Overview and Benefits

Kidney stones are hard masses that form inside the kidneys. They are made up of minerals found in the urine. They may form due to dehydration. They can also form when the urine lacks certain substances that keep minerals from sticking together.

The kidneys are important internal organs. They are responsible for filtering the blood to produce urine. They are a part of the urinary tract. The urine from the kidneys flows through the ureters. These are tubes that connect the kidneys to the bladder. The bladder stores urine until it becomes full. When its full, the brain signals its muscles to contract. This allows the person to pee.

Stones that form in the kidneys can travel to other parts of the urinary tract. Some are small while some are big enough to block the ureters. These can prevent the urine from exiting the body. Stones that are too large to pass on their own require treatment. One of the treatment options is fragmenting (breaking) them up into small pieces. This procedure is called extracorporeal shock wave lithotripsy (ESWL). ESWL is an outpatient procedure. This means that patients are able to go home the same day.

Who Should Undergo and Expected Results

ESWL translates to crushing (lithotripsy) stones using pressure waves (shockwaves) from outside of the body (extracorporeal). It can be used to treat stones that are between 4mm and 2cm in diameter. The procedure is often not an option for very large stones.

Aside from ESWL, there are other ways to treat kidney stones. These include medications that make the muscles of the ureter more relaxed. The kidney stones can also be removed by passing a thin, lighted tube through the urinary tract. In severe cases, open surgery is considered.

ESWL may be used depending on the size and shape of the stone and whether or not it is lodged in the urinary tract. The patient’s health and the kidney’s general condition are also considered. ESWL is often not an option for morbidly obese people and pregnant women. It is also not for patients who have infections, bleeding disorders, and severe bone or muscle problems. Others who do not qualify for the procedure are those with chronic kidney infections and scar tissue in the ureter. These can prevent the stone fragments from passing.

Doctors may also explore other treatment options if the condition is considered an emergency. This is often the case in patients who only have one kidney or those who have undergone a kidney transplant. Because the risk of complications is high in such cases, doctors often resort to surgery to remove the stones right away.

As for the expected results, patients will be able to pass stone fragments within days or weeks after the procedure. They are advised to increase their water intake to speed up this process. In appropriately selected patients, ESWL is very effective. The overall success rate is higher than 90%. Most patients remain stone-free for at least two years.

How is the Procedure Performed?

Patients suspected of having kidney stones are referred to kidney specialists. Before the treatment, doctors order urine and blood tests. The results of the tests are used to assess the overall condition of the kidneys. Any abnormalities detected by these tests are confirmed by imaging tests. Doctors may order a simple abdominal x-ray. This can show bigger kidney stones. A CT scan may also be used. This can detect even tiny stones.

Many cases of kidney stones can be treated without surgery. Small stones that cause minimal to zero symptoms can be treated with medications that relax the muscles in the ureter. This provides the kidney stones an easy way to pass through the urinary tract.

ESWL is considered if the kidney stones do not respond to medications. For this treatment, the patient lies on an exam table on top of a water-filled cushion. An x-ray machine is then used to identify the exact location of the stone. The patient is then given sedatives or anaesthesia. The choice depends on the type of the stone and the patient’s preference. Although the procedure does not require incisions, most patients describe it as painful or uncomfortable. Patients may also be given antibiotics to prevent infection. High-energy shock waves are then delivered to the kidneys. This action breaks up the stones into very small pieces. The treatment often lasts an hour.

The doctor will monitor the patient for any side effects after the procedure. Patients are discharged once the effects of sedatives wear off. Patients are given instructions before they are sent home. The most important is increasing the amount of water they drink. They may also be advised to take antibiotics and pain relievers.

In some cases, doctors ask patients to strain their urine. Patients may then be asked to come back with stone pieces for further testing.

Possible Risks and Complications

EWSL is preferred over other treatment methods because it is not invasive. Because it does not require incisions, patients are not at risk of bleeding and scarring. However, it has its own disadvantages. In some patients, stone fragments remain in their kidneys months or years after the procedure. There is also a risk of kidney injury. It is also possible for stone fragments to get stuck in the urinary tract.


  • Goldman L, et al., eds. Nephrolithiasis. In: Goldman-Cecil Medicine. 25th ed. Philadelphia, Pa.: Saunders Elsevier; 2016. http://www.clinicalkey.com. Accessed Jan. 21, 2017.

  • Melmed S, et al. Kidney stones. In: Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa.: Saunders Elsevier; 2011. https://www.clinicalkey.com.

  • Kidney stones. National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/urologic-diseases/kidney-stones. Accessed December. 03, 2017.

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