Urol. int. 34 : 403 409 (1979)

A Test for Bladder Neck Competence: the Fluid Bridge Test Malcolm Brown and John Sutherst Bioengineering and Medical Physics Unit, and Department of Obstetrics and Gynaecology, University of Liverpool, Liverpool

Key Words. Urinary incontinence • Bladder • Urethral pressure • Coughing Abstract. The momentary entry of urine into the proximal urethra during coughing can be demonstrated by a new test which can be conducted using apparatus now commonly available for urodynamic investigations. If the bladder neck opens, a fluid bridge is established between points of pressure measurement in the bladder and in the proximal urethra. Thus, the pressures at these two points momentarily become equal. The clinical value and relevance to physiology may not become clear for some time, but the relatively simple apparatus and procedure, and the ease with which the results can be translated into physical facts, provide important advantages over other dynamic tests of the urethra which are currently possible.

Apparatus

Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/18/2018 4:18:58 PM

Figure 1 shows the simplest apparatus required to perform the ‘fluid bridge’ test (excluding a two-channel pressure recorder which must have a maximum paper speed o f at least 5 cm/sec). Refinements may be added to the infusion system, catheter design or catheter positioning mechanism, but these will not improve the value of the results. The apparatus is essentially that required for recording the urethral closure pressure profile (UCPP) (Brown and Wickham, 1969), with simultaneous re­ gistration of bladder pressure via a second catheter lumen (Glen and Rowan, 1973) which opens at the tip. The catheter shown in figure 1 is a double lumen bladder/urethral catheter (Portex Ltd., Hythe, Kent, England). Urethral pressure is recorded via side holes 5 cm back from the tip. The design o f this catheter is not critical, though

Brown/Sutherst

404

Fig. 1. The simplest apparatus required for the 'fluid bridge’ test. A Double lumen catheter opening at the tip for bladder pressure recording, and 5 cm from the tip for urethral pressures. B Y connector. C Compression infusion regulator. D Infusion set and water supply which must be mounted at the highest possible level (at least 1.5 m) above the patient. E Two manometer extension tubes. FTwo pressure transducers which are con­ nected to a two-channel pressure recorder.

Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/18/2018 4:18:58 PM

excessive diameter or stiffness may affect the behaviour of the urethro-vesical junction. The infusion apparatus may be replaced by a syringe pump, but this simple system is well understood and has a well-defined performance, provided the drip bag is held high. The response time of the pressure measuring circuits (tubing, transducers and recorder) should be less than 0.1 sec. Most recording systems in use meet this specification without difficulty. The rate of rise in recorded pressure when the urethral recording eyes are sealed should be better than 100 cm H2 O rise in 0.5 sec when the infusion rate is 2 ml/min. This latter requirement is for faithful UCPP recording. Most apparatus in use should meet this criterion.

A Test for Bladder Neck Competence: the Fluid Bridge Test

405

Fig. 2. The form of recordings for a sequential UCPP and 'fluid bridge’ test. A UCPP. B The result for a cough when both recording eyes open into the bladder. C The result from a point in the urethra which has remained dry during the test.

Method A UCPP is recorded in the normal way, as shown in figure 2A. This may be part of the diagnostic procedure, but it also provides the positional information for the 'fluid bridge’ test. The catheter is then moved back into the bladder, so that both channels record bladder pressure. At this point the patient is asked to cough and the recording paper is set in motion. If the apparatus is working correctly the recordings from the two channels should be identical, as shown in figure 2B. If not, a bubble, leak or blockage must be located (and removed). Next, the urethro-vesical junction is located by easing the catheter down the urethra until the first rise in the urethral pressure recording. The catheter is then moved a chosen distance down the urethra (e.g. 0.5, 1.0 cm). This position can also be checked against the UCPP by comparing pressures. The catheter should then be retained in this position by the fingers, or a suitable mechanism. The infusion is now stopped and the cough procedure repeated. It is the form of this recording (fig. 2C) which shows whether urine has reached the test position in the urethra. If it is required to test a second position in the urethra (e.g. closer to the urethrovesical junction) the infusion must be restarted during the relocation process. If a variable speed syringe pump is used then the infusion need not be arrested for the test but simply reduced to less than 0.5 ml/min. Relocation of the catheter can then be performed without further change of infusion rate.

In the water infusion method of UCPP recording, rises in urethral closure pressure are registered because the compliance demands o f the pressure circuit are met by the water infusion. Thus the rate of water infusion must be high

Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/18/2018 4:18:58 PM

Theory and Results

4

Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/18/2018 4:18:58 PM

Brown/Sutherst 406

407

Fig. 3. When the urethra remains dry at the measuring point the urethral pressure recording does not follow the bladder pressure during the cough. Fig. 4. If the urethra opens as far as the measuring point, a 'fluid bridge’ is established linking the bladder fluid with the urethral pressure recording system. In this condition the urethral recording is identical to the recording of bladder pressure. Fig. 5. Some examples of test results. Calibration is: vertical axis 40 cm HaO/div; horizontal axis 0.1 sec/div. 1 = The urethra remains dry at the test point. 2 = The urethra opens during the cough. 3 = The urethra opens shortly after the start of the cough. 4 = Opening occurs at the end of the cough. 5 = This urethra opens, and stays open until a short time after the cough has ended. Urethral pressure is re-established at the marker. 6 = The urethra remains dry. Also the catheter was not adequately secured causing the catheter to move down the urethra during the cough (note the rising urethral pressure).

Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/18/2018 4:18:58 PM

A Test lor Bladder Neck Competence: the Fluid Bridge Test

Brown/Sutherst

408

enough to produce pressure rises which are fast enough to accurately register the contours of the UCPP during withdrawal. In the ‘fluid bridge' test the infusion is removed or reduced so that registration of pressure rises is slow; much too slow to record the rapid rises in urethral pressure occurring during coughing. If, however, during the cough, a ‘fluid bridge’ is established between the urethral recording eyes and the bladder there will be ample fluid to satisfy the compliance o f the measuring system and the pressure registered will be the bladder pressure. The two extreme situations which may arise are illustrated in figures 3 and 4: If the bladder neck remains closed during the cough, as in figure 3, the urethral pressure recording will fall short of the bladder pressure because the measuring system (without infusion) cannot respond to the rapid change in wall pressure. If the bladder neck opens down to the selected measuring point, as in figure 4, the urethral pressure recording will follow the bladder trace. This is because the response time is greatly improved by the existence o f free fluid around the eyes of the catheter. Some examples of actual recordings are shown in figure 5. It will be seen that there are a variety of possible results for which there is little difficulty in arriving at a physical explanation. Particularly interesting are those on which the urethra does open, but only at a late stage in the cough. These may be associated with a particular group of patients. The recordings shown in figure 5 are polaroid prints o f the superimposed urethral and bladder pressure recordings displayed on a storage cathode ray tube. This is a useful, though inessential addition.

Discussions and Conclusions

Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/18/2018 4:18:58 PM

Measurement of the UCPP has not gained recognition in some centres since the method and the interpretation o f the results require considerable under­ standing and expertise {Glen, 1977). The search for a cause for incontinence in each patient is therefore often abandoned after bladder instability has been excluded, even though no urethral abnormality has been detected. In every urodynamic clinic there is probably a proportion of patients whose incontinence is still unexplained after investigation. There is still a need, therefore, for better methods of studying urethral dynamics. This new method may help to complete the picture by direct detection of incompetence at the bladder neck, even when no leak has been demonstrated on clinical examination. Used in conjunction with measurement of the UCPP the

A Test for Bladder Neck Competence: the Fluid Bridge Test

409

two tests are complementary, and the position of the test point is known from the profile calibration. It may also be useful as a substitute for radiological screening o f the bladder neck where such facilities are not available or are not suitable for every patient. Alternatively, it may be more sensitive than screening since the smallest quantity of urine, present in the urethra for only a fraction o f a second, will be clearly detected. These possible uses need further evaluation. One criticism of the method is that the catheter may be moved during the cough. According to Henriksson (1977) movement o f the catheter during stressprofiles need not be a problem. Also if the catheter does move during the test, the urethral pressures immediately before and after will be different, and this will be noticed. Some further investigation is, however, indicated to clarify the effects o f catheter movement. All the tests so far have been done with the patients supine. We appreciate the method could be improved by using a smaller catheter and by recording pressures with patients in the erect position. This paper is based on previous work (Brown and Sutherst, 1978) presented at the 8th Annual Meeting o f the International Continence Society, Manchester 1978. There are, however, important details which are different in the methods described which should be noted by intending users o f the technique.

References

Dr. Malcolm Brown, 131 Mount Pleasant, PO Box 147, University of Liverpool, Liverpool L69 3BX (England)

Downloaded by: Univ. of California Santa Barbara 128.111.121.42 - 3/18/2018 4:18:58 PM

Brown, M. and Wickham, J.E.A.: The urethral pressure profile. Br. J. Urol. 41: 211 (1969). Brown, M. and Sutherst, J.: Detection of fluid entry into the proximal urethra during coughing. VIIIth Int. Continence Soc. Meet., Manchester 1978, p. 147. Glen, E.S.: Stress incontinence. Br. mcd. J. ii 261 (1977). Glen, E.S. and Rowan, D.: Continuous flow cystometry and UPP measurement with monitored intravesical pressure: a diagnostic and prognostic investigation. Urol. Res. 1: 97-100 (1973). Henriksson, L.: Studies on urinary stress incontinence in women (Litos Reprotryek, Malmo 1977).

A test for bladder neck competence: the fluid bridge test.

Urol. int. 34 : 403 409 (1979) A Test for Bladder Neck Competence: the Fluid Bridge Test Malcolm Brown and John Sutherst Bioengineering and Medical P...
1MB Sizes 0 Downloads 0 Views