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The unstable female urethra
The unstable female urethra ULF
ULMSTEN,
LARS
HENRIKSSON,
SERAFIM Arhus,
M.D.
IOSIF,
Denmark,
M.D. M.D.
and Malmo
and Lund,
Sweden
Four hundred forty-seven patients with urinary incontinence were examined at the outpatient clinic and then referred to unxlynamic investigation by urethral pressure profile measurement and simultaneous urethrocystometry. On urodynamic investigation, 55 patients showed signs of an unstable urethra (momentary variations in urethral pressure exceeding an amplitude of 15 cm of water by or without registration of bladder instability). Urethral instability was found in 15 patients with stress incontinence, in 23 patients with urge incontinence, and in 13 patients with combined stress and urge incontinence (i.e., signs and symptoms of both stress and urge incontinence). In four patients, urethral instability was the only pathologic finding when the recordings were made. From the pressure recordings, three types of urethral instability could be recognized: type 1, relatively small fluctuations in the urethral pressure at large bladder volumes; type 2, relatively large variations in urethral pressure with frequent decreases in the pressure, often combined with signs of unstable bladder; type 3, marked variations in the urethral pressure which appeared already at the start of urethrccystometry, i.e., at low bladder volumes. The variations in urethral pressure prevailed during the whole recording procedure, whereas bladder pressure was completely stable at all times. (AM. J. OBSTET. GYNECOL. 144:93, 1982.)
URINARY URGE incontinence in women is frequently caused by uninhibited contractions of the detrusor muscle (unstable bladder or dyssynergia of the detrusor muscle). Consequently, urodynamic examinations of women with that symptom are mainly focused on bladder dysfunctions, whereas urethral disorders are dealt with less. At simultaneous urethrocystometry by a technique previously described,‘* I3 we reported some years ago on the occurrence of prominent variations in the urethral pressure in patients with symptoms and signs of urge incontinence. I4 The existence of this phenomenon which, in line with bladder instability, was referred to as urethral instability received further confirmation later.6* ‘1 l2 To our knowledge, there are no studies on the existence of the disorder in a large number of women suffering from urinary incontinence. Therefore, the
From the Departments of Obstetrics and Gynecology, UniversiQ of Arhus, and Malti General Hospital and University Hospital of Lund. Received for publication Revised January Acceptid
May
November
5, 1981.
8, 1982. 3, 1982.
Reprint requests: Dr. lJlf Ulmsten, Department of Obstetrics and Gynecology, University of ;8rbus, 8000 Arhus C, Denmark.
0002-9378/82/170093+05$00.50/0@
1982 The C.V.Mosby Co.
present investigation was undertaken to ascertain the prevalence and significance of urethral instability in female patients referred for urodynamic investigation because of symptoms of urinary incontinence.
Material and methods Four hundred forty-seven consecutive patients were investigated during a 2-year period (1979-1980). They were allocated to one of two groups. Group 1 was composed of 239 women referred to the urodynamic laboratory in the Department of Obstetrics and Gynecology, Malmo General Hospital; and group 2 was composed of 208 women referred to the urodynamic laboratory, University Hospital, Lund. All women were referred to the laboratories because of symptoms of urinary incontinence. Table I gives the diagnoses after urodynamic investigation, i.e., the number of patients suffering from stress, urge, or combined stress and urge incontinence. Before urodynamic investigation, all patients had undergone a gynecologic examination to exclude abnormalities in the genital tract. Moreover, a urethrocystoscopy was performed and the urine was cultured for bacteria. Patients with abnormalities in the genital tract and symptoms or signs of urinary infection were excluded from the investigation. Investigative technique. All patients were examined with simultaneous urethrocystometry according to the technique described by Asmussen and Ulmsten.i* ’ 93
94
Ulmsten,
Henriksson,
September 1, 1982 Am. J. Obstet. Gynecol.
