ABSTRACT
From the point of view of detrusor muscle physiology, the bladder presents two problems: (1) the overactive bladder, whereby large, uncontrolled changes of detrusor pressure occur; and (2) the underactive bladder, whereby an insufficient increase of intravesical pressure occurs for complete expulsion of the contents. When there are no obvious neurological defects in patients, the presumption is that changes to the cellular characteristics of tissue in the bladder wall, including detrusor smooth muscle, are the primary cause of the conditions, and the problem may be classified as myogenic. It is important to emphasize that from a clinical aspect a syndrome such as bladder instability is associated with a number of conditions (such as outflow tract obstruction) or symptoms (such as frequency and/or urge). However, these give no indication to the researcher as to what is the basic cause of the problem. Outflow tract obstruction, for example, may precipitate a chain of events which eventually causes bladder instability, but it is essential to identify the fundamental changes which manifest themselves as instability.
