AUA 2025: Management of Stones

Genetics and Therapeutics in Stone Disease (UAA Lecture)

Speaker: Professor Anthony CF Ng

Genetics of Stone Disease: Monogenic vs. Polygenic Influences

1. Monogenic Disorders (1–2% of cases): Rare but often severe. Includes:
   1. Hypercalciuria via calcium metabolism gene defects.
   2. Cystinuria, primary hyperoxaluria, xanthinuria.
   3. Associated with systemic signs (hearing loss, seizures, ocular issues).
   4. Often autosomal dominant or X-linked inheritance.
2. Polygenic Risk Factors: More common but individually low impact.
   1. Require cumulative genetic hits.
   2. Studied via GWAS (Genome-Wide Association Studies).

Genetic Risk Scores:

• Over 40 SNPs associated with nephrolithiasis.
• Early models from UK Biobank showed promise but lacked validation across diverse populations.
• Validation in African-American cohorts was suboptimal, indicating ethnic specificity of risk scores.
• Integration with environmental and metabolic data may improve predictive power.

Clinical Utility and Guidelines:

EAU and AUA guidelines recognize genetic influence but lack clear protocols for screening. AOA guidelines suggest testing in patients with rare stone types or primary hyperoxaluria.

Who to Screen?

1. Pediatric stone formers, especially with recurrent disease.
2. Patients with systemic manifestations or rare biochemical abnormalities.
3. Adults with unusual stone composition or phenotypic features may be considered.
4. Low-risk patients: general preventive measures remain adequate.

Future Directions and Therapeutic Implications:

1. Current Tools and Interventions: Available genetic panels for cystinuria, hyperoxaluria, and calcium stone disease.
2. Positive findings may guide:
   1. Targeted diet (e.g., low oxalate or methionine)
   2. Urinary alkalinisation
   3. Thiazide diuretics or pharmacotherapy
   4. Screening family members for early detection

Conclusion:

Genetic factors significantly contribute to urinary stone disease. Selective genetic screening is valuable for high-risk individuals, enabling personalized prevention and counselling. However, broader implementation awaits more robust data on cost, effectiveness, and clinical outcomes.

Do we Need to do Percutaneous Nephrolithotomy Anymore?

Speaker: Dr. Roger Sur

Introduction: Evolution of Stone Surgery:

Dr. Sur opened the session with a provocative question reflecting shifts in endourology: with the rise of advanced suction technologies, is percutaneous nephrolithotomy (PCNL) still necessary? He outlined three modern alternatives:

• Suction ureteral access sheaths (SUAS)
• Direct in-scope suction (DISS)
• Steerable ureteroscopic renal evacuation (SHURE)

 

1. Suction Ureteral Access Sheaths (Dr. Naeem Bhojani, Montreal)
   1. Technology & Advantages:
      1. SUAS devices combine flexible, malleable tips and active suction.
      2. Provide enhanced visibility by clearing dust/fragments during lithotripsy.

• Reduces intrarenal pressure and possibly heat.

1. Tips & Techniques:
   1. Requires high inflow irrigation (200–250 mmHg) and wall suction.
   2. Scope should ideally be positioned against the stone.

• Back walling the sheath into a calyx helps control flow and fragment egress.

1. Intermittent scope withdrawal helps flush accumulated dust and avoid pressure spikes.

1. Clinical Data:
   1. RCT showed superior early and 3-month stone-free rates (81% and 87%) vs traditional UAS (49% and 70%).
   2. Lower ureteral injury and postoperative fever rates.

• Improved patient-reported quality of life due to fewer retained fragments and lower complication rates.

