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Kidney stones
Definition:
A kidney stone is a solid mass that consists of a collection of tiny crystals. There can be one or more stones present at the same time in the kidney or in the ureter. (See also cystinuria.) Alternative Names:
Renal calculi; Nephrolithiasis; Stones - kidney Text Continues Below
Causes, incidence, and risk factors:
Kidney stones may form when your urine becomes too concentrated with certain substances. These substances may create small crystals that become stones. The kidney stones may not produce symptoms until they begin to move down the ureter, causing pain. The pain is usually severe and often starts in the flank region, then moves down to the groin. Kidney stones are common. About 5% of women and 10% of men will have at least one episode by age 70. A person who has had kidney stones often gets them again in the future. Kidney stones are common in premature infants. Other risk factors include renal tubular acidosis and resultant nephrocalcinosis. Some types of stones tend to run in families. Some types may be associated with bowel disease, ileal bypass for obesity, or renal tubule defects. Types of stones include: - Calcium stones are most common. They are two to three times more common in men, usually appearing at age 20 to 30. Recurrence is likely. The calcium may combine with other substances such as oxalate (the most common substance), phosphate, or carbonate to form the stone. Oxalate is present in certain foods. Diseases of the small intestine increase the tendency to form calcium oxalate stones.
- Uric acid stones are also more common in men. They are associated with gout or chemotherapy. Uric acid stones make up about 10% of all stones.
- Cystine stones may form in persons with cystinuria. It is a hereditary disorder affecting both men and women.
- Struvite stones are mainly found in women as a result of urinary tract infection. They can grow very large and may obstruct the kidney, ureter, or bladder.
Other substances may crystallize, precipitate, and form stones.
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