Urodynamic investigations in patients with spinal cord injury: should the ice water test follow or precede the standard filling cystometry?

Objectives: To evaluate whether the ice water test (IWT) should be performed before or after the standard urodynamic investigation (UDI). Patients and Methods: Two cohorts of patients suffering from neurogenic lower urinary tract dysfunction (NLUTD) due to spinal cord injury (SCI) were matched by lesion level and age. The patients of cohort A (n=55, retrospective cohort) underwent the IWT before and the patients of cohort B (n=110, prospective cohort) after standard UDI. The IWT effect on urodynamic parameters has been compared between the two groups using the Mann-Whitney U-test for independent samples. UDI was performed according to good urodynamic practices recommended by the International Continence Society. Results: The mean age of both cohorts was 49 years. Performing the IWT before versus after standard UDI resulted in a significantly lower maximum cystometric bladder capacity (P=0.01), lower incidence of detrusor overactivity (P=0.017) and lower maximum detrusor pressure during IWT (P=0.04). All other urodynamic parameters assessed demonstrated no significant difference (P>0.05). Conclusions: Our results are in line with findings from animal studies demonstrating a bladder cooling-induced gating effect on the micturition reflex volume threshold on the level of sacral interneurons. Since the IWT is an unphysiological investigation that might significantly bias subsequent urodynamics, we suggest that the IWT should not precede more physiological standard UDI.