Cystinuria

Causes

To have the symptoms of cystinuria, you must inherit the faulty gene from both parents. Your children will also inherit a copy of the faulty gene from you.

Cystinuria is caused by too much of an amino acid called cystine in the urine. After entering the kidneys, most cystine normally dissolves and goes back into the bloodstream. But people 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.

About one in every 10,000 people have cystinuria. Cystine stones are most common in young adults under age 40. Less than 3% of urinary tract stones are cystine stones.

Symptoms

• Blood in the urine
• Flank pain or pain in the side or back
  • Pain is usually on one side; it is rarely felt on both sides
  • Pain is often severe
  • It may get worse over days
  • You may also feel pain in the pelvis, groin, genitals, or between the upper abdomen and back

Exams and Tests

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

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

• 24-hour urine collection
• Abdominal CT scan, MRI, or ultrasound
• Intravenous pyelogram (IVP)
• Urinalysis

Treatment

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

Treatment involves drinking plenty of fluids, especially water, to produce large amounts of urine. You should drink at least 6 - 8 glasses per day.

In some cases, fluids may need to be given through a vein (by IV).

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

You may need pain relievers to control pain in the kidney or bladder area when you pass stones. Smaller stones usually pass through the urine on their own. Larger stones may need extra treatments. Some large stones may need to be removed with surgery:

• Extracorporeal shock wave lithotripsy (ESWL) -- this procedure does not work as well for removing cystine stones as it does for other types of stones
• Percutaneous nephrostolithotomy or nephrolithotomy
• Ureteroscopy, for stones in the lower urinary tract

Outlook (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.

Possible Complications

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

When to Contact a Medical Professional

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.

Alternative Names

Stones - cystine; Cystine stones

References

Elder JS. Urinary lithiasis. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 541.

Update Date: 9/21/2011

Updated by: Herbert Y. Lin, MD, PhD, Nephrologist, Massachusetts General Hospital; Associate Professor of Medicine, Harvard Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.