SMOOTH-MUSCLE OF THE BLADDER IN THE NORMAL AND THE DISEASED STATE - PATHOPHYSIOLOGY, DIAGNOSIS AND TREATMENT

The smooth muscle of the normal bladder wall must have some specific p roperties. It must be very compliant and able to reorganise itself dur ing filling and emptying to accommodate the change in volume without g enerating any intravesical pressure, but whilst maintaining the normal shape of the bladder. It must be capable of synchronous activation to generate intravesical pressure at any length to allow voiding. The ce lls achieve this through spontaneous electrical activity combined with poor electrical coupling between cells, and a dense excitatory innerv ation. In the diseased state, alterations of the smooth muscle may lea d to failure to store or failure to empty properly. The diseased state s discussed are bladder instability and diabetic neuropathy, Bladder i nstability is characterised urodynamically by uninhibitable rises in p ressure during filling, and is seen idiopathically and in association with bladder outflow obstruction and neuropathy. In diabetic neuropath y, many of the smooth muscle changes are a consequence of diuresis, bu t there is evidence for alterations in the sensory arm of the micturit ion reflex. In the unstable bladder, additional alterations of the smo oth muscle are seen, which are probably caused by the patchy denervati on that occurs. The causes of this denervation are not fully establish ed. Nonsurgical treatment of instability is not yet satisfactory; neur omodulation has some promise, but is expensive, and the mechanisms poo rly understood. Pharmacological treatment is largely through muscarini c receptor blockade. Drugs to reduce the excitability of the smooth mu scle are being sought, since they may represent a better pharmacologic al option. (C) 1997 Elsevier Science Inc.