- Email: [email protected]
Reduction of urethral pressure in response to stress: Relationship to urethral mobility
Reduction of urethral pressure in response to stress: Relationship to urethral mobility David A. Richardson, M.D. Detroit, Michigan It has been post~lated that one factor involved in the pathophysiology of stress urinary incontinence is the sustained decrease in urethral closure pressure in response to a sudden increase in intra-abdominal pressure. Twenty-one patients with stress-related pressure decrease (group 1) and seven patients with stable pressures (group 2) were studied. Although closure pressure in group 1 decreased approximately 27% in response to a single cough in a static setting, when studied dynamically with pressure profiles before and after coughing, there was no pressure decrease seen. The evidence presented suggests that the phenomenon of pressure decrease is in actuality an artifact of measurement and not a true physiologic event. The degree of urethral mobility is related to the perceived pressure decrease. (AM J OB~TET GVNECOL 1986;155:20-5.)
Key words: Urethral pressure, stress incontinence, decreased urethral pressure in response to stress
An adequate urethral pressure is necessary for the maintenance of urinary continence. This pressure is equally dependent on striated muscle, smooth muscleelastic tissue, and a vascular component.! The maximum urethral closure pressure has been demonstrated to be decreased in women with stress urinary incontinence and related to the severity of incontinence."' " Other variables potentially influencing the impairment of the urethral closure mechanism are intrinsic urethral pressure variability and the pressure transmission ratio."" Recently, it has been postulated that another variable is actively involved in the lowering of urethral pressure in women with stress urinary incontinence. Any acute stress will produce a sustained decrease in urethral closure pressure (Fig. 1).7.8 The loss of pressure and duration of recovery time are dependent on the magnitude and number of stresses applied. Possible explanations for this phenomenon include expulsion of blood from the suburethral vascular plexus, striated muscle relaxation, smooth muscle relaxation, or a combination of all three factors. In order to further understand and clarify this phenomenon of urethral pressure relaxation after stress, the following investigation was undertaken.
From the Department of Obstetrics and Gynecology, Wayne State University and Grace Hospital. Received for publication May 16,1985; revised January 1,1986; accepted February 3, 1986. Reprint requests: David A. Richardson, M.D., Department of Obstetrics and Gynecology, Wayne State University, Grace Hospital, 18700 Meyers Road, Detroit, M148235.
20
URETHRAL 100t
PRE~SURE
I!!
(cm H20)
CLOSURE PRESSURE (cm H20) 100-
Fig. 1. Urethral pressure decrease in response to one, two, and three coughs, respectively, is demonstrated. The degree of pressure loss and the time necessary for full pressure recovery is related to the magnitude and number of stresses applied.
Mater.ial and methods
Twenty-eight consecutive patients undergoing complete urodynamic evaluation for a variety of clinical problems were studied. Detailed history, physical examination, negative urine culture, cystometry, cystourethroscopy, uroflowmetry, and urethral pressure profiles were obtained in all cases. A stress test was performed in the dorsal lithotomy and standing position. The patients were asked to cough, laugh, and occa-
Urethral pressure and stress 21
Volume 155 Number 1
1 mm/s
PROXIMAL URETHRA
DISTAL URETHRA
5 mm/s
POST·COUGH PROFILE 5 mm/s
COUGH PROFILE
Fig. 2. Urethral pressure profiles were taken at 1 mm/sec, at 5 mm/sec, and after the patient had coughed repeatedly. Distance to maximum closure pressure (A), urethral functional length (B), and maximum closure pressure (C) were recorded from each profile type. The magnitude of pressure decrease (D) and the time necessary for pressure recovery (E) were recorded in the proximal urethra in response to a single cough. In the distal urethra the direction of change was noted (increase, decrease, or no change). A postcough pressure profile was then obtained.
sionally exercise with a full bladder to see if urinary leakage could be documented. A Q-tip test was performed to measure the degree of urethral mobility.9 The patients were placed in the dorsal lithotomy position and a lubricated Q-tip was introduced into the urethra. A resting angle was obtained with the horizontal position used as a reference zero point. The patient was asked to cough and bear down, and the maximum excursion was measured. The angle measurements were obtained with an orthopedic goniometer. Although this technique is in standard use, the precision, accuracy, and normative values have not been well defined. Urethral, intravesical, and abdominal (vaginal) pressures were obtained simultaneously with microtip pressure transducers, * by methods similar to those previously described. lo Electronic subtraction was used to obtain urethral closure pressure (urethral minus intravesical) and detrusor pressure (intravesical minus abdominal). Pressures were plotted on a six-channel recorder.t Evaluations were obtained in the supine position with 150 ml of 0.9% saline solution. Variables measured and procedures performed are summarized in Fig. 2. Three urethral closure pressure profiles were taken by use of a mechanical puller at a withdrawal rate of 1 mm/sec and then repeated at 5 mm/sec. Measurements were recorded from the third profile and all recordings were taken with the microtransducers in the left lateral position. Recorder speed was set to match profilometer speed in each case. Variables recorded included maximum urethral closure pressure, length to peak pressure, and functional profile lengths. Urethral closure pressure response to stress was eval-
*Models PC-680 Band PC-380, Millar Instruments, Houston, Texas. tUrolab Model 1106, Life Tech, Inc., Houston, Texas.
