The natural history of asymptomatic calyceal stones.

OBJECTIVES: To evaluate the outcomes of patients with incidentally detected asymptomatic calyceal stones on active surveillance, and to identify risk factors for stone-related adverse events (AEs).

PATIENTS AND METHODS: In this retrospective case series, we identified all renal units with non-contrast computed tomography diagnosed asymptomatic calyceal stones in a single reference centre between August 2005 and August 2016. Primary endpoints were spontaneous stone passage and need for stone-related surgical intervention. The secondary endpoints were stone-related symptoms and AEs. Cox proportional hazards models were used.

RESULTS: We identified 301 renal units from 238 adult patients. The median average age of the study group was 56 years, with two-thirds consisting of males. The mean average cumulative stone size was 10.8 mm. At the end of the study, 58.8% of renal units with stones remained on surveillance with a median follow-up of 63 months. Overall, 26.6% of patients proceeded to surgical intervention with the majority secondary to pain with no stone relocation (30%) or stone relocation to the ureter with or without pain (25%). Over the 5-year period, 14.6% of stones passed spontaneously. On analysis of the secondary endpoints, 39.5% had a stone-related AE (either symptoms and/or need for surgical intervention). Younger patients (aged <50 years), and those with stone growth >1 mm annually were significantly more likely to have an AE (P = 0.012 and P = 0.006, respectively). The risk of an AE during surveillance at 1, 3, and 5 years was 3.4%, 18.9%, and 30.7% respectively.

CONCLUSIONS: Long-term conservative approaches for asymptomatic renal stones are an effective management option with ~60% of renal units remaining on active surveillance in >5 years of follow-up. Appropriate counselling with careful patient selection is advocated, as younger patients and those with evidence of stone growth were found to be at greatest risk of an adverse outcome.