These symptoms result from instability in the detrusor muscle in the bladder. The origin of this instability is presently idiopathic. Some consider it a major reason for social isolation among the elderly. It is a possible reason for the smells associated with nursing homes. Spontaneous contraction of the detrusor muscle usually occurs when the bladder fills to approximately 150 to 250 ml.
Most people can suppress the urge to void under normal circumstances.
The elderly have difficulty suppressing this urge, losing the capacity to inhibit flow despite the bladder being not full. The urge to void is very transient and is incompletely suppressible. You will see this problem in individuals who have had a stroke or are demented, but also it is not uncommon among individuals over 65 years of age. The symptoms of overactive bladder tend to adversely affect the patient's quality of life, but typically do not cause progressive bladder deterioration or subsequent renal failure. Subsequently, without aggressive intervention neurogenic bladder can compromise patient's renal function.