DETRUSOR PRESSURE
100-
URETHRAL PRESSURE
10rJ:rJ-JJj~ URETHRAL CLOSURE PRESSURE
(em H20) Fig. 3. This tracing of a patient in group 2 demonstrates: A, baseline closure profile; E, no pressure change in the proximal urethra; C, no pressure change in the distal urethra; and D, a negative cough profile.
uated by measuring the magnitude of pressure change and the duration of recovery after a single cough in both proximal and distal urethral segments approximately 0.5 em from peak closure pressure. A cough urethral pressure profile was then obtained with the patient instructed to cough continuously while the transducer was withdrawn through the urethra. To further evaluate the extent of the urethral pressure decrease, the patient was asked to cough vigorously 10 times after which a postcough urethral pressure profile at 5 mm/sec was immediately determined. It was previously reported that the pressure decrease appeared to plateau after four to five stresses. 7 • S In our
22 Richardson
July, 1986 Am J Obstet Gynecol
(em H201
DETRUSOR PRESSURE
Table I. Urethral closure pressure before and after post cough profiles
II, I
/,1"
100-,
~\'---~I,--l
__
I
~WM~----,
Group
1
2
URiETHRAL PRE,-URE
100-,
URETHRAL CLOSURE PRES.URI!
B
Control no. 2 (5 mm/sec)
Post cough (5 mm/sec)
58 ± 26 81 ± 27*
58 ± 24 77 ± 31
59 ± 37 76 ± 31
*Group 1 (I mm/sec) with group 2 (I mm/sec): p < 0.05.
I
JvV'1 A
Control no. 1 (l mm/sec)
c
o
E
Fig. 4. This tracing of a patient in group 1 demonstrates: A, pressure decrease in proximal urethra in response to cough; B, slight pressure increase in the distal urethra in response to a slightly stronger cough; C, baseline profile at 5 mm/sec; D, repetitive coughing followed by a repeat urethral pressure profile; E, postcough profile demonstrating the decrease in functional length and distance to maximum pressure that was consistently seen in group I.
own clinical experience, this could vary between two and seven stresses. Ten coughs were selected to ensure that maximum pressure decrease and the corresponding longest possible recovery time had been reached. The objective was to obtain a pressure profile wherein peak pressure was reached in less than 50% of the time necessary for urethral pressure to recover under the previous static measurements of a single cough. Thus, if the urethral relaxation in response to stress was present, maximum closure pressure should be consistently decreased from baseline values. The condition of stress incontinence was diagnosed on the basis of pressure equalization during a cough profile with simultaneous urinary leakage or a positive stress test in a patient documented to have a stable bladder. The patients were divided into two groups according to urethral closure pressure response to a single cough in the proximal urethral segment: group I-pressure decrease in response to stress (Fig. 1); group 2-no change or a pressure increase in response to stress (Fig. 3). Grou p 1 consisted of 21 patients. The mean age was 49.4 ± 10.4 years. Mean parity was 2.7 ± 1.5. Two patients had previously undergone unsuccessful operation for stress urinary incontinence. The primary urodynamic diagnosis included stress incontinence (57%), unstable detrusor (24%), and normal evaluation (19%).
The normal examinations were in patients having urodynamic assessments before radical hysterectomy. Group 2 consisted of seven patients with a mean age of 42.6 ± 15 years. The mean parity was 2.9 ± 2. In two patients the diagnoses were unstable bladder and sensory urgency, respectively. Three patients had normal examinations before undergoing radical hysterectomy. There were no patients with stress incontinence in this group. The following statistical analyses were performed: Wilcoxon matched pairs test, a Mann-Whitney U test, and Spearman rank correlation. Results
In gr?up 1, the average pressure drop in the proximal urethra was 15.3 ± 8.4 em/H 2 0 with a mean recovery time of 9.1 ± 4.2 seconds. This pressure drop represents a 27% decrease from baseline maximum closure pressure. Recovery time and pressure drop were not significantly different between patients with stress urinary incontinence and those with other urodynamic diagnoses. The pressure reduction in group 1 was not consistently seen in the distal urethral segment (Fig. 4). A pressure increase was seen in 52% (n = 11), there was no pressure change in 33% (n = 7), and there was a pressure decrease in 14% (n = 3). The pressure increase was consistently less and the recovery time consistently shorter than the corresponding values in the proximal urethral segment. The different profilometer speeds used in performing urethral pressure profiles did not alter the maximum closure pressure in either group 1 or group 2 (Table I). The only statistical difference between groups was in the closure pressure measurement taken at 1 mm/sec (p < 0.05). Although the urethral pressure was lower in patients with genuine stress urinary incontinence (55 ± 25 cm/H 2 0, n = 12), this was not significantly different from that in patients with other urodynamic diagnoses (71 ± 28 cm/H 2 0, n = 16). After prolonged coughing, there was no change in maximum closure pressure in either group (Table I). Fig. 5 is a typical representation of a patient in group 1 with pressure decrease in the proximal urethral segment without a change in pressure in the postcough
Urethral pressure and stress 23
Volume 155 Number 1
I
URETHRAL
l--A CLOSURE
f\
'--==S=T;':COUGH
Fig. 5. This patient demonstrates the phenomenon of pressure decrease in the proximal urethra with pressure increase in the distal urethra. Recovery time from a single cough (not shown) was 5.5 seconds. Post-cough profile shows an increase in closure pressure. Elapsed time from last cough to peak closure pressure was 2.8 seconds.
