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.
Renal calculi; Nephrolithiasis; Stones - kidney
Kidney stones are common. Some types run in families. They often occur in premature infants.
There are different types of kidney stones. The cause of the problem depends on the type of stone.
Stones can form when urine contains too much of certain substances that form crystals. These crystals can develop into stones over weeks or months.
- Calcium stones are most common. They are most likely to occur in men between ages 20 - 30. Calcium can combine with other substances to form the stone.
- Oxalate is the most common of these. Oxalate is present in certain foods such as spinach. It's also found in vitamin C supplements. Diseases of the small intestine increase your risk of these stones.
Calcium stones can also form from combining with phosphate or carbonate.
Other types of stones include:
- Cystine stones can form in people who have cystinuria. This disorder runs in families. It 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 such as certain medicines also can form stones.
The biggest risk factor for kidney stones is not drinking enough fluids. Kidney stones are more likely to occur if you make less than 1 liter of urine a day.
You may not have symptoms until the stones move down the tubes (ureters) through which urine empties into your bladder. When this happens, the stones can block the flow of urine out of the kidneys.
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:
Exams and Tests
The health care provider will perform a physical exam. The belly area (abdomen) or back might feel sore.
Tests that may be done include:
- Blood tests to check calcium, phosphorus, uric acid, and electrolyte levels
- Kidney function tests
- Urinalysis to see crystals and look for red blood cells in urine
- Examination of the stone to determine the type
Stones or a blockage can be seen on:
Treatment depends on the type of stone and the severity of your symptoms.
Kidney stones that are small usually pass through your system on their own.
- Your urine should be strained so the stone can be saved and tested.
- Drink at least 6 - 8 glasses of water per day to produce a large amount of urine. This will help the stone pass.
- Pain can very bad. Over the counter pain medicines (e.g. ibuprofen, naproxen), either alone or along with narcotics, can be very effective.
Some people with severe pain from kidney stones need to stay in the hospital. You may need to get fluids through a vein.
For some types of stones, your doctor may prescribe medicine to prevent stones from forming or help break down and remove the material that is causing the stone. These medicines can include:
- Allopurinol (for uric acid stones)
- Antibiotics (for struvite stones)
- Phosphate solutions
- Sodium bicarbonate or sodium citrate
- Water pills (thiazide diuretics)
Surgery is often 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.
- The pain cannot be controlled.
Today, most treatments are much less invasive than in the past.
- Lithotripsy is used to remove stones slightly smaller than a half an inch that are located in the kidney or ureter. It uses sound or shock waves to break up stones. Then, the stone fragments leave the body in the urine. It is also called extracorporeal shock-wave lithotripsy or ESWL.
- Procedures performed by passing a special instrument through a small surgical cut in your skin and into your kidney or ureters are used for large stones in or near the kidney, or when the kidneys or surrounding areas are incorrectly formed. The stone is removed with a tube (endoscope).
- Ureteroscopy may be used for stones in the lower urinary tract.
- Rarely, open surgery (nephrolithotomy) may be needed if other methods do not work or are not possible.
Talk to your doctor about what treatment options may work for you.
Kidney stones are painful but most of the time can be removed from the body without causing lasting damage.
Kidney stones often come back. This occurs more often if the cause is not found and treated.
You are at risk for:
- Urinary tract infection
- Kidney damage or scarring if treatment is delayed for too long
- Obstruction of the ureter (acute unilateral obstructive uropathy)
When to Contact a Medical Professional
Call your health care provider if you have symptoms of a kidney stone.
- Very bad pain in your back or side that will not go away
- Blood in your urine
- Fever and chills
- Urine that smells bad or looks cloudy
- A burning feeling when you urinate
If you have been diagnosed with blockage from a stone, passage must be confirmed either by capture in a strainer during urination or by follow-up x-ray.
If you have a history of stones:
- Drink plenty of fluids (6 - 8 glasses of water per day) to produce enough urine.
- You may need to take medicine or make changes to your diet for some types of stones.
- Your doctor may want to do blood and urine tests to help determine the proper prevention steps.
Curhan GC. Nephrolithiasis. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 128.
Finkelstein VA. Strategies for preventing calcium oxalate stones. CMAJ. 2006;174:1407-1409.
Ferrandino MN, Peitrow PK, Preminger GM. Evaluation and medical management of urinary lithiasis In: Wein AJ, ed. Campbell-Walsh Urology. 10th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 46.
Reviewed By: Scott Miller, MD, Urologist in private practice in Atlanta, Georgia. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.