Complications

Between 70 - 90% of crystals remain tiny enough so that they can travel through the urinary tract and pass out of the body in the urine without being noticed. When they cause symptoms, however, kidney stones have been described as one of the most painful disorders to afflict humans. The pain that they cause is sometimes referred to as renal colic. ("Renal" means "kidney.")

Effects on the Urinary Tract and Kidneys

Obstruction and Infection. Although kidney stones often lead to obstruction of the urinary tract, it is usually temporary and causes no lasting damage. In some cases, however, particularly if the obstruction progresses silently, infection may occur, which can be serious and which warrants prompt attention.

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Kidney Failure. It is very rare for kidney stones to cause kidney failure, although some people have risk factors that make them more susceptible to this serious complication. They include the following:

• Very frequent recurrences (such as in people with cystine stones or other inherited forms of kidney stone disorders)
• Accompanying episodes of urinary tract infections with obstruction, a particular risk with struvite stones
• A history of multiple urologic procedures for kidney stones
• Greater size of the kidney stone gravel

Long Term Outlook: Risk for Recurrence

Without preventive treatment, calcium stones recur in 10% of patients within a year of the first attack, and in half of patients within 5 to 7 years. Individual risk for recurrence, however, varies depending on the stone and the underlying condition. For example, a 15-year-old with inherited cystine stones has a very high risk for recurrence, while a middle-aged man with a first calcium oxalate stone has a good chance of never passing another.