What is the role of Retrograde Intrarenal Surgery (RIRS) in treating calyceal diverticulum calculi?

Role of RIRS in Treating Calyceal Diverticulum Calculi

RIRS is an effective first-line treatment option for calyceal diverticulum calculi with low to moderate stone burdens, particularly when stones are less than 1.5 cm, offering stone-free rates of 75-97% with minimal morbidity. 1, 2

Primary Treatment Indications

RIRS should be the initial treatment choice in the following scenarios:

• Low to moderate stone burden contained within calyceal diverticula 1
• Stone size less than 1.5 cm, which significantly improves stone-free outcomes (P=0.015) 2
• Anteriorly located diverticula with manageable stone burden 1
• Patent infundibulum allowing flexible ureteroscope access 3
• Patients with contraindications to percutaneous approaches, such as those who are anticoagulated or obese 4

Technical Approach and Success Rates

The procedure utilizes flexible ureteroscopy with holmium YAG laser lithotripsy:

• Stone-free rates range from 75-97% depending on stone characteristics 2, 5
• Mean operative time is approximately 46-117 minutes 2, 3
• Hospital stay averages 2.9-6.9 days 2, 3
• Diverticular neck length less than 0.4 cm correlates with better outcomes 2

Comparative Effectiveness

When compared to alternative treatments:

• RIRS is more efficacious than ESWL monotherapy for calyceal diverticular stones 1
• MPCNL achieves higher stone-free rates (90.5% vs 60%) but RIRS offers shorter operative time and hospital stay 3
• RIRS avoids potential complications of percutaneous and laparoscopic procedures 1
• Diverticular obliteration rates are lower with RIRS (33.3%) compared to MPCNL (76.2%), though this may not affect symptomatic improvement 3

When to Choose Alternative Approaches

RIRS should be deferred in favor of other modalities when:

• Posteriorly located diverticula with large stone burden favor percutaneous approach as first choice 1
• Stone size exceeds 1.5 cm, where MPCNL demonstrates superior stone-free rates (90.5%) 2, 3
• Failed RIRS with unsuccessful stenotic segment repair warrants conversion to percutaneous antegrade surgery under the same anesthesia 1

Technical Innovations Enhancing RIRS

Several techniques improve outcomes:

• Autologous blood clot occlusion of the lower calyx after fragmentation prevents stone reaccumulation, achieving 94-97% stone-free rates at 3-6 months 5
• Stone relocation to favorable positions before fragmentation (required in 60% of cases) 5
• Holmium laser fragmentation to less than 3 mm facilitates spontaneous passage 5
• Use of access sheaths and displacement techniques increasingly employed 4

Complications and Safety Profile

RIRS demonstrates acceptable safety:

• Fever occurs in 9.3% and sepsis in 6.3% of cases 2
• Overall complication rate of 13.3-19%, comparable to MPCNL 3
• Minimal ureteral trauma compared to multiple instrument passages needed for active fragment removal 5
• Most patients require only overnight hospital stay (91.4%) 5

Critical Success Factors

Stone size is the single most important predictor of stone-free outcomes on multivariate analysis (P=0.015), with a critical cutoff of 1.5 cm 2. Length of diverticular neck also significantly affects outcomes (P=0.038) 2.