Passing a kidney stone can be very painful

Q. I’ve heard the worst pain you can experience is from passing a kidney stone. True?

I had a friend who served in the Royal Air Force in World War II. On a bombing run over Germany, his co-pilot started to pass a kidney stone. The pain was so bad that the poor guy wanted to jump out of the plane. He had to be knocked unconscious.

Kidney stones have been inflicting extreme pain for at least 7,000 years; evidence of them was found in an Egyptian mummy.

In the U.S., there are about 1 million cases of kidney stones each year. The number of people in the United States with kidney stones has been increasing inexplicably over the last three decades. Stones occur more frequently in men. And the frequency increases with age.

Kidney stones are composed of crystals of substances in urine. Many small stones pass unnoticed from the two kidneys down the tubes (ureters) leading to the bladder. But if they are too large to pass, you may feel pain.

The crystals that make up stones are likely to form when your urine contains a high level of certain substances. Crystals also may form if your urine becomes too concentrated.

Kidney stones can be caused by heredity, diet, drugs, climate, infection and other conditions that create an increased concentration of calcium, oxalate and uric acid in the urine.

There are four primary types of stones. Calcium stones are the most common; about 80 percent of kidney stones are composed of calcium. Struvite stones usually occur in women and are almost always caused by urinary tract infections. Uric acid stones can develop from a high-protein diet. Cystine stones are caused by a hereditary disorder.

Kidneys are located below the ribs toward the middle of the back. They’re shaped like beans and they’re about the size of your fist. The kidneys remove excess water and waste from the blood and convert it to urine. They have other functions, too, that affect blood.

The most common symptom of a kidney stone is severe pain that usually starts in the back or side just below the ribs. The pain may spread to the lower abdomen, groin and genitals if the stone moves down a ureter toward your bladder. Other symptoms include blood in the urine, nausea and vomiting, constant need to urinate, and fever.

There are various treatments for kidney stones.

Taking a painkiller and drinking a lot of water with increased physical activity can work. Extracorporeal shock wave lithotripsy uses shock waves to break up the stone. If the stone is very large, surgery may be needed. Medication or dietary changes may be prescribed to prevent more stones.

Medications known as alpha blockers are used to help you pass a kidney stone. These drugs relax muscles in your ureter.

Percutaneous nephrolithotomy is a procedure to remove a kidney stone. The surgeon uses instruments inserted through a small incision in your back.

To remove small stones, a doctor may run a thin lighted tube with a camera through your urethra and bladder to get to the ureter. Then surgical tools are used to remove the stone.

If you don’t drink enough fluids, your urine can become concentrated, and that can lead to stone formation. People exposed to heat are more likely to get kidney stones. That’s why kidney stones are more common in summer.

Here are a few tips for reducing the chances of getting a stone:

• Drink about six glasses of water daily. When it gets hot, try to drink twice as much.

• Cut down on meat in your diet.

• Reduce your salt intake. Remember, most of the salt you eat is in prepared foods, not the shaker on your table.

• Drink decaffeinated beverages because caffeine can dehydrate you.

• Lemons inhibit kidney stones, so try to incorporate them in your food and beverages.