and losif
Table I. Diagnoses after simultaneous urethrocystometry in 447 patients referred urodynamic investigation because of symptoms of urinary incontinence Diagnosis after simultaneous urethrocystomehy
for
m
Stress incontinence Urge incontinence Combined stress and urge incontinence Normal (continent) Total
140 45
109
58.5 18.9 9.2
22 32
13.4
239
100.0
52.4 14.4
30 31
14.9
38 208
18.3
100.0
Table II. Urethral instability in 55 patients related to stress incontinence, urge incontinence, or combined stress and urge incontinence (i.e., symptoms and signs of both stress and urge incontinence) Diagnosis after simultanetns urethrocystometry
Unstable urethra only Unstable urethra plus stress
No. of #nAnra 4
15
Group
1
Group
2
1
3 3
12
10
13
4
9
incontinence
Unstable urethra plus urge
23
incontinence
Unstable urethra plus combined stress and urge incon-
13
tinence
Total No.
55
The patients in group 1 were investigated according to the following procedure. The woman was placed in the lithotomy position. After control of the residual, the bladder was filled with body-warm saline solution to a volume of 300 ml. In two cases, because the bladder capacity was less than 300 ml, the investigation was made at bladder volumes of 225 and 275 ml. The rate of infusion was 50 ml/min. The recording catheter was introduced transurethrally into the bladder, and three consecutive urethral pressure profile measurements were made.’ For simultaneous urethrocystometry, the urethral microtransducer was then located in the highpressure zone of the urethra.3 Bladder instability was provoked, with the patient in both lying and standing positions, by strong coughing, i.e., inducing increases in intra-abdominal pressure ~100 cm of water. In case no instability was observed, additional saline solution was infused during simultaneous urethrocystometry up to maximum bladder capacity, i.e., the infusion was not stopped until either the patient complained of a strong desire to void or leakage occurred.
Patients in group 2 were investigated in a similar manner, with the following exceptions. After the woman had been placed in the lithotomy position, the bladder was initially filled with only 100 ml of saline solution. Three urethral pressure profile measurements were then made, after which simultaneous urethrocystometry was performed during filling of the bladder up to maximum capacity. At every 100 ml of infused saline solution, i.e., at bladder volumes of 200 ml, 300 ml, etc., the patient was requested to cough vigorously. At completion of the investigation, the catheter was removed and the patient was asked to micturate, after which the amount of residual was assessed. Definitions. Bladder instability was defined according to the recommendations of the International Continence Society Standardization Committee.4 Urethral instability was defined as variations in the urethral pressure >15 cm of water (positive or negative) not associated with increase in intra-abdominal pressure or with pulsations of the urethral vascular bed (Fig. 1).
Results Urethral instability was seen in 55 (12.3%) of the 447 patients investigated (Table II). In group 1,20 (8.3%) of the 239 patients had signs of urethral instability; 14 of these already displayed instability at the start of the pressure recordings at bladder volumes of 300 ml or less. In the other six patients, urethral instability occurred during the subsequent filling of the bladder up to maximum capacity. The bladder capacity was between 225 and 650 ml (mean, 424 ml). As seen from Table II, urethral instability occurred in three patients with stress incontinence, in 10 patients with urge incontinence, in four patients with combined stress and urge incontinence, and in three patients without signs of stress or urge incontinence. Among the 208 patients in group 2, urethral instability was recorded in 35 (16.8%). In 34 patients, urethral instability already appeared at bladder volumes between 100 and 150 ml. In one patient, the instability was elicited at bladder volumes of 200 to 300 ml, The bladder capacity was between 100 and 800 ml (mean, 527 ml). Twelve of the 35 patints suffered from stress incontinence, 13 from urge incontinence, nine from combined stress and urge incontinence, and one had urethral instability without other symptoms. From the pressure recordings, three types of urethral instability could be recognized. Type 1 was relatively small fluctuations in the urethral pressure at large bladder volumes, i.e., ~400 ml (Fig. 1). The pressure oscillations occurred simultaneously with the patient’s report of strong urge sensations. As a rule, the detrusor muscle started to contract shortly after the
