Kidney stones, also known as urinary lithiasis, are solid masses that form inside the kidney from substances present in the urine in abnormally high quantities. There are several types of kidney stones, which are divided into different categories according to their formation conditions and composition. The wide variety of stone sizes means that they can remain in the kidney, travel through the urinary tract and be expelled spontaneously or, conversely, block the flow of urine and cause very intense pain. Kidney stone disease is a chronic condition that leads to a high recurrence of stone formation, which is why it is important to properly diagnose your stone to prevent recurrence in a way that is adapted to the type of stone.
What are they?
Cystine stones are caused by a rare disorder called "cystinuria." The disorder causes a natural substance called "cystine" to be excreted in the urine. When there is too much cystine in the urine, kidney stones can form. These stones can get trapped in the kidneys, bladder, or anywhere in the urinary tract. Most people with cystinuria have highly recurrent stones. It is a chronic disease that can be managed, but not cured.
What are the causes? (1)
Cystinuria is a hereditary disorder passed down from parents to children through a defect in a specific gene. To have cystinuria, a person must inherit the gene from both parents.
Approximately 1 in 7,000 people worldwide have cystinuria. According to a recent study, most people with cystinuria get their first stones in their twenties or thirties, with 30-40% of people developing cystine stones in adolescence. But some adults have their first cystine stone after age 40. Children can also get cystine stones. In fact, according to some research, 8-10% of kidney stones in children are cystine stones.
How to prevent them?
Treatment is recommended to prevent stone formation. In adults and children, this means drinking more water, reducing salt, and eating less meat. If these recommendations are not enough, you may also need to take a special medication to help prevent stones from forming.
1. Drink enough fluids
Drinking plenty of water will reduce cystine's ability to form stones in the urine as it allows the substances that can crystallize and form new stones to be diluted. We will know that the amount of water ingested is sufficient when the color of our urine is almost transparent.
2. Maintain a balanced diet (2)
At a high urinary pH (alkaline urine), the formation of cystine stones is more difficult. Eating more fruits and vegetables can make urine more alkaline, and conversely, eating meat makes urine more acidic, which can increase the risk of cystine stone formation. This includes fish, shellfish, poultry, pork, lamb, and game meat.
3. Pharmacological treatment
The main therapeutic option to prevent cystine crystallization is to maintain urine pH above 7.5 to improve cysteine solubility and ensure adequate hydration with a minimum of 3.5 L/day in adults (3). When urine is very acidic, alkalizing substances must be used to raise its pH. For this, your doctor may recommend citrate-based products such as Lit-Control pH Up.
Certain medications can also help decrease the amount of cystine in the urine. You can ask your doctor about these different options, and they will help you find the right medication for you.
References:
(1) https://www.kidney.org/atoz/content/what-are-cystine-stones
(2) Preventing Kidney stones, Urology Care Foundation.
(3) Turk C. EAU Guidelines on Urolithiasis, European Association of Urology 2019.
