Kidney stones: Diagnosis, treatment, and prevention

Kidney stones are one of the most common and painful kidney disorders. About 10% of people will develop a kidney stone at some point in their lives. For many, stones become a chronic problem. People who get one stone are more likely to develop others.

The kidneys, each about the size of a fist, are located in the lower back. They are connected to the bladder by narrow tubes called ureters. The kidneys act as filters for the bloodstream, catching needed substances and returning them to circulation. They also dispose of unneeded substances in urine. Urine collects in the bladder and then passes through another narrow tube called the urethra before exiting the body.

Kidney stones are formed when minerals and other substances build up in the kidneys. They become so concentrated that they crystallize into solid particles. Under normal circumstances, urine contains chemicals that keep this from happening but this action can fail under certain conditions. If the resulting crystallized particles remain small, they pass through the urinary system without problems. Larger stones, though, can become lodged in the kidney or further down the urinary tract.

Types of Kidney Stones

There are 5 main types of kidney stones:

• Calcium oxalate and calcium phosphate stones — These 2 types are the most common. They make up about 80% of cases. These kidney stones usually form when the concentration of calcium or other minerals in the urine becomes too high.
• Struvite stones — These stones are composed of ammonium, magnesium, and phosphate salts. These develop as the result of a urinary tract infection.
• Uric acid stones — These stones form when urine is acidic. They may also occur in people with gout or those having chemotherapy.
• Cystine stones — The result of a rare genetic disorder that causes the kidneys to build up excess amounts of cystine, one of the amino acids that make up proteins.

Risk Factors

A risk factor is something that increases your likelihood of getting a disease or condition. It is possible to develop kidney stones with or without the risk factors listed below, but the more risk factors you have the greater your likelihood of developing kidney stones. Personal or family history of kidney stones is one of the more common factors. Kidney stones also are more common in adults under 40 years old who are Caucasian or Asian. Risk factors for specific types of kidney stones include:

• Excess dietary sodium and oxalate. Oxalate can be found in green, leafy vegetables, chocolate, nuts, or tea.
• Low fluid intake, especially during warmer weather, which can lead to dehydration
• Overactive parathyroid gland
• Chronic bowel disorders such as Crohn's disease or ulcerative colitis
• Some diuretics
• Calcium-based antacids
• History of urinary infection
• More common in women
• Excess dietary red meat or poultry
• Gout

Symptoms

Usually, the first sign of a kidney stone is intense pain in your mid-back or side. The stone irritates or blocks a section of your urinary tract. The pain may spread to your groin area and inner side of your thigh (depending on the location of the stone), and the sudden onset of pain may cause nausea and vomiting. The pain may come and go in waves. Those who are passing kidney stones often find it difficult to find a comfortable position. There may also be pain with urination, urgency, or urinary frequency and some blood in your urine if the stone has irritated the surrounding tissue.

Call your doctor if you are experiencing:

• Extreme pain in your mid-back or side
• Blood in your urine
• Signs of infection, including fever or chills
• Vomiting
• Increased frequent urination or burning and pain as you urinate
• Difficulty urinating
• Nausea

How are kidney stones diagnosed?

Your doctor will ask you questions about your family and medical history. A physical exam will be done. Tests to help determine the location of the stone include:

• Urine tests look for the presence of an infection or an increased amount of the chemicals that cause stones.
• Most kidney stones can be seen on an x-ray. This test is helpful for knowing what type of stone you have. Other studies often are needed to determine the specific spot in the kidney where the stone is located.
• An ultrasound is a diagnostic technique that combines sound waves and computer imaging to view internal organs. This procedure provides a more detailed picture than you would get from a single x-ray.
• A CT scan can spot small kidney stones that regular x-rays might miss.
• Intravenous Pyelogram — for this test, a dye is injected into a vein. The dye highlights otherwise hard-to-see areas of your urinary tract as it passes out of your system. This makes it easier for your doctor to see the kidney stone on an x-ray. This procedure is less commonly used today because of better imaging available with CT scans.

Tests to help determine the type of kidney stone include:

• Blood tests can identify high levels of calcium, uric acid, or the presence of infection that can cause a kidney stone to develop.
• Urine testing for acidity and levels of calcium, uric acid, citrate, and oxalate, can get from a single urine sample.

Once a stone is recovered, it is analyzed in a laboratory to determine its chemical make-up. This helps your doctor make decisions about how you can prevent further stone formation.