Volume Number
144 I
Unstable
fernate
urethra
95
50 01
b
BLADDER
P
CLOSURE
P
10 LCC
Fig. 1. Urethral
pressure profile and simultaneous urethrocystometry in a patient with urethral a urethral pressure profile is recorded. From this measurement, the high-pressure zone of the urethra is identified and simultaneous urethrocystometry is then carried out during filling of the bladder. Note the small pulsations of the urethral pressure, which are synchronous with the patient’s Pulse rate. Coughing does not provoke urethral or bladder instability. At the first arrow (bottom), the patient experiences the first desire to void, At the second arrow, there is a strong desire fo void, and marked variations in the urethral pressure are seen. Shortly after onset of these variations in urethral pressure, the detrusor muscle is activated, as indicated by a marked elevation in the bladder pressure. At the last arrow, the urethral closure pressure (bottom tracing) has reached zero, and urine is now escaping the urethra. instability
type
1. To the left,
onset of the urethral instability. Type 2 urethral instability was relatively large variations in urethral pressure with frequent decreases in the pressure, often combined with urodynamic evidence of an unstable bladder (Fig. 2). The urethral instability was seen at relatively low bladder volumes, i.e., ~200 ml. Type 3 urethral instability was characterized by marked variations in the urethral pressure which appeared already at the start of the urethrocystometry, i.e., at bladder volumes of 100 ml. The variations in urethral pressure prevailed during the whole recording procedure, whereas the bladder pressure was completely stable all the time (Fig. 3). Residuals >50 ml were only registered in one patient with urethral instability.
Comment Presently, no definitive explanation for the occurrence of urethral instability can be given. It is tempting to speculate upon whether the disorder might be a part of the enigmatic urethral syndrome.5 As shown previously, the urethral pressure is dependent on the urethral striated muscles, the urethral smooth muscles, and the vascular bed of the urethra.** Moreover, pressure transmitted from the abdominal cavity will affect the urethral pressure. As is clearly seen from Fig. 1, the arterial pulsations are easily separated from the variations in pressure that occur with urethral instability. Moreover, an increase in abdomi-
nal pressure with coughing does not seem to affect urethral instability. The disorder might then be ascribed to phenomena that occur within the striated and smooth muscles. In some patients suffering from urethral instability type 1, part of the variations in pressure could be explained by the fact that these patients, at high bladder volumes, tried to prevent urine from escaping the urethra by voluntarily contracting the striated muscles of the urethra and the pelvic floor. The significance of such activity of striated muscle for the observed variations in urethral pressure could be elucidated by simultaneous electromyographic and pressure recordings. It has also been shown that, immediately before the start of normal micturition, the urethral pressure decreases, after which the intravesical pressure is increased.‘, ” Perhaps, type 1 urethral instability is just a normal physiologic phenomenon that signals that the patient is close to bladder capacity and has to micturate. From the present investigation, no conclusions can be drawn about the significance of urethral instability in patients with decreased ability to empty the bladder, since only one of our patients had residual urine >50 ml. Urethral instability might also be secondary to a bladder defect that manifests itself first within the urethra. This explanation might be valid in patients suffering from type 2 instability. However, with type 3 instability, the variations in pressure started almost at the beginning of the investigation at low bladder volumes
96
Ulmstsn,
Hsnriksson,
September 1, 1982 Am. J. Obstet. Gynecol.
and losif
100
BLADDER
URETHRAL
0
ml D
P
P
10 ret
Fig. 2. Urethral instability type 2 and bladder instability during simultaneous urethrocystometry in a patient with prominent symptoms of urge incontinence. The patient already experienced a strong desire to void at a bladder volume of 100 ml, and, as seen, there are marked variations in both the bladder and the urethral pressures. The filling rate was 50 mhmin.
