Definition of Cystinuria:

Cystinuria is a condition passed down through families in which stones form in the the kidney, ureter, and bladder. It is an autosomal recessive disorder.

See also: Nephrolithiasis

Causes, incidence, and risk factors:

Cystinuria is caused by excessive levels of an amino acid called cystine in the urine. After entering the kidneys, most cystine normally dissolves and goes back into the bloodstream. But persons with cystinuria have a genetic defect that interferes with this process. As a result, cystine builds up in the urine and forms crystals or stones, which may get stuck in the kidneys, ureters, or bladder.

Cystinuria affects approximately 1 out of 10,000 people. Cystine stones are most common in young adults under age 40. Less than 3% of known urinary tract stones are cystine stones.

Symptoms:

• Blood in the urine
• Flank pain or pain in the side or back
  • Usually on one side; rarely felt on both sides
  • Often severe
  • May get increasingly worse over days
  • Pain may also be felt in the pelvis, groin, genitals, or between the upper abdomen and the back.

Signs and tests:

The disorder is usually diagnosed after an episode of stones. Analysis of the stones shows they are made of cystine.

Tests that may be done to detect stones and diagnose this condition include:

• Abdominal CT scan, MRI, or ultrasound
• Intravenous pyelogram (IVP)
• 24-hour urine collection (shows high levels of cystine)
• Urinalysis (may show cystine crystals)

Treatment:

The goal of treatment is to relieve symptoms and prevent the development of more stones. A person with severe symptoms may need to be admitted to a hospital.

Treatment involves drinking plenty of fluids, particularly water, so that large amounts of urine are produced. The patient should drink at least 6-8 glasses per day.

In some cases, fluids may need to be given through a vein.

Medications may be prescribed to help dissolve the cystine crystals. Eating less salt can also decrease cystine excretion and stone formation.

Pain relievers may be needed to control pain in the kidney or bladder area associated with the passage of stones. The stones usually pass through the urine on their own. If they do not, surgery may be needed.

Lithotripsy may be an alternative to surgery. However, this procedure is not as successful for removal of cystine stones as it is for other types of stones.

Expectations (prognosis):

Cystinuria is a chronic, lifelong condition. Stones commonly return. However, the condition rarely results in kidney failure, and it does not affect other organs.

Complications:

• Bladder injury from stone
• Ureteral obstruction
• Kidney injury from stone
• Kidney infection
• Urinary tract infection

Calling your health care provider:

Call your health care provider if you have symptoms of urinary tract stones.

Prevention:

There is no known prevention for cystinuria. Any person with a known history of stones in the urinary tract should drink plenty of fluids to regularly produce a high amount of urine. This allows stones and crystals to leave the body before they become large enough to cause symptoms.