber of the urethra in normal women grouped by ages Min. Max. Mean S.D. Age No. Pts. Observed (yrs.) Caliber Calibrated Observed of Mean Caliber Caliber
TABLE
20-30 30-40 40-50 50-60 60-70 70-80 80-90 Totals
MATERIALS AND METHODS
The 250 women who underwent urethral calibration as part of a urologic evaluation and clinical staging of gynecological cancer ranged from 20 to 90 years old. Most patients had stage IA or IB cervical cancer. Patients were excluded if they had a history of urinary tract infection, had any bladder symptoms, had undergone any urologic instrumentation except catheterization at the time of a delivery or had cancer that caused bladder infiltration or distortion as judged by the subsequent cystoscopy. During the study approximately as many women were excluded for these reasons as were included. Calibration was done with the Otis conical bougies (bougie a boule). After instillation of a local urethral anesthetic bougies were passed, beginning with smaller sizes. When substantial resistance to withdrawing the shoulder of the instrument was noted the urethral caliber was considered to be lF size smaller. For instance, if the 20F bougie passed satisfactorily and the 22F bougie required a stronger pull to withdraw the urethral caliber was considered to be 20F. The usual point in the urethra to offer first resistance to the bougie was approximately 1 cm. from the external meatus, although some patients seemed to have the narrowest caliber at the meatus. Mean caliber and the standard deviation of the mean were calculated for each age group. Means were compared by Student's t test. In addition to age the patient's height, .weight, gravidity and parity were considered possible factors that might affect urethral caliber. Correlation coefficients were determined between these factors and urethral caliber in an effort to find significantly linear relationships. RESULTS
The mean urethral caliber in each of the adult age groups was 22F (table 1). In addition, the 22F urethral caliber was the most common value observed. However, small and large caliber urethras were encountered in this series of supposedly normal women. When the mean ± 2 standard deviations is used to yield a range in which 95 per cent of normal values would be expected, an 18 to 28F urethral caliber might be considered within the usual range. 4 With the correlation Accepted for publication October 14, 1977.
TABLE
14 20 58 59 58 35 6 250
18 18 14 16 14 14 18 14
24 28 32 30 28 28 32 32
22.0 22.7 22.3 22.3 22.3 22.0 21.3 22.2
1.4 2.9 2.7 3.2 2.9 3.1 3.3 2.8
2. Correlations between urethral caliber and age, weight, height, gravidity and parity
Variable Age Weight Height Gravidity Parity
Correlation Coefficient -0.031 0.225 -0.032 -0.069 -0.086
p Value 0.6 0.001 0.6 0.3 0.2
coefficients the only significantly linear relationship (p < 0.05) was that between increasing patient weight and a correspondingly increasing urethral caliber (table 2). DISCUSSION
The normal values reported here generally agree with the 37 normal calibrations reported by Hole, who noted that patients with voiding symptoms did not differ from normal patients in urethral caliber. 3 Gleason and associates also have questioned the usefulness of bougie calibration because of an absence of correlation among symptoms, trabeculation, reflux, residual urine and urethral caliber. 5 Additionally, they noted a strong negative correlation between urethral caliber as measured by bougies and urethral flow rate, proposing that bougies define limits of distension rather than functional urethral diameter. A negative correlation between urethral caliber and flow rate would seem to be an argument against the continued usage of bougie calibration. However, accurate urodynamic evaluation is not accessible to all patients seeking urologic care and the use of bougies is a common part of urologic practice. The present study shows a surprisingly large range of values for urethral caliber in women without symptoms or infection. Although awareness of the normal range of urethral caliber may not be helpful in determining treatment for women with symptoms or infections it may be helpful in eliminating unnecessary operative procedures on women who are found to have a urethral caliber previously thought to be out of the normal range.
176
177 REFERENCES
EDITORIAL COY.AMEl'\TT
1. Graham, J. B., King, L. R., Kropp, K. A. and Uehling, D. T.:
Since effective urethral caliber in normal female subjects has been shown to be 9F the therapeutic use of urethral dilatation is based not on correcting a stricture to increase maximum flow but on altering the flow characteristics through the entire urethra. The final statement in this article is over-modest; awareness of normal ranges will help even those urologists addicted to urethral dilatation. Frank Hinman, Jr. Division of Urology University of California Medical Center San Francisco, California
The significance of distal urethral narrowing in young girls. J. Urol., 97: 1045, 1967. 2. Immergut, M., Culp, D. and Flocks, R. H.: The urethral caliber in normal female children. J. Urol., 97: 693, 1967. 3. Hole, R.: The caliber of the adult female urethra. Brit. J. Urol., 44: 68, 1972. 4. Siegel, S.: Nonparametric Statistics for the Behavioral Sciences. New York: McGraw-Hill Book Co., 1956. 5. Gleason, D. M., Bottaccini, M. R. and Lattimer, J. K.: What does the bougie a boule calibrate? J. Urol., 101: 114, 1969.
