The natural history of asymptomatic calyceal stones

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).

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.

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.

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.