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Overview

Kidney stones (renal lithiasis, nephrolithiasis) are hard deposits made of minerals and salts that form inside your kidneys.

Kidney stones have many causes and can affect any part of your urinary tract — from your kidneys to your bladder. Often, stones form when the urine becomes concentrated, allowing minerals to crystallize and stick together.

Passing kidney stones can be quite painful, but the stones usually cause no permanent damage if they’re recognized in a timely fashion. Depending on your situation, you may need nothing more than to take pain medication and drink lots of water to pass a kidney stone. In other instances — for example, if stones become lodged in the urinary tract, are associated with a urinary infection or cause complications — surgery may be needed.

Symptoms

A kidney stone may not cause symptoms until it moves around within your kidney or passes into your ureter — the tube connecting the kidney and bladder. At that point, you may experience these signs and symptoms:

• • Severe pain in the side and back, below the ribs
• • Pain that radiates to the lower abdomen and groin
• • Pain that comes in waves and fluctuates in intensity
• • Pain on urination
• • Pink, red or brown urine
• • Cloudy or foul-smelling urine
• • Nausea and vomiting
• • Persistent need to urinate
• • Urinating more often than usual
• • Fever and chills if an infection is present
• • Urinating small amounts

Pain caused by a kidney stone may change — for instance, shifting to a different location or increasing in intensity — as the stone moves through your urinary tract.

Causes

Kidney stones often have no definite, single cause, although several factors may increase your risk.

Kidney stones form when your urine contains more crystal-forming substances — such as calcium, oxalate and uric acid — than the fluid in your urine can dilute. At the same time, your urine may lack substances that prevent crystals from sticking together, creating an ideal environment for kidney stones to form.

Types of kidney stones

Knowing the type of kidney stone helps determine the cause and may give clues on how to reduce your risk of getting more kidney stones. If possible, try to save your kidney stone if you pass one so that you can bring it to your doctor for analysis.

Types of kidney stones include:

• • Calcium stones. Most kidney stones are calcium stones, usually in the form of calcium oxalate. Oxalate is a naturally occurring substance found in food and is also made daily by your liver. Some fruits and vegetables, as well as nuts and chocolate, have high oxalate content.
• Dietary factors, high doses of vitamin D, intestinal bypass surgery and several metabolic disorders can increase the concentration of calcium or oxalate in urine.
• Calcium stones may also occur in the form of calcium phosphate. This type of stone is more common in metabolic conditions, such as renal tubular acidosis. It may also be associated with certain migraine headaches or with taking certain seizure medications, such as topiramate (Topamax).
• • Struvite stones. Struvite stones form in response to an infection, such as a urinary tract infection. These stones can grow quickly and become quite large, sometimes with few symptoms or little warning.
• • Uric acid stones. Uric acid stones can form in people who don’t drink enough fluids or who lose too much fluid, those who eat a high-protein diet, and those who have gout. Certain genetic factors also may increase your risk of uric acid stones.
• • Cystine stones. These stones form in people with a hereditary disorder that causes the kidneys to excrete too much of certain amino acids (cystinuria).

Risk factors

Factors that increase your risk of developing kidney stones include:

• • Family or personal history. If someone in your family has kidney stones, you’re more likely to develop stones, too. And if you’ve already had one or more kidney stones, you’re at increased risk of developing another.
• • Dehydration. Not drinking enough water each day can increase your risk of kidney stones. People who live in warm climates and those who sweat a lot may be at higher risk than others.
• • Certain diets. Eating a diet that’s high in protein, sodium (salt) and sugar may increase your risk of some types of kidney stones. This is especially true with a high-sodium diet. Too much salt in your diet increases the amount of calcium your kidneys must filter and significantly increases your risk of kidney stones.
• • Being obese. High body mass index (BMI), large waist size and weight gain have been linked to an increased risk of kidney stones.
• • Digestive diseases and surgery. Gastric bypass surgery, inflammatory bowel disease or chronic diarrhea can cause changes in the digestive process that affect your absorption of calcium and water, increasing the levels of stone-forming substances in your urine.
• • Other medical conditions. Diseases and conditions that may increase your risk of kidney stones include renal tubular acidosis, cystinuria, hyperp arathyroidism, certain medications and some urinary tract infections.

