What are the current management strategies for infundibular stenosis of the kidney using Ureteroscopy (URS) with Retrograde Intrarenal Surgery (RIRS)?

Management of Infundibular Stenosis Using Ureteroscopy and Retrograde Intrarenal Surgery

Ureteroscopy (URS) with Retrograde Intrarenal Surgery (RIRS) is an effective and safe treatment option for infundibular stenosis of the kidney, particularly in cases where the stenosis is associated with stone disease or when percutaneous approaches are contraindicated.

Pathophysiology and Clinical Significance

Infundibular stenosis is characterized by narrowing of the infundibulum connecting a calyx to the renal pelvis, leading to:

• Dilation of the affected calyx
• Potential stone formation behind the stenosis
• Progressive renal dysfunction if left untreated 1

Diagnostic Evaluation

Before proceeding with treatment, comprehensive imaging is essential:

• Low-dose CT scan is recommended as the primary imaging modality 2
• Evaluation should assess:
  • Location and severity of stenosis
  • Associated stone burden
  • Collecting system anatomy
  • Renal function of the affected kidney

Treatment Algorithm for Infundibular Stenosis

First-Line Approach:

1. For stenosis with stones ≤10 mm:

   • RIRS is recommended as first-line therapy 2, 3
   • Offers high stone-free rates with minimal morbidity

2. For stenosis with stones 10-20 mm:

   • RIRS is preferred over SWL due to superior stone-free rates 2
   • May require staged procedures for complete clearance

3. For stenosis with stones >20 mm:

   • Percutaneous nephrolithotomy (PCNL) is the preferred first-line approach 2
   • RIRS may be considered in cases where PCNL is contraindicated

Special Considerations:

• In patients with bleeding disorders or on anticoagulation therapy that cannot be discontinued, RIRS is preferred 2
• In patients with skeletal deformities or obesity that make positioning difficult, RIRS offers advantages over PCNL 3

Technical Aspects of RIRS for Infundibular Stenosis

Equipment Requirements:

• Flexible dual-channel ureteroscope
• Holmium:YAG laser for incision of stenosis and lithotripsy
• Nitinol baskets for stone extraction
• Access sheath (recommended but optional)

Procedural Technique:

1. Access and Preparation:

   • Placement of safety guidewire is recommended 2
   • Use of ureteral access sheath is optional but facilitates multiple entries and reduces intrarenal pressure 2
   • Pre-stenting is not routinely recommended but may facilitate access in difficult cases 2

2. Management of Stenosis:

   • Direct visualization of the stenotic infundibulum
   • Holmium laser incision of the stenosis (typically at 3,6,9, and 12 o'clock positions)
   • Balloon dilation may be used as an adjunct

3. Stone Management:

   • Laser lithotripsy of any stones present
   • Basket extraction of fragments
   • Flexible nephroscopy to ensure complete stone clearance 2

4. Post-Procedure:

   • Ureteral stent placement is recommended following infundibular incision to maintain patency
   • Stent duration typically 2-4 weeks

Outcomes and Success Rates

• Stone-free rates: 87-92% for intermediate-sized stones (1-3 cm) 4
• Complications: Generally low (Clavien grade I in 8-12% of cases) 4
• Hospital stay: Typically 1-1.5 days 4

Limitations and Challenges

• Success may be limited by:

  • Unfavorable infundibular-calyceal anatomy 4
  • Stone migration to inaccessible calyces
  • Severe stenosis requiring more invasive approaches

• In cases of severe stenosis with significantly impaired renal function, more aggressive approaches may be necessary 5

Alternative and Complementary Approaches

• Micropercutaneous nephrolithotomy (Microperc): Emerging as an effective alternative with comparable success rates (87.5% vs. 91.7% for RIRS) 4

• Combined approach: In complex cases, combining RIRS with percutaneous access may be necessary 4

• Conversion to standard PCNL: May be required for severe stenosis or large stone burden 2

Follow-up Protocol

• Imaging at 4-6 weeks post-procedure to assess:

  • Resolution of hydronephrosis
  • Patency of the infundibulum
  • Clearance of stone fragments

• Long-term monitoring for recurrence of stenosis or stone formation

RIRS represents a minimally invasive approach for managing infundibular stenosis with high success rates and minimal morbidity, particularly for cases with associated stone disease. The technique continues to evolve with improvements in flexible ureteroscope technology and auxiliary equipment.