When to Taper the Ureter During Reimplantation for Obstructed Megaureter
Ureteral tapering should be performed when the distal ureteral diameter exceeds approximately 10-13 mm, as ureters of this caliber are too dilated to achieve a reliable anti-reflux tunnel without size reduction.
Diameter-Based Decision Making
The primary determinant for tapering is ureteral diameter:
- Ureters ≤10 mm diameter: Reimplantation without tapering is typically feasible and successful 1, 2
- Ureters >10-13 mm diameter: Tapering is generally required to create an adequate length-to-diameter ratio for a functional anti-reflux mechanism 3, 4
- Severely dilated ureters (>15-20 mm): Tapering is mandatory, as these cannot be reimplanted successfully without size reduction 3
The critical principle is achieving a tunnel length-to-diameter ratio of approximately 3-5:1 for successful anti-reflux reimplantation. When the ureter is too wide, this ratio becomes impossible without tapering 3.
Age and Timing Considerations
Infants (<1 year old)
For neonates and young infants with severe obstructive megaureter, alternative temporizing approaches should be considered first rather than immediate tapering and reimplantation:
- Refluxing reimplantation (without tapering) can serve as temporary internal diversion, allowing the child to mature before definitive repair at >1 year of age 2
- High-pressure balloon dilation shows 80% success rates in avoiding open surgery in infants, particularly effective when distal ureteral diameter is <15 mm 4
- Modified orthotopic reimplantation without tapering (using a 1:1.5-2 diameter-to-tunnel ratio) has shown success in small series of infants 1-7 months old 1
These approaches avoid the technical challenges and potential complications of extensive ureteral tailoring in very small infants 2, 4.
Children >1 Year Old
Definitive tapered reimplantation is appropriate once the child is older and the anatomy is more favorable for extensive reconstruction 2, 3.
Renal Function Considerations
While renal function should be assessed preoperatively, the decision to taper is primarily anatomic (based on diameter) rather than functional 3. However:
- Severely compromised renal units may warrant nephrectomy rather than complex reconstruction 2
- Progressive hydronephrosis despite adequate bladder drainage indicates need for intervention 4
Technical Approach Selection
When tapering is required, both intravesical and extravesical approaches are effective 3:
- Intravesical reimplantation: May be preferable when voiding dysfunction or preoperative reflux is present (93% vs 50% success with extravesical in this subset) 3
- Extravesical reimplantation: Effective for primary obstructive megaureter (90% success rate) but less successful with concurrent voiding dysfunction 3
- Excisional tapering is the standard technique when reduction is needed 3
Common Pitfalls
- Attempting reimplantation without tapering when diameter >13 mm: This leads to inadequate tunnel length and high failure rates 3
- Performing extensive tailoring in young infants: Consider temporizing measures instead 2, 4
- Ignoring voiding dysfunction: This significantly impacts surgical approach selection and outcomes 3
- Inadequate tunnel length after tapering: Must maintain 3-5:1 ratio even after size reduction 3
Duplex Systems
When megaureter occurs with renal duplication, tapering with common sheath reimplantation is safe and effective when the dilated segment requires size reduction 5.