What is the best course of treatment for a patient presenting with renal calculi (kidney stones)?

Management of Renal Calculi

Percutaneous nephrolithotomy (PNL) should be the first-line treatment for staghorn calculi, while for non-staghorn renal stones, management is determined by stone size: observation for stones <10mm, flexible ureteroscopy (fURS) or shock wave lithotripsy (SWL) for stones 10-20mm, and PNL for stones >20mm. 1, 2

Initial Diagnostic Workup

• Obtain non-contrast CT scan as the gold standard imaging modality to detect and characterize stones, though low-dose protocols should minimize radiation exposure 1
• Ultrasound is acceptable as first-line imaging but may miss stones <3mm 1
• Perform stone analysis when material is available to guide preventive strategies 1
• Check serum calcium and intact parathyroid hormone if primary hyperparathyroidism is suspected (high or high-normal calcium) 1
• Quantify stone burden through imaging to assess for multiple/bilateral stones or nephrocalcinosis, which indicate higher recurrence risk 1

Treatment Algorithm Based on Stone Size and Type

Small Renal Stones (<10mm)

• Observation with periodic imaging is the initial management approach for asymptomatic or mildly symptomatic stones ≤5mm, as spontaneous passage rates are high 1
• Follow-up imaging at 3-6 months to assess for stone passage or growth 1
• For stones 5-10mm, both SWL and URS are acceptable first-line treatments when intervention is needed 1
• URS yields significantly higher stone-free rates but has higher complication rates compared to SWL 1

Moderate Renal Stones (10-20mm)

• Flexible ureteroscopy (fURS) or shock wave lithotripsy (SWL) are first-line options for stones in the renal pelvis or upper/middle calyx 1
• For lower pole stones 10-20mm, fURS and PCNL are the primary options, as SWL is less effective due to unfavorable anatomy for fragment passage 1
• PNL is recommended as another option for stones between 10-20mm 1

Large Renal Stones (>20mm)

• PCNL is the first-line treatment for stones >20mm regardless of location, achieving superior stone-free rates with acceptable morbidity 1
• Modern PNL utilizes flexible nephroscopy after rigid nephroscopy debulking to remove stones remote from the access tract, with stone-free rates of 95% with mean 1.6 procedures per patient 1
• Second-look flexible nephroscopy via the existing nephrostomy tract retrieves residual stones identified on post-procedure imaging 1

Staghorn Calculi Management

Primary Treatment

• Percutaneous nephrolithotomy (PNL) must be the first treatment for most patients with staghorn calculi, as it achieves stone-free rates more than three times greater than SWL monotherapy 3, 2
• The only randomized prospective trial (Meretyk trial) demonstrated PNL achieved stone-free rates >3 times higher than SWL monotherapy 2
• Single-access PNL with flexible nephroscopy and holmium:YAG laser can achieve 95% stone-free rates 2

Combination Therapy Approach

• If combination therapy is used, percutaneous nephroscopy must be the final procedure 3, 2
• The optimal sequence is: initial PNL debulking → SWL for residual fragments → final nephroscopy for remaining stones ("sandwich therapy") 2
• Avoid ending with SWL alone—this approach yields only 23% stone-free rates 3, 2
• SWL should only be used for stones unreachable by flexible nephroscopy or unsafe for additional access tracts 3, 2

Treatments to Avoid for Staghorn Calculi

• SWL monotherapy should NOT be used for most patients with staghorn calculi, as meta-analysis shows significantly lower stone-free rates than PNL-based approaches 3, 2
• If SWL monotherapy is undertaken despite limitations, establish adequate drainage (ureteral stent or percutaneous nephrostomy) before treatment to prevent severe obstruction and sepsis 3, 2
• Open surgery should NOT be used for most patients—reserved only for extremely large staghorn calculi with unfavorable collecting system anatomy 3, 2
• Anatrophic nephrolithotomy is the preferred open approach when necessary, with estimated transfusion rate 20-25% and mortality ~1% 3, 2

Surgical Technique Considerations

• Counsel patients that URS provides better stone-free rates with single procedure but carries higher complication risks 1
• SWL complications include sepsis, steinstrasse, stricture, and UTI 1
• URS complications include sepsis, ureteral injury, stricture, and UTI 1
• Routine stenting is not recommended with SWL as it provides no improved fragmentation 1
• Hospitalization after PNL ranges from one to five days, with most patients resuming normal activities one to two weeks after removal of all drainage tubes 3

Special Clinical Situations

Pediatric Patients with Staghorn Calculi

• Either SWL monotherapy or percutaneous-based therapy may be considered 2
• Stone-free rates with SWL approach 80% in children—higher than adults due to body size differences, ureteral elasticity, and length 2
• Important caveat: Animal studies show developing kidneys may be more susceptible to SWL bioeffects, and SWL is not FDA-approved for this specific pediatric indication 2

Non-Functioning Kidney

• Nephrectomy should be considered when the involved kidney has negligible function and the contralateral kidney is normal 3, 1, 2
• Indicated for poorly functioning, chronically infected kidneys with recurrent UTI, pyelonephritis, or sepsis 2
• Laparoscopic nephrectomy is an option, but open surgical nephrectomy may be safer if there is intense perirenal inflammation from xanthogranulomatous pyelonephritis 3

Medical Prevention Strategies

• Increase fluid intake to achieve urine volume ≥2.5 liters daily as the most critical preventive measure 1
• Potassium citrate is effective for alkalinizing urine in patients with uric acid and cystine calculi, maintaining an alkaline urinary pH around the clock without producing systemic alkalosis 4
• Urease inhibitors (acetohydroxamic acid) can be used for recurrent infection stones after removal 1
• Dietary modification includes reduction in animal protein and salt content 5

Critical Pitfalls to Avoid

• Do not rely solely on ultrasound for small stones—use CT for definitive diagnosis when clinical suspicion is high 1
• Do not assume absence of hydronephrosis rules out obstruction—dehydration can mask hydronephrosis 1
• Do not routinely stent with SWL—no benefit and increases morbidity 1
• Never withhold treatment options from patients due to physician inexperience or local equipment unavailability—patients must be informed of all treatment alternatives 2
• For patients electing observation or medical expulsive therapy, ensure well-controlled pain, no sepsis, and adequate renal function before proceeding 1
• Non-contrast CT is the gold standard for determining stone-free status, though fragments adjacent to nephrostomy tubes may not be detected 2