Kidney Stones

Kidney stones are a major health problem, affecting up to 10% of all Americans at some time in their lives. Men are affected three times as often as women, and most frequent stone formers have their first stone in their 20s. Kidney stones are more common during hot weather, but can occur at any time of the year.

A kidney stone is a collection of mineral salts and protein that collect to form a solid crystalline mass. They can start as tiny stones that pass in the urine unnoticed, or they may grow to a size that cannot be passed and become symptomatic. Most kidney stones are composed of calcium-containing crystals, but some are due to metabolic disturbances, which may cause stone composed of uric acid, or chronic urinary tract infections, which may cause stone made of phosphate.

If a stone grows large enough it can get caught in the kidney or the ureter (the tube that drains the kidney into the bladder). Once it gets caught, the stone may partially or completely block the flow of urine. This blockage causes pain that is usually felt in the middle of the back or side and may radiate toward the groin. Sometimes the pain can be so severe as to cause nausea and vomiting. Fevers and chills may accompany a stone that is associated with infection. If a stone that is blocking urine flow is left untreated it can cause damage to the kidney or ureter.

If your symptoms sound like you may have a stone your doctor may perform a full history and physical examination, check laboratory tests on your blood and urine, and order x-rays. The x-ray tests often include a plain film and/or CT scan of your abdomen. Other tests that may be considered include intravenous pyelography (IVP) or an ultrasound of your kidneys to detect blockage.

If your stone is relatively small (5 mm or less, or less than 1/5 of an inch), your doctor may decide to treat your symptoms with pain medications and allow the stone to pass on its own. Your doctor may ask you to urinate into a strainer so that if you pass a stone, it can be caught and analyzed, which will give important information as to why you formed the stone. Most stones that are 5 mm or less (less than one-fifth of an inch) will pass on their own, usually within a few days, sometimes a few weeks. Smaller stones pass more quickly.

If the stone is large, or continues to cause problems or appears infected, your doctor may refer you to a urologist, who may elect to perform a procedure during which a small tube is placed in your ureter via a scope. This tube can serve to allow the urine to pass, which alleviates pain, and may allow the ureter to dilate, letting the stone pass as well.

Until the advent of more modern techniques in the early 1980s, most stones were treated with open surgery. Now, the majority of stones can be treated without open surgery or with minimally-invasive endoscopic techniques (see "Lithotripsy" section). Many of these procedures are same-day surgery, allowing you to return home the same day.

Preventing future stones from forming is a very important part of stone management, and cooperation with your doctor’s advice is vital to staying stone-free. Many stones can be prevented by maintaining adequate oral fluid intake, especially water or citrus juices like lemonade. Your doctor may ask you to collect your urine for a 24-hour period so that more information can be gained about why you are forming stones. After reviewing the results with you, your doctor may re-emphasize adequate oral fluid intake, or he/she may prescribe a medication to correct any abnormalities found during the 24-hour collection.

Decreasing dietary protein and salt intake in the diet also helps to reduce the likeliness of recurrent stones. Calcium is found in most stones (about 80%), but it is not necessary to restric dietary calcium unless you ingest an unusually large amount.

Treatment with Lithotripsy

Lithotripsy is a treatment for kidney stones which has been in wide use since 1982. Lithotripsy works without open surgery. Kidney stones can be broken up with shock waves, and then the stone fragments pass out of the body in the urine.

Lithotripsy is generally performed on an outpatient basis, often using sedation, but most frequently under a general anesthetic. The process uses a device called a lithotriptor. Because all the energy is generated by a machine outside the body and no incisions are made, the process is called Extracorporeal Shock Wave Lithotripsy (ESWL). This treatment can be used to break stones located in the kidney or in the ureter. Stones that are larger than 1.5 centimeters (1/2 inch) may be too large to fully break up with one treatment, and might be better treated by some other method, including open surgery. ESWL can be used in adults and in children, but care must be used to avoid injuring adjacent organs, such as the lungs, in children.

Lithotriptors generate shock waves by various mechanisms but all fragment stones based on the same principles. Shock waves travel easily through the soft tissues of the body with minimal damage to surrounding structures, but are focused on the kidney stones. The stones absorb the energy from these waves and break up. Small stone fragments are then passed in the urine. The treatment is rarely painful, but passing the stone fragments may be.

Depending of the location and size of the stone, as well as the number of fragments produced, your doctor may or may not place a stent in your ureter (the tube that connects the kidney to the bladder to drain urine). A stent is a small plastic tube that allows the kidney to drain into the bladder and the stones to pass around the tube. The stent is located entirely on the inside and will have to be removed in the clinic at a later time, using a scope passed into the bladder. Removal of the stent is done without anesthesia, and is slightly uncomfortable, but takes only about 1 minute.

Kidney stones are crystalline masses that form from minerals and proteins in the urine. Stones come in various sizes and compositions. Certain types of stones will respond to this treatment better than others. Most kidney stones are very small, less than one-quarter of an inch, and pass without the need for lithotripsy or any other treatment.

If you have kidney stones that are too large to pass, lithotripsy may make removal fairly simple. Your recovery time will be much shorter than with surgery. However, this procedure does not alter the reasons that the stones formed. To prevent future stones, follow the therapy and dietary changes that your healthcare provider suggests. The most important suggestion will be a large fluid intake, which results in a lot of urine output and dilution of the chemicals which may produce stones.

Bernard Fallon, MD, Professor of Urology
University of Iowa Hospitals and Clinics