profile. It was felt that the postcough profile was an accurate reflection of events, since the time from the last cough to peak profile pressure averaged 3.5 ± 1 second. (Single cough recovery time was 9.1 ± 4.2 seconds.) There was no statistical difference in baseline functionallength at the various control profilometer speeds (Table II). Although the average baseline functional length in group 2 was increased compared with that in group 1, this was not statistically significant. In the postcough profile, there was a significant decrease in both functional length and distance to peak pressure in group 1. In group 2 there was no significant change in functional length to peak pressure after coughing. There was a significant difference in the extent of urethral relaxation present between group 1 and group 2. In group 1, the average Q-tip angle change was 39 ± 14 degrees. In group 2 the change was 10 ± 8 degrees (p < 0.01). A significant correlation was seen between Q-tip angle change and pressure droplrecovery time in group 1. (Spearman correlation coefficients: pressure drop to Q-tip angle change, R = 0.48, P = 0.013; recovery time to Q-tip angle change, R = 0.3838, P = 0.41; pressure drop to recovery time, R = 0.5034, P = 0.01). The data from which the correlations were drawn are presented in Fig. 6.
Comment This study demonstrated the following: 1. The urethral pressure decrease in response to stress is present only on static profiles. The pressure
Table II. Functional length and length to peak pressure before and after post cough profiles Functional length
Length to peak
Group
Control (5 mmlsec)
I Postmmlsec) cough (5
Control (5 mmlsec)
I Postmmlsec) cough
1 2
2.6 ± 0.6 2.8 ± 0.5
2.3 ± 0.6* 2.8 ± 0.6
1.5 ± 0.5 1.3 ± 0.3
1.2 ± 0.6t 1.3 ± 0.3
(5
*Comparison of group I, control, with group I, post cough: p < 0.01. Comparison of group I, post cough, with group 2, post cough: p < 0.001. tComparison of group I, control, with group I, post cough: p < 0.05.
decrease is not a true physiologic event. Maximum closure pressure in the postcough profile demonstrated no consistent change from that in the resting profiles. 2. The pressure decrease in response to stress appears to be an indicator for patients with stress urinary incontinence. However, 43% of patients presenting with urethral relaxation had other urodynamic diagnoses. 3. In individuals with a pressure decrease in the proximal urethra, there was a pressure increase or no pressure change in 88% of the patients in the distal urethral segment. 4. There was a marked difference in urethral mobility between patients with and those without a pressure decrease. The amount of urethral pressure decrease and the duration of recovery time were significantly correlated with the degree of urethral mobility.
24
Richardson
0.
July, 1986 Am J Obstet Gynecol
35
70
30
60
25
50
-;; CD
~
~
:t: .,
E~ 20 u 0 -u
40
W
W CD
(!I
a:.!
z
-<
:::lW
:g;l
'"CD
~
30
15
~i=
:t:
0
W
..l (!I
II.
Z
10
20
5
10
0
PRESSURE DROP
RECOVERY TIME
-<
Q TIP ANGLE CHANGE
Fig. 6. The relationship in group I between pressure drop, recovery time, and Q-tip angle change is demonstrated. The greater the pressure drop or the recovery time, the greater the angle change observed.
5. In the postcough profile, functional length and length to peak pressure were significantly decreased over control profile measurements. The observed phenomenon of a urethral pressure decrease in response to stress appears to be an artifact caused by a fixed pressure transducer in the presence of a mobile urethra. The downward and outward rotation of the urethra shifts the stationary microtip sensor toward the urethral-vesical junction. In the proximal urethral segment there is an apparent decrease in urethral pressure as the catheter moves from a highpressure zone to a low-pressure zone. This same catheter shift in the distal urethra causes movement from a low-pressure zone toward urethral peak pressure. After abdominal stress (coughing) the urethra returns to its original location. In the postcough profile this results in the catheter moving out as the urethra moves in, producing an apparent decrease in functional length and a decrease in the distance to peak pressure. It has long been recognized that urethral descensus from the symphysis pubis is an important aspect in the pathophysiologic features of stress incontinence and that this mobility results in a decreased abdominal pressure transmission to the proximal urethra. Although not all patients with relaxation have stress urinary incontinence, the majority of patients with genuine stress incontinence have relaxation. Traditionally, this anatomic defect has been measured on either a Q-tip test or a cystogram. 9 . II The observation that urethral pressure decrease is essentially a function of urethral mo-
bility at times of acute stress opens the possibility of a urodynamic method of quantifying urethral relaxation. Individuals with a pressure decrease in response to stress in the proximal urethra generally were found to have a pressure increase or no change in pressure in the distal urethral segment. This difference can be explained by the fact that the urethra perforates the urogenital diaphragm approximately 0.5 cm from maximum urethral pressure. 12 The urethra has increased mobility in its proximal segment, but as it enters the urogenital diaphragm it becomes more fixed in its attachments to the symphysis pubis . Standard urethrocystometry is performed by placing the transducer at peak closure pressure. In the presence of a mobile urethra, we have noticed marked variations in recorded urethral pressure. This is especially apparent in patients in whom the maximum pressure covers a spatial area of limited urethral length. Slight body movement, breathing, or perineal muscle contractions can produce urethral movement that can mimic so-called urethral instability (change in urethral pressure> 15 cm H 20). It is possible that what is being interpreted as urethral instability in some cases is artifactual and related to urethral mobility. Further investigation will be required to clarify this point. The measurement of the urethral pressure profile continues to be an integral part of the urodynamic evaluation. The measurement of closure pressure identifies patients with inherent sphincter weakness who have a significantly lower cure rate with incontinence operations than patients with normal pressure. The cough profile provides the physician with objective evidence of genuine stress incontinence and enables the physician to determine the actual amount of pressure transmission. Although pressure decrease in response to stress does not appear to be an independent variable in the pathophysiologic features of stress incontinence, it enables the physician to assess the relative degree of urethral mobility. REFERENCES I. Rud T, Andersson KE, Asmussen M, et al. Factors main-
2.
