Kidney Stones: What You Need to Know

Guido R. Zanni

Kidneys are bean-shaped organs. Each person is born with two kidneys, which are located in the mid to lower back, with one kidney on each side. Kidneys filter blood and remove waste. Kidney stones are hard objects that are made from chemicals in the urine. When there is too little urine and a lot of waste, chemicals begin to form crystals. These crystals attract other chemicals that form a hard mass resembling a stone. Most stones are formed in the kidneys. When large stones leave the kidneys, they get stuck in the tube that connects the kidney to the bladder. This tube is called the ureter.

There are several types of stones, which can be smooth or jagged. Different stones contain different chemicals. If you pass a stone, try to retrieve it and take it to your doctor. Knowing the type of stone you passed helps determine treatment options.

Types of Kidney Stones

Ten percent of people will have a kidney stone during their lifetime. The following types of stones are most likely to develop:

-- Calcium stones are the most common type. They occur in two forms: calcium oxalate (the most common kidney stone) and calcium phosphate.

-- Uric acid stones form when the urine is acidic. A diet rich in purines increases uric acid in urine. Purines are substances found in animal protein, such as meats and fish.

-- Struvite stones form in infected bladders or kidneys.

-- Cystine stones result from a genetic disorder that causes cystine to leak into the urine. Cystine then forms crystals and stones.

What are the symptoms of kidney stones? Small stones are usually passed without any symptoms. Medium to large stones eventually begin to move from the kidney to the ureter, where they get stuck. The main symptom is severe pain on either side of the back. This pain results from the body's attempt to move the stone out of the ureter and into the bladder. Many people describe the pain as the worst they have ever experienced. Pain often spreads to the lower stomach area and the groin. The pain comes and goes, lasting 20 to 60 minutes. Other symptoms may include fever, vomiting, nausea, diarrhea, blood in the urine, a burning sensation when urinating and frequent urges to urinate.

Why do some people get kidney stones? Kidney stones tend to run in families. If your parents or siblings had kidney stones, you have a higher risk of developing a kidney stone. Eating a diet high in salt, sugar and animal protein is also associated with kidney stone formation.

Some medical conditions and medications increase the risk for stone development. Medical conditions that increase the risk include high blood pressure, bladder infection, obesity and diseases of the intestine and colon. Medications that increase the risk include drugs to treat HIV/AIDS and chemotherapy.

What is the treatment? The first goal of treatment is to remove kidney stones that are stuck in the kidney, ureter or bladder. The second goal is to treat the pain. The third goal is to prevent future stones from forming.

If you have a kidney stone that is stuck in the ureter, you will be asked to drink lots of water in a short period of time to flush out the stone. Minor pain is treated with over-the-counter pain relievers. If pain is severe, you will be given a prescription pain medication. If the stone does not pass within five to seven days, your doctor may try to break it into smaller pieces by using a machine that delivers shockwaves to the stone. This procedure does not work for large stones, which must be removed in a hospital. Your doctor will insert a scope (a tube with an eyepiece) and a laser into your genitals, up to the bladder and into the ureter. The stone is then removed or broken into smaller pieces. Extremely large stones require surgery. A small incision is made into the back so the surgeon has direct access to the kidney and ureter.

Once kidney stones are removed, your doctor may prescribe medication to prevent future stones. The choice of medication depends on the composition of the stone. Medications are not 100 percent effective. Even with treatment, there is a 50 percent chance of having a second stone five to seven years after the first episode.

Can dietary changes help? Diet can play a key role in preventing kidney stones. Here are some things you can do to prevent kidney stones:

-- Drinking large amounts of water (two to three quarts a day) is the best way to prevent future stones. Drink whatever amount it takes so that your urine is light yellow or clear.

-- If you have calcium stones, you will need to limit sodium intake to 200 milligrams a day.

-- Do not eliminate calcium from your diet. This will lead to bone loss. Calcium intake from food actually prevents stones from forming. Dairy products are excellent sources of calcium.

-- Avoid taking calcium supplements. They increase the risk of stone formation.

-- If you have an oxalate stone, you should decrease oxalate intake. Foods high in oxalate include most nuts, soy products, wheat germ, wheat bran, spinach, tea, rhubarb, beets, most dried beans, chocolate and sweet potatoes.

-- Reduce the amount of animal protein you eat. Cut back on beef, chicken, port, fish and eggs.

-- If you take vitamins, discuss this with your doctor. Some vitamins, such as vitamin C, increase the risk for stone formation.

-- Avoid using herbal products. There is no medical evidence supporting herbal treatments.

-- Use sugar substitutes. Buy sugar-free products whenever possible.

-- If you are overweight, lose the extra pounds.

Note: This article was originally published on Sept. 13, 2013 on It has been edited and republished by U.S. News. The original version, with references, can be seen here.