What is the management of kidney stones in Autosomal Dominant Polycystic Kidney Disease (ADPKD)?

Management of Kidney Stones in ADPKD

Medical management of nephrolithiasis in ADPKD patients should follow the same protocols used in the general population, but obstructing stones require referral to specialized centers with expertise in ADPKD due to increased technical complexity. 1

Medical Management

The cornerstone of stone prevention in ADPKD mirrors general population guidelines:

• Maintain high fluid intake of 2.5-3.0 L/day with target urine output >2.0-2.5 L/day 2
• Dietary modifications include limiting sodium to 2-3 g/day (or 3-5 g/day of NaCl), ensuring adequate calcium intake of 1000-1200 mg/day, limiting oxalate-rich foods, and restricting animal protein to 0.8-1.0 g/kg body weight/day 2
• Increase citrus fruit consumption and consider alkaline citrate supplementation for stone prevention 2
• Avoid vitamin C and vitamin D supplements which can increase stone risk 2

Stone Composition Considerations

ADPKD patients have a distinct stone composition profile compared to the general population:

• Uric acid stones comprise 47% of stones in ADPKD patients 3
• Calcium oxalate stones account for 39% 3
• This differs from the general population and may require tailored preventive strategies including allopurinol for hyperuricosuria 2

Diagnostic Approach

• Ultrasonography is the first-line imaging modality to rule out stones or urinary tract obstruction 1
• CT scanning (unenhanced) provides superior detection and can distinguish between renal calculi and cyst calcifications, which occur in 25% of ADPKD patients 4
• Investigate additional risk factors for stone disease when stones are identified 1

Interventional Management

When conservative management fails or obstruction occurs:

Extracorporeal Shockwave Lithotripsy (ESWL)

• ESWL can be used as primary management for symptomatic or obstructive stones in ADPKD 5
• Achieves 85% stone-free rate at 3 months 5
• Place double-J stent when stones are larger than 8 mm in diameter 5

Minimally Invasive Percutaneous Nephrolithotomy (MPCNL)

• MPCNL should be considered first-line treatment for large stone burden, including staghorn calculi 6
• Provides 95.7% final stone-free rate after second-look procedures when needed 6
• Safe even with staghorn stones without compromising renal function (mean creatinine unchanged: 148.17 vs 149.24 μmol/L, P=0.48) 6
• Clavien grade I-II complications occur in approximately 39% of cases but are managed conservatively 6

Critical Clinical Considerations

Symptom Recognition

• Flank pain occurs in 87% of ADPKD patients with stones and should prompt evaluation 6
• Patients with stones have significantly higher rates of previous flank pain (68% vs 35%) and UTIs (63% vs 18%) compared to those without stones 4

Differentiation from Other Complications

• UTIs must be differentiated from cyst hemorrhage or kidney stones in ADPKD patients presenting with pain 1
• Cyst calcifications (present in 25% of patients) result from hemorrhage and are more common in older patients with larger kidneys and worse renal function 4

Impact on Disease Progression

• Recurrent gross hematuria before age 30-35 years is associated with worse renal survival and may indicate higher stone risk 1, 3
• Proper treatment of UTIs, which are more common with stones, decreases infection frequency and may slow progression to renal failure 3

Special Considerations with Tolvaptan

• Tolvaptan reduces the incidence of kidney stones in ADPKD patients (demonstrated in TEMPO 3:4 trial) 1
• However, tolvaptan must be interrupted during stone episodes if volume depletion risk exists 1
• Patients need a "sick-day plan" to skip tolvaptan doses during situations with limited water access or increased fluid losses 7

Referral Indications

Obstructing kidney stones mandate management by centers of expertise due to the technical challenges posed by massively enlarged polycystic kidneys, difficulty in anatomical localization, and increased complication risk 1. Complicated nephrolithiasis may also be an indication for native nephrectomy in transplant candidates, though this should only occur at or after transplantation 1.