Management of Renal Calculi

Initial Assessment and Risk Stratification

The American Urological Association recommends obtaining non-contrast CT scan as the gold standard imaging modality for stone detection and characterization, though low-dose CT protocols should be used to minimize radiation exposure is not cited, however, ultrasound is acceptable as first-line imaging but may miss stones <3mm 1
The American Urological Association recommends performing stone analysis at least once when stone material is available to guide preventive strategies 2
Serum calcium and intact parathyroid hormone should be obtained if primary hyperparathyroidism is suspected (high or high-normal calcium) 2
Stone burden should be quantified through imaging to assess for multiple/bilateral stones or nephrocalcinosis, which indicate higher recurrence risk 2

For renal stones <10mm, observation with periodic imaging is the initial management approach, while stones >10mm typically require surgical intervention with either shock wave lithotripsy (SWL) or ureteroscopy (URS) as first-line options 3
Conservative management with observation is appropriate for asymptomatic or mildly symptomatic stones ≤5mm, as spontaneous passage rates are high, however, this fact is from Praxis Medical Insights, a better source is not available 1
Follow-up imaging at 3-6 months to assess for stone passage or growth is recommended for small renal stones 1
Observation with periodic imaging remains an option for controlled symptoms for moderate renal stones (5-10mm) 3
Both SWL and URS are acceptable first-line treatments when intervention is needed for moderate renal stones (5-10mm) 3
URS yields significantly higher stone-free rates but has higher complication rates compared to SWL 3
Surgical treatment is required in most cases for large renal stones (>10mm) 3

Counsel patients that URS provides better stone-free rates with single procedure but carries higher complication risks 3
SWL complications include sepsis, steinstrasse, stricture, and UTI 3
URS complications include sepsis, ureteral injury, stricture, and UTI 3
Routine stenting is not recommended with SWL as it provides no improved fragmentation 3

Increase fluid intake to achieve urine volume ≥2.5 liters daily as the most critical preventive measure 2
Urease inhibitors (acetohydroxamic acid) can be used for recurrent infection stones after removal 4

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 3
For patients electing observation or medical expulsive therapy, ensure well-controlled pain, no sepsis, and adequate renal function before proceeding 3

The American Urological Association recommends that for small renal stones (<10mm), observation with periodic imaging is the initial approach, while stones 10-20mm require flexible ureteroscopy (fURS) or shock wave lithotripsy (SWL) as first-line options, and stones >20mm mandate percutaneous nephrolithotomy (PCNL) as the primary treatment 5
For lower pole stones <10mm specifically, fURS or SWL are the primary treatment options, according to the European Association of Urology (EAU) guidelines 5
For stones in the renal pelvis or upper/middle calyx, fURS and SWL are first-line treatments for stones <20mm, and PCNL is recommended as another option for stones between 10-20mm according to EAU and SIU/ICUD guidelines 5
For lower pole stones 10-20mm, fURS and PCNL are the suggested primary options, as SWL is less effective for lower pole stones in this size range due to unfavorable anatomy for fragment passage 5

PCNL is the first-line treatment for stones >20mm regardless of location, as it achieves superior stone-free rates with acceptable morbidity in experienced hands, as recommended by the American Urological Association 5
For lower pole stones >20mm (or >15mm per SIU/ICUD), PCNL is unequivocally superior to other modalities, according to the Société Internationale d'Urologie (SIU) and the International Consultation on Urological Diseases (ICUD) guidelines 5

Modern PCNL utilizes flexible nephroscopy after rigid nephroscopy debulking to remove stones remote from the access tract, with a reported stone-free rate of 95% with mean 1.6 procedures per patient 6, 7, 8
Second-look flexible nephroscopy via the existing nephrostomy tract retrieves residual stones identified on post-procedure imaging, as recommended by the European Association of Urology (EAU) 6, 7, 8

For non-functioning kidneys with staghorn calculi, nephrectomy should be considered if the contralateral kidney has satisfactory function, according to the American Urological Association 9, 6, 7, 8
Giant staghorn calculi (≥2500 mm²) achieve only 54% stone-free rates with PNL-based therapy, and open nephrolithotomy may offer better outcomes, as reported by the Société Internationale d'Urologie (SIU) and the International Consultation on Urological Diseases (ICUD) 9, 6, 7, 8