IOOML
27s
ML
350ML
Fig. 3. Urethral instability type 3 in a patient with severe sensory urge incontinence. Throughout the recording, there are marked variations in pressure within the urethra, whereas the bladder is completely stable.
that did not exceed 100 ml. In all these patients, the detrusor muscle was relaxed, as seen by a normal intravesical pressure, but most of the patients expressed a desire to void. Studies in the cat* have shown that the urethral pressure is decreased when the pelvic nerve is stimulated. This response can be blocked by propranolol, thus indicating that adrenergic p-receptors may play an important role in regulating the urethral pressure in cats. However, in humans, in whom u-receptors dominate in the urethra, this seems to be less likely. In 19’78, Torrens.*2 upon stimulation of the sacral nerves at S2-4 in humans, found an initial increase
in both intravesical and intraurethral pressure, after which there was a marked decrease in the urethral pressure that remained as long as the stimulation continued. Stimulation at S4 gave a more pronounced decrease in urethral pressure than did stimulation of S2. The same result was obtained also after section of the nerves when the distal but not proximal nerve end was stimulated. According to Torrens, inhibition of parasympathetic efferent nerve pathways could be the pathophysiologic background for the unstable urethral syndrome. However, the reason for this increased inhibition of parasympathetic efferent nerve pathways remains unclear.
Volume
Number
144 1
Although the etiology of urethral instability in most cases is unknown, we have to realize that the phenomenon exists and must be taken into consideration when evaluating patients who are suffering from urinary incontinence. The disorder cannot be revealed by conventional urologic investigations, but should be studied with a proper technique for simultaneous urethrocystometry. Furthermore, there have been no systematic investigations on the treatment of urethral instability. In contrast to urge incontinence caused by
Unstable
female
urethra
97
dyssynergia of the detrusor muscle or bladder instability, in which drugs that relax the detrusor muscle have proved to be useful, urethral instability has recently been reported to be improved by drugs that increase the tonus ofthe urethral smooth muscles, i.e., Lu-adrenoceptor stimulators.6 However, further studies are necessary to establish the significance and the etiology of urethral instability before recommendations in regard to the treatment of the disorder can be given.
REFERENCES
1. Asmussen, M., and Ulmsten, U.: Simultaneous urethrocystometry and urethra pressure profile measurement with a new technique, Acta Obstet. Gynecol. Stand. 54: 385, 1975. 2. Asmussen, M., and Ulmsten, U.: Simultaneous urethrocystometry with a new technique, Stand. J. Urol. Nephrol. 10~7, 1976. 3. Asmussen, M., Ulmsten, U.: A new technique for measurements of the urethra pressure profile, Acta Obstet. Gynecol. Stand. 55:167, 1976. 4. Bates, C. P., Bradley, W., Glen, E., Griffiths, D., Melchior, H., Rowan, D., Sterling, A., Zimmer, M., and Hald, T.: Standardization of terminology of lower urinarv tract function, Urology 9:237, 1977Y’ 5. Acute urethral syndrome in women. Br. Med. Y1. 282:3. 1981. 6. Fossberg, E., Beisland, H. O., and Sander, S.: Sensory urgency in females: Treatment with phenylpropanolamine, Eur. Urol. 7:157, 1981, 7. Iosif, S. C., Henriksson, L., and Ulmsten, U.: Urethrocystometry as a routine method for the objective evaluation of women with urinary incontinence, Arch. Gynecol. 230~41, 1980.
