PURPOSE: We investigated if the detrusor contraction during rapid bladder filling is provoked by cold or warm water.
PATIENTS & METHODS: Patients suffering from neurogenic lower urinary tract dysfunction (NLUTD) were included into this randomized controlled double-blind trial. At the end of standard urodynamic investigation, the patients received 2 fillings of the bladder using a 4°C (ice water test, IWT) or 36°C (warm water test, WWT) saline solution with a speed of 100 mL/min. The order was randomly selected and patients and investigators were blinded for the order sequence. Primary outcome measure was the occurrence of detrusor overactivity, maximum detrusor pressure and maximum bladder filling volume during IWT and WWT.
RESULTS: 40 patients (9 women, 31 men) where used for data analysis. NLUTD was caused by spinal cord injury in 33 and by other neurological disorders in 7 patients. Detrusor overactivity occurred significantly (p=0.02) more often during the IWT (30/40, 75%) than during the WWT (25/40, 63%), irrespective of the order of the test. Comparing IWT versus WWT, the maximum detrusor pressure was significantly (p<0.001) higher and the maximum bladder filling volume significantly (p<0.001) lower during the IWT. The order of performing the test (IWT first versus WWT first) had no effect on the parameters.
CONCLUSIONS: Our findings imply that the more frequent occurrence of detrusor overactivity, higher maximum detrusor pressure and lower bladder filling volume in the IWT compared to the WWT are caused by cold water, underlying the theory of a C-fiber mediated bladder cooling reflex in humans.