5-year-follow-up of patients with clinically insignificant residual fragments after extracorporeal shockwave lithotripsy

Abstract

Objectives: After SWL treatment, many patients have residual fragments in the kidney or ureter. Fragments </=4mm have high probability to pass spontaneously and are normally not further treated. The term clinically insignificant residual fragment (CIRF) has been established for these stones. However, this term is still controversial, as persisting fragments might be important risk factors for stone growth and recurrence. Aim of this study was to evaluate the impact of CIRF on stone recurrence.

Methods: We evaluated 173 patients (age 3-89 years) who have been treated by SWL and released with CIRF. Mean follow up was 4.9 years (4.5-5.3). 78% of the patients were recurrent stone formers with >2 stones episodes. These patients and their referring urologist received follow-up questionnaires which contained questions about stone clearance, late complications, auxillary measures and dietary or drug metaphylaxis.

Results: Most residual stone fragments were located within the lower calyx (17%) and the renal pyelon (14%). Stone analysis was available in 142 patients with CIRF and revealed calciumoxalate calculi in 93.6% of the cases. In 78.6%, CIRF cleared spontaneously within few weeks and did not recur within 5 years. However, residual stones led to stone recurrence and need of re-treatment in 21.4%. Renal pyelon (23%) and calices showed comparable growth of former CIRF (lower calices 26.5%, middle calices 27%, upper calices 26%). Only 48% of the patients with recurrent stone formation followed dietary metaphylaxis. However, a significant correlation between a general or specific metaphylaxis and stone growth of CIRF could not be demonstrated.

Conclusions: Most of the CIRF after SWL pass spontaneously without any complications. But considering that one fifth of the patients developed new stones at the side of residual fragments, it is obvious that close follow-up is required. Although we could not demonstrate a relation between metaphylaxis and stone re-growth, it is conceivable that adequate metaphylaxis can reduce stone recurrences.