The Integrative Physiology of the Bladder

Abstract

Some years ago, a drug was available for use in patients who failed to pass urine after a catheter was removed, in the hope that it would aid return of normal voiding. The drug, bethanechol, was a logical choice in this context, because the parasympathetic nerves supplying the bladder release acetylcholine to make the detrusor muscle contract. Giving a drug that stimulates the detrusor muscle in the same way, it was thought, should increase bladder tone and so re-establish voiding. Sadly, the clinical outcome was usually disappointing, resulting in suprapubic discomfort and a stubborn persistence of urinary retention. The experience with bethanechol is illuminating, as it illustrates a failure to grasp the fundamental complexity of bladder function; the specific weakness lies in the fallacy that whole bladder function can be extrapolated from any individual cell type (in the case of bethanechol, the smooth muscle). Integrative physiology, the study of how intact tissue behaves, focuses on the cellular interactions; these appear to be fundamental to a clear understanding of normal bladder function and the pathophysiological changes underpinning clinical lower urinary tract problems. The clinical settingThe normal bladder has storage and voiding phases, the onset of the latter being determined by the pontine micturition centre in the brainstem. Clinical problems affecting urine storage are highly prevalent, and result in urinary urgency, frequency and urgency incontinence. They are commonly associated with detrusor overactivity (DO), which is the presence of inappropriate detrusor contractions detected during pressure cystometry while the bladder is being filled. Voiding problems also show a high prevalence, and result in a weak urinary stream and incomplete bladder emptying, the latter detectable as the presence of a post voiding residual volume (PVR). Improved understanding of the mechanisms underlying these problems is desirable, as current management options available are only effective in a proportion of cases and can carry significant risk of adverse effects. Cellular phenotypes present in the bladderUnderstanding cell interactions is a challenge, because the bladder wall, perhaps a little unexpectedly, has quite a complicated structure. Tw o particularly interesting cell classes are the interstitial cells (ICs) and the peripheral neurones. The existence of bladder ICs was only recently established, but they have spawned much interest, since they appear to share some of the properties of the interstitial cells of Cajal (ICCs) in the gut. Since the ICCs ABSTRACT Normal bladder function is complex, resulting from the co-operative interaction of numerous regulatory cell types, of which the interstitial cells and the peripheral neurones are particularly interesting. Collectively, these comprise the myovesical plexus, which appears to confer structural and functional characteristics on the bladder loosely akin to those of the gut. These include functional modularity, which gives rise to the potential for localise...

Physiological and pathophysiological implications of micromotion activity in urinary bladder function

“…). Such loss of contractility would be worth evaluating in terms of the possibility that the autonomous activity of the bladder has a role in normal voiding (Drake ), such that deficient micromotions may be a feature of DUA. Although the correspondence between findings from studying the micromotion activity of the ageing bladder in animal models and clinical experience with the lower urinary tract symptoms in the geriatric population is a long way from being established, these studies could provide an insight into the potential complexity of the changes that occur in the ageing bladder.…”

The effect of acute increase in urge to void on cognitive function in healthy adults

“…1,2 Functionally, the urinary system acts in a straightforward manner whereby the bladder fills to a threshold and then an urge to void is initiated with micturition occurring soon thereafter. 1 Although this process occurs automatically in healthy adults, micturition itself is under voluntary control so that it will occur only when deemed appropriate. 3 The voluntary control of micturition means, that in healthy adults, urinary retention can occur beyond the normal threshold for voiding.…”

Prostaglandin E2 excitatory effects on rat urinary bladder: a comparison between the β-adrenoceptor modulation of non-voiding activity in vivo and micro-contractile activity in vitro

“…It has been speculated that this intrinsic activity represents the system in the bladder wall that underlies or contributes to non-voiding activity (NVA) in vivo (Drake 2007;De Jong et al 2007).…”