3. 4. 5. 6.
taining the intraurethral pressure in women. Invest Urol 1980;17:343. Enhorning G. Simultaneous recording of intravesical and intraurethral pressure: a study of urethral closure in normal and stress incontinent women. Acta Chir Scand 1961 ;276(suppl): 1-68. Low JA, Kao MS. Patterns of urethral resistance in deficient urethral sphincter function. Obstet Gynecol 1972; 40:634. Herbert DB, Francis LN, Ostergard DR. Significance of urethral vascular pulsations in genuine stress incontinence. AM J OBSTET GYNECOL 1982; 144:828. Heidler H, Wolk H,Jonas U. Urethral closure mechanism under stress conditions. Eur Urol 1979;5: 110. Hilton P, Stanton SL. A clinical and urodynamic assessment of the Burch colposuspension for genuine stress incontinence. Br J Obstet Gynaecol 1983;90:934.
Urethral pressure and stress
Volume 155 Number I
7. Hilton P, Stanton SL. Urethral pressure measurement by microtransducers: the results in symptom free women and in those with genuine stress incontinence. Br J Obstet Gynaecol 1983;90:919. 8. Bunne G, Obrink A. Urethral closure pressure at stressa comparison between stress incontinent and ocontinent women. Urol Res 1978;6:127. 9. Chrystle CD, Charmel S, Copeland WE. Q-tip test for stress urinary incontinence. Obstet GynecoI1971;38:3I3.
10. Richardson DA. Use of vaginal pressure measurement in urodynamic testing. Obstet Gynecol 1985 (in press). II. Hodgkinson CPo Stress urinary incontinence-I970. AM J OBSTET GYNECOL 1970; 108: 1141. 12. Westby M, Asmussen M, Ulmsteri U. Location of maximum intraurethral pressure related to urogenital diaphragm in the female subject as studied by simultaneous urethrocystometry and voiding urethrocystography. AM J OBSTET GYNECOL 1982;144:408. 0
Acceptability of chorionic villi sampling for prenatal diagnosis Margaret M. McGovern, Ph.D., James D. Gol!Iberg, M.D., and Robert J. Desnick, Ph.D., M.D. New York, New York The factors that influence women in choosing between first-trimester chorionic villi sampling and second-trimester amniocentesis for prenatal diagnosis were investigated. Five hundred twenty women of advanced maternal age who had previously undergone prenatal diagnosis by amniocentesis ano were delivered of a normal infant were requested to complete a questionnaire concerning their attitudes toward amniocentesis and chorionic villi sampling. The majority of respondents indicated that the time at which chorionic villi sampling is performed (76%), the rapid availability of diagnostic-results (72%), and the type of abortion procedure available (68%) would make them choose this method. In contrast, the factors that influenced women to choose amniocentesis included the known low risk of spontaneous abortion (76%) and confidence in the skill of the obstetrician who would perform the procedure (56%). When all factors were considered together, 68% of the respondents chose amniocentesis based on the known low risk of spontaneous abortion, whereas for those who chose chorionic villi sampling (32%), the major criterion was the fact that the procedure is performed in the first trimester. However, 87% of women who preferred amniocentesis indicated that if the risk of spontaneous abortion associated with chorionic villi sampling were equal to or less than that of amniocentesis, they would choose chorionic villi sampling. These results indicate that for many women of advanced maternal age, the acceptability and the use of chorionic villi sampling will be dependent on the demonstration that the risk of fetal loss is low, approaching that of amniocentesis. (AM J OesTET GVNECOL 1986;155:25-9.)
Key words: Chorionic villi sampling, amniocentesis, prenatal diagnosis Recently a new method of obtaining fetal tissue for prenatal diagnosis, called chorionic villi sampling, has been developed.'o2 This procedure, which is performed at 8 to 12 weeks of pregnancy, involves the ultrasoundguided transcervical aspiration of a small amount of chorionic villi. This tissue is used directly or can be cultured for diagnostic chromosomal and/or biochemical analyses. Test results are usually available within 2 weeks, thereby providing rapid relief of parental anxiety when the fetus is found normal or, if a fetus with a genetic defect is detected, permitting the parents to choose a safer, easier termination of the pregnancy durFrom the Division of Medical Genetics and Maternal-Fetal Medicine, Mount Sinai School of Medicine. Received for publication July 22, 1985; revised December 5, 1985; accepted February 3, 1986. Reprint requests: Dr. Robert). Desnick, Mount Sinai School of Medicine, Fifth Ave. and 100th St., New York, NY 10029.
