Application of bladder scan in ambulatory management protocol for acute urinary retention with presumed diagnosis of benign prostatic hypertrophy

Objective: Bladder scan was firstly used in the ambulatory management protocol for acute urinary retention (AUR) in Princess Margaret Hospital (PMH) emergency department (ED) since 2012. Bladder scan measurement was performed immediately after triage for early catheterisation in the new protocol for AUR. The primary objective of this study was to evaluate the accuracy of bladder scan in estimating the volume of urinary retention. The secondary objectives were to evaluate the change in unnecessary catheterisation rate and the change in door to catheterisation time (DTCT) after the implementation of new protocol. Setting: Emergency department of a regional hospital. Methods: Male patients over 40 years old presenting to the ED of PMH for difficulty to void within the study period were enrolled and managed according to the study protocol. Agreement analysis was carried out by the Bland and Altman method. The changes in DTCT were assessed by comparing data of current study and historical control. Results: A total of 121 male patients were recruited. The bias between bladder scan readings and catheterised volume was 26.09 ml when the average bladder scan measurement and catheterised volume was 300ml. The 95% upper and lower limit were -95.82 ml and 151 ml, respectively. The relative risk reduction of unnecessary catheterisation was 90.9%. The absolute risk reduction was 8.26%. Number need to treat was 12 (95% CI 8-30). The DTCT of current study were shorter than that of historical control (DTCT: 22.85 minutes vs. 48.42 minutes; p<0.001). Conclusions: Agreement between bladder scan readings and catheterised volume is satisfactory. Bladder scan can serve as a device to facilitate nurses to make decision on early catheterisation for AUR patients with presumed diagnosis of benign prostatic hypertrophy.