WTP4.18 Long title: Re-evaluating Routine Urinary Catheterisation in Elective EVAR: risks, complications and the need for individualised Patient Management Short title: No Urinary Catheter in eLective Endovascular Aneurysm Repair - NUCLEAR study

Introduction and aim Urinary catheterization has traditionally been a standard practice during surgery to ensure continuous bladder drainage, prevent urinary retention and to monitor peri-operative urine output. However, the necessity of routine catheterization in elective endovascular aneurysm repair (EVAR) is increasingly questioned. This is particularly relevant for older male patients, who commonly have prostatic conditions. Catheterization may cause distress and complications such as haematuria, urinary retention after removal and urinary tract infections Methods In our retrospective cohort analysis, 215 patients who underwent EVAR between October 2020 and March 2024 were identified from the Hospital In-Patient Enquiry (HIPE) database. The patient’s baseline demographics, urological co-morbidities, operative details (including catheterization details) and adverse events were recorded, excluding all open, hybrid or complex endovascular procedures. The cohort has a mean age of 74.7±7.4, with 85.6% male patients, all of whom had urinary catheters. Results The incidence of composite adverse urological events (CAUE) was 29 (13.5%). The most common complications were urinary retention / failure of trial without catheter (n=12, 6%) and haematuria (n=9, 4%). Five patients required prolonged duration of catheterization, and three needed a flexible cystoscopy. Patients with CAUE had significantly longer hospital stays (6±2 vs 2±5 days, median ±SD). Multiple logistic regression identified prostatic hypertrophy ((OR=3.54(1.36-10.5), P=0.012)) and larger catheter ((OR = 3.18 (1.33-13.8), P=0.03)) as independent risk factors for CAUE. Conclusion Routine urinary catheterisation in EVAR should be re-considered. Thoughtful patient selection is essential to minimize complications and ensure optimal outcomes.