8. McGuire, J. E., and Wagner, C. F.: The effects of sacral denervation on bladder and urethral function, Surg. Gynecol. Obstet. l&343, 1977. 9. Rud, T., Ulmsten, U., and Andersson, K. E.: Initiation of voiding in healthy women and those with stress incontinence, Acta Obstet. Gynecol. Stand. 57:457, 1978. 10. Rud, T., Ulmsten, U., and We&y, M.: Initiation of micturition: A study of combined urethrocystometry and urethrocystography in healthy and stress incontinent females, Stand. J. Urol. Nephrol. 13:259, 1979. 11. Rud, T., Asmussen, M., Andersson, K. E., Hunting, A., and Ulmsten, U.: Factors maintaining the intraurethral pressure in women, Invest. Ural. 17:343, 1980. 12. Torrens, M. J.: Urethral sphincteric responses to stimulation of the sacral nerves in the human female, Urol. Int. 33:22, 1978. 13. Ulmsten, U., Asmussen, M., and Lindstriim, K.: A new technique for simultaneous urethrocystometry including measurements of the urethral pressure profile, Urol. Int. 32:127, 1977. 14. Ulmsten, U., Andersson, K. k:., and Persson, C. G. A.: Diagnostic and therapeutic aspects of urge incontinence in women, Urol. Int. 32:88, 1977.
ULMSTEN,
LARS
HENRIKSSON,
SERAFIM Arhus,
M.D.
IOSIF,
Denmark,
M.D. M.D.
and Malmo
and Lund,
Sweden
Four hundred forty-seven patients with urinary incontinence were examined at the outpatient clinic and then referred to unxlynamic investigation by urethral pressure profile measurement and simultaneous urethrocystometry. On urodynamic investigation, 55 patients showed signs of an unstable urethra (momentary variations in urethral pressure exceeding an amplitude of 15 cm of water by or without registration of bladder instability). Urethral instability was found in 15 patients with stress incontinence, in 23 patients with urge incontinence, and in 13 patients with combined stress and urge incontinence (i.e., signs and symptoms of both stress and urge incontinence). In four patients, urethral instability was the only pathologic finding when the recordings were made. From the pressure recordings, three types of urethral instability could be recognized: type 1, relatively small fluctuations in the urethral pressure at large bladder volumes; type 2, relatively large variations in urethral pressure with frequent decreases in the pressure, often combined with signs of unstable bladder; type 3, marked variations in the urethral pressure which appeared already at the start of urethrccystometry, i.e., at low bladder volumes. The variations in urethral pressure prevailed during the whole recording procedure, whereas bladder pressure was completely stable at all times. (AM. J. OBSTET. GYNECOL. 144:93, 1982.)
URINARY URGE incontinence in women is frequently caused by uninhibited contractions of the detrusor muscle (unstable bladder or dyssynergia of the detrusor muscle). Consequently, urodynamic examinations of women with that symptom are mainly focused on bladder dysfunctions, whereas urethral disorders are dealt with less. At simultaneous urethrocystometry by a technique previously described,‘* I3 we reported some years ago on the occurrence of prominent variations in the urethral pressure in patients with symptoms and signs of urge incontinence. I4 The existence of this phenomenon which, in line with bladder instability, was referred to as urethral instability received further confirmation later.6* ‘1 l2 To our knowledge, there are no studies on the existence of the disorder in a large number of women suffering from urinary incontinence. Therefore, the
From the Departments of Obstetrics and Gynecology, UniversiQ of Arhus, and Malti General Hospital and University Hospital of Lund. Received for publication Revised January Acceptid
May
November
5, 1981.
8, 1982. 3, 1982.
Reprint requests: Dr. lJlf Ulmsten, Department of Obstetrics and Gynecology, University of ;8rbus, 8000 Arhus C, Denmark.
0002-9378/82/170093+05$00.50/0@
1982 The C.V.Mosby Co.
present investigation was undertaken to ascertain the prevalence and significance of urethral instability in female patients referred for urodynamic investigation because of symptoms of urinary incontinence.
