When I moved to North Carolina in 2005, I knew that I would be living in a part of the country that has the highest rate of kidney stones. Two short years later, I had an episode of visible blood in my urine and pain in my side. Thankfully, it was not the excruciating pain that some people experience, but it was unpleasant, to say the least. A quick CT scan later, I knew that I had several very small stones in each kidney and had probably just passed one. I became another reluctant member of the kidney stone club.
What are kidney stones and who gets them?
Kidney stones are mineral deposits that form in the kidneys and can block the flow of urine. They are commonly made of calcium oxalate and calcium phosphate. Less commonly, they can be made of uric acid, cystine, or struvite (an infection stone). About 10-to-15 percent of Americans will have a kidney stone in their lifetime, and the occurrence of stones seems to be increasing.
Certain medical diseases and obesity can also predispose to stone formation. Men are two-to-three times more likely to have stones than women, but this gender gap seems to be decreasing. Caucasians have a higher incidence than Hispanics, Asians, or African-Americans. Stones are more common in the South than the North and more common in the East than the West. The Mid-Atlantic region has been nicknamed the “Stone Belt” and North Carolina has one of the highest rates of kidney stones in the country.
What symptoms would I have from stones?
If stones are not blocking the urinary flow, there may be no symptoms at all. Many of my patients have had stones found on x-rays done for other reasons. They are surprised because they thought that all stones cause pain. If stones block the urine flow, and the kidney backs up, people can experience pain from the upper back, around to their side, and radiating into the groin area. This pain can range from mild to excruciating. The pain can come in waves and can be associated with nausea, vomiting, fevers, and chills. As stones get closer to the bladder, you can feel a significant urge to urinate. When stones go through the urethra tube (the tube through which you urinate), you may experience a burning sensation. Stones can also cause blood in your urine that may or may not be visible.
The symptoms of a stone tend to correlate with the degree of blockage. Sometimes a large stone that is not blocking the urinary tract has no symptoms, but a very small stone that blocks the urinary flow can cause high levels of pain.
What tests can be done to diagnose kidney stones?
One of the most common and best tests to find kidney stones is a CT scan. Depending on which treatment option a patient is considering, their doctor may also want to obtain plain x-rays of the abdomen. Kidney ultrasound can show swelling and evidence of blockage, but is not very accurate in evaluating the entire urinary tract. Your doctor may also want to check to make sure there is not an associated urinary tract infection, blood in the urine, or abnormal kidney function.
How are kidney stones treated?
As long as they are not very sick with fevers, chills, or vomiting, patients can be monitored to see if they can pass their stone without procedures. If your stone is large, there is less of a chance to pass it on your own. Medications called alpha blockers have been shown to increase the likelihood of passing stones without procedures. If pain is too severe, patients may decide to have their stones treated. If patients are very sick, their doctor may want to put in an internal stent to drain any associated infection from the kidney prior to performing any procedure.
If stones are visible on plain x-rays, it may be possible to fragment them into smaller pieces with extracorporeal shock wave lithotripsy (ESWL). This procedure concentrates a shock wave onto the stone to break it into multiple small pieces that are easier to pass. Patients are awake, but need medication to keep them comfortable. ESWL feels like a strong rubber band slapping on the skin. We typically attempt to shock the stone 4000 times during the procedure. Success rates with this procedure vary based on the composition and location of the stone.
One of the most definitive treatments is to visualize the stone with a thin, fiber-optic camera and break it into small pieces with a laser. This is called a ureteroscopy. Pieces can be left to pass on their own, or can be removed completely. This procedure requires anesthesia, but does not require any incisions. Often times, an internal stent is inserted, so that the kidney can drain freely while any internal swelling dissipates. If this is placed, it is removed in the office five-to-ten days later.
When patients have very large stones, a more invasive procedure called a percutaneous nephrostolithotomy (PCNL) can be performed. A small incision is made in the upper back, and a scope is passed directly through the muscles and into the kidney. Patients typically stay in the hospital one or two days.
In the past, big incisions were used to remove stones. Now this is very rare.
How can I prevent future stones?
One of the main ways to prevent recurrent stones, or to prevent existing stones from getting bigger, is to keep the urine as dilute as possible. This helps prevent the salts in the urine from crystallizing. That means drinking enough water so that you make two liters of urine each day. Small amount of other beverages (coffee, tea, soda, exercise drinks, etc.) should be limited.
If you are taking diuretic “fluid” pills, you should check with your primary doctor to make sure your other medical issues will remain stable with increased fluid intake.
It has been shown that reducing the amount of sodium in your diet can decrease the amount of calcium excreted into the urine. Limiting the use of table salt and keeping your sodium intake to less than 2500 mg per day can help decrease the risk of recurrence. Average intake in a typical American diet is over 3000 mg. Start to pay attention to nutrition labels on the foods you eat and monitor the amount of sodium you take in.
Meats (chicken, pork, beef, fish, etc.) and other animal proteins contain purines, which increase the uric acid in urine. This increases the risk of developing kidney stones. Organ meats are especially high in purines. Limiting meat protein intake to six-to-eight ounces each day may help decrease recurrence rates. Calcium and oxalate have an interesting relationship when it comes to stones. Most people believe they should decrease calcium intake, but calcium is very much needed for your general health, especially for healthy bones. Recommended daily intake of calcium is 800 mg.
Calcium can also bind with oxalate in the intestines and prevents increasing calcium in the urine. Foods high in oxalate can increase stone rates. The most common foods high in oxalate are nuts and spinach. Limiting these may also help decrease stone formation.
I grew up in the Midwest. I spent a great deal of time outside and did not stay well-hydrated, even during the hot summer months. My diet was based around a large portion of meat with each meal and several shakes of salt on everything. Since my diagnosis of kidney stones, I have dramatically increased my fluid intake, have stopped using table salt, and have tried to decrease my animal protein intake. These behavioral changes are often the hardest to start and to maintain. My motivation is that I hope my stones never grow, and that I do not form any new stones.
This article was written by
Harrison K. Rhee, MD