Kidney Stones

Overview

Kidney stones are one of the most common conditions that urologists treat. Stones of the urinary tract are more common in males than in females and are more predominate in Caucasians than other ethnic groups.

Most stones form in the kidney itself and may or may not cause pain at this point. If a stone migrates out of the kidney and down the tube that drains the kidney into the bladder (the ureter), the kidney may not be able to drain completely, and severe pain may result from the increased pressure.

Kidney stones are treated by letting the stone pass through the body if it is small enough or by using shock wave technology, lasers or ultrasound to dissolve the kidney stone.

Evaluation

As most people are aware, the pain from a stone is typically sudden in onset and quite severe. Although the pain is usually located in the flank region, some patients will experience pain in the abdominal region, which may be mistaken for other conditions.

Associated symptoms may include nausea and vomiting as well as fever and chills if any infection is present. At times the patient may notice urinary frequency and a sense of bladder irritation as the stone nears the bladder. Although gross urinary tract bleeding is sometimes seen, microscopic bleeding is more common.

Kidney Stone Treatment

If the diagnosis of a kidney stone is being entertained, a kidney x-ray called an IVP is typically performed. This exam entails injecting a contrast material intravenously which is subsequently excreted by the kidneys. When x-rays are taken following injection of this contrast material, the kidneys and associated structures can be visualized.

A significant percentage of smaller stones in the lower ureter will pass spontaneously. Stones located in the upper part of the urinary tract or those that are too large to pass may require intervention. Most kidney stone treatment is done with shock wave technology, which utilizes externally generated shock waves that travel through the body and fragment the stone into particles that can pass through the urinary tract. Utilizing the newest technology available, patients are treated with this technique on an outpatient basis and in most cases don't even require an anesthetic.

Stones that are not amenable to treatment with shock waves can generally be treated with a small instrument called a ureteroscope inserted into the ureter tube under anesthesia. Once the stone is visualized, a small laser fiber is passed through the scope and laser energy is used to fragment the stone.

Larger stones in the kidney may require treatment with a scope called a nephroscope inserted directly into the kidney so an ultrasound probe can be used to fragment the stone and evacuate the fragments. Rarely, open surgery will be necessary to treat a stone that is not amenable to the more conservative treatment options outlined above.

Once the acute stone event has been managed, the emphasis shifts to prevention of subsequent attacks. The stone fragments passed by the patient following a lithotripsy (shock wave) treatment will be collected in a strainer and analyzed to determine the exact composition of the stone. This information is important for subsequent management.

Most stones will be found to be composed of calcium complexed with either oxalate (more common) or phosphate. Approximately 5-10 percent of stones will be found to be composed of a material called uric acid. Although calcium stones are the most common, they are probably the most difficult to treat. Most patients with calcium-containing stones do not have elevated urinary calcium levels due to dietary overindulgence, rather they have a subtle defect in the kidneys that allows excess amounts of calcium to "leak" from the kidneys.

The mainstay of the treatment of calcium stones is increased water intake to keep the urine as dilute as possible. Although this strategy does not affect the number of calcium molecules excreted every 24 hours, the more dilute urine resulting from an increased water intake minimizes the risk of the calcium salts precipitating from the urine and forming a stone.

Stones composed of substances like uric acid can typically be managed more easily than calcium stones by utilizing medications to either decrease the production of uric acid or to alter the urine pH and thereby increase the solubility of uric acid.

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