Content uploaded by Paul Hilton
Author content
All content in this area was uploaded by Paul Hilton on Oct 21, 2017
Content may be subject to copyright.
The Mechanism of Continence
Abstract
Urinary incontinence may be defined as “a condition in which involuntary loss of urine is a social or hygienic problem, and is objectively demonstrable” (Bates et al. 1983). Continence then, by inference, might be considered as the ability to retain urine within the bladder, between episodes of voluntary micturition. In order to comprehend fully the pathological processes which lead to the development of urinary incontinence, a clear understanding of the normal mechanisms for the maintenance of continence is of course fundamental; this in turn must be based on a knowledge of the development, anatomy, and physiology of the bladder and urethra, and their supporting structures. This chapter aims to provide this background information.
It has long been recognised that urogenital fistulas in low- and middle-income countries are predominantly of obstetric aetiology, whereas those in high-income countries usually follow pelvic surgery. This disparity was confirmed in systematic review (included as paper 1) and in large cohort studies undertaken in Nigeria (paper 2) and the UK (paper 3). Whilst there is no standardisation of outcome measures, the same studies report treatment ‘success’ in approximately 80-90% of cases in low- and middle-income countries (papers 1 & 2) and 95% in high-income countries (papers 1 & 3).
It is recognised that obstetric fistula patients commonly suffer debilitating stress urinary incontinence even after successful closure of their fistula (paper 1). Urodynamic investigation in a cohort of fistula patients in UK also showed a high incidence of functional abnormalities (paper 4). Many of these resolved after repair, and most women reported minimal impact on quality of life in the long-term (paper 5). Success rates were found to be lower following second operations than first in cohort studies from Nigeria (paper 2) and UK (paper 3), and in a UK national cohort study (paper 8). This latter study also found idiosyncratic patterns of care, with re-operation rates related to workload, varying between 0% and 50% (paper 8).
Evidence is presented to support an increase in risk of iatrogenic (post-hysterectomy) fistulas in high-income countries (papers 6 & 7). There also is a growing perception by colleagues in low- and middle-income countries of an increase in urogenital fistulas that may be, in part, iatrogenic in nature. These trends may reflect supervision and surgical experience accrued in training and workload maintained in independent practice. In both situations, it behoves those responsible for training and workforce planning in healthcare to ensure an appropriately trained and supervised workforce is maintained in the correct working environment.
This review article on neurogenic urinary retention is divided into three main sections. The first covers the neuroanatomy of the bladder and urethral sphincters, developing the peripheral innervation as well as the spinal cord organization and the cortical and subcortical brain control of micturition. The second discusses the main central and peripheral neurological lesions and diseases causing urinary retention. The last section gives an updated view of the neurophysiological techniques which are now available to test the central and peripheral pathways controlling micturition.
Data about the use of tension-free vaginal tape (TVT) in the management of recurrent urodynamic stress incontinence (RUSI) after previous failed midurethral sling procedure (MUSP) are limited.
Assessment of the efficacy and the indications of the TVT procedure in the management of patients with RUSI after failed previous MUSP.
Thirty-one patients with RUSI after previous failed MUSP were prospectively enrolled at a single tertiary academic center.
Preoperatively and postoperatively, patients were assessed with physical examination, urinalysis, urine culture, bladder diary for 2-3 d, Q-tip test, uroflow, filling and voiding cystometry, urethral profilometry, and 1-h pad test. Mean follow-up was at 18.6 mo (range: 12-28 mo).
Overall, the objective cure rate based on the pad test findings was 74%, the improvement rate was 6.5%, and the failure rate was 19.5%. The objective cure rate based on cough stress test during filling cystometry was 77.4%, and the subjective cure rate based on patients' answers was 71%. The study could have some limitations. The relatively small number of patients enrolled could affect the findings of study to some degree. Additionally, because urethral pressure profiles show a significant degree of directional dependence when side-hole microtip transducers are used, as in the present study, the orientation of the transducer could affect the values measured.
The TVT procedure as a second operation could provide an overall cure rate of 74% with a low complication rate in female patients with RUSI after previous failed midurethral tape procedures.
