Are small residual stone fragments really insignificant in children?

Abstract

Objectives: To assess the significance of asymptomatic residual stone fragments of less than 4mm (clinically insignificant residual fragments [CIRFs]) after shock wave lithotripsy (SWL), percutaneous nephrolithotomy (PNL), and retrograde intrarenal surgery (RIRS) in children.

Patients and methods: Eighty-five children were followed up for 6 to 50months (median 22). Outcomes measured were fragment re-growth, stone events (emergency department visits, hospitalization, or additional interventions) and spontaneous fragment passage.

Results: During follow-up, 22 children (25.8%) passed residual fragments spontaneously. Highest spontaneous passage rate was found for renal pelvis stones and the lowest for the lower pole stones (57.1% vs. 16.1%; p<0.001). When the number of the fragments increased, the chance of the spontaneous passage decreased (30% vs 20%; p<0.05). Symptomatic episodes including renal colic, hematuria, or urinary tract infection were documented in 34 (40%) patients, and re-growth of fragments was observed in 18 (21.2%). Stone size had no significant effect on spontaneous passage (p=0.079), stone growth (p=0.528), and symptomatic episodes (p=0.402). Twenty-five patients (29.4%) required secondary intervention for stone re-growth or stone related events and the remaining 20 patients (23.5%) needed medical treatment for bothersome symptoms or complications.

Conclusions: Our results suggest that 40% of children with CIRFs will become symptomatic and 20% will develop stone re-growth over the following 6months. Only one fifth of the fragments will pass spontaneously without any complications. Therefore, the use of the term "CIRF" is not appropriate for postoperative residual fragments in children.