Underactive bladder
Underactive bladder syndrome describes symptoms of difficulty with bladder emptying, such as hesitancy to start the stream, a poor or intermittent stream, or sensations of incomplete bladder emptying. The physical finding of detrusor activity of insufficient strength or duration to ensure efficient bladder emptying is properly termed "detrusor underactivity". Historically, UAB and DU have been often used interchangeably, leading to both terminologic and pathophysiologic confusion.
Patients with underactive bladder have a diminished sense of bladder filling and consequently are often found to have DU as an underlying finding, however bladder [outlet obstruction] and less frequently volume hypersensitivity can be associated with UAB symptoms.
Causes
Without diagnostic evaluation, the cause of underactive bladder is unclear, as there are multiple possible causes. UAB symptoms can accurately reflect impaired bladder emptying due either to DU or obstruction, or can result from a sense of incomplete emptying of a hypersensitive bladder. UAB potentially might also result from inaccurate perceptions of bladder function, such as in neurologic or psychiatric disease. DU itself is often linked to a weak detrusor muscle, however this association is weak. Both UAB and DU have been associated with diminished sensitivity to bladder volumes rather than objective detrusor weakness, suggesting both symptoms and function have a significant component of sensory dysfunction, leading to impaired bladder sensations and control.The underlying contributors to UAB include neurologic disease, metabolic disease, chronic bladder outlet obstruction, cognitive decline, psychiatric disorders, and adverse effects of medications. Additionally, structural abnormalities expanding the urinary reservoir beyond the bladder, such as massive vesicoureteral reflux or large bladder diverticulae, can result in UAB. While aging itself is often associated with UAB, there is scant evidence to support this claim.