Informing the Management of Asymptomatic Nephrolithiasis: Markov Decision Analysis for the 1 cm Renal Stone

The management of an incidentally discovered, asymptomatic renal stone includes watchful waiting, shock wave lithotripsy, ureteroscopy with basket extraction of fragmented stones (URS-B) or ureteroscopy with laser "dusting" (URS-D). Each intervention has varying stone-free rates, requirements for ureteral stenting, and variable impact on a patient's quality of life. Decision analysis was used to assess the optimal quality adjusted life-years associated with each treatment option.

A Markov model was constructed to represent potential outcomes for a single 1 cm renal stone after treatment. The cohort was followed for 1-month cycles over 3 years and toll penalties for receiving a stent and undergoing surgery were standardized and incorporated into each subtree. Probabilities, utilities and toll penalties were derived from existing literature or clinical extrapolation when no published data were available. One-way sensitivity analyses were performed to determine threshold probabilities/utilities that may alter preferred options.

Watchful waiting was the preferred intervention, preserving 2.82 quality adjusted life-years over 3 years. The remaining options had similar but decreasing quality adjusted life-years: URS-B provided 2.78 quality adjusted life-years; shock wave lithotripsy provided 2.72 quality adjusted life-years, and URS-D provided 2.67 quality adjusted life-years. One-way sensitivity analysis showed that URS-D was preferred when stone-free rates from URS-B dropped below 37%. Shock wave lithotripsy was preferred over URS-B when stone-free rates from URS-B dropped below 62%. As stents became progressively less bothersome, watchful waiting is preferred, followed by URS-B, shock wave lithotripsy and URS-D.

Watchful waiting is the preferred management decision for asymptomatic renal stones. However, these results are sensitive to both actual stone-free rate and individual stent tolerance.