| - Kidney Stones -
What Are Kidney Stones?
Kidney stones are aggregates of crystals that separate from urine due to the presence of insoluble chemicals. If the crystals are small enough, they flow out with the urine, unnoticed. If the crystals grow large enough, or form a larger conglomerate, then they may not be able to pass and then cause symptoms. Kidney stones can be made of a variety of substances, most commonly calcium and oxalate. Another common stone-forming substance is uric acid. Some stones, particularly in the presence of a chronic urinary tract infection, can grow to be very large and fill the inside of the kidney (staghorn kidney stone below).
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x-ray of Staghorn Kidney Stone |
same kidney stone after surgery |
Symptoms of Kidney Stones
Symptoms from kidney stones are usually due to the obstruction of the flow of urine once the stone leaves the kidney and starts down the ureter toward the bladder. Since the kidney continues to make urine despite the obstruced flow, the inside of the kidey stretches, causing the severe pain known as "renal colic." Often, hydration and pain meds are all that is necessary to help pass the stone. It is important to know that obstruction (kidney stone pain) with fever is an emergency. Anyone with fever and flank pain must seek medical care immediately. Sometimes a large kidney stone may be stuck inside the kidney and cause a chronic dull ache in the flank, or intermittent symptoms for many years.
Evaluation of Kidney Stones
Urine analysis often demonstrates the presence of microscopic blood. CAT scan is the best imaging study to evaluate for the presence, location, and size of kidney stones. Plain X-rays are often used, too, but not all stones show up on these films. In particular, uric acid stones are radiolucent, meaning they will not show up on plain x-rays. IVP (intravenous pyelogram) is an older study in which IV contrast is given before a series of plain x-rays. This is an excellent study to delineate the internal antomy of the kidney before some types of kidney stone procedures. If one has recurrent kidney stones, a metabolic evaluation can be performed to determine what a person might do to reduce their risk of further stones. This study involves a 24-hour urine collection and analysis, as well as a blood draw for calcium and sometimes parathyroid hormone levels. If a kidney stone is passed or removed, it should be sent for chemical analysis, as this information can assist wtih recommendations to prevent further episodes.
Treatment of Kidney Stones
Observation - not all stones require treatment. The risks of treatment must be weighed against the benefits. Some will pass spontaneously.
Medical Expulsive Therapy - trials have shown that certain medications help stones to pass through the ureter. The most commonly used drug for this purpose currently is tamsulosin (Flomax). A variety of other drugs are sometimes used including calcium channel blockers and steroids.
Extracorporeal Shockwave Lithotripsy (ESWL) - focused sound waves are used to break up a stone into pieces that can be passed more easily. This is a non-invasive treatment, but requires general anesthesia. Stones that are most appropriate for this treatment are in the kidney or upper ureter, visible under plain x-ray, and measure less than 2cm in greatest dimension.
| Ureteroscopy - many stones pass down the ureter, but get stuck before they pass into the bladder. These stones are often amendable to endoscopic treatment. This field is now highly developed and many useful tools are available to overcome the obstacles that may be encountered. Long, narrow scopes can be passed into the bladder, then up the ureter to the level of the stone. Usually, the stone is then fragmented with a laser and the fragments washed out or snared with a basket and retrieved. |
View of stone in ureter through ureteroscope
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Laparoscopic Stone Removal - Depending on the stone location and kidney anatomy, removing the stone intact through a laparoscopic approach is occasionally the best option.
Prevention of Kidney Stones
Ask anyone who has had a stone and you will be convinced that the preferred means of treating a kidney stone is to prevent it from forming in the first place. Kidney stone formation and growth are dependent on the concentration of substances in the urine. The easiest way to reduce the risk of crystal formation is to increase the amount of urine in which to dissolve the same amount of minerals - drink more fluids! Water is a great option, but if water is not particularly palatable, drink lemonade-flavored Crystal Light, which contains citrate, a potent kidney stone inhibitor. To make specific recommendations about how one can reduce their risk of recurrent kidney stones, a metabolic evaluation must be performed. The information is obtained from a blood draw and a 24-hour urine collection. With this information, certain dietary changes can be recommended. Often, a diet with reduced oxalate can help decrease recurrence of the most common types of stones. There are several good books about preventing kidney stones and even a cookbook dedicated to the low-oxalate diet. If one has high calcium in the urine, then a medication may be provided to decrease it. If one makes uric acid stones, then a medication that decreases the amount of uric acid production (allopurinol) and/or a medication that makes the urine less acidic (Urocit-K) can be both stone treatment and prevention.
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