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.

See also: Cystinuria

Kidney stones can form when the urine contains too much of certain substances. These substances can create small crystals that become stones. Kidney stones may not produce symptoms until they begin to move down the ureter, causing pain. The pain is usually severe and often starts in the flank region, then moves down to the groin.

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.

Risk factors include renal tubular acidosis and resultant nephrocalcinosis.

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.

Types of stones include:

• 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 mainly 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.

• Abdominal pain
• Abnormal urine color
• Blood in the urine
• Chills
• Excess urination at night
• Fever
• Flank pain or back pain
  • Colicky (spasm-like)
  • May move lower in flank, pelvis, groin, genitals
  • On one or both sides
  • Progressive
  • Severe
• Groin pain
• Nausea, vomiting
• Painful urination
• Testicle pain
• Urinary frequency/urgency
• Urinary hesitancy

Pain can be severe enough to need narcotic pain relievers. The abdomen or back might feel tender to the touch. If stones are severe, persistent, or come back again and again, there may be signs of kidney failure.

Tests for kidney stones include:

• Analysis of the stone to show what type of stone it is
• Straining the urine to catch urinary tract stones
• Uric acid level
• Urinalysis to see crystals and red blood cells in urine

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

• Abdominal CT scan
• Abdominal/kidney MRI
• Abdominal x-rays
• Intravenous pyelogram (IVP)
• Kidney ultrasound
• Retrograde pyelogram

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

The goal of treatment is to relieve symptoms and prevent further symptoms. (Kidney stones 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 analgesics.

Depending on the type of stone, your doctor may prescribe medicine to decrease stone formation and/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)

Stones that don't pass on their own might need to be removed with surgery. Lithotripsy may be an alternative to surgery. It uses ultrasonic waves or shock waves to break up stones. Then the stones can either exit the body in the urine (extracorporeal shock-wave lithotripsy) or be removed with an endoscope that is inserted into the kidney via a small opening (percutaneous nephrolithotomy).

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

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.

• 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

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.

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.