Standard Suprapubic Tube Upsizing
Small caliber percutaneous suprapubic catheters should be upsized to 18-20 French, as this represents the optimal balance between flow efficiency and diminishing marginal returns. 1, 2
Rationale for Upsizing
The AUA Urotrauma Guideline explicitly states that "small caliber percutaneous catheters will require upsizing in the setting of hematuria, prolonged use or in anticipation for future definitive surgical repair" 1. This recommendation is supported by biomechanical evidence showing that:
- Beyond 18 Fr, marginal improvement in flow diminishes significantly 2
- Upsizing from 18 Fr to 20 Fr reduces catheter resistance by only 19%, which represents the lowest improvement between consecutive catheter sizes 2
- All catheter sizes beyond 18 Fr provide diminishing marginal returns in urinary flow 2
Practical Sizing Algorithm
Initial placement:
- Small caliber percutaneous kits typically place 12-14 Fr catheters 3
- These are acceptable for initial emergency drainage but require subsequent upsizing
Target size for upsizing:
- 18-20 Fr represents the optimal endpoint for most clinical scenarios 2
- This size provides adequate flow while avoiding the diminishing returns of larger catheters
- Larger catheters (>20 Fr) may be considered for specific indications like significant hematuria with clots 3
Clinical Considerations
When to upsize:
- Presence of hematuria requiring clot drainage 1
- Anticipated prolonged use 1
- Planning for future definitive surgical repair 1
- Catheter blockage or inadequate drainage 3
Common pitfall: Placing initial small-bore catheters (12-14 Fr) and failing to upsize appropriately leads to catheter dysfunction, particularly with hematuria or sediment 1, 2. The research demonstrates that even small amounts of urinary sediment significantly prolong drainage times in smaller catheters 2.
Advanced technique: For patients requiring initial large-bore placement, the nephrostomy balloon/sheath technique allows direct placement of ≥20 Fr catheters in a minimally invasive fashion, avoiding the need for serial upsizing 3.