Nephrolithiasis in a Portuguese Pediatric Population

Introduction and Aims: Nephrolithiasis incidence in children has increased considerably. It is associated with substantial morbidity, recurrence and increased adulthood cardiovascular risk and chronic kidney disease. A thorough investigation is essential, as rare forms of urolithiasis have increased risk of renal failure. We aim to determine the epidemiology and outcomes of a pediatric population with nephrolithiasis presented in a nephrology unit of a tertiary centre. Methods: Retrospective study of the records of all children (<18 years) with nephrolithiasis diagnosis between 2008‑17. Clinical features, etiology, recurrence, treatment, and outcomes were evaluated and compared throughout the study period through two equal periods (2008‑12 versus 2013‑17). Results: We identified 80 cases: isolated nephrolithiasis (86%) and associated with nephrocalcinosis (14%). Mean follow‑up was 36 months (14–120). Median age at presentation was 8.6 years [3 months – 17 years]: 21% < 2 years‑old and 46% ≥ 10 years. The annual ratio of referrals for nephrolithiasis increased on average 1.2% per year [0.3‑11.8%]. Multiple etiological factors were present in 34%. A metabolic abnormality was identified in 54%: hypocitraturia (34%), hypercalcuria (24%), hyperoxaluria (15%), hyperuricosuria (15%) and cystinuria (1%), without age predominance (p=0.2). Urinary tract infection (24%) was the next most significant etiology and was more frequent below 2 years of age (p=0.001) and associated with struvite calculi (p=0.033). Median age at diagnosis was significantly lower in the study’s first half (5 vs 10 years; p=0.019) and an infectious etiology was more frequent (p=0.043). In a logistic‑regression analysis, a family history of nephrolithiasis was associated with a metabolic cause (p