ing the first trimester. Preliminary data from 10,000 procedures performed worldwide have revealed that chorionic villi sampling is safe for the mother and that the rate of fetal loss is about 4% when performed by experienced obstetricians. Since most conditions that can be diagnosed by amniocentesis are detectable by chorionic villi sampling, this procedure represents an attractive alternative to amniocentesis, which cannot be safely performed until the second trimester. Previous studies have documented the safety and accuracy of amniocentesis for prenatal diagnosis. 3o ' However, experience has identified several disadvantages of the procedure. Amniocentesis cannot be safely performed until the second trimester of pregnancy, usually during weeks 16 to 18, and the diagnostic results are often unavailable for 2 to 4 weeks after the procedure. Several investigators have reported that the period of waiting for the
25
Key words: Urethral pressure, stress incontinence, decreased urethral pressure in response to stress
An adequate urethral pressure is necessary for the maintenance of urinary continence. This pressure is equally dependent on striated muscle, smooth muscleelastic tissue, and a vascular component.! The maximum urethral closure pressure has been demonstrated to be decreased in women with stress urinary incontinence and related to the severity of incontinence."' " Other variables potentially influencing the impairment of the urethral closure mechanism are intrinsic urethral pressure variability and the pressure transmission ratio."" Recently, it has been postulated that another variable is actively involved in the lowering of urethral pressure in women with stress urinary incontinence. Any acute stress will produce a sustained decrease in urethral closure pressure (Fig. 1).7.8 The loss of pressure and duration of recovery time are dependent on the magnitude and number of stresses applied. Possible explanations for this phenomenon include expulsion of blood from the suburethral vascular plexus, striated muscle relaxation, smooth muscle relaxation, or a combination of all three factors. In order to further understand and clarify this phenomenon of urethral pressure relaxation after stress, the following investigation was undertaken.
From the Department of Obstetrics and Gynecology, Wayne State University and Grace Hospital. Received for publication May 16,1985; revised January 1,1986; accepted February 3, 1986. Reprint requests: David A. Richardson, M.D., Department of Obstetrics and Gynecology, Wayne State University, Grace Hospital, 18700 Meyers Road, Detroit, M148235.
20
URETHRAL 100t
PRE~SURE
I!!
(cm H20)
CLOSURE PRESSURE (cm H20) 100-
Fig. 1. Urethral pressure decrease in response to one, two, and three coughs, respectively, is demonstrated. The degree of pressure loss and the time necessary for full pressure recovery is related to the magnitude and number of stresses applied.
Mater.ial and methods
Twenty-eight consecutive patients undergoing complete urodynamic evaluation for a variety of clinical problems were studied. Detailed history, physical examination, negative urine culture, cystometry, cystourethroscopy, uroflowmetry, and urethral pressure profiles were obtained in all cases. A stress test was performed in the dorsal lithotomy and standing position. The patients were asked to cough, laugh, and occa-
Urethral pressure and stress 21
Volume 155 Number 1
1 mm/s
PROXIMAL URETHRA
DISTAL URETHRA
5 mm/s
POST·COUGH PROFILE 5 mm/s
COUGH PROFILE
Fig. 2. Urethral pressure profiles were taken at 1 mm/sec, at 5 mm/sec, and after the patient had coughed repeatedly. Distance to maximum closure pressure (A), urethral functional length (B), and maximum closure pressure (C) were recorded from each profile type. The magnitude of pressure decrease (D) and the time necessary for pressure recovery (E) were recorded in the proximal urethra in response to a single cough. In the distal urethra the direction of change was noted (increase, decrease, or no change). A postcough pressure profile was then obtained.
sionally exercise with a full bladder to see if urinary leakage could be documented. A Q-tip test was performed to measure the degree of urethral mobility.9 The patients were placed in the dorsal lithotomy position and a lubricated Q-tip was introduced into the urethra. A resting angle was obtained with the horizontal position used as a reference zero point. The patient was asked to cough and bear down, and the maximum excursion was measured. The angle measurements were obtained with an orthopedic goniometer. Although this technique is in standard use, the precision, accuracy, and normative values have not been well defined. Urethral, intravesical, and abdominal (vaginal) pressures were obtained simultaneously with microtip pressure transducers, * by methods similar to those previously described. lo Electronic subtraction was used to obtain urethral closure pressure (urethral minus intravesical) and detrusor pressure (intravesical minus abdominal). Pressures were plotted on a six-channel recorder.t Evaluations were obtained in the supine position with 150 ml of 0.9% saline solution. Variables measured and procedures performed are summarized in Fig. 2. Three urethral closure pressure profiles were taken by use of a mechanical puller at a withdrawal rate of 1 mm/sec and then repeated at 5 mm/sec. Measurements were recorded from the third profile and all recordings were taken with the microtransducers in the left lateral position. Recorder speed was set to match profilometer speed in each case. Variables recorded included maximum urethral closure pressure, length to peak pressure, and functional profile lengths. Urethral closure pressure response to stress was eval-
*Models PC-680 Band PC-380, Millar Instruments, Houston, Texas. tUrolab Model 1106, Life Tech, Inc., Houston, Texas.
