Diet may be best defense against kidney stones
Dr. Leslie Spry likes to tell a story about one of his friends who thought he was a tough guy -- until the day his pal, a surgeon, ended up as a patient with a kidney stone.
“He just kept telling them to bring the morphine,” says Spry, a spokesman for the National Kidney Foundation. “He had never experienced anything like that in his life.”
Spry, who is a nephrologist in Lincoln, Neb., tells male patients that passing a kidney stone is the closest they will come to understanding the pain women go through during childbirth. It’s a form of anguish men are more likely to experience. One in seven males has a kidney stone in his lifetime, while only about one in 20 women will develop one. Doctors treat about a million Americans for kidney stones each year.
A more accurate name for this menace is “urinary stones,” since they can turn up in the kidney, bladder or ureters (the slender tubes that drain urine from the kidneys to the bladder).
These stones are actually crystals that clump together because the urine’s concentration of certain minerals and other compounds is too high or its concentration of chemicals that inhibit stone formation is too low.
There are four types of urinary stones. About 80% are made of calcium combined with either oxalate (an acid) or phosphate (a salt); the remainder are formed by uric acid, struvite (a mineral) or cystine (an amino acid). Some are smooth, but more often stones have jagged edges that help them cling to the walls of the urinary tract. Stones come in all sizes, from sand-like grains to behemoths that measure several inches across.
As a kidney stone tries to pass through the urinary tract, it can cause sudden, sharp pain in the lower back, abdomen or side, which may travel to the groin. “They’re amazingly incapacitating,” says Dr. Peter G. Schulam, associate professor of urology at the David Geffen School of Medicine at UCLA. “You can’t do anything to comfort yourself.”
To confirm that a patient’s pain is caused by a kidney stone, a doctor will look for microscopic traces of blood in the urine and take an X-ray of the abdomen to determine the size and location of the stone.
As a rule, says Schulam, if the stone is smaller than 5 millimeters in diameter (or roughly the width of these three ooo’s), it will pass on its own within a few days or weeks. Patients are sent home with pain relievers and orders to drink plenty of fluids (preferably water) to help flush the stone.
Because medical treatments for this condition involve a small degree of risk and may result in some bruising and further discomfort, doctors usually don’t intervene unless a stone is larger than 5 millimeters or a patient is experiencing unbearable pain, nausea or fever.
The safest, least invasive method for removing a rock, says Schulam, is a technique known as extracorporeal shock wave lithotripsy, which uses sound waves delivered from outside the body to break up a stone.
If that fails, doctors can insert a slender tube called a ureterscope into the urethra (the channel that drains urine from the bladder to the penis) and into the urinary tract in search of the stone.
Once it is located, lasers or ultrasound devices at the tip of the scope then break the stone into tiny fragments, or a small basket at the end of the scope may be used to remove the stone.
Surgery is required to extract very large or hard stones, usually by entering the kidney through a small incision in the back.
Estimates vary, but at least 30% of people who pass kidney stones will have another in their lifetime; some experts say the figure is much higher. Depending on the composition of the stone passed, a physician may give a prescription for medicine that will reduce the risk of recurrence.
All patients should drink plenty of fluids to discourage stone growth. Guzzle eight to 10 cups of water a day, and more if you’re active, says Linda Massey, a professor of human nutrition at Washington State University in Spokane, Wash.
Although doctors used to tell patients with calcium stones to cut back on dairy and other calcium-rich foods, they now know that consuming too little of this crucial mineral actually promotes the formation of stones.
Massey recommends consuming a small serving of dairy or other calcium-rich food with every meal, along with five to seven daily servings of fruit and vegetables, which are good for the kidneys.
Meanwhile, patients with stones should avoid foods high in oxalates, which include spinach, parsley and rhubarb, she says, and go easy on other oxalate-rich foods, including chocolate, tea, berries, nuts and bran. (Oxalate is produced in the body too; men make more, which may be why males are more prone to stones.)
A 2002 study in Italy found that men with calcium-based stones had half as many recurrences if they ate a normal amount of calcium but cut back on meat and salt, which both cause stone formation. So beware, high-protein dieters: Moderation is the key.
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Timothy Gower can be reached by e-mail at tgower@comcast .net. The Healthy Man runs the second Monday of the month.
