Urge incontinence can be a disease of bladder sensors

In many cases of urge incontinence the pathophysiology is unclear. Detrusor instability, detrusor hyperreflexia, urethral instability and poor sensory perception all have been suggested as requirements for urge incontinence. Sensory perception, as proposed recently, may be mediated by 2 bladder sensors. The first sensor, located at the trigone and posterior urethra, is sensitive to small changes in pressure and may function as an early warning system of bladder filling. In the diagnostic evaluation of urge incontinence 5 patients had a triad of absence of the first sensor, an intact second sensor, that is the urge to void when the bladder is stretched with fluid, and normal spontaneous detrusor contraction. Based upon these findings it is suggested that some instances of urge incontinence result when the early warning system fails and detrusor contraction occurs just shortly after the second sensor is stimulated. Detrusor instability was identified in 3 of the 5 patients with urge incontinence, and when present it was associated with urinary frequency. Thus, 2 forms of urge incontinence may be associated with loss of the first sensor: 1 with and the other without associated frequency, with the difference being the presence or absence of detrusor instability.