Positive bladder cooling reflex in patients with bladder outlet obstruction due to benign prostatic hyperplasia

The bladder cooling reflex was evaluated in patients with bladder outlet obstruction to study the effect of obstruction on the afferent neural function of the bladder, especially on the C-afferents. The bladder cooling test was performed by infusion of 0 degree C saline into the bladder with simultaneous detrusor pressure measurement in 104 patients with bladder outlet obstruction due to benign prostatic hyperplasia. In 49 patients (47%) a positive cooling reflex was observed. This was defined as a rise in the detrusor pressure following cold saline instillation exceeding 15 cmH2O (range 15-130 cmH2O, mean 60.6 cmH2O; positive group). In the remainder of cases the pressure rise ranged from 0 to 12 cmH2O (mean 6.1 cmH2O; negative group). Bladder outlet obstruction may cause some alteration in the afferent neural function of the bladder, in particular of the C-afferent fibers.