The Painful Problem That Likes to Come Back
Forget the doctor's office... If you've got a kidney stone, you might want to try Disney World instead...
Specifically, you might want to hop on the Big Thunder Mountain Railroad. And then ask for a seat in the back.
Sound crazy? Well, some scientists put the idea to the test...
It all started after several kidney-stone patients reported something peculiar: They had passed their stones after riding the Big Thunder Mountain Railroad roller coaster at Walt Disney World.
One patient even said he had ridden the coaster three times – and passed a kidney stone after each ride. So researchers 3D-printed a silicone model of that patient's kidney, with three different sizes of kidney stones inside of it.
Then the team trekked to Disney World, where they rode the Big Thunder Mountain Railroad 60 times – 20 rides for each stone size.
Interestingly, when the researchers sat in the front of the coaster, the stones in the model passed nearly 17% of the time. When they sat in the back, the stones passed roughly 64% of the time. The researchers suspected that the forces of the coaster jostled and helped shake small stones loose to move them toward the ureter – the narrow tube carrying urine from the kidney to the bladder – where they could eventually leave the body.
Now, if you're suffering from kidney stones, I'm not suggesting you book a flight to Orlando as the first line of treatment. After all, this was a small experiment using a model... not a clinical trial.
As amusing as the idea of riding a coaster to shake loose a stone might seem, there's nothing funny about actually passing one.
Even normal-sized kidney stones can produce waves of pain intense enough to leave you vomiting and sweating.
Worst of all, kidney stones – and the agony they can bring – like to come back...
One in four folks who get their first kidney stone develop a second one within five years. And once you've had multiple kidney stones, your risk of developing another jumps to 50%.
Kidney stones afflict an estimated 20% of men and 10% of women by age 70. And we get more vulnerable to them as we age...
Older folks are more likely to have diabetes, chronic kidney disease, weakened immunity, or other health problems that make it tougher to regulate fluid levels and battle a severe infection. Warning signs of kidney stones may be easier to miss.
And because folks feel less of a thirst drive as they age, many start drinking less water. It's estimated that up to 40% of folks aged 65 and up suffer from chronic dehydration. As I'll discuss, being less hydrated makes it easier for kidney stones to form.
The Five Types of Kidney Stones
Now, "kidney stone" is a bit of an umbrella term. Here are the five major types and how they form...
1. Calcium-oxalate stones are the most common. Calcium-containing stones account for roughly 80% of kidney stones, and most of those contain calcium oxalate. Your body makes oxalate naturally as a waste product. Some oxalate comes from food, but much of it is made as the liver breaks down other compounds. These stones can form when calcium and oxalate become too concentrated in urine, stick together, and grow into a solid mass. Another risk factor for this type of stone is insufficient citrate, a chemical compound that binds to calcium and prevents it from forming crystals.
2. Uric-acid stones form when urine is too acidic. Gout, insulin resistance, and obesity are three conditions that raise your risk of developing these stones. But you can also increase your risk by eating lots of purine-rich foods like red meat and organ meat (such as tongue, liver, or kidneys).
3. Calcium-phosphate stones can form in urine that is more alkaline (less acidic). These stones may be linked to certain medications or health problems that affect the balance of calcium or acid.
4. Struvite stones are also called "infection stones" because they're the result of infections from certain bacteria. These bacteria make an enzyme called urease, which breaks down urea in the urine. This enzyme also makes urine less acidic... Both of these factors cause magnesium, ammonium, and phosphate to crystallize into struvite.
5. Cystine stones form due to cystinuria, a rare genetic condition that allows excessive amounts of the amino acid cystine to leak into the urine.
Sometimes, a stone can occupy your kidney for years without causing obvious symptoms. The notorious pain often begins when it moves into the ureter. The ureter squeezes and spasms around the stone. Urine backs up behind it, stretching the kidney and producing intense waves of pain known as renal colic.
How to Know If You Have a Kidney Stone
You could have a kidney stone in one of your ureters if you notice any of these symptoms:
- Sharp, aching pain from the back to the lower abdomen, usually on one side, not improving with rest, and coming in waves
- Bloody urine
- A strong urge to urinate and more frequent urination
- Pain in groin area
These symptoms may also be paired with nausea or vomiting.
For many small, uncomplicated stone cases, doctors recommend drinking plenty of water while waiting for the stone to pass.
But you should also watch for signs of infection...
When a stone obstructs the flow of infected urine, bacteria and inflammatory substances can spill into the bloodstream and trigger urosepsis.
This can soon become a urologic emergency. Treating it requires antibiotics and prompt draining of the kidney using a small tube. If urosepsis isn't treated quickly enough, it could lead to septic shock – an advanced stage of sepsis that can cause your organs to shut down.
Urologists won't remove a kidney stone during an active infection because disturbing a stone or increasing pressure inside an infected urinary tract can push bacteria into your bloodstream (leading to urosepsis).
However, when a stone is colonized with bacteria, it can also serve as a reservoir from which bacteria can repeatedly reenter the urine. So it's critical to address potential infections when you have a kidney stone.
If you know or think you have a kidney stone and you develop a fever, it's time to get to the ER.
Surgically removing a kidney stone isn't great news. Many patients face weeks of recovery. And, as I mentioned before, you're more likely to develop another stone within a few years.
So while it's important to know how to recognize and respond to a kidney stone, the best thing is to avoid getting one in the first place. In last month's issue of my flagship newsletter, Retirement Millionaire, I shared my three favorite tips to protect yourself from this painful and potentially dangerous condition. Plus, I revealed a connection between your gut and your kidneys that might surprise you. (If you're not an existing Retirement Millionaire subscriber, you can sign up here for a free trial run.)
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Here's to our health, wealth, and a great retirement,
Dr. David Eifrig and the Health & Wealth Bulletin Research Team
August 11, 2026