Kidney Stones


 Unfortunately, kidney stones are a fact of life. One out of ten Americans will experience a kidney stone sometime during their lives. They seem to occur with greater frequency in the Southern United States, hence the name, “The Stone Belt.” Although a great number of tiny stones are probably never recognized during passage, when they start to get up to a few millimeters in size, their physical symptoms can be excruciating.

“Renal colic” is the term commonly used for kidney stone pain. It usually begins as waves of sharp pain below the rib area on one or both sides of the back which radiate down toward the bladder area of the groin. These are often first accompanied by nausea vomiting, and diarrhea. Patients usually pace around or move continuously trying to find a comfortable position. What is happening is that the stone is caught in a section of the ureter, the tubular structure which runs from the kidney to the bladder. Urine flow may be restricted or even blocked causing some of the pain. The ureter is, as well, vigorously contracting and trying to move the stone along. Often the stone is tearing the delicate lining of the ureter causing blood to be seen in the urine. This process goes on until the stone finally moves into the bladder or until some form of medical therapy is initiated.

What can a physician do about an acute kidney stone? Well, he/she may first of all hook up one or two bags of I.V. fluids to try to wash the stone through the ureter. Usually he will give either an injection of a Non-Steroidal Inflammatory Drug such as ketoralac to diminish the inflammatory process, or he may decide that an injection of an opioid drug is needed for the pain, to dilute the ureter and to dilute the urine. Sometimes he/she may give a diuretic to try to increase the urine flow down the ureter. The good news is that 90% of stones 4 mm or less in size will pass. Once the initial pain has been relieved he may send you home to strain your urine to try to catch the stone. Stone analysis can be very helpful in preventing future stones. Sometimes it is apparent that the stone is larger, and is probably not going to move.

At this point he might refer you to a urologist for more specific therapy. There are several options available to this specialist. He may look into the ureter with a special scope and decide to place a stent tube around the obstruction to let the urine flow past it. He may insert a stone basket to remove the stone if it is not too large. He may try to break the stone up with direct ultrasound on the stone, or prescribe the Extracorporeal Lithotripsy Treatment in which a powerful sound wave is directed at the stone from outside the body. Sometimes this technique can damage other organs, so it has to be used very expertly. Once the stone is broken, it will often go ahead and pass through the ureter.

So, what causes a stone anyhow? Did you ever see the rock candy making experiment where a string is suspended in a saturated sugar solution, and crystals start to grow on it? This is what happens with a kidney stone. There is too much of a mineral or other substance in the urine which causes crystals to form. The crystal enlarges with time until it is too large to pass. The most common stone (e.g., crystal) is calcium oxalate. This forms over 80% of stones. The next most common stone is calcium phosphate. About 5% to 10% are formed from uric acid which is the same process which causes gout in the joints. People with chronic urinary tract infections can form struvite stones from the bacteria splitting urea. There are several other metabolic conditions which can lead to stone formation. Stone analysis can suggest several of these, and laboratory tests such as blood chemistry and urinalysis can suggest others.

There are several techniques for specifically diagnosing a kidney stone if it is clinically suspected. One is a plain x-ray of the abdomen called a KUB. Since most of the stones contain calcium, many can be seen and measured by this study. Another technique is ultrasound. This sometimes shows the actual stone, but more often demonstrates the swollen condition of the blocked kidney. A CT scan is very useful for showing the size and position of a stone. Recently, there has been concern about the amount of radiation exposure in a CT scan, so this may or may not be used. A special dye can be used with plain x-rays or CT scan to show the position of the stone and the extent of blockage.

There are a few caveats about preventing kidney stones. One is adequate fluid intake, or about 6 to 8 glasses of water a day. If stones are calcium oxalate (the most common type), one might avoid oxalate rich foods like chocolate, nuts, spinach, and soybeans, black tea, peanut butter, green leafy vegetables except Iceberg lettuce. Orange juice seems to inhibit the formation of oxalate stones. Taking big doses of Vitamin C seems to be a risk factor for stone formation. If one has high levels of uric acid in the blood, prevention of this type of stone would proceed from treatment with the medicine allopurinol which decreases uric acid formation. Sometimes, the physician may prescribe thiazide diuretics which decreases calcium excretion in the urine. Proper resolution of urinary tract infections would cut down on the incidence of struvite stone formation. Regular follow-ups with your physician might result in treatments for underlying medical conditions, like hyperparathyroidism, which would prevent future recurrences of kidney stones.

John Drew Laurusonis

Doctors Medical Center

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