Treatment

Most kidney stones are small enough to eventually pass through the urinary tract without further complications. To facilitate this, your doctor will likely advise you to:

• Drink 2-3 quarts of water a day.
• Take pain medication as needed.
• Take antibiotics if an infection is present or possible.
• Save the stone by catching it in a cup or a sieve during urination. Knowing what kind of stone it is can help prevent a recurrence.

If the stone does not pass on its own, your doctor has several treatment options. The goals of treatment are to remove the stone and to reduce the chance that you will develop another one.

The treatment and management of kidney stones may involve:

Lifestyle changes

Your lifestyle plays an active role in the treatment of kidney stones. By making certain lifestyle changes, you may be able to reduce your risk of developing another kidney stone. One of the goals of kidney stone treatment is to keep your urine as dilute as possible. This helps to keep the substances that could potentially form a kidney stone, such as calcium and oxalate, moving quickly through the urinary tract:

• Try to drink at least 2 liters of fluid a day. A good gauge of whether or not you are drinking enough fluids is urine color. Except for the first thing in the morning, it should be pale in color. If your urine is dark yellow, that is an indication that you should drink more fluids.
• If you are hesitant to drink too much during the day because you have a bladder control problem, discuss this concern with your doctor.

Whether or not diet can help you avoid another kidney stone depends on what kind of stone you had and what caused it to form in the first place. If your stone was made up of calcium oxalate, calcium phosphate, or uric acid, what you eat or do not eat can help prevent a recurrence. Note that these are only guidelines. People taking certain kinds of medications will need to avoid certain foods. Always follow the advice of your doctor or registered dietitian in making any diet changes. Nutrients to consider include:

• Reduce your intake of dietary sodium. Some of these include:
  • Lunch meats and cured meats like ham, sausage, and bacon
  • Salted snacks
  • Prepared salad dressings, mustard, ketchup, soy sauce, and barbecue sauce
  • Pickled foods and olives
  • Canned soup and bouillon
• Reduce your intake of animal protein, including meat, poultry, fish, and eggs.
• Maintain proper calcium intake from food or calcium supplements.
• If your kidney stones contained calcium oxalate, you may also need to avoid certain plant foods that bind with calcium and other minerals. If your body is not absorbing and using calcium correctly, you could end up with too much oxalate in your urine. You can reduce the level of oxalate in your system by avoiding these foods:
  • Spinach
  • Rhubarb
  • Strawberries
  • Chocolate
  • Wheat bran
  • Nuts
  • Beets
  • Brewed tea
• Limit your intake of animal protein from meat, poultry, fish, and eggs. If you have gout, ask your doctor about other dietary restrictions.
• Make sure to drink plenty of fluids. This may require more than the 2 liters recommended for other types of kidney stones. Talk to your doctor about how much fluid you need.

Medication

Medications to help treat kidney stones may include:

• Nonsteroidal Anti-inflammatory Drugs (NSAIDs) to reduce pain or discomfort. These can be over-the-counter medications, like ibuprofen and naproxen, or prescription.
• Prescription opioids, like morphine, in cases of moderate to severe pain.

Medications also are available to treat or manage other medical conditions that can put you at a high risk for kidney stones.

Call your doctor immediately if you experience any unusual symptoms, including:

• Mental confusion
• Mood changes
• Muscle spasms
• Irregular heartbeat
• Peripheral neuropathy—numbness of arms and legs
• Bruising
• Rash
• Weakness

Surgery

Surgery is an option when the stone is a size or shape that will prevent its passage and it is blocking the flow of urine, or when it is causing damage to the kidney or another part of the urinary tract. If the stone is very large, or in a spot that would be difficult to treat with extracorporeal shock wave lithotripsy (ESWL), your doctor may elect surgical removal of your kidney stones. Surgical procedures may include:

• Percutaneous Nephrolithotomy — the stone is removed through a small incision in the back.
• Ureteroscopy — a flexible tube is passed through the urethra and bladder into the ureter to retrieve the kidney stone.
• Open Surgery — in rare instances, open surgery is required to remove a very large or oddly shaped stone that is obstructing the flow of urine.

Other treatments

Extracorporeal Shockwave Lithotripsy (ESWL) is used to remove a stone that:

• Does not pass after a reasonable period of time and causes constant pain
• Is too large to pass on its own
• Blocks the flow of urine
• Causes ongoing urinary tract infections
• Damages kidney tissue or causes constant bleeding

During this procedure, the doctor uses a special machine to direct shock waves at the stone. The waves pass through the soft tissues of the body and shatter the hard stone on contact. It is then pulverized into smaller particles that can be passed in the urine more easily.

Visit the National Kidney Foundation® for additional information on the prevention and treatment of kidney stones.