DETRUSOR PRESSURE
100-
URETHRAL PRESSURE
10rJ:rJ-JJj~ URETHRAL CLOSURE PRESSURE
(em H20) Fig. 3. This tracing of a patient in group 2 demonstrates: A, baseline closure profile; E, no pressure change in the proximal urethra; C, no pressure change in the distal urethra; and D, a negative cough profile.
uated by measuring the magnitude of pressure change and the duration of recovery after a single cough in both proximal and distal urethral segments approximately 0.5 em from peak closure pressure. A cough urethral pressure profile was then obtained with the patient instructed to cough continuously while the transducer was withdrawn through the urethra. To further evaluate the extent of the urethral pressure decrease, the patient was asked to cough vigorously 10 times after which a postcough urethral pressure profile at 5 mm/sec was immediately determined. It was previously reported that the pressure decrease appeared to plateau after four to five stresses. 7 • S In our
22 Richardson
July, 1986 Am J Obstet Gynecol
(em H201
DETRUSOR PRESSURE
Table I. Urethral closure pressure before and after post cough profiles
II, I
/,1"
100-,
~\'---~I,--l
__
I
~WM~----,
Group
1
2
URiETHRAL PRE,-URE
100-,
URETHRAL CLOSURE PRES.URI!
B
Control no. 2 (5 mm/sec)
Post cough (5 mm/sec)
58 ± 26 81 ± 27*
58 ± 24 77 ± 31
59 ± 37 76 ± 31
*Group 1 (I mm/sec) with group 2 (I mm/sec): p < 0.05.
I
JvV'1 A
Control no. 1 (l mm/sec)
c
o
E
Fig. 4. This tracing of a patient in group 1 demonstrates: A, pressure decrease in proximal urethra in response to cough; B, slight pressure increase in the distal urethra in response to a slightly stronger cough; C, baseline profile at 5 mm/sec; D, repetitive coughing followed by a repeat urethral pressure profile; E, postcough profile demonstrating the decrease in functional length and distance to maximum pressure that was consistently seen in group I.
own clinical experience, this could vary between two and seven stresses. Ten coughs were selected to ensure that maximum pressure decrease and the corresponding longest possible recovery time had been reached. The objective was to obtain a pressure profile wherein peak pressure was reached in less than 50% of the time necessary for urethral pressure to recover under the previous static measurements of a single cough. Thus, if the urethral relaxation in response to stress was present, maximum closure pressure should be consistently decreased from baseline values. The condition of stress incontinence was diagnosed on the basis of pressure equalization during a cough profile with simultaneous urinary leakage or a positive stress test in a patient documented to have a stable bladder. The patients were divided into two groups according to urethral closure pressure response to a single cough in the proximal urethral segment: group I-pressure decrease in response to stress (Fig. 1); group 2-no change or a pressure increase in response to stress (Fig. 3). Grou p 1 consisted of 21 patients. The mean age was 49.4 ± 10.4 years. Mean parity was 2.7 ± 1.5. Two patients had previously undergone unsuccessful operation for stress urinary incontinence. The primary urodynamic diagnosis included stress incontinence (57%), unstable detrusor (24%), and normal evaluation (19%).
The normal examinations were in patients having urodynamic assessments before radical hysterectomy. Group 2 consisted of seven patients with a mean age of 42.6 ± 15 years. The mean parity was 2.9 ± 2. In two patients the diagnoses were unstable bladder and sensory urgency, respectively. Three patients had normal examinations before undergoing radical hysterectomy. There were no patients with stress incontinence in this group. The following statistical analyses were performed: Wilcoxon matched pairs test, a Mann-Whitney U test, and Spearman rank correlation. Results
In gr?up 1, the average pressure drop in the proximal urethra was 15.3 ± 8.4 em/H 2 0 with a mean recovery time of 9.1 ± 4.2 seconds. This pressure drop represents a 27% decrease from baseline maximum closure pressure. Recovery time and pressure drop were not significantly different between patients with stress urinary incontinence and those with other urodynamic diagnoses. The pressure reduction in group 1 was not consistently seen in the distal urethral segment (Fig. 4). A pressure increase was seen in 52% (n = 11), there was no pressure change in 33% (n = 7), and there was a pressure decrease in 14% (n = 3). The pressure increase was consistently less and the recovery time consistently shorter than the corresponding values in the proximal urethral segment. The different profilometer speeds used in performing urethral pressure profiles did not alter the maximum closure pressure in either group 1 or group 2 (Table I). The only statistical difference between groups was in the closure pressure measurement taken at 1 mm/sec (p < 0.05). Although the urethral pressure was lower in patients with genuine stress urinary incontinence (55 ± 25 cm/H 2 0, n = 12), this was not significantly different from that in patients with other urodynamic diagnoses (71 ± 28 cm/H 2 0, n = 16). After prolonged coughing, there was no change in maximum closure pressure in either group (Table I). Fig. 5 is a typical representation of a patient in group 1 with pressure decrease in the proximal urethral segment without a change in pressure in the postcough
Urethral pressure and stress 23
Volume 155 Number 1
I
URETHRAL
l--A CLOSURE
f\
'--==S=T;':COUGH
Fig. 5. This patient demonstrates the phenomenon of pressure decrease in the proximal urethra with pressure increase in the distal urethra. Recovery time from a single cough (not shown) was 5.5 seconds. Post-cough profile shows an increase in closure pressure. Elapsed time from last cough to peak closure pressure was 2.8 seconds.