Material and methods Four hundred forty-seven consecutive patients were investigated during a 2-year period (1979-1980). They were allocated to one of two groups. Group 1 was composed of 239 women referred to the urodynamic laboratory in the Department of Obstetrics and Gynecology, Malmo General Hospital; and group 2 was composed of 208 women referred to the urodynamic laboratory, University Hospital, Lund. All women were referred to the laboratories because of symptoms of urinary incontinence. Table I gives the diagnoses after urodynamic investigation, i.e., the number of patients suffering from stress, urge, or combined stress and urge incontinence. Before urodynamic investigation, all patients had undergone a gynecologic examination to exclude abnormalities in the genital tract. Moreover, a urethrocystoscopy was performed and the urine was cultured for bacteria. Patients with abnormalities in the genital tract and symptoms or signs of urinary infection were excluded from the investigation. Investigative technique. All patients were examined with simultaneous urethrocystometry according to the technique described by Asmussen and Ulmsten.i* ’ 93
94
Ulmsten,
Henriksson,
September 1, 1982 Am. J. Obstet. Gynecol.
and losif
Table I. Diagnoses after simultaneous urethrocystometry in 447 patients referred urodynamic investigation because of symptoms of urinary incontinence Diagnosis after simultaneous urethrocystomehy
for
m
Stress incontinence Urge incontinence Combined stress and urge incontinence Normal (continent) Total
140 45
109
58.5 18.9 9.2
22 32
13.4
239
100.0
52.4 14.4
30 31
14.9
38 208
18.3
100.0
Table II. Urethral instability in 55 patients related to stress incontinence, urge incontinence, or combined stress and urge incontinence (i.e., symptoms and signs of both stress and urge incontinence) Diagnosis after simultanetns urethrocystometry
Unstable urethra only Unstable urethra plus stress
No. of #nAnra 4
15
Group
1
Group
2
1
3 3
12
10
13
4
9
incontinence
Unstable urethra plus urge
23
incontinence
Unstable urethra plus combined stress and urge incon-
13
tinence
Total No.
55
The patients in group 1 were investigated according to the following procedure. The woman was placed in the lithotomy position. After control of the residual, the bladder was filled with body-warm saline solution to a volume of 300 ml. In two cases, because the bladder capacity was less than 300 ml, the investigation was made at bladder volumes of 225 and 275 ml. The rate of infusion was 50 ml/min. The recording catheter was introduced transurethrally into the bladder, and three consecutive urethral pressure profile measurements were made.’ For simultaneous urethrocystometry, the urethral microtransducer was then located in the highpressure zone of the urethra.3 Bladder instability was provoked, with the patient in both lying and standing positions, by strong coughing, i.e., inducing increases in intra-abdominal pressure ~100 cm of water. In case no instability was observed, additional saline solution was infused during simultaneous urethrocystometry up to maximum bladder capacity, i.e., the infusion was not stopped until either the patient complained of a strong desire to void or leakage occurred.
Patients in group 2 were investigated in a similar manner, with the following exceptions. After the woman had been placed in the lithotomy position, the bladder was initially filled with only 100 ml of saline solution. Three urethral pressure profile measurements were then made, after which simultaneous urethrocystometry was performed during filling of the bladder up to maximum capacity. At every 100 ml of infused saline solution, i.e., at bladder volumes of 200 ml, 300 ml, etc., the patient was requested to cough vigorously. At completion of the investigation, the catheter was removed and the patient was asked to micturate, after which the amount of residual was assessed. Definitions. Bladder instability was defined according to the recommendations of the International Continence Society Standardization Committee.4 Urethral instability was defined as variations in the urethral pressure >15 cm of water (positive or negative) not associated with increase in intra-abdominal pressure or with pulsations of the urethral vascular bed (Fig. 1).
