Anyone who has been waylaid by a kidney stone vows to do whatever it takes to avoid a recurrence.

Kidney stones are one of the most common and painful disorders of the urinary tract. Each year, these mineral and acidic salt deposits – some as tiny as grains of sand, others as big as golf balls – result in nearly three million visits to health care providers and send more than half a million people to hospital emergency rooms.

What is a kidney stone?

A kidney stone is a crystalized mass that forms in the kidneys, the two bean-shaped, fist-sized organs that filter waste from the bloodstream. Normally, this material leaves the kidneys in urine, but sometimes, due to genetics, infection or dehydration – low urine volume invites kidney stone formation – it hardens.

When a kidney stone is small enough, it can travel down the entire urinary tract – ureters, bladder and urethra – and exit the body without causing much discomfort. In fact, sometimes people have kidney stones and do not even know it. Other times, a kidney stone gets stuck somewhere along the way. This disrupts urine flow and causes pain.

Although it may take weeks, many kidney stones pass out of the body on their own. When they do not, medication, medical intervention and, sometimes, surgery are necessary.

Symptoms of a kidney stone include:

• Extreme pain in your back or side that will not go away
• Blood in your urine
• Urine that smells bad or looks cloudy
• A burning feeling when you urinate
• Fever and chills
• Vomiting

Call your health care provider if you are experiencing any of these symptoms.

There are several kinds of kidney stones, and if you are in need of medical treatment, it is helpful to know which one is the source of your discomfort. Your health care provider may give you a strainer and ask that you try to catch your stone so that it can be tested. Depending on the type, diet modification and, sometimes, maintenance medication may be helpful in avoiding another.

Anyone can develop a kidney stone, but staying hydrated reduces the risk. Drinking lots of water is particularly important. Water helps the kidneys flush away the waste products that form stones and, unlike juices, coffee and other liquids, is free of substances that contribute to kidney stones. Consuming the equivalent of eight glasses of water a day is sufficient for most people (see Hydration Keeps You Healthy). However, for anyone who has had a kidney stone, fluid intake should be higher. The National Institutes of Health (NIH) recommend drinking 12 full glasses of water a day. This can be challenging, but previous experience with a kidney stone is motivating.