Detecting postoperative urinary retention with an ultrasound scanner

Background: Retention of urine is a common postoperative problem associated with risk of overdistention and permanent detrusor damage. Prevention of urinary retention by insertion of indwelling catheter may increase the risk of urinary infection. We have performed a reliability test of an ultrasound scanner, implemented in the postoperative monitoring equipment. Methods: Patients were monitored after different types of surgery under spinal anesthesia with an ultrasound scanner in the postanesthesia care unit (PACU). Patients: Patients who according to current guidelines required a urinary bladder catheter, were scanned before a catheter was inserted and urine volume was measured. These two urine volumes were compared and analyzed for agreement. Results: Nineteen female and 17 male patients were included. The mean difference between ultrasound estimates and catheter urine volume measurements was -21.5 mL, and limits of agreement, calculated as a 95% confidence interval, were -147 and +104mL. This means that the urine volume estimated by ultrasound was on average 21.5 mL smaller than the urine volume when the bladder was emptied. Conclusion: This study confirms a good agreement between the ultrasound scanner estimates of urinary bladder volume and urine volume measured after emptying the bladder. Nurses in the PACU could operate the ultrasound scanner after a brief instruction and training period. Considering the potentially serious long-term consequences of undiagnosed postoperative urinary retention, introducing this equipment for routine monitoring of urinary bladder volume should be considered.