1. Conclusion: SUAS reshapes the kidney stone management paradigm. PCNL is now often reserved for stones >3–4 cm.

 

2. Mini-PCNL in the Era of Suction (Dr. Wilson Sui, Michigan)
   1. Clinical Perspective:
      1. Despite suction advances, mini-PCNL retains value, especially for:
      2. Lower pole stones

• Dense or complex calculi

1. Fluoro-free procedures and stent avoidance

1. Efficiency Arguments:
   1. Based on Poiseuille’s Law, percutaneous access allows 10x higher flow than ureteral access due to larger diameter and shorter length.
   2. Mini-PCNL achieves superior stone clearance, particularly for bulky fragments.
2. Case Demonstration:
   2. Supine, ultrasound-guided access; efficient treatment of 2.5 cm stone.
   3. Demonstrated safe dilation and stone retrieval with no fluoroscopy.
3. Conclusion: Mini-PCNL is far from obsolete. Selection should be patient- and anatomy-specific, with both modalities coexisting.

 

3. Suction Ureteroscopy & SHURE (Dr. Brian Eisner, Harvard)
   1. Technological Evolution: DISS: Alternating irrigation/suction through a single channel; best for dust <250 microns.
   2. SHURE (CVAC systems):
      1. Gen 1: Dual-lumen with suction, used post-URS under fluoroscopy.
      2. Gen 2: Integrated optics, suction, irrigation, and lithotripsy.
   3. Clinical Outcomes:
      1. ASPIRE RCT (Gen 1): Greater stone volume removed and fewer 1–2 year complications vs URS alone.
      2. Gen 2 Preliminary Results: Real-time aspiration eliminates dust accumulation while clear visual field aids complete stone clearance.
   4. Case Examples:
      2. Successful treatment of 2.5 cm stones by both experienced and novice users.
      3. Demonstrated simplicity and efficacy of aspiration-integrated ureteroscopy.
   5. Conclusion: Suction ureteroscopes offer meaningful advances in stone management, particularly for dusting and reducing recurrence, though PCNL remains vital for large burden cases.

Final Takeaways:

• Suction-enhanced technologies are redefining endourological practice.
• They offer higher stone-free rates, fewer complications, and better visualization.
• Intrarenal pressure control remains critical to avoid postoperative sepsis.
• PCNL still has a role, particularly for large, complex stones.
• The future likely lies in technique integration and patient-specific selection.

Crossfire Debate Overview: Management of the Asymptomatic Kidney Stone

Moderator: Dr. James Lingeman

Debators Treat: Dr. Necole Streeper & Dr. Alana Desai

Debators Observe: Dr. Ryan Hsi & Dr. Matthew Dunn

Index Case

• Patient Profile: 44-year-old healthy male
• Presentation: Spontaneously passed a distal right ureteral stone
• Incidental Finding: Contralateral asymptomatic renal stone detected on CT and confirmed on ultrasound
• Labs: Normal renal function, clean urinalysis except for a few RBCs

This case formed the basis of the panel's debate on whether to observe or proactively treat asymptomatic non-obstructing kidney stones.

Arguments for Observation (Drs. Dunn & Hsi):

1. Guideline & Evidence-Based Justification:
   1. AUA 2016 guidelines support observation for asymptomatic, non-obstructing stones (Level C evidence).
   2. Multiple studies showed low surgical intervention rates (5.6–11.1%) over 3–4 years.
   3. A systematic review found intervention risk ranges from 12–35% over ≥2 years.
2. Clinical Philosophy:
   1. Observation avoids overtreatment and surgical morbidity (e.g., stent pain).
   2. “Observation is active treatment”: requires regular surveillance and shared decision-making.
   3. Allows for tailored management based on risk evolution.
3. Patient-Centered Considerations:
   1. Most patients remain asymptomatic or have mild symptoms manageable without intervention.
   2. Observation respects patient autonomy and lifestyle choices.
   3. Many patients prefer to “seize the day” rather than undergo prophylactic surgery.

