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What to Know About Cystinuria

Medically Reviewed by Jabeen Begum, MD on November 17, 2021

Cystine stones are a type of kidney stone. They are also called renal calculi, nephrolithiasis, or urolithiasis, and they are caused by a genetic condition. Here’s what to know about cystine crystals and stones in urine. 

What Are Cystine Stones?

Cystine stones are a type of kidney stone that forms when an amino acid called cystine builds up in your urine. 

Amino acids are the building blocks of protein, which you need to repair tissue, build muscle, and fight infection. When you eat protein, your body breaks it down into these individual amino acids. They are absorbed in your gut, sent to your blood, and then to your kidneys to be filtered and reabsorbed. 

Problems with your kidneys can lead to trouble absorbing cystine. This leads to high amounts in your urine and, eventually, the formation of stones.

There are other types of kidney stones. These are formed when you have more crystal in your urine than your body can dilute. These include:

What Causes Cystine Stones?

Cystine stones are caused by a rare inherited condition called cystinuria. Cystinuria affects how your kidneys and intestines transport and absorb cystine. Without the ability to absorb cystine well, it leaks into your urine. 

Cystinuria also complicates transporting and absorbing three other amino acids: ornithine, arginine, and lysine. These dissolve well in water, though, and you can get rid of them easily in your urine. Cystine, which doesn’t dissolve in water very well, leads to high levels in your urine and eventually forms stones

Cystinuria is called an autosomal recessive genetic metabolic disorder. This means you must inherit a copy of the changed gene from each parent to have symptoms. If your partner doesn’t have the cystinuria gene, your children have a 50% chance of being a carrier without symptoms. 

Cystinuria can affect both men and women, and it often starts causing stones early in childhood

What Are Symptoms of Cystine Stones?

Cystine stones only cause symptoms when they start to move through your ureters, the tubes that connect your kidney to your bladder. If a stone gets stuck in a ureter, urine can’t flow. This causes inflammation, spasms, and pain. Other cystine stone symptoms include:

What Is the Treatment for Cystine Stones?

The mainstay in any kidney stone treatment is hydration. Drinking more water helps dissolve stones and keeps the material diluted enough to urinate out. 

Your doctor might recommend drinking one cup of water every hour during the day, two cups before bed, and even recommend waking up in the night to drink water

If you have stones, it’s likely that you’re drinking less water than you need, so this might feel like a lot. Some people can manage cystinuria and prevent stones, though, just by drinking lots of water every day. 

Generally, prevention is the best treatment. This can also include making dietary changes and keeping a neutral urine pH. Treatment includes:

Low-protein diets are often recommended for cystinuria, but they may not always help. Your body needs protein, so try to eat plant-based proteins rather than animal proteins. Growing children need protein, so don’t restrict it unless directed to by your doctor. 

If dietary changes don’t help, your doctor will prescribe medications for cystine stone treatment. Different medications include:

You can often pass small stones on your own with extra water intake and some pain medication. In some cases, though, you might need surgery to remove stones from your kidney or bladder. This is usually a last resort, because cystine stones come back regularly. Other procedures include:

  • Laser treatment to dissolve stones
  • Ureteroscopy, where stones are removed with special tools through a thin tube in your urinary tract
  • Ultrasound waves

Complications of Cystine Stones

Cystinuria is a lifelong disease, which means you’re likely to have repeated episodes of cystine stones. This can cause lots of pain, kidney damage, urinary tract damage, and scarring, which can lead to repeated surgeries. Some people also experience kidney failure. 

Preventing stones is key to managing cystinuria complications. Talk to your doctor about your condition. 

Show Sources

SOURCES:

Amino Acids: “Amino acids and the kidney.”

Genetic and Rare Diseases Information Center: “Cystinuria.”

Harvard Medical School Harvard Health Publishing: “What causes kidney stones (and what to do).”

Leslie, S., Sajjad, H., Nazzal, L, StatPearls, “Cystinuria,” StatPearls Publishing, 2021.

Mayo Clinic: “Kidney stones.”

National Kidney Foundation: “Cystine Stones.”

Postgraduate Medical Journal: “Cystine calculi: challenging group of stones.”

U.S. National Library of Medicine MedlinePlus: “If a genetic disorder runs in my family, what are the chances that my children will have the condition?”

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