Kidney Stones

The kidneys continuously create urine to remove excess water, minerals and waste products from the blood. Kidney stones are hard deposits of minerals that grow slowly over months or years. Some may pass from the kidneys and become lodged in the ureters or bladder. The most common kidney stones are formed from excess calcium or uric acid in the urine. People who tend to form stones can usually prevent them by following specific recommendations from their physicians.


Diagnosis

The urogram and the CT scan are the preferred ways at Mayo to diagnose kidney stones. Ultrasound is an option but may not detect small stones.

Intravenous Pyelography (Excretory Urogram)
A contrast dye is injected into the patient's vein, and a series of X-rays is taken as the dye moves from the bloodstream into the kidneys, ureters and bladder. If abnormalities are seen, the doctor may follow up with a CT scan — a series of thin X-ray beams that produce two-dimensional images of the organs.

Spiral CT Scan
This high-speed imaging test is used for patients who cannot tolerate contrast dye. A CT scan checks the abdomen in three minutes, and can reveal the presence of very small kidney stones that do not appear on conventional X-rays.

Ultrasound
These high-frequency radio waves allow physicians to look at a patient's internal organs. This test is painless and noninvasive, but it may not detect small stones, especially those outside the kidneys.


Treatment

Waiting and Watching
In about 85 percent of cases, kidney stones are small enough to pass during urination, usually within 72 hours of symptom onset. The best treatment for these stones is to drink plenty of water (as much as 2 to 3 quarts per day), stay physically active and wait. Painkillers may be prescribed to help alleviate the discomfort associated with passing a stone.

For patients who can pass a stone without medical intervention, urinating through a strainer may be recommended so that the stone can be recovered and analyzed. The mineral composition of the kidney stone will dictate appropriate treatment and future preventive measures.

Stones that are too large to pass on their own or that may cause bleeding, kidney damage or ongoing urinary tract infection may need surgical treatment.


Minimally Invasive Treatments:

Extracorporeal Shock Wave Lithotripsy (ESWL)
This procedure is the usual treatment to remove stones about 1 centimeter or smaller.

Patients lie on a cushion during the procedure. In many cases the stone will begin to crumble after 200 to 400 shock waves. The sandlike particles that remain after treatment are easily passed in the urine.

The shock waves are painful, so the procedure is performed with sedatives, local anesthesia or general anesthesia.

Some side effects of extracorporeal shock wave lithotripsy include blood in the urine for a short time after the procedure and minor bruising on the back or abdomen. Some patients may also experience discomfort as the stone fragments pass through the urinary tract. Others may need another treatment if the stone doesn't shatter completely. Most patients resume normal activity in a few days, but it may take months for all stone fragments to pass.

Parathyroid Surgery
Some calcium stones are caused by overactive parathyroid glands, which are located on the four corners of the thyroid gland. Usually, a small benign growth in one of these glands causes it to be overactive. As a result, the body's level of calcium becomes too high, which can lead to kidney stone formation. Removing the growth on the parathyroid gland will cure the kidney stone problem. This operation is performed by a general surgeon, not a urologist.