profile. It was felt that the postcough profile was an accurate reflection of events, since the time from the last cough to peak profile pressure averaged 3.5 ± 1 second. (Single cough recovery time was 9.1 ± 4.2 seconds.) There was no statistical difference in baseline functionallength at the various control profilometer speeds (Table II). Although the average baseline functional length in group 2 was increased compared with that in group 1, this was not statistically significant. In the postcough profile, there was a significant decrease in both functional length and distance to peak pressure in group 1. In group 2 there was no significant change in functional length to peak pressure after coughing. There was a significant difference in the extent of urethral relaxation present between group 1 and group 2. In group 1, the average Q-tip angle change was 39 ± 14 degrees. In group 2 the change was 10 ± 8 degrees (p < 0.01). A significant correlation was seen between Q-tip angle change and pressure droplrecovery time in group 1. (Spearman correlation coefficients: pressure drop to Q-tip angle change, R = 0.48, P = 0.013; recovery time to Q-tip angle change, R = 0.3838, P = 0.41; pressure drop to recovery time, R = 0.5034, P = 0.01). The data from which the correlations were drawn are presented in Fig. 6.
Comment This study demonstrated the following: 1. The urethral pressure decrease in response to stress is present only on static profiles. The pressure
Table II. Functional length and length to peak pressure before and after post cough profiles Functional length
Length to peak
Group
Control (5 mmlsec)
I Postmmlsec) cough (5
Control (5 mmlsec)
I Postmmlsec) cough
1 2
2.6 ± 0.6 2.8 ± 0.5
2.3 ± 0.6* 2.8 ± 0.6
1.5 ± 0.5 1.3 ± 0.3
1.2 ± 0.6t 1.3 ± 0.3
(5
*Comparison of group I, control, with group I, post cough: p < 0.01. Comparison of group I, post cough, with group 2, post cough: p < 0.001. tComparison of group I, control, with group I, post cough: p < 0.05.
decrease is not a true physiologic event. Maximum closure pressure in the postcough profile demonstrated no consistent change from that in the resting profiles. 2. The pressure decrease in response to stress appears to be an indicator for patients with stress urinary incontinence. However, 43% of patients presenting with urethral relaxation had other urodynamic diagnoses. 3. In individuals with a pressure decrease in the proximal urethra, there was a pressure increase or no pressure change in 88% of the patients in the distal urethral segment. 4. There was a marked difference in urethral mobility between patients with and those without a pressure decrease. The amount of urethral pressure decrease and the duration of recovery time were significantly correlated with the degree of urethral mobility.
24
Richardson
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July, 1986 Am J Obstet Gynecol
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Fig. 6. The relationship in group I between pressure drop, recovery time, and Q-tip angle change is demonstrated. The greater the pressure drop or the recovery time, the greater the angle change observed.
5. In the postcough profile, functional length and length to peak pressure were significantly decreased over control profile measurements. The observed phenomenon of a urethral pressure decrease in response to stress appears to be an artifact caused by a fixed pressure transducer in the presence of a mobile urethra. The downward and outward rotation of the urethra shifts the stationary microtip sensor toward the urethral-vesical junction. In the proximal urethral segment there is an apparent decrease in urethral pressure as the catheter moves from a highpressure zone to a low-pressure zone. This same catheter shift in the distal urethra causes movement from a low-pressure zone toward urethral peak pressure. After abdominal stress (coughing) the urethra returns to its original location. In the postcough profile this results in the catheter moving out as the urethra moves in, producing an apparent decrease in functional length and a decrease in the distance to peak pressure. It has long been recognized that urethral descensus from the symphysis pubis is an important aspect in the pathophysiologic features of stress incontinence and that this mobility results in a decreased abdominal pressure transmission to the proximal urethra. Although not all patients with relaxation have stress urinary incontinence, the majority of patients with genuine stress incontinence have relaxation. Traditionally, this anatomic defect has been measured on either a Q-tip test or a cystogram. 9 . II The observation that urethral pressure decrease is essentially a function of urethral mo-
bility at times of acute stress opens the possibility of a urodynamic method of quantifying urethral relaxation. Individuals with a pressure decrease in response to stress in the proximal urethra generally were found to have a pressure increase or no change in pressure in the distal urethral segment. This difference can be explained by the fact that the urethra perforates the urogenital diaphragm approximately 0.5 cm from maximum urethral pressure. 12 The urethra has increased mobility in its proximal segment, but as it enters the urogenital diaphragm it becomes more fixed in its attachments to the symphysis pubis . Standard urethrocystometry is performed by placing the transducer at peak closure pressure. In the presence of a mobile urethra, we have noticed marked variations in recorded urethral pressure. This is especially apparent in patients in whom the maximum pressure covers a spatial area of limited urethral length. Slight body movement, breathing, or perineal muscle contractions can produce urethral movement that can mimic so-called urethral instability (change in urethral pressure> 15 cm H 20). It is possible that what is being interpreted as urethral instability in some cases is artifactual and related to urethral mobility. Further investigation will be required to clarify this point. The measurement of the urethral pressure profile continues to be an integral part of the urodynamic evaluation. The measurement of closure pressure identifies patients with inherent sphincter weakness who have a significantly lower cure rate with incontinence operations than patients with normal pressure. The cough profile provides the physician with objective evidence of genuine stress incontinence and enables the physician to determine the actual amount of pressure transmission. Although pressure decrease in response to stress does not appear to be an independent variable in the pathophysiologic features of stress incontinence, it enables the physician to assess the relative degree of urethral mobility. REFERENCES I. Rud T, Andersson KE, Asmussen M, et al. Factors main-
2.
