Integrated control of lower urinary tract--clinical perspective

Abstract

The neural mechanisms that determine social bladder control are reviewed, with a particular emphasis on the role played by sensation in the process. Much has been learnt about the neural control of the bladder from studying patients with neurological disease and those disorders that are known to disrupt bladder storage are described. Possible approaches to treatment of the resulting incontinence are reviewed and it is acknowledged that in the future, the optimal treatment for incontinence may be determined by its precise underlying pathophysiology in each instance, for example, suprapontine causes requiring different medication to spinal causes. Although the main emphasis of urological research and development so far has been the treatment of incontinence, effective therapy for other bladder disorders such an impaired emptying or bladder pain could have an important impact on the bladder symptoms of many patients.

Figure 1

An analysis of human bladder control as an example of goal orientated behaviour. FS, first sensation; FD, first desire; SD, strong desire to void.

Figure 2

Pathways of the guarding reflex by kind permission of Professor Michael Craggs.

Figure 3

Summary of regions of interest comparing ‘full vs empty' bladder conditions based on the co-ordinates published in five PET studies (Blok et al., 1997; 1998; Nour et al., 2000; Athwal et al., 2001; Matsuura et al., 2002). The figure from Kavia et al. (2005) was prepared using MRIcro (Rorden & Brett, 2000) (with permission from Journal of Comparative Neurology).

Figure 4

The neural pathways involved in the control of the bladder. The pontine micturition centre (PMC) is the final brain efferent nucleus, activation of which results in co-ordinated sphincter relaxation followed by detrusor contraction. Pathways connecting the PMC to peripheral bladder innervation (the pelvic and pudendal nerves) pass down the spinal cord, and through the sacral roots (S2–S4) (with permission from Seandanavian Journal of Urology and Nephrology).

Figure 5

A schematic diagram showing the main ultrastructural constituent elements of the superficial layers of the human bladder. Flattened cells with pale nuclei, known as ‘umbrella cells' form the innermost layer of the bladder with tight and adhaerens junctions linking them to one another. These are supported by basal epithelial cells which are closely attached to the basal lamina (bl). Naked axons can be seen between the basal processes of the epithelial cells and immediately beneath the basal lamina. In the zone immediately beneath the epithelial basal lamina are fine axons, either naked or in intimate association with flattened cells have the cytological characteristics of myofibroblasts (mf). Also in this layer are fenestrated capillaries orientated towards the urothelial surface. Within the deeper zones of the lamina propria is a diffuse plexus of unmyelinated fibres containing slender axons linking periodic varicosities which enclose numerous small clear and dense cored vesicles. Close to the smooth muscle of the detrusor (det) nerves consist of small myelinated fibres and numerous unmyelinated strands, partially or completed invested by perineurium. From (Fowler et al., 2002) with permission.