Kidney Stones Are Painful, Yet Treatable
A kidney stone is a hard mass developed from crystals that separate from the urine and build up on the inner surfaces of the kidney. "The stones form as aggregates of crystals, and it's the crystals that vary from one patient to another," said Jeffrey A. Wesson, MD, PhD. Dr. Wesson is a Medical College of Wisconsin Associate Professor of Medicine (Nephrology) and practices at the Zablocki VA Medical Center and the Nephrology Clinic at Froedtert & Medical College Clinics.
Most Stones Contain Calcium Oxalate
"The Medical College has been one of the major centers of kidney stone research for several decades," said Dr. Wesson. "Our work is aimed at understanding the processes that lead to stone formation, and my work, in particular, is focused on the process of crystal aggregation."
"Calcium oxalate crystals are found in 70 to 80 percent of the stone samples. Calcium phosphate crystals are found in 30 to 35 percent of the samples," Dr. Wesson explained. "We're already over 100 percent. Obviously, you can have two kinds of crystals together." Uric acid, struvite and cystine are three other types of crystals found in stones. "Calcium oxalate stones account for the majority of cases, and we don't really know why they occur."
Ten percent of people are affected by stone disease, so some people form kidney stones and others do not. Family history might be a contributor. "Certainly we see kidney stones running in family clusters, but the genetics are not understood," Dr. Wesson said. "The reason behind that, we think, is that there are multiple factors contributing to stone formation, similar to diseases like hypertension and Type II diabetes."
Diagnosis: Pain Usually First Indicator
Discovering a kidney stone can be a painful experience when the stone breaks loose and travels down the urinary tract. "The classic presentation of a kidney stone is known as renal colic; a severe, cramping pain, which is related to obstruction of the ureter," Dr. Wesson said. "Stones can be several millimeters to even centimeters in diameter. They can be extraordinarily large, but even small stones can get stuck in the tube between the kidney and bladder. It's the blockage of urine flow that causes the colicky pain."
Dr. Wesson said his female patients have told him they would rather go through childbirth again than have to experience the pain of passing another kidney stone. Other symptoms include blood in the urine, fever or chills, nausea, vomiting, urine that looks cloudy, or a burning feeling when urinating.
While pain may be the first indicator, the diagnosis is made by a CT scan, X-ray, or sonogram to give the physician information about the stone's size and location. "The gold standard for diagnosis is to have a high resolution, non-contrast CT scan from the kidneys down to the bladder," Dr. Wesson said. "It's superior to ultrasound in both identifying and defining the size of the stone."
Treatment Depends on Size of Stone
"If the stone is only a few millimeters, most of them will pass on their own as long as the symptoms can be controlled," Dr. Wesson said. "There are combinations of drug therapies that can help facilitate passage." For larger stones, extracorporeal shockwave lithotripsy (ESWL) is often used. In ESWL, intense pulses of high frequency sound waves are used to break stones into sand-like particles that are more easily passed through the urinary tract.
In some cases, surgery may be required when kidney stones are large or in a location that does not allow for ESWL. Two types of procedures are used - percutaneous nephrolithotomy involves entering the kidney with a fiber optic camera and small instruments through a small incision in the back; and ureteroscopic stone removal involves using a small fiber optic instrument (a ureteroscope) and similar small instruments to enter the urinary tract through the urethra and bladder to the ureter, so the stone can be removed.
Prevention is the Best Cure: Water and Dietary Changes
"The primary issue with stone disease in terms of prevention is trying to adjust the urine chemistry to make the possibility of crystal formation smaller," Dr. Wesson said. "The crystals form in the urine because the urine has too much of the components that combine to make the crystals to be stable." To change the chemistry, patients need to make the urine more diluted, and the primary method is to drink more water and other liquids.
"An example I use with my patients is to think of boiling salt water on the stove. If you boil away enough of the water, the salt crystals come back because there just isn't enough water around to hold it. If you add water back to the pot, the crystals dissolve again. The crystals that make kidney stones are forming for the same reason. There isn't enough water under normal conditions."
How much water is enough? Dr. Wesson said the best measure is not to count liters of water consumed, but instead to look at urine production. The typical person makes one to one and a half liters of urine daily, but a patient who is prone to kidney stones needs to increase that output. "We try to get stone formers to reduce the concentration of urine by half, so they need to make twice as much urine, which means twice as many times to the bathroom."
The prospect of drastically increasing water intake can be quite challenging. "The difficulty for people really comes down to the fact that everyone normally drinks according to thirst. To make more than the usual amount of urine, you have to drink more than you're thirsty for. You have to force yourself to take more in," Dr. Wesson said. "That being said, I've seen a few patients with very active disease who have trained themselves to drink water to the point where they're making five to six liters of urine every day. They spend a lot of time in the bathroom, but it's effective."
There are a few medications that reduce stone formation rates, but changes in diet are the second most important way to control how often stones form. While the changes are dependent on the type of crystals found in the stones, patients forming calcium containing stones (most patients) are treated effectively by following diet recommendations. Citrate or citric acid has been found to be a natural inhibitor of crystal formation, and Dr. Wesson said some patients take supplements of citric acid for that reason, though they can also obtain citrate from food sources, particularly fruit. High salt diets increase the risk for forming stones, and so do protein-rich diets, such as the Atkins diet.
Finally, he pointed out that, contrary to earlier thinking, we now know that dietary calcium intake should be maintained at normal levels (1000-1500 milligrams per day). "There have been several very good research studies demonstrating that reduced calcium intake actually increases both the risk of forming the first stone as well as subsequent stones, so now we tell our patients to maintain normal calcium intake to treat their stones," Dr. Wesson added.
Melissa Rigney Baxter
HealthLink Contributing Writer