Cystinuria is an inherited autosomal recessive metabolic disorder that is characterized by the formation of cystine stones in the kidneys, ureter, and bladder. It is a rare, lifelong condition in which too much of a certain amino acid, called cystine, builds up in the urine. Cystine stones tend to reoccur and are typically larger and harder than other types of kidney stones and often require medical procedures to remove.
It is important to have kidney stones analyzed to help get the right treatment for this condition. About 1 in 10,000 people in the U.S. have cystinuria. More than 80% of people with cystinuria develop their first stone by the age of 20. 25% of people with cystinuria will develop cystine stones by the age of 10.
- Cystine stones are caused by a rare, inherited disorder called “cystinuria.”
- Cystinuria is a lifelong condition that will need to be actively managed to keep stones from forming.
- Treatment starts with doing things to keep stones from forming, such as drinking lots of water, reducing salt, and eating less meat. If these steps are not enough, certain prescription medicine may be needed to help keep stones from forming.
- Small kidney stones may pass out of the body during urination. Larger stones may require surgery.
- With the right treatment, you can help keep new stones from forming. Most people can control cystinuria by drinking lots of water, reducing salt, eating less meat, and taking medicine to keep stones from forming.
Renal colic is often the first symptom which gives the doctors a clue to diagnosing cystinuria. Renal colic in young children and adults in the general population is rare. Kidney stones normally take a lifetime to grow. Only in people with cystinuria and patients with other stone forming disorders are stones present at a young age. Renal colic is described as a moderate to severe sharp spasmodic pain in the back, side and groin area, often traveling from front to back. Over time it can be tracked downwards. Sometimes it is described as the worst pain a patient has ever had. It can be accompanied by cystitis and bladder spasms, especially when the stone has traveled that far down. Some people talk of transferred pain to the center of their back and in their bladder. They tend to describe this pain as “excruciating, stabbing, feels like a knife twisting, doubles me over, it feels like someone sticking a knife into your side and slowly turning it” and “sharp, stabbing pain.”Other symptoms include pain while urinating, blood in the urine, nausea and vomiting.
Cystinuria is an inherited disorder characterized by the inadequate reabsorption of cystine during the filtering process in the kidneys, thus resulting in an excessive concentration of this amino acid in the urine. Cystine may precipitate out of the urine and form crystals and grow into stones in the kidneys, ureters, or bladder
Cystinuria is a rare, genetic condition. There is no cure for cystinuria, but there are ways to reduce and prevent painful cystine stones from forming.
Screening for cystinuria should be considered in people with recurrent or bilateral (i.e. affecting both kidneys) stones; those who develop stones at an early age (before age 30); and people who have a family history of cystinuria; and a presence of cystine crystals in the urine. A diagnosis is typically made after an episode of kidney stones when testing reveals that the stones are made of cystine.
A proper diagnosis is important to help get the right treatment for this condition.The following tests may be recommended to detect cystine kidney stones and diagnose cystinuria:
- 24-hour urine collection
- Abdominal imaging (CT scan, MRI, or ultrasound)
- Intravenous pyelogram (IVP)
- Genetic testing
Treatment starts with doing things to keep stones from forming. For adults and children, this means drinking more water, reducing salt, and eating less meat. If these steps are not enough, you may also need to take prescription medication to help keep stones from forming.
- Drinking more water. Drinking lots of water will lower the ability for the cystine to form stones in the urine. Ask your healthcare provider how much water you should drink each day to help keep stones from forming.
- Changing your diet. Cystine stones are less able to form in urine that is less acidic. Eating more fruits and vegetables can make the urine less acidic. Eating meat produces urine that has more acid, which can increase your risk for cystine stones.
- Reducing salt. Eating less salt can help keep cystine stones from forming. Try not to eat salty foods, including potato chips, French fries, sandwich meats, canned soups, and packaged meals.
- Medicine. Some people may also need to take prescription medicine to help keep stones from forming. Different medicines work in different ways. Some types help to keep your urine less acidic. Other types help keep cystine stones from forming by not allowing crystals to come together. Your healthcare provider can explain these different options and help you find the right medicine for you.
Because cystine stones tend to reoccur, it is important to monitor if treatment is working and lowering urinary cystine levels. A 24-hour urine collection is a way of checking urinary cystine levels. The results will help determine whether any treatment adjustments are needed.
The goal of treatment is to help keep stones from forming by reducing the amount of cystine in the urine. With less cystine in the urine, stones are less likely to form. It is important to work with healthcare providers to reach this goal. Kidney stones may be very painful. Pain relievers may be needed while the stone is passed out of your body.
Stone Removal Procedures
If a stone is very large and painful, or if it blocks the flow of urine, surgery may be needed to remove it. These include:
- Percutaneous nephrostolithotomy (or nephrolithotomy):
A patient is given a general anesthetic. The surgeon will make three or four small one inch incisions in the back. A camera is passed through one of the incisions. A laser or lithoclast is inserted into the kidney and the stone is broken up. Some of the stone can be removed through the incisions. Others are left to pass naturally. Hospital stay 4-7 days. Recovery time 2 weeks depending on the patient. A nephrostomy tube may be left in temporarily to aid drainage and to allow the kidney to heal. A Stent tube is sometimes inserted, especially if there is a narrowing of the ureters.
This is typically an outpatient procedure in which a small, flexible scope is passed into the bladder, and then up the ureter (the tube that drains urine from the kidneys to the bladder), to remove the stone. It requires general anesthesia. This instrument allows a surgeon to look into the ureter and locate the stone. Once located, a tiny wire basket instrument may be used to collect the stone and remove it. A surgeon may also use a laser instrument to break up the stone and remove the stone fragments. A stent is typically placed and is removed during the follow-up visit. Oral pain medication is provided for post-operative pain. It is common for sand-like particles to pass over the following weeks post-procedure. Patients can return to work once the stent has been removed.
- Extracorporeal shock wave lithotripsy (ESWL):
This procedure that uses shock waves to break up stones into smaller fragments so that they can be passed in the urine. If the fragments are too large to pass, another procedure may be required. Because cystine stones are typically larger and harder than other stones, this procedure does not work as well for cystine stones.
Open Surgery (Extended Pyelolithotomy) A patient is given a general anesthetic. Surgeons physically remove the whole stone by cutting into the kidney and removing the stone. Recovery time 6 weeks. Hospital stay 10-14 days. Complications such as severe pain on recovery from the anesthetic, initial mobility problems as associated with any major surgery, need for recovery time and time off work, reduced kidney function. The kidney will only tolerate this procedure a few times. Benefits include quick fix and possibly only solution for very large stones. The procedure leaves a 10 to 12 inch scar.
Cystinuria is a chronic condition and many affected people experience recurrent kidney stones in the urinary tract (kidneys, bladder and ureters). People with cystinuria will continue to form kidney stones. The number and frequency of cystine stone formation varies by individuals. Without proper management, painful cystine stones may continue to form. In rare cases, frequent kidney stones can lead to tissue damage or even kidney failure.