Cystinuria: urine sediment as a diagnostic test

OBJECTIVES: To demonstrate the importance of carrying out the urinary sediment study with the correct interpretation and crystals typification as a clinical laboratory diagnostic tool, as well as the elaboration of protocols that determine the need to realize this type of microscopic urinary sediment examination routinely. CASE PRESENTATION: Elderly male patient with no personal or family history of interest that presented with left iliac fossa fixed and non-irradiated pain lasting three days. This is the first time that he suffered pain episodes of this type. The urine analysis reveals proteinuria, hematuria and the sediment shows abundant flat and hexagonal crystals, typical of cystine. Amino acid analysis confirms the finding, showing high dibasic amino acids and cystine concentrations. CONCLUSIONS: The study of the urinary sediment by the clinical laboratory reveals the presence of a case of cystinuria due to the appearance of their pathognomonic crystals at an advanced age and without a previous history. The case reported in this paper is of interest for clinical laboratory practice, as it demonstrates the utility of urine sediment examination in the diagnosis of a genetic disease that manifests as a simple renal colic.