Cystinuria
Cystinuria is a condition characterized by the buildup of cystine crystals or stones in the kidneys and bladder. Cystinuria is one of the more common genetic disorders. It is caused by excessive excretion of certain amino acids due to a genetic abnormality. One of the building blocks of proteins. Normally, cystine is reabsorbed back into the bloodstream after blood entering the kidneys is filtered to create urine. One of the peculiar things about cystinuria is that the amount of cystine excreted by the kidneys is not always related to the number and size of the stones formed. Some cystinurics with very high cystine levels form very few, if any stones. Other cystinurics with comparatively low cystine levels are prolific stone formers. Only small amounts of cystine can stay dissolved in urine. People with cystinuria cannot properly reabsorb cystine into their bloodstream. As urine becomes more concentrated in the kidneys, the cystine cannot stay dissolved and forms crystals. As these crystals become larger, they form stones that may lodge in the kidneys or in the bladder. Sometimes cystine crystals combine with calcium in the kidneys to form large stones. Blockages in the urinary tract by these crystals and stones reduce the ability of the kidneys to eliminate wastes through urine. The stones also provide sites where bacteria may cause infections. Cystinuria has been linked to the chromosome 2P. A mutation in the gene causes cystinuria. Cystine stones are most common in young adults. People who are carriers of the gene for this variety of the disease typically have slightly elevated levels of cystine and lysine in the urine. In Hypercystinuria, there is generally a moderate elevation of cystine in the urine; intestinal absorption of cystine and the dibasic amino acids is normal.
Cystinuria, cystine and lysine transport is severely impaired in the kidneys and only somewhat impaired in the intestines. Within the body, many molecules are able to pass across the membranes that surround cells. These molecules can accomplish this feat due to specific transport systems. These systems include special receptors on the membrane of the cell and special carrier proteins. The receptor recognizes the molecule and receives it on the cell membrane. Then the molecule hitches a ride through the cell membrane on the back of a carrier protein. This condition is inherited in an autosomal recessive pattern, which means two copies of the gene in each cell are altered. Hydronephrosis is where the kidney is enlarged due to an obstruction. It is a very serious condition. If left untreated Hydronephrosis causes the fluid in the kidney to become stagnant leading to kidney infection, possible septicemia and further complications.
Causes of Cystinuria
Common causes of Cystinuria
- Protein building blocks.
- Stones in the kidney.
- Ureter.
- Bladder.
- Blocking the flow of urine.
- Depression.
- Tiredness.
Symptoms of Cystinuria
Common symptoms of Cystinuria.
- Renal colic.
- Rarely.
- May be progressive, getting increasingly worse over days.
- Radiate to lower flank.
- pain in the side or back.
Treatment of Cystinuria
Common Treatment of Cystinuria
- Analgesics may be needed to control renal or ureteric colic.
- Lithotripsy may be an alternative to surgery. In this procedure, ultrasonic waves or shock waves are used to break up stones so that they may be expelled in the urine or removed with an endoscope that is inserted into the kidney via a small flank incision but Lithotripsy is not as successful for removal of cystine stones.
- penicillamine, tiopronin These drugs react with cystine to keep it dissolved.Captopril is slightly less effective than the other drugs, but has fewer serious side effects. Although the treatments are usually effective, there is a fairly high risk that stones will continue to form.
- Percutaneous Surgery- 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.
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