Cystinuria: Symptoms, Causes & Treatments
Author: Thomas C. Weiss
Contact : Disabled World
Information regarding Cystinuria, an inherited disease that causes stones of amino acid cysteine to form in the bladder, kidneys and urethra.
Cystinuria is a form of inherited disease that causes stones made of the amino acid, 'cysteine,' to form in a person's bladder, kidneys and urethra. 'Inherited,' means the disease is passed down from parents to their children through a defect in their genes. To get cystinuria, a person has to inherit the defect from both of their parents.
Cystinuria is defined as an inherited autosomal recessive disease that is characterized by the formation of cystine stones in the kidneys, ureter, and bladder. Cystinuria is caused by mutations in the SLC3A1 and SLC7A9 genes. These defects prevent proper re-absorption of basic, or positively charged, amino acids:Cystine, lysine, ornithine, arginine. Cystinuria is a cause of persistent kidney stones.
The defect in the gene causes cysteine to accumulate inside the person's kidneys which are organs that help to regulate what goes in and out of a person's bloodstream. The kidneys have a number of functions, to include re-absorbing essential proteins and minerals back into a person's body, filtering their blood to remove toxic waste, as well as producing urine to the person may excrete the waste out of their body.
Instead of returning to the person's bloodstream, the amino acid cysteine builds up and forms stones. The stones may then become stuck in the person's bladder, kidneys and urethra; something that can be very painful until the stones pass via urination. Larger stones might need to be removed surgically. The stones can recur several times; however, treatments are available to manage pain while helping to prevent more stones from forming.
Causes of Cystinuria
Defects or, 'mutations,' in the genes called, 'SLC7A9,' and, 'SLC3A1,' cause cystinuria. The genes provide instructions for a person's body to make a certain transporter protein found in the kidneys. The protein usually controls the re-absorption of certain amino acids.
Amino acids are formed when a person's body digests and breaks down proteins. The amino acids are used to perform a number of bodily functions. They are important to a person's body and are not considered to be waste. When they enter the person's kidneys, the amino acids are usually absorbed back into the bloodstream. In people with cystinuria, their genetic defect interferes with the transporter proteins' ability to re-absorb the amino acids.
One of the amino acids, 'cysteine,' is not very soluble in a person's urine. If it is not re-absorbed it will accumulate inside the person's kidneys and form cysteine stones. The rock-hard stones then become stuck in the person's bladder, kidneys and urethra, something that may be very painful. A person is only at risk of getting cystinuria if their parents both have the specific defect in their gene that causes the disease. Cystinuria happens in around 1 in every 10,000 people in the world.
Symptoms of Cystinuria
While cystinuria is a life-long condition, the symptoms usually appear first in young adults in their 20's and 30's. The symptoms can be unpleasant at times. The symptoms may include the following.
- Blood in the urine
- Nausea and vomiting
- Pain near the pelvis, groin, or abdomen
- Severe pain in the back or side, nearly always on one side
When an affected person does not have any stones it is considered to be, 'asymptomatic,' meaning it causes no symptoms. The symptoms; however, will recur every time stones form in the person's kidneys. The stones usually return more than once.
Cystinuria is commonly diagnosed when a person experiences an episode of cysteine stones. A diagnosis is then made by testing the stones to find out if they are made out of cysteine. More diagnostic testing might include the following.
24-Hour Urine Collection: An affected person will be asked to collect their urine in a cup over the course of a day. The urine is then sent to a laboratory for analysis.
Abdominal Computed Tomography (CT) Scan: An abdominal computed tomography (CT) scan is an imaging method that uses X-rays to create images of the structures inside of a person's abdomen to look for stones inside the kidneys.
Intravenous Pyelogram: An intravenous pyelogram is an X-ray examination of the person's bladder, kidneys and urethra to look for the presence of stones. The method uses a dye in the person's bloodstream to help with visualizing the stones.
Urinalysis: Urinalysis is an examination of the person's urine in a laboratory, something that might involve looking at the physical appearance and color of the person's urine, viewing the urine underneath a microscope, as well as conducting chemical tests to detect certain substances such as cysteine.
Treatment of cystinuria is aimed at preventing stones from forming. Treatment may include a number of different approaches. The approaches might include the following.
Dietary Changes: Reducing salt intake to less than 2 grams per day has been shown to be helpful in the prevention of stone formation.
Increasing Water Intake: Drinking large amounts of water is crucial to lowering the concentration of cysteine in a person's urine. According to a study from 2006 in European Urology, hydration of itself may prevent the re-occurrence of stones in approximately 30% of those affected.
Adjusting pH Balance: Cysteine is more soluble in urine at a higher pH, which is a measure of how acidic or basic a substance is. Alkalinizing agents such as potassium citrate will increase the pH of a person's urine to make cysteine more soluble. Some alkalinizing medications may be purchased over-the-counter. It is strongly recommended; however, that person communicate with their doctor prior to taking any kind of supplement.
Medications: Medications known as, 'chelating agents,' help to dissolve cysteine crystals. The medications work by chemically combining with cysteine to form a complex that can then dissolve in a person's urine. Examples of these medications include D-Penicillamine and alpha-mercaptopropionylglycine. D-Penicillamine works effectively, although it does have a number of side-effects. Medication for pain may also be prescribed to control pain as the stones pass through the affected person's bladder and out of their body.
Surgery: If the stones are painful and very large, or block one of the tubes leading from the kidney, they may need to be removed surgically. There are a few different types of surgeries to break up the stones to include percutaneous nephrosolithotomy, which is a procedure involving passing an instrument through the person's skin and into their kidney to take out the stones or break them up. Another procedure is extracorporeal shock wave lithotripsy, which is a procedure that uses shock waves to break apart large stones into smaller ones.
If cystinuria is not treated appropriately, it may be extremely painful and might lead to complications that are serious. The complications may include the following:
- Kidney infections
- Urinary tract infections
- Bladder or kidney damage from a stone
- Blockage of the ureter, which is the tube that drains urine from a person's kidneys to their bladder
Cystinuria is a life-long condition; however, it may be managed effectively with treatment. The stones themselves appear more commonly in young adults who are under the age of 40. Cystinuria does not affect other parts of an affected person's body and rarely causes kidney failure.
Cystinuria cannot be prevent if both of a person's parents carry a copy of the genetic defect. Drinking large amounts of water and reducing salt intake can help to prevent stones from forming.
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