Symptoms versus ultrasound for monitoring urinary retention after total knee arthroplasty: The UREA randomized clinical trial protocol

Background: Postoperative urinary retention (POUR) is a frequent complication after total knee arthroplasty (TKA), contributing to prolonged hospital stays, higher healthcare costs, and an increased risk of urinary tract infections (UTIs) and other postoperative complications. Despite the widespread use of bladder ultrasound to guide catheterization decisions, evidence supporting its superiority over symptom-based monitoring is limited. The UREA trial evaluates whether patients undergoing TKA can be safely monitored for POUR based solely on urinary symptoms, potentially reducing unnecessary catheterizations and resource use. Methods: The UREA study is a randomized clinical open-label single-center trial including 170 patients undergoing elective TKA. Participants are randomized in a 1:1 ratio through a sex-stratified sealed-envelope method into either (1) an ultrasound monitoring group or (2) a symptoms monitoring group. In the ultrasound group, bladder volume is assessed repeatedly with a portable scanner, with catheterization performed at a threshold of 800 mL or upon symptoms. In the symptoms monitoring group, follow-up relies exclusively on patient-reported urinary symptoms, with catheterization performed only if symptoms occur or if no spontaneous urination has occurred by 10 h postoperatively. The primary outcome is the difference in International Prostate Symptom Score (IPSS) between groups at 3 months. Secondary outcomes include IPSS at 12 months, urinary complications, and health-related quality of life assessed with the 15D instrument at 3 and 12 months. Statistical analyses will be performed on an intention-to-treat basis, with adjustments for relevant baseline variables. Discussion: This trial is the first randomized study to compare symptom-based with ultrasound-based monitoring of postoperative urinary retention after TKA. If symptom-based monitoring is found to be safe, it may allow for substantial reductions in unnecessary catheterization, procedural discomfort, infection risk, and resource burden. The findings have the potential to inform future clinical guidelines and promote more efficient, patient-centered postoperative care.