Cold sensation and bladder instability in patients with outflow obstruction due to benign prostatic hyperplasia.

A series of 73 patients with bladder outflow obstruction caused by benign prostatic hyperplasia underwent urodynamic investigation, including the cold water test. The presence of detrusor instability was associated with a higher urethral opening pressure, maximum detrusor pressure and detrusor pressure at maximum flow. Instability was more common and more pronounced in patients with a lack of cold sensation, but there were some patients who, whilst lacking cold sensation, still possessed the cold reflex. This suggests partial denervation of the bladder or some form of altered modulation of sensory activity within the spinal cord or central nervous system. On the other hand, some of the patients lacked cold sensation but showed a stable detrusor and a high maximum cystometric capacity. This leads to the conclusion that there are different mechanisms by which the bladder reacts to outflow obstruction.