Prevention

• Drink water throughout the day. For people with a history of kidney stones, doctors usually recommend passing about 2.6 quarts (2.5 liters) of urine a day. Your doctor may ask that you measure your urine output to make sure that you’re drinking enough water.

If you live in a hot, dry climate or you exercise frequently, you may need to drink even more water to produce enough urine. If your urine is light and clear, you’re likely drinking enough water.

• Eat fewer oxalate-rich foods. If you tend to form calcium oxalate stones, your doctor may recommend restricting foods rich in oxalates. These include rhubarb, beets, okra, spinach, Swiss chard, sweet potatoes, nuts, tea, chocolate, black pepper and soy products.

• Choose a diet low in salt and animal protein. Reduce the amount of salt you eat and choose nonanimal protein sources, such as legumes. Consider using a salt substitute, such as Mrs. Dash.

• Continue eating calcium-rich foods, but use caution with calcium supplements. Calcium in food doesn’t have an effect on your risk of kidney stones. Continue eating calcium-rich foods unless your doctor advises otherwise.

Treatment

Treatment for kidney stones varies, depending on the type of stone and the cause.

Small stones with minimal symptoms

Most small kidney stones won’t require invasive treatment. You may be able to pass a small stone by:
•Drinking water. Drinking as much as 2 to 3 quarts (1.9 to 2.8 liters) a day may help flush out your urinary system. Unless your doctor tells you otherwise, drink enough fluid — mostly water — to produce clear or nearly clear urine.
•Pain relievers. Passing a small stone can cause some discomfort. To relieve mild pain, your doctor may recommend pain relievers such as ibuprofen (Advil, Motrin IB, others), acetaminophen (Tylenol, others) or naproxen sodium (Aleve).
•Medical therapy. Your doctor may give you a medication to help pass your kidney stone. This type of medication, known as an alpha blocker, relaxes the muscles in your ureter, helping you pass the kidney stone more quickly and with less pain.

Large stones and those that cause symptoms

Kidney stones that can’t be treated with conservative measures — either because they’re too large to pass on their own or because they cause bleeding, kidney damage or ongoing urinary tract infections — may require more-extensive treatment. Procedures may include:

•Using shockwave to break up stones. For certain kidney stones — depending on size and location — your doctor may recommend a procedure called extracorporeal shock wave lithotripsy (ESWL).

ESWL uses sound waves to create strong vibrations (shock waves) that break the stones into tiny pieces that can be passed in your urine. The procedure lasts about 45 to 60 minutes and can cause moderate pain, so you may be under sedation or light anesthesia to make you comfortable.

ESWL can cause blood in the urine, bruising on the back or abdomen, bleeding around the kidney and other adjacent organs, and discomfort as the stone fragments pass through the urinary tract.

•Surgery to remove very large stones in the kidney. A procedure called percutaneous nephrolithotomy (nef-row-lih-THOT-uh-me) involves surgically removing a kidney stone using small telescopes and instruments inserted through a small incision in your back.

You will receive general anesthesia during the surgery and be in the hospital for one to two days while you recover. Your doctor may recommend this surgery if ESWL was unsuccessful.

•Using a scope to remove stones. To remove a smaller stone in your ureter or kidney, your doctor may pass a thin lighted tube (ureteroscope) equipped with a camera through your urethra and bladder to your ureter.

Once the stone is located, special tools can snare the stone or break it into pieces that will pass in your urine. Your doctor may then place a small tube (stent) in the ureter to relieve swelling and promote healing. You may need general or local anesthesia during this procedure.