Trial Without Catheter (TWOC): Definition and Management
TWOC (Trial Without Catheter) is a clinical procedure to remove an indwelling urinary catheter and assess a patient's ability to void spontaneously, typically performed after a period of catheterization for urinary retention. 1
Key Components of TWOC
Definition and Purpose
- TWOC is a standardized procedure to evaluate if a patient can void normally after catheter removal
- Used primarily after acute urinary retention (AUR) or following surgical procedures where catheterization was required
- Aims to determine if normal bladder function has returned and if the patient can empty their bladder effectively
Timing of Catheter Removal
- For patients with AUR related to BPH, alpha blockers should be prescribed prior to TWOC 2
- Patients newly treated for AUR should complete at least 3 days of alpha blocker therapy before attempting TWOC 2, 1
- For post-cesarean patients, remove the urinary catheter immediately if strict urine output monitoring is not needed 2
- For most surgical patients, remove the Foley catheter on postoperative day 1 1
TWOC Procedure
Preparation:
Catheter Removal Technique:
- Some practitioners use a backfill technique where the bladder is filled with sterile saline before catheter removal 1
- Remove the catheter with the drainage bag below bladder level to prevent retrograde flow
Post-Removal Monitoring:
- Monitor for successful voiding within 4-6 hours
- Measure post-void residual (PVR) volume using ultrasound or in-and-out catheterization
- Success is typically defined as voiding with PVR <100ml 3
Factors Affecting TWOC Success
Predictors of Successful TWOC
- Age (younger patients have higher success rates) 3
- Initial retention volume (volumes <800ml have better outcomes) 4
- Prostate size (<40g more favorable) 4
- Intravesical prostatic protrusion (<8mm more favorable) 4
- Lower IPSS scores (<16 more favorable) 4
- Non-spinal surgery (vs. spinal surgery) 3
Management of Failed TWOC
- Options include:
Special Considerations
Alpha Blocker Therapy
- Alpha blockers (alfuzosin, tamsulosin) work by antagonizing alpha1-adrenoreceptors in the prostate and bladder neck 1
- They reduce smooth muscle tone, decrease bladder outlet resistance, and improve urinary flow 1
- Standard dose of alfuzosin is 10mg once daily, taken with food 1
- Improves TWOC success rates from 29-39% (placebo) to 47-60% (with alpha blockers) 2, 5
Catheter Valve Consideration
- Using a catheter valve instead of free drainage before TWOC may help maintain bladder tone and capacity 6
- May optimize outcomes by allowing the bladder to fill and empty in a more physiological manner
Long-term Outcomes and Follow-up
- Patients who pass a successful TWOC for AUR from BPH remain at increased risk for recurrent urinary retention 2
- Long-term data suggests that 80% of patients who initially voided successfully with alpha blockers eventually required surgical intervention 1
- Follow-up should include PVR measurement and assessment of lower urinary tract symptoms 1
Common Pitfalls and Caveats
- Failing to administer alpha blockers for the full 3 days before attempting TWOC in BPH patients
- Not measuring post-void residual volume to confirm successful voiding
- Attempting TWOC too early after catheterization, especially in BPH patients
- Failing to recognize that a successful TWOC doesn't eliminate the risk of future retention
- Neglecting to schedule definitive management (e.g., TURP) for patients with BPH after successful TWOC
TWOC is a critical procedure in urological practice that requires proper preparation, monitoring, and follow-up to ensure optimal patient outcomes and reduce the risk of recurrent retention.