It seems amazing that something so tiny can cause so much suffering. But while a small minority of people are genetically destined to develop a kidney stone, some simple lifestyle changes may greatly reduce your odds of getting one.
Source: Adapted from Know Your Options: The Definitive Guide to Choosing The Best Medical Treatments, Reader
What are kidney stones?
Your kidneys are meant to efficiently flush microscopic particles of salts and minerals into the ureter—the long, narrow tube that leads to the bladder—and they’re expelled when you urinate. Trouble looms when chemical imbalances and other processes cause these tiny particles to bind into crystals, which grow into a kidney stone. When the stone moves from the kidney into the delicate ureter, it produces anything from a nagging ache to excruciating pain, often accompanied by nausea and vomiting. This blockage may trigger a urinary tract infection. Sometimes stones get stuck in the kidney, causing an infection but not usually immediate pain.
Suspected causes of kidney stones include high levels of urinary calcium and oxalate (a chemical that enables stone formation); excessive absorption of calcium from the intestine; too much dietary sodium; chemical imbalances; diseases (such as gout, recurrent urinary tract infections, and hyperparathyroidism); and even some medications. Kidney stones are categorized by their chemical composition. It’s likely made of calcium and oxalate, a combination responsible for 70% to 80% of all stones. About 7% of kidney stones are formed from uric acid, and a small fraction are either struvite stones (almost always caused by urinary tract infections) or cystine stones, which are due to a rare genetic disorder.
Who is at risk for kidney stones?
Doctors don’t entirely understand all the physiological changes that lead to formation of kidney stones (medically known as renal calculi), and aren’t certain why some people are more susceptible than others to the most common types. Yet everyone agrees on one point: Kidney stones can hurt—a lot. In fact, it is commonly cited as the most painful reported condition. Even kidney stones smaller than a pencil eraser can cause misery and a trip to the emergency room.
Treatment for kidney stones
If you think you’re passing a kidney stone, call your doctor right away, or rush to an emergency room. You may be hospitalized if your pain is severe or you have signs of complications such as an obstruction or infection. However, about 85% of kidney stones are small enough (a quarter of an inch or less in diameter) to move through the ureter and enter the bladder within about 72 hours after they’re discovered by x-ray. Once the stone leaves the ureter, your pain leaves with it.
In the meantime, immediate pain relief will be at the top of your wish list. Anti-inflammatory medications and narcotics are very effective and work quickly. You’ll also receive antibiotics if you’ve developed a urinary tract infection. Stones lodged in the kidney or ureter must be removed, either surgically or nonsurgically.
Medications for kidney stones
If you have a kidney stone, your doctor will prescribe a painkiller, probably ketorolac (Toradol) or the narcotic meperidine (Demerol). You may also be given an antispasmodic drug so you can pass the kidney stone more easily. If your urine chronically contains high levels of calcium, oxalate, or uric acid, your doctor might prescribe drugs to help prevent kidney stone formation. The decision will be based on the chemical makeup of your stone and whether your lab tests and blood work indicate you are at high risk for recurrence.
- For calcium-based stones: Preventive medications include thiazide diuretics, commonly used to treat high blood pressure and eliminate fluid and sodium from the body. You will probably be given hydrochlorothiazide (Esidrix, Hydro-D), chlorothiazide (Diuril), or trichlormethiazide (Metahydrin, Naqua).
- For uric acid stones: Commonly prescribed drugs include allopurinol (Zyloprim) and potassium citrate (Polycitra-K).
- For struvite stones: Medications such as acetohydroxamic acid (Lithostat) and long-term antibiotics may help.
- For cystine stones: Doctors will typically prescribe tiopronin (Thiola) and penicillamine (Cuprimine, Depen).
If your doctor advises watchful waiting until the kidney stone passes, you can lessen the wait by drinking fluids—three to four quarts a day. Walking can also help speed the stone along. Be sure to strain your urine (the doctor will provide a collection kit) so the stone can be sent for analysis. If you’ve had a kidney stone but take no precautions to prevent another, you have a 50% chance of repeating the ordeal within five years, but you can reduce your risk considerably with the following measures:
- Drink lots of fluids—mostly water. Your goal is to dilute your urine enough to prevent crystals from forming.