3. 4. 5. 6.
taining the intraurethral pressure in women. Invest Urol 1980;17:343. Enhorning G. Simultaneous recording of intravesical and intraurethral pressure: a study of urethral closure in normal and stress incontinent women. Acta Chir Scand 1961 ;276(suppl): 1-68. Low JA, Kao MS. Patterns of urethral resistance in deficient urethral sphincter function. Obstet Gynecol 1972; 40:634. Herbert DB, Francis LN, Ostergard DR. Significance of urethral vascular pulsations in genuine stress incontinence. AM J OBSTET GYNECOL 1982; 144:828. Heidler H, Wolk H,Jonas U. Urethral closure mechanism under stress conditions. Eur Urol 1979;5: 110. Hilton P, Stanton SL. A clinical and urodynamic assessment of the Burch colposuspension for genuine stress incontinence. Br J Obstet Gynaecol 1983;90:934.
Urethral pressure and stress
Volume 155 Number I
7. Hilton P, Stanton SL. Urethral pressure measurement by microtransducers: the results in symptom free women and in those with genuine stress incontinence. Br J Obstet Gynaecol 1983;90:919. 8. Bunne G, Obrink A. Urethral closure pressure at stressa comparison between stress incontinent and ocontinent women. Urol Res 1978;6:127. 9. Chrystle CD, Charmel S, Copeland WE. Q-tip test for stress urinary incontinence. Obstet GynecoI1971;38:3I3.
10. Richardson DA. Use of vaginal pressure measurement in urodynamic testing. Obstet Gynecol 1985 (in press). II. Hodgkinson CPo Stress urinary incontinence-I970. AM J OBSTET GYNECOL 1970; 108: 1141. 12. Westby M, Asmussen M, Ulmsteri U. Location of maximum intraurethral pressure related to urogenital diaphragm in the female subject as studied by simultaneous urethrocystometry and voiding urethrocystography. AM J OBSTET GYNECOL 1982;144:408. 0
Acceptability of chorionic villi sampling for prenatal diagnosis Margaret M. McGovern, Ph.D., James D. Gol!Iberg, M.D., and Robert J. Desnick, Ph.D., M.D. New York, New York The factors that influence women in choosing between first-trimester chorionic villi sampling and second-trimester amniocentesis for prenatal diagnosis were investigated. Five hundred twenty women of advanced maternal age who had previously undergone prenatal diagnosis by amniocentesis ano were delivered of a normal infant were requested to complete a questionnaire concerning their attitudes toward amniocentesis and chorionic villi sampling. The majority of respondents indicated that the time at which chorionic villi sampling is performed (76%), the rapid availability of diagnostic-results (72%), and the type of abortion procedure available (68%) would make them choose this method. In contrast, the factors that influenced women to choose amniocentesis included the known low risk of spontaneous abortion (76%) and confidence in the skill of the obstetrician who would perform the procedure (56%). When all factors were considered together, 68% of the respondents chose amniocentesis based on the known low risk of spontaneous abortion, whereas for those who chose chorionic villi sampling (32%), the major criterion was the fact that the procedure is performed in the first trimester. However, 87% of women who preferred amniocentesis indicated that if the risk of spontaneous abortion associated with chorionic villi sampling were equal to or less than that of amniocentesis, they would choose chorionic villi sampling. These results indicate that for many women of advanced maternal age, the acceptability and the use of chorionic villi sampling will be dependent on the demonstration that the risk of fetal loss is low, approaching that of amniocentesis. (AM J OesTET GVNECOL 1986;155:25-9.)
Key words: Chorionic villi sampling, amniocentesis, prenatal diagnosis Recently a new method of obtaining fetal tissue for prenatal diagnosis, called chorionic villi sampling, has been developed.'o2 This procedure, which is performed at 8 to 12 weeks of pregnancy, involves the ultrasoundguided transcervical aspiration of a small amount of chorionic villi. This tissue is used directly or can be cultured for diagnostic chromosomal and/or biochemical analyses. Test results are usually available within 2 weeks, thereby providing rapid relief of parental anxiety when the fetus is found normal or, if a fetus with a genetic defect is detected, permitting the parents to choose a safer, easier termination of the pregnancy durFrom the Division of Medical Genetics and Maternal-Fetal Medicine, Mount Sinai School of Medicine. Received for publication July 22, 1985; revised December 5, 1985; accepted February 3, 1986. Reprint requests: Dr. Robert). Desnick, Mount Sinai School of Medicine, Fifth Ave. and 100th St., New York, NY 10029.
ing the first trimester. Preliminary data from 10,000 procedures performed worldwide have revealed that chorionic villi sampling is safe for the mother and that the rate of fetal loss is about 4% when performed by experienced obstetricians. Since most conditions that can be diagnosed by amniocentesis are detectable by chorionic villi sampling, this procedure represents an attractive alternative to amniocentesis, which cannot be safely performed until the second trimester. Previous studies have documented the safety and accuracy of amniocentesis for prenatal diagnosis. 3o ' However, experience has identified several disadvantages of the procedure. Amniocentesis cannot be safely performed until the second trimester of pregnancy, usually during weeks 16 to 18, and the diagnostic results are often unavailable for 2 to 4 weeks after the procedure. Several investigators have reported that the period of waiting for the
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