Intravesical and urethral pressure signals during cough and Valsalva maneuvers for 15 continent women were analyzed with frequency spectrum analysis. Clear modulation of the urethral pressure changes by the intravesical pressure rise during stress maneuvers was demonstrated in the frequency bands of 14 and 7 Hz for cough and Valsalva, respectively. The linearity between the urethral and intravesical pressure signals was strong for cough, but relatively weaker for Valsalva. The observed linearity lead to the formulation of a modified continence equation to mathematically quantify stress leak point pressure (sLPP): sLPP=MUCP/(1-alpha1)+RBP. This algebraic equation demonstrated that sLPP depends on pressure transmission, resting bladder pressure, and maximum urethral closure pressure. The equation was validated with excellent theoretical predictions for the 15 continent subjects (R(2)=0.98 and 0.97 for cough and Valsalva leak point pressure, respectively) and good but somewhat weaker predictions for 46 stress incontinent women (R(2)=0.79 and 0.48, respectively). It has been shown that pressure transmission plays the most important role in female continence function, while it may be attributable to passive structural origin as evidenced by the minimal time delay between the two pressure signals, in the order of a few milliseconds. It can be concluded that coughing seems to have a more mechanical, rather than neuromuscular basis for its signal dynamics. This study suggests that a complete assessment of female stress continence function requires comprehensive urodynamic information in terms of pressure transmission, maximum urethral closure pressure, and resting bladder pressure.
The aim of this study was to investigate the anatomical origins and clinical significance of cough pressure transmission ratio (CTR) by using virtual-operation (VO) techniques.
Thirty-four patients underwent perineal ultrasound examination, standard urethral pressure cough testing both with and without unilateral midurethral anchoring (VO), all tests being performed without urethral elevation. In eight patients where there was no change in CTR, a one-sided fold of suburethral vagina (VO) was taken (pinch test) and the CTR repeated.
After midurethral anchoring, maximal urethral pressure increased from a mean of 33.25 cm H2O to a mean of 58.06 cm H2O (P < 0.0001) and restoration of anatomy was noted in all 11 patients who had obvious funneling on straining. Conversion of a <100% CTR to >100% CTR in the proximal urethra was observed in 14 of 22 patients (P < 0.005), with no significant change noted in the distal urethra. Further conversion of CTR was noted in six of the remaining eight patients with unilateral plication of suburethral vagina (pinch test).
A musculoelastic closure mechanism most likely activates urethral closure. CTR is most likely an index of changed intraurethral area, not necessarily closure, and may be a more sensitive objective test than perineal ultrasound for diagnosing urethral narrowing, especially when used with virtual-operation techniques.
Urinary incontinence is a depressing and demoralising condition with far reaching consequences for the sufferer and for the health services as a whole . In women the commonest cause of urinary incontinence is genuine stress incontinence . This thesis aims to improve knowledge of urethral function in this condition and of the effects of its surgical and pharmacological treatment .
The work contained herein was carried out in a specialist Urodynamic Unit over a two-year period. In the Introduction the Unit is described, and the problem of incontinence in general discussed. In subsequent background chapters the anatomy, physiology and current methods of investigation of the lower urinary tract are reviewed, with particular reference to the urethra and urethral pressure measurement. The microtransducer technique of urethral pressure measurement was selected for use during these studies, and various methodological aspects are investigated in Section II. The reproducibility of parameters of the profile recorded at rest and on stress is defined, and a standardised method for recording multiple parameters of urethral function is outlined.
In Section III the technique is applied to a group of 120 stress incontinent women, and to 20 women entirely free from urinary symptoms. Several parameters of urethral function recordable from the profiles and showing distinction between these two groups of women are defined, and from these a new concept relating to the determinants of continence and the severity of stress incontinence is developed.
Various therapeutic approaches to the problem of genuine stress incontinence are investigated in Section IV. The effects of surgical treatment by the Burch colposuspension and ' Marlex' sling procedures on urethral function are defined i n both successful and unsuccessful cases; reasons for their success and failure are proposed. The alpha adrenergic stimulant drug Phenylpropanolamine, and oestrogen replacement in the form of intravaginal cream are also investigated in terms of their effects on urinary symptoms, and the urethral profiles.
In conclusion those areas where the rationalisation of treatment for genuine stress incontinence is considered possible are discussed.
Available for download from British Library EthOS website, at: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257745
A number of new experimental and clinical results have been obtained through the use of the voiding dynamometer. The investigators have adapted the rationale of the hydraulician and have discovered concepts which would otherwise have remained hidden. Since the vocabulary of the hydraulics engineer and the urodynamicist are often mutually incomprehensible it is necessary prior to the introduction of the results to present a review of the basic theory and the pertinent physical principles.
This report contains the first set of recommendations dealing with the terminology of lower urinary tract function. Specifically, it covers the storage of urine in the bladder, urinary incontinence and units of measurement. The recommendations were subject to discussion during the Fourth Annual Meeting of the International Continence Society in Mainz, Germany in September, 1974.