Cystinuria: Diagnosis, Medical and Surgical Management, and Emerging Therapies. A Narrative Review

Cystinuria is a hereditary aminoaciduria causing recurrent cystine nephrolithiasis, impaired quality of life and potential renal function decline. Despite established treatment guidelines, real-world data reveal a persistent gap between recommended targets and clinical outcomes. Preliminary data from the EUROCYS 2024 prospective European registry (269 patients, 29 centers, 8 countries) showed that only 16.3% of patients achieved the target urinary pH range, 55.2% remained above the conventional urinary cystine threshold of 250 mg/L, and approximately 39% experienced a new stone event within the preceding 12 months, despite follow-up in specialist centers. Discontinuation rates for available thiol drugs have been reported to reach 30-50%. This narrative review, based on a structured non-systematic search of major databases and guideline repositories (2009-2026), synthesizes current evidence on cystinuria diagnosis and management and appraises emerging adjunctive interventions. Next-generation sequencing-based genetic testing and the cystine capacity assay represent key recent advances in monitoring. Thulium fiber laser lithotripsy and miniaturized percutaneous approaches offer less traumatic surgical options in this high-burden population. Oral N-acetylcysteine has mechanistic plausibility and a favorable, well-characterized safety profile in other clinical settings, making it a rational candidate for formal prospective evaluation; however, robust clinical trial evidence in cystinuria using contemporary monitoring parameters is lacking. Current standard treatment remains insufficient for a substantial proportion of patients, underscoring the need to evaluate accessible adjunctive therapies with defined mechanisms and measurable outcomes.