[Cystine lithiasis: study of a series of 116 cases]

Cystine stones is a rare disease, related to a genetic metabolic disease. Its management must treat both the stones and their complications, and prevent recurrences by controlling cystinuria.

The objective of this study was to define the natural history of cystine stones, identify reliable diagnostic criteria and propose a simple treatment regimen.

The authors studied the clinical, biochemical and radiological data of a retrospective series of 116 cases, treated by the same urologist between 1953 and 1999.

Cystinuria is often diagnosed in young adults on the basis of urine biochemistry (Brand's reaction, urinary cystine assay) or spectrophotometric analysis of the stones or urinary crystals. This assessment, not performed routinely, must be guided by a family history, recurrent stones or following failure of lithotripsy. The appearance of the stones, macroscopically a waxy yellow, radiologically only slightly opaque with a large component in the renal pelvis associated with a small round caliceal stones, is highly suggestive. Radiological assessment by IVU is generally sufficient. Treatment of the disease is medical and surgical: dietary measures, alkalinization of the urine and possibly drug treatments, are associated with extracorporeal lithotripsy or surgical treatment. These modalities eliminate cystine stones in 70% of cases. Recurrent stones are observed in 42% of cases followed for more than 5 years, mainly due to the presence of residual fragments (60% of recurrences). Surveillance and dietary measures must be maintained for life. Surveillance is based on biannual radiographic follow-up (plain x-rays +/- ultrasound) to detect and consequently treat small stones. A test for cystinuria must be proposed to all relatives of affected patients.

This disease presents very polymorphic clinical features and clinical course. It can be responsible for impaired renal function and must therefore be investigated in the presence of suggestive clinical signs or history to avoid a delayed diagnosis, as treatment modalities are available to decrease the frequency of recurrence and which can potentiate treatment by surgical or lithotripsy. However, there are no predictive factors of deterioration of the disease, and biannual surveillance, for life, is essential to detect and treat small stones.