Cystinuria—Diagnosis and Management

Cystinuria is an autosomal recessive disorder of cystine and dibasic amino acid transport across the luminal membrane of proximal tubule and small intestine. Two responsible genes have been identified: mutations in the SLC3A1 gene, located on the chromosome 2p, cause cystinuria type I, while variants in SLC7A9 have been demonstrated in non-type I cystinuria. The poor urinary solubility of cystine can lead to stone formation in affected individuals which typically manifests in the second and third decades of life. Typical management involves copious oral fluid intake, urinary alkalisation and thiol medications to decrease the urinary cystine concentration below 300 mg/l. Recurrent stone formation necessitates repeated urological interventions. Fortunately, contemporary minimally invasive approaches to stone treatment are applicable in the treatment of cystine stones. The management of cystinuria is often challenging and requires a close co-operation between radiologist, nephrologist and urologist.