Methods to Help with Trial Without Catheter (TWOC)
Physicians should prescribe an oral alpha blocker prior to a voiding trial to treat patients with acute urinary retention (AUR) related to BPH, and patients should complete at least three days of medical therapy before attempting TWOC. 1
Alpha Blocker Therapy - The Foundation of Successful TWOC
Alpha blockers work by relaxing prostatic smooth muscle cells, decreasing resistance to urinary flow, which significantly improves the chances of successful catheter removal. The evidence strongly supports their use:
- Alpha blockers increase TWOC success rates compared to placebo (RR 1.39,95% CI 1.18 to 1.64) 2
- Both alfuzosin and tamsulosin have demonstrated efficacy (alfuzosin: RR 1.31,95% CI 1.10 to 1.56; tamsulosin: RR 1.86,95% CI 1.17 to 2.97) 2
- Side effects are low and comparable to placebo 2
Optimal Timing and Dosing
- Administer alpha blockers for at least 3 days before attempting TWOC 1
- Consider double-dose alpha blocker therapy (tamsulosin 0.4mg + alfuzosin 10mg) for potentially higher success rates (77% vs 54% with single dose) 3
Predicting TWOC Success
Several factors can help predict the likelihood of successful TWOC, which can guide clinical decision-making:
Ultrasound Parameters
- Intravesical prostatic protrusion (IPP) < 10mm is a strong predictor of success (OR 6.10,95% CI 2.61-14.20) 4
- Smaller prostate volume on TRUS (OR 0.96,95% CI 0.95-0.97) 4
- Thinner bladder wall thickness 4
Other Predictive Factors
- Lower IPSS score (OR 0.95% CI 0.89-0.99) 4
- Residual urine volume < 800ml at initial catheterization 5
TWOC Protocol
- Insert urethral catheter for initial management of AUR
- Start alpha blocker therapy (tamsulosin 0.4mg daily or combination therapy)
- Continue alpha blocker for at least 3 days before attempting TWOC
- Perform TWOC, ideally on day 2-3 after catheterization
- Monitor for successful voiding and assess post-void residual volume
Pitfalls and Caveats
- Even with alpha blocker therapy, TWOC failure rates remain significant (approximately 40-50%)
- Patients should be informed that they remain at increased risk for recurrent urinary retention even after successful TWOC 1
- Consider prostate size and IPP before attempting TWOC, as patients with larger prostates (>40g) and significant IPP (>8mm) have higher failure rates 5
- Ultrasound assessment before TWOC can help identify patients more likely to succeed and avoid unnecessary attempts in those with poor prognostic factors 4
Special Considerations
- For patients already on alpha blocker therapy who develop AUR, they still have approximately 54% probability of successful TWOC 4
- If first TWOC fails, options include a second attempt or scheduling definitive management (e.g., TURP)
- Service restrictions and operative cancellations may result in increased numbers of catheterized men in the community awaiting definitive management 6
By following these evidence-based recommendations, the likelihood of successful TWOC can be maximized, reducing the need for prolonged catheterization or urgent surgical intervention.