Results Urethral instability was seen in 55 (12.3%) of the 447 patients investigated (Table II). In group 1,20 (8.3%) of the 239 patients had signs of urethral instability; 14 of these already displayed instability at the start of the pressure recordings at bladder volumes of 300 ml or less. In the other six patients, urethral instability occurred during the subsequent filling of the bladder up to maximum capacity. The bladder capacity was between 225 and 650 ml (mean, 424 ml). As seen from Table II, urethral instability occurred in three patients with stress incontinence, in 10 patients with urge incontinence, in four patients with combined stress and urge incontinence, and in three patients without signs of stress or urge incontinence. Among the 208 patients in group 2, urethral instability was recorded in 35 (16.8%). In 34 patients, urethral instability already appeared at bladder volumes between 100 and 150 ml. In one patient, the instability was elicited at bladder volumes of 200 to 300 ml, The bladder capacity was between 100 and 800 ml (mean, 527 ml). Twelve of the 35 patints suffered from stress incontinence, 13 from urge incontinence, nine from combined stress and urge incontinence, and one had urethral instability without other symptoms. From the pressure recordings, three types of urethral instability could be recognized. Type 1 was relatively small fluctuations in the urethral pressure at large bladder volumes, i.e., ~400 ml (Fig. 1). The pressure oscillations occurred simultaneously with the patient’s report of strong urge sensations. As a rule, the detrusor muscle started to contract shortly after the
Volume Number
144 I
Unstable
fernate
urethra
95
50 01
b
BLADDER
P
CLOSURE
P
10 LCC
Fig. 1. Urethral
pressure profile and simultaneous urethrocystometry in a patient with urethral a urethral pressure profile is recorded. From this measurement, the high-pressure zone of the urethra is identified and simultaneous urethrocystometry is then carried out during filling of the bladder. Note the small pulsations of the urethral pressure, which are synchronous with the patient’s Pulse rate. Coughing does not provoke urethral or bladder instability. At the first arrow (bottom), the patient experiences the first desire to void, At the second arrow, there is a strong desire fo void, and marked variations in the urethral pressure are seen. Shortly after onset of these variations in urethral pressure, the detrusor muscle is activated, as indicated by a marked elevation in the bladder pressure. At the last arrow, the urethral closure pressure (bottom tracing) has reached zero, and urine is now escaping the urethra. instability
type
1. To the left,
onset of the urethral instability. Type 2 urethral instability was relatively large variations in urethral pressure with frequent decreases in the pressure, often combined with urodynamic evidence of an unstable bladder (Fig. 2). The urethral instability was seen at relatively low bladder volumes, i.e., ~200 ml. Type 3 urethral instability was characterized by marked variations in the urethral pressure which appeared already at the start of the urethrocystometry, i.e., at bladder volumes of 100 ml. The variations in urethral pressure prevailed during the whole recording procedure, whereas the bladder pressure was completely stable all the time (Fig. 3). Residuals >50 ml were only registered in one patient with urethral instability.
Comment Presently, no definitive explanation for the occurrence of urethral instability can be given. It is tempting to speculate upon whether the disorder might be a part of the enigmatic urethral syndrome.5 As shown previously, the urethral pressure is dependent on the urethral striated muscles, the urethral smooth muscles, and the vascular bed of the urethra.** Moreover, pressure transmitted from the abdominal cavity will affect the urethral pressure. As is clearly seen from Fig. 1, the arterial pulsations are easily separated from the variations in pressure that occur with urethral instability. Moreover, an increase in abdomi-
nal pressure with coughing does not seem to affect urethral instability. The disorder might then be ascribed to phenomena that occur within the striated and smooth muscles. In some patients suffering from urethral instability type 1, part of the variations in pressure could be explained by the fact that these patients, at high bladder volumes, tried to prevent urine from escaping the urethra by voluntarily contracting the striated muscles of the urethra and the pelvic floor. The significance of such activity of striated muscle for the observed variations in urethral pressure could be elucidated by simultaneous electromyographic and pressure recordings. It has also been shown that, immediately before the start of normal micturition, the urethral pressure decreases, after which the intravesical pressure is increased.‘, ” Perhaps, type 1 urethral instability is just a normal physiologic phenomenon that signals that the patient is close to bladder capacity and has to micturate. From the present investigation, no conclusions can be drawn about the significance of urethral instability in patients with decreased ability to empty the bladder, since only one of our patients had residual urine >50 ml. Urethral instability might also be secondary to a bladder defect that manifests itself first within the urethra. This explanation might be valid in patients suffering from type 2 instability. However, with type 3 instability, the variations in pressure started almost at the beginning of the investigation at low bladder volumes
96
Ulmstsn,
Hsnriksson,
September 1, 1982 Am. J. Obstet. Gynecol.
and losif
100
BLADDER
URETHRAL
0
ml D
P
P
10 ret
Fig. 2. Urethral instability type 2 and bladder instability during simultaneous urethrocystometry in a patient with prominent symptoms of urge incontinence. The patient already experienced a strong desire to void at a bladder volume of 100 ml, and, as seen, there are marked variations in both the bladder and the urethral pressures. The filling rate was 50 mhmin.
