A kidney stone is a solid piece of material that forms in the kidneys from substances in the urine. Stones can occur in any part of the urinary system, from the kidney to the bladder. They may be small or large. You may have just 1 stone or many.
The kidneys are located in the abdomen, on either side of your spine, just above your waist. They filter your blood and excrete waste products and excess water as urine.
Kidney stones are most common in middle-aged people. They are more common in men than in women. They tend to come back.
There are several types of kidney stones, but most stones are calcium stones. They occur when there is too much calcium in the urine. If your kidneys don't work properly or if too much calcium is absorbed from your stomach and intestines, you may have excess calcium in your urine. Some calcium stones are caused by too much of a chemical called oxalate that is found in many foods including spinach, rhubarb, leafy vegetables, coffee, chocolate, and tomatoes. Oxalate binds easily with calcium to form a stone. Also, the risk of forming calcium stones increases if you have certain medical conditions such as an overactive parathyroid gland (a gland in the neck that regulates calcium levels in the body) or inflammatory bowel disease.
A second type of kidney stone occurs because you have too much uric acid in your urine. Uric acid stones might result if you become dehydrated, for example, during strenuous exercise on a hot day or during an illness. Uric acid stones are common in people who have gout, a disease that causes high uric acid levels in the blood.
Struvite stones are a third type. They are also called infection stones because they form in urine that is infected with bacteria.
Finally, a rare type of kidney stone is a cystine stone. It occurs if you have the genetic disease called cystinuria. This disease results from a birth defect that causes the kidney to allow too much cystine into the urine. This type of stone formation is almost always diagnosed during childhood.
Some kidney stones do not cause any symptoms. When they do, the symptoms usually are:
Sometimes the presence of kidney stones causes a urinary tract infection. If you have a urinary tract infection, your symptoms may include fever, chills, sweats, and pain when you urinate.
Kidney stones and urinary tract infection can cause blood to be in the urine. Usually the blood is seen only with a microscope, but it can turn the urine pink or red.
Some people have no symptoms until they pass gravel-like stones in their urine. Others never have any symptoms, and their stones are found during testing for other problems.
Your healthcare provider will ask about your symptoms and examine you. Samples of your urine and blood will be tested.
Sometimes the pattern of pain over time is helpful in the diagnosis. The pain may move from the upper to the lower abdomen over a few hours. As the stone moves lower, the pain may be felt in the genitals, especially the testicles in men and the labia in women.
In addition to a urine test, you may have 1 or more of these tests:
Treatment depends on the size, type, and location of the stone(s), whether one or more stones are blocking urine flow out of the kidney, and whether there are signs of infection.
You may be treated at home by drinking lots of liquids and taking pain medicine. Kidney stones that are 3/16 of an inch (0.5 centimeters) or less in diameter usually pass on their own. Your healthcare provider may ask you to strain all urine until the stone is passed. When the stone is caught, it can be tested in the lab to see what kind of stone it is. Your healthcare provider may prescribe medicine that will help you pass stones or prevent more stones from developing.
You may need to be in the hospital if:
The stones may be broken into small pieces with an instrument, machine, or probe. The smaller fragments may then be able to pass in the urine. This is a procedure called lithotripsy. Shock waves, ultrasound, or a laser may be used to break up the stones. A frequently used, noninvasive procedure using shock waves is called extracorporeal shockwave lithotripsy, or ESWL.
If you have a stone in the bladder that needs to be removed with surgery, it may be broken up with lithotripsy and then removed, under anesthesia, through a cystoscope. If the stone is in the ureter or kidney, it may be removed through a ureteroscope. These instruments are thin, lighted, usually flexible tubes. They can be passed through the urethral opening into the urinary tract. Tiny tools can be passed through the scope to trap and remove the stone using special baskets.
Another surgical procedure that might be used is called percutaneous nephrolithotomy or nephrolithotripsy. After you are given an anesthetic, your healthcare provider makes a small cut in your back and makes a narrow tunnel through the skin into the kidney. With a scope that goes through the tunnel, your provider can find and remove the stone or break it into small pieces using either a laser or ultrasound machine.
Sometimes a stent may be placed. The stent is a tube that goes from the bladder to the kidney. It may be used if:
Usually you have pain off and on for several hours up to 1 or 2 days. However, a stone may take days or even weeks to pass. Sometimes weekly X-rays will be taken to track the progress of the stone as it moves down the urinary tract. If a stone has not passed after a month or so, it may need to be surgically removed.