- Lower your salt intake. Too much salt can raise calcium levels in your urine. Aim to consume less than 2,400 mg of sodium a day.
- Eat less meat. Animal protein encourages the body to excrete calcium and uric acid. Get more of your protein from nonmeat sources like soy.
- Get more potassium in your diet. Foods rich in this mineral include orange juice, bananas, and other fruits and vegetables.
Although doctors typically recommend that patients reduce the oxalates in their diets (oxalate-rich foods range from spinach to cranberry juice), it’s not clear if doing so really makes any difference. Doctors also routinely tell patients to cut back on calcium. Now, even the accuracy of that widely accepted piece of advice is under fire.
Related Procedures for Kidney Stones
Not long ago, the only option for removing a larger kidney stone was major surgery, lengthy recovery, and a big scar. Today, doctors can choose from several far gentler alternatives. Extracorporeal shock wave lithotripsy (ESWL) is the technique most frequently used to break up stones in the kidney or upper ureter. Your doctor may place a small tube, called a stent, within the ureter to widen it and allow the stones to move more easily. You may go home just a few hours after an ESWL, although a day or two of hospitalization may be necessary as a precaution. Success rates range from 50% to 90%, depending on the stone’s location and chemical composition. Multiple treatments may be needed. ESWL does not work for cystine stones or, usually, for larger stones (more than about an inch). After ESWL, expect to see blood in your urine and feel soreness in your side or abdomen for a few days. Complications are rare.
Kidney stones caught in the middle or lower part of the ureter aren’t good candidates for ESWL. Instead, your doctor may attempt a minimally invasive technique called ureteroscopy, in which a small fiberoptic scope (called a ureteroscope) is threaded into the urethra and through the bladder. Smaller stones are plucked out manually with small baskets or graspers. Larger ones may first be shattered with lasers, ultrasonic shock waves, or electric shocks delivered through the scope. The procedure is successful 90% of the time. Sometimes, ESWL is used prior to ureteroscopy to break up stones, making them easier to remove.
Larger stones wedged in the kidney or upper ureter and those that simply prove too stubborn for ESWL or ureteroscopy are candidates for percutaneous nephrolithotomy (PNL). This is the preferred therapy for cystine stones. For a PNL, the urologist cuts a tiny incision in your back, creates a tunnel into the kidney and, through an instrument called a nephroscope, locates and removes the stone. Ultrasound or a laser may be needed to break up very large kidney stones. The success rate for PNL is a whopping 98% for stones in the kidney, 88% for those in the ureter. Serious complications are very rare.
The rarer types of kidney stones—uric acid, struvite, and cystine stones—may be chemically dissolved in a process called chemolysis. Special chemicals are delivered through a catheter inserted through the urethra in a series of treatments. Chemolysis may be used as a primary treatment or in combination with others but doesn’t work for calcium stones. Fewer than 2% of people will require standard open surgery (nephrolithotomy). It’s used only when all other attempts to blast or remove the stone have failed, or if there are special circumstances, such as obesity or an abnormal kidney structure.
Questions for Your Doctor
- If my pain is under control but the kidney stone hasn‘t passed, must I still restrict my activities?
- Should I take a vitamin or mineral supplement? What about calcium?
- Could an undiagnosed condition be making me form kidney stones?
Prevention of kidney stones
- Treat a urinary tract infection promptly. Struvite stones form only in infected urine. If you have an infection, call your doctor.
- Rehydrate after sweating. If you live in a warm climate or take part in strenuous physical activities, drink more than the recommended three to four quarts of water or non-caffeinated fluids a day—enough to keep your urine almost colorless. Carry a water bottle with you as a reminder.
- Maintain a healthy weight. Kidney stones seem to be more common among overweight people. If you need to lose some pounds, don‘t go on a crash diet: It can make you produce more uric acid, which promotes kidney stones. Lose weight gradually.