IOOML
27s
ML
350ML
Fig. 3. Urethral instability type 3 in a patient with severe sensory urge incontinence. Throughout the recording, there are marked variations in pressure within the urethra, whereas the bladder is completely stable.
that did not exceed 100 ml. In all these patients, the detrusor muscle was relaxed, as seen by a normal intravesical pressure, but most of the patients expressed a desire to void. Studies in the cat* have shown that the urethral pressure is decreased when the pelvic nerve is stimulated. This response can be blocked by propranolol, thus indicating that adrenergic p-receptors may play an important role in regulating the urethral pressure in cats. However, in humans, in whom u-receptors dominate in the urethra, this seems to be less likely. In 19’78, Torrens.*2 upon stimulation of the sacral nerves at S2-4 in humans, found an initial increase
in both intravesical and intraurethral pressure, after which there was a marked decrease in the urethral pressure that remained as long as the stimulation continued. Stimulation at S4 gave a more pronounced decrease in urethral pressure than did stimulation of S2. The same result was obtained also after section of the nerves when the distal but not proximal nerve end was stimulated. According to Torrens, inhibition of parasympathetic efferent nerve pathways could be the pathophysiologic background for the unstable urethral syndrome. However, the reason for this increased inhibition of parasympathetic efferent nerve pathways remains unclear.
Volume
Number
144 1
Although the etiology of urethral instability in most cases is unknown, we have to realize that the phenomenon exists and must be taken into consideration when evaluating patients who are suffering from urinary incontinence. The disorder cannot be revealed by conventional urologic investigations, but should be studied with a proper technique for simultaneous urethrocystometry. Furthermore, there have been no systematic investigations on the treatment of urethral instability. In contrast to urge incontinence caused by
Unstable
female
urethra
97
dyssynergia of the detrusor muscle or bladder instability, in which drugs that relax the detrusor muscle have proved to be useful, urethral instability has recently been reported to be improved by drugs that increase the tonus ofthe urethral smooth muscles, i.e., Lu-adrenoceptor stimulators.6 However, further studies are necessary to establish the significance and the etiology of urethral instability before recommendations in regard to the treatment of the disorder can be given.
REFERENCES
1. Asmussen, M., and Ulmsten, U.: Simultaneous urethrocystometry and urethra pressure profile measurement with a new technique, Acta Obstet. Gynecol. Stand. 54: 385, 1975. 2. Asmussen, M., and Ulmsten, U.: Simultaneous urethrocystometry with a new technique, Stand. J. Urol. Nephrol. 10~7, 1976. 3. Asmussen, M., Ulmsten, U.: A new technique for measurements of the urethra pressure profile, Acta Obstet. Gynecol. Stand. 55:167, 1976. 4. Bates, C. P., Bradley, W., Glen, E., Griffiths, D., Melchior, H., Rowan, D., Sterling, A., Zimmer, M., and Hald, T.: Standardization of terminology of lower urinarv tract function, Urology 9:237, 1977Y’ 5. Acute urethral syndrome in women. Br. Med. Y1. 282:3. 1981. 6. Fossberg, E., Beisland, H. O., and Sander, S.: Sensory urgency in females: Treatment with phenylpropanolamine, Eur. Urol. 7:157, 1981, 7. Iosif, S. C., Henriksson, L., and Ulmsten, U.: Urethrocystometry as a routine method for the objective evaluation of women with urinary incontinence, Arch. Gynecol. 230~41, 1980.
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