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Articles » Health-&-Fitness » Cystine Kidney Stones
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| Cystine Kidney Stones |
By:
John S |
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Cystinuria is a genetic disorder of the amino acid transport that results in the defective absorption of the amino acid called cystine by the kidneys. Amino acids are organic compounds responsible for the availability of proteins as well as normal functions of the body. The inability of kidneys to absorb cystine in urine increases the amount of cystine in the urine which also increases the number of crystals. When large numbers of cystine crystals form, they clump together forming a stone.
Humans have two copies of each gene. When both are abnormal, the condition is called homozygous for the disease. When one copy is normal and the other is abnormal, the condition is called heterozygous for the disease.
Serious cases of cystinuria occur in people who are homozygous for the disease. Cystinuria does cause other abnormal bodily functions. Apart from the excess levels of the amino acid cystine, high amounts of the amino acids lysine, arginine, and ornithine are found in the urine. These cystine stones cause a lot of pain when they block portions of the interior of the kidney or the ureter that connects the kidney to the urinary bladder. Cystine stones also cause blood in the urine whenever the urinary tract is blocked, urinary tract infections, as well as kidney failure.
Diagnosis:
· Small stones don’t have any clear symptoms, although they can be detected by an x ray. Large stones are usually painful and easily noticed by the patient. Blood in the urine can also mean that a stone has formed.
· High amounts of cystine in urine form yellow-brown hexagonal crystals visible when examined under the microscope. Urine samples can also be mixed with chemicals that change color when high levels of cystine are present.
· When the compound nitroprusside is added to urine that has been made alkaline by the addition of ammonia, the urine specimen turns red if it contains excess cystine.
Treatment:
· Cystine excretion can not be treated or decreased. Therefore the best treatment for cystinuria is to prevent stones from forming. This can be achieved by drinking a lot of liquids each day in order to produce at least 8 pints of urine; this keeps the concentration of cystine in the urine low. Since people don’t drink liquids throughout the night, less urine is produced, and the likelihood of stone formation increases.
· Taking sodium bicarbonate and acetazolamide increases the alkalinity of urine. Cystine dissolves more easily in alkaline urine. Penicillamine is a drug that increases the solubility of cystine, usually prescribed for patients who do not respond well to other therapies.
· Most stones can be removed from the body by normal urination through drinking large amounts of water. Large stones that cannot be eliminated this way must be removed by surgical procedures. Large stones can be surgically removed by having a device called uretoscope placed into the urethra, up through the bladder and into the ureter, where the trapped stone can be seen and removed. This external technique is called extracorporeal shock-wave or lithotripsy. For large stones in the kidney, a procedure called percutaneous nephrolithomy may be used. An instrument called a nephroscope is inserted through the incision into the kidney. The surgeon uses the nephroscope to locate and remove the stone. If the stone is very large, it may be broken up into smaller pieces by an ultrasonic or other kind of probe before removal.
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