Arguments for Treatment (Drs. Streeper & Desai):

1. Risk of Future Complications:
   1. Up to 40% of stones >5 mm will require surgery.
   2. Half of observed patients experience a symptomatic event within 3–5 years.
   3. Delay may result in stone growth, necessitating more invasive procedures like PCNL.
2. Planned vs. Unplanned Surgery:
   1. Planned surgery offers better outcomes, reduced morbidity, and avoids ER visits or urgent interventions.
   2. Surgeons and patients can coordinate care, reducing stress and system burden.
3. Quality of Life:
   1. Studies show improved WISQOL and CREST scores post-elective surgery.
   2. Symptom prevention aligns with patient preference, especially among those with prior painful stone events.
4. Emerging Innovations: Ultrasound-Based Therapies
   1. Ultrasonic Propulsion: Moves stone fragments using transcutaneous ultrasound.
   2. Burst Wave Lithotripsy (BWL): Noninvasive stone fragmentation with less renal trauma.
5. Clinical Impact:
   1. RCTs show increased stone passage (by 58%) and reduced stone-related events (by 70%) with ultrasonic propulsion.
   2. Both technologies are now used in-office on awake patients, with minimal side effects and promising outcomes.
6. Future Outlook:
   1. Technologies may shift treatment thresholds, making early, low-risk intervention more feasible.
   2. Could reduce debate by enabling minimally invasive management of borderline stones (e.g., 6–8 mm) in asymptomatic patients.

Panel Reflections and Takeaways:

• Consensus: Observation remains valid but must be selective and closely monitored.
• Surgery: Prophylactic treatment is justified in high-risk patients and offers quality-of-life benefits.
• Technological Advances: Noninvasive ultrasound treatments may revolutionize office-based stone care, improving patient outcomes and decision-making flexibility.

Prevention of Urinary Stones with Hydration: A Randomized Clinical Trial

Speaker: Dr. Alana Desai

Background & Rationale:

• Clinical Context: Increased fluid intake is widely advised to prevent urinary stone recurrence, but sustaining adherence remains challenging.
• Objective: To evaluate whether a multicomponent behavioural intervention improves fluid intake and reduces stone recurrence in patients with low urine volume.

Study Design: Multicentre, randomized controlled trial (RCT) with pragmatic features.

1. Participants:
   1. Total: 658
   2. Age: ≥12 years
2. Inclusion: ≥1 symptomatic stone in 3 years or stone progression in 5 years, and low urine volume (<2L/day in adults; <25cc/kg/day in adolescents)
3. Arms:
   1. Intervention group: Received a structured hydration program with:
      1. Smart water bottle & fluid prescriptions
      2. Financial incentives (loss-framed) & structured problem-solving & low-touch supports (texts, gamification)
   2. Control group: Received guideline-based advice and smart bottle for optional use
4. Outcomes
   1. Primary Outcome: Symptomatic stone events (stone passage, surgery for symptomatic/asymptomatic stones)
   2. Secondary Outcomes:
      1. Radiographic progression (new stones, ≥2 mm growth)
      2. 24-hour urine volume

• Lower urinary tract symptoms (LUTS)

1. Safety: Hyponatremia requiring hospitalization

Key Findings:

• Symptomatic Recurrence: No significant difference: 18.6% (intervention) vs. 19.8% (control)
• Urine Volume: Significantly higher in intervention arm at all-time points, though average volumes remained below guideline targets in both arms.
• Radiographic Outcomes: No differences in new stone formation, growth, or composite progression.
• LUTS: Higher symptom reporting at months 6 and 12 in the intervention arm.
• Safety: No hospitalizations for hyponatremia.

Interpretation:

The intervention increased fluid intake but did not translate into a reduction in stone recurrence. It highlighted the disconnect between surrogate endpoints (urine volume) and clinical outcomes (stone events). It, also, suggested that simpler, patient-centred strategies may be more practical than intensive behavioural programs.

Conclusion:

Behavioural intervention modestly improved urine output but did not reduce stone recurrence. Hydration remains a low-cost, low-risk recommendation, but this study underscores the need for realistic, sustainable prevention strategies rooted in meaningful outcomes.

American Urological Association 2025, April 26-29, Las Vegas, NV