Why Kidney Stones Increase in Summer

When does summer officially start? Does it begin with the solstice? What about Memorial Day? Or is it the day school lets out? Whatever your answer, chances are, kidney stone season began a couple of weeks before.

That’s right: Summer kidney stones are a thing.

Urologist Adam Cohen, MD, explains why more people get kidney stones in summer and how to decrease your risk.

Why are kidney stones more common in summer?

Kidney stones are more common in summer for many reasons, but most of them come down to seasonal behavioral changes. In fact, the stones that make people miserable during the dog days of summer oftentimes form in the depths of winter.

A key player in this is calcium — not in your bones, but in your pee. Studies suggest that pee tends to contain more calcium in the winter.

“Excess calcium in your urine can eventually develop into kidney stones,” Dr. Cohen explains. It does that by binding to oxalate in your urine (a natural substance that’s found in your body and the food you eat).

“Being physically active can protect you from stone development because your muscles take in calcium to function, and your bones are literally built from the stuff. That leaves lower amounts in your pee,” he continues.

He adds that many of us are less active in the winter and may also enjoy richer foods during the holiday season.

“That inactivity may result in bone breakdown, increasing calcium in our urine,” Dr. Cohen explains. “And the salt and oxalate in rich foods further increase the risk of stones.”

Then, the warm weather hits. And the tiny pebbles that were growing in your kidneys during the winter start moving. They also start growing.

Stones may be more likely to start their voyage down your ureter (the tube that pee uses to travel from your kidney to your bladder) during the summertime for a couple reasons:

1. You’re more active. Physical activity helps keep stones from forming. But if they’re already there? Then, everyday summer activities — like doing yardwork, running errands or playing outside — can jostle the stone, upping the chances it will dislodge.
2. Your fluid needs are changing. It’s crucial to drink more during the summer to make up for the fluids you lose sweating in the sun. Your hydration levels can impact everything from stone formation and symptoms to how fast they pass. Concentrated urine is more likely to build up stones.

So, while they may not be the first thing you think of, kidney stones are definitely a summer health risk to look out for.

Signs and symptoms

Kidney stones don’t typically cause symptoms until they leave your kidney and enter your ureter, which is why you can form stones in the winter months and not notice them until summertime.

“The pain starts when the stone creates a blockage; the ureter is only 2 to 3 millimeters wide in most people,” Dr. Cohen explains. “It contracts in an attempt to squeeze the stone through into the bladder, which causes painful spasms and urinary irritation.”

These urinary symptoms may include:

• Bloody, cloudy or foul-smelling pee
• Pain or difficulty peeing
• Feeling the urge to pee a lot

While your ureter is trying to clear the blockage, there’s also very little pee getting through to your bladder. The urine that can’t get through builds up behind the stone — and backs up into your kidney. As the pressure builds in your kidney and stretches out the collecting system, it can cause:

• Stabbing pain in your lower back or abdomen
• Nausea and vomiting
• Fever or chills

Once the stone passes into your bladder, your symptoms should subside quickly. But if the stone doesn’t pass on its own within a few weeks, you may need to have a procedure to remove it.

Who is at most risk?

Anyone can develop a kidney stone — and it can happen at any time. But the odds of it happening to you go up if you:

• Have had them before
• Have biological family members with a history of kidney stones
• Are living with certain medical conditions, like diabetes, gout, Crohn’s disease or recurrent UTIs
• Have had weight loss surgery
• Take certain medications, like diuretics, antacids and antiseizure medications
• Eat foods that promote stone formation
• Don’t drink enough water to keep your urine diluted
• Have mobility issues
• Have a condition, injury or surgical procedure that affects how pee collects or flows through your urinary tract
• Spend a lot of time sweating outside, either for work or leisure

Tips to prevent summer kidney stones

If you’re hoping for a stone-free summer, following these prevention tips from Dr. Cohen may help.

• Eat plenty of fruits and vegetables. “They make your urine less acidic and decrease your risk of forming and growing stones,” he says.
• Cut down on animal proteins. Eating a lot of meat can change your urine chemistry, making it more acidic and prone to stone formation.
• Limit sodium. Overdoing it on packaged, processed and salty foods can increase your urinary calcium level. The more calcium there is in your pee, the greater your chances of developing calcium-based stones.
• Stay hydrated. “Drinking plenty of water helps dilute your urine and reduce the formation of crystals such as calcium oxalate. Dilution is always the solution to pollution,” Dr. Cohen explains.
• Monitor your pee. If you’re at high risk of developing stones, Dr. Cohen suggests drinking enough water each day to produce 2.5 liters of pee. Not keen to whip out a measuring cup? Aim for your pee to be a very pale shade of yellow. “Two and a half liters is a tough goal, so don’t be discouraged,” he adds. “Any increase in hydration ultimately reduces your risk.”

Nobody wants to spend their summer passing kidney stones. While you can’t prevent them completely, dietary adjustments and a proactive conversation with a provider about your risk factors can stack the odds in your favor.