Kidney stones

Kidney anatomy — The kidneys are responsible for removing wastes from the body, regulating electrolyte balance and blood pressure, and stimulating red blood cell production.

Also known as: Renal calculi, Nephrolithiasis or Stones - kidney

Definition

A kidney stone is a solid mass made up of tiny crystals. One or more stones can be in the kidney or ureter at the same time.

Causes, incidence, and risk factors

Kidney stones can form when urine contains too much of certain substances. These substances can create small crystals that become stones.

The biggest risk factor for kidney stones is dehydration.

Kidney stones may not produce symptoms until they begin to move down the tubes (ureters) through which urine empties into the bladder. When this happens, the stones can block the flow of urine out of the kidneys. This causes swelling of the kidney or kidneys, causing pain. The pain is usually severe.

Kidney stones are common. A person who has had kidney stones often gets them again in the future. Kidney stones often occur in premature infants.

Some types of stones tend to run in families. Certain kinds of stones can occur with bowel disease, ileal bypass for obesity, or renal tubule defects.

There are different types of kidney stones. The exact cause depends on the type of stone.

Calcium stones are most common. They occur more often in men than in women, and usually appear between ages 20 - 30. They are likely to come back. Calcium can combine with other substances, such as oxalate (the most common substance), phosphate, or carbonate to form the stone. Oxalate is present in certain foods. Diseases of the small intestine increase the risk of forming calcium oxalate stones.
Cystine stones can form in people who have cystinuria. This disorder runs in families and affects both men and women.
Struvite stones are mostly found in women who have a urinary tract infection. These stones can grow very large and can block the kidney, ureter, or bladder.
Uric acid stones are more common in men than in women. They can occur with gout or chemotherapy.

Other substances also can form stones.

Symptoms

The main symptom is severe pain that starts suddenly and may go away suddenly:

Pain may be felt in the belly area or side of the back
Pain may move to groin area (groin pain) or testicles (testicle pain)

Other symptoms can include:

Signs and tests

Pain can be severe enough to need narcotic pain relievers. The belly area (abdomen) or back might feel tender to the touch.

Tests for kidney stones include:

Analysis of the stone to show what type of stone it is
Uric acid level
Urinalysis to see crystals and red blood cells in urine

Stones or a blockage of the ureter can be seen on:

Tests may show high levels of calcium, oxylate, or uric acid in the urine or blood.

Treatment

The goal of treatment is to relieve symptoms and prevent further symptoms. (Kidney stones that are small enough usually pass on their own.) Treatment varies depending on the type of stone and how severe the symptoms are. People with severe symptoms might need to be hospitalized.

When the stone passes, the urine should be strained and the stone saved and tested to determine the type.

Drink at least 6 - 8 glasses of water per day to produce a large amount of urine. Some people might need to get fluids through a vein (intravenous).

Pain relievers can help control the pain of passing the stones (renal colic). For severe pain, you may need to take narcotic pain killers or nonsteroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen.

Depending on the type of stone, your doctor may prescribe medicine to decrease stone formation or help break down and remove the material that is causing the stone. Medications can include:

Allopurinol (for uric acid stones)
Antibiotics (for struvite stones)
Diuretics
Phosphate solutions
Sodium bicarbonate or sodium citrate (which make the urine more alkaline)

Surgery is usually needed if:

The stone is too large to pass on its own
The stone is growing
The stone is blocking urine flow and causing an infection or kidney damage

Today, most treatments are much less invasive than in the past.

Extracorporeal shock-wave lithotripsy is used to remove stones slightly smaller than a half an inch that are located near the kidney. This method uses ultrasonic waves or shock waves to break up stones. Then, the stones leave the body in the urine.
Percutaneous nephrolithotomy is used for large stones in or near the kidney, or when the kidneys or surrounding areas are incorrectly formed. The stone is removed with an endoscope that is inserted into the kidney through a small opening.
Ureteroscopy may be used for stones in the lower urinary tract.
Standard open surgery (nephrolithotomy) may be needed if other methods do not work or are not possible.

Expectations (prognosis)

Kidney stones are painful but usually can be removed from the body without causing permanent damage. They tend to return, especially if the cause is not found and treated.

Complications

Decrease or loss of function in the affected kidney
Kidney damage, scarring
Obstruction of the ureter (acute unilateral obstructive uropathy)
Recurrence of stones
Urinary tract infection

Calling your health care provider

Call your health care provider if you have symptoms of a kidney stone.

Also call if symptoms return, urination becomes painful, urine output decreases, or other new symptoms develop.

Prevention

If you have a history of stones, drink plenty of fluids (6 - 8 glasses of water per day) to produce enough urine. Depending on the type of stone, you might need to take medications or other measures to prevent the stones from returning.

You may need to change your diet to prevent some types of stones from coming back.

References

Cameron MA, Sakhaee K. Uric acid nephrolithiasis. Urol Clin North Am. 2007;34(3):335-346.

Chandhoke PS. Evaluation of the recurrent stone former. Urol Clin North Am. 2007; 34(3):315-322.

Finkielstein VA. Strategies for preventing calcium oxalate stones. CMAJ. 2006;174(10):1407-1409.

Pietrow PK, Preminger GM. Evaluation and medical management of urinary lithiasis. In: Wein AJ, ed. Campbell-Walsh Urology. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 43.

Disease

Urinary tract infection - adults

A urinary tract infection, or UTI, is an infection that can happen anywhere along the urinary tract. Urinary tract infections have different names, depending on what part of the urinary tract is infected. Bladder — an infection in the bladder is also called cystitis or a bladder ...
Test

Uric acid - blood

Uric acid is a chemical created when the body breaks down substances called purines. Purines are found in some foods and drinks, such as liver, anchovies, mackerel, dried beans and peas, beer, and wine. Most uric acid dissolves in blood and travels to the kidneys, where it passes out in urine. If ...
Special Topic

Chemotherapy

Chemotherapy is the use of drugs to kill bacteria, viruses, fungi, and cancer cells. Most commonly, the term is used to refer to cancer-killing drugs. This article focuses on cancer chemotherapy.
Disease

Cystinuria

Cystinuria is a condition passed down through families in which stones form in the kidney, ureter, and bladder. See also:
Disease

Proximal renal tubular acidosis

Proximal renal tubular acidosis is a condition that occurs when the kidneys don’t properly remove acids in the urine, leaving the blood too acidic.
Symptoms

Overweight

Nearly two-thirds of the United States population is overweight. There are many ways to determine if a person is overweight, but experts believe that a person’s body mass index (BMI) is the best way to assess an adult’s weight in relation to their height. A BMI between 18.5 and 24.9 is ...
Disease

Injury - kidney and ureter

Injury to the kidney and ureter is damage to these organs of the upper urinary tract.
Special Topic

Renal

The term “renal” refers to the kidney. For example, renal failure means kidney failure. Related topics:
Disease

Gout

Gout is a kind of arthritis that occurs when builds up in the joints. Acute gout is a painful condition that typically affects one joint. Chronic gout is repeated episodes of pain and inflammation, which may involve more than one joint.
Disease

Acute unilateral obstructive uropathy

Acute unilateral is a sudden blockage in one of the tubes (ureters) that drain urine from the kidneys. See also:
Disease

Nephrocalcinosis

Nephrocalcinosis is a disorder in which there is excess calcium deposited in the kidneys.
Surgery

Percutaneous urinary procedures

Percutaneous (through the skin) urinary procedures help drain urine from your bladder and get rid of .

Review date:: January 14, 2009
Reviewed by:: Louis S. Liou, MD, PhD, Assistant Professor of Urology, Department of Surgery, Boston University School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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