Clinically Insignificant Residual Fragments After Percutaneous Nephrolithotomy: Medium-term Follow-up

Background And Purpose: Clinically insignificant residual fragments (CIRFs), defined as asymptomatic, noninfectious, ≤4  mm fragments, are sometimes observed after percutaneous nephrolithotomy (PCNL). Because the natural history of these fragments is unclear, we investigated the medium-term outcome of these fragments.

Patients And Methods: During a 3-year period, 430 patients underwent PCNL. Overall stone-free rate was 74.5%, and CIRFs were encountered in 22% of cases 3 months after surgery. A total of 38 patients who had CIRFs immediately after PCNL with at least 24 months of follow-up were included in the study. All patients were subjected to periodic follow-up with detailed history, clinical examination, and radiographic follow-up. Serum biochemistry together with urine metabolic evaluation was also performed.

Results: The median follow-up was 28.4±5.3 months (range 24-38  mos). Ten (26.3%) patients had a symptomatic episode that necessitated medical therapy during follow-up while others remained asymptomatic. Radiologic assessment showed an increase in the size of the fragments in 8 (21.1%) patients, while the size of the fragments was stable or decreased in 27 (71.1%) cases. Three (7.9%) patients had spontaneous stone passage. Metabolic evaluation revealed abnormalities in 10 (26.3%) patients. Stone analysis revealed magnesium ammonium phosphate in three of eight patients who had an increase in residual fragment size. Also, only two of these eight patients had a metabolic abnormality (one hypocitraturia and one hypercalciuria).

Conclusion: Medium-term follow-up of CIRFs after PCNL revealed that progression within 2 years is relatively common. Increase in fragment size is common in patients with struvite stones, and presence of risk factors on 24-hour urine metabolic analysis does not seem to predict growth of observed fragments.