Initial Voiding Trial Thresholds After Aquablation
Remove the Foley catheter on postoperative day 1 and perform a backfill voiding trial with 300 mL saline; success requires voiding at least two-thirds of total bladder volume (voided volume plus post-void residual) with a post-void residual ≤100 mL. 1, 2
Timing of Catheter Removal
- Remove the indwelling catheter on postoperative day 1 in uncomplicated Aquablation cases to minimize infection risk and patient discomfort. 1
- Patients with preoperative acute urinary retention have a 40% failure rate on initial void trial compared to 7.2% in those without retention, which may warrant delaying the trial by 24-48 hours in this population. 3
Voiding Trial Technique
- Use the backfill (active) technique rather than spontaneous filling (passive) because backfill demonstrates superior correlation with successful voiding (κ = 0.91 vs κ = 0.56) and reduces urinary tract infection rates by 63%. 2, 4
- Instill 300 mL of saline into the bladder via the catheter before removal, then have the patient attempt to void within 15 minutes. 2
Success Criteria
Volume Requirements
- A successful void requires the patient to void at least two-thirds (≥67%) of the total bladder volume, calculated as voided volume divided by (voided volume plus post-void residual). 2
- Post-void residual must be ≤100 mL for patients with neurogenic bladder dysfunction; this threshold is extrapolated from stroke guidelines and applies to post-surgical voiding dysfunction. 5
- For urogynecologic surgery populations, post-void residual >150 mL is considered abnormal and warrants catheter replacement. 6
Functional Parameters
- The patient should demonstrate ability to void at least twice without significant discomfort before discharge. 2
- Peak urinary flow rate (Qmax) ≥10 mL/s is the expected outcome at 12 months post-Aquablation, but this parameter is not routinely measured during the initial void trial. 7
Management of Failed Void Trial
- If the initial void trial fails, re-insert the catheter and repeat the trial after 24-48 hours. 1
- Intermittent catheterization every 4-6 hours is an alternative when post-void residual exceeds 100 mL, preventing bladder overdistention beyond 500 mL. 5, 1
- Among men with preoperative acute or chronic retention who undergo Aquablation, 98% achieve spontaneous voiding by mean 5-month follow-up despite initial void trial failures. 3
Common Pitfalls
- Do not use the passive (auto-fill) technique where the bladder fills spontaneously after catheter removal; this method takes 3.6 hours longer to complete the void trial and increases UTI risk without improving retention detection. 4
- Avoid leaving indwelling catheters in place beyond postoperative day 1 unless medically necessary, as they markedly increase urinary tract infection risk. 1
- Monitor for bladder spasm, clot retention, or urinary retention as causes of severe pain or inability to void after catheter removal. 1
- Patients with preoperative chronic retention (post-void residual >300 mL) have a 12.5% failure rate on initial void trial, intermediate between acute retention (40%) and no retention (7.2%), requiring individualized timing of catheter removal. 3