Updated on March 1, 2021.
You hear people say all the time that passing kidney stones is one of the most painful things they've ever experienced—and in some cases, worse than childbirth. And even though stones propel more than 500,000 people to the emergency room annually, many who show up there don’t have a clue what’s causing their pain—or they attribute it to something else like appendicitis.
“Once you’ve had a kidney stone, though, you will surely recognize the characteristic pain if it happens again,” says Anita Mehrotra, MD, a transplant nephrologist at Our Lady of Lourdes Organ Transplant Center in Camden, New Jersey.
And chances are it will happen again. Not only are kidney stones relatively common, affecting around 10 percent of people at some point in their lives, recurrences are likely too—50 percent of people experience another within 10 years.
The scoop on stones
Many factors determine who gets kidney stones, says Dr. Mehrotra. Family history and conditions like obesity, diabetes, and inflammatory bowel disease can predispose you to developing them. But dietary habits, particularly how well hydrated you are, top the list.
Stones form when minerals or salts, most frequently calcium and oxalate, build up in the urine. Over time, they join together to create crystals in the kidneys that gradually increase in size, creating a solid mass called a kidney stone.
After forming, a stone may stay in the kidney or travel down the urinary tract in the ureter, the tubes that connect the kidney to the bladder. Precisely what causes it to become dislodged isn’t known, reports Mehrotra. What is known, she says: “The more stones you have, the more likely it is that one of them will eventually cause a problem.”
Kidney stones on the rise
That’s troubling, since a 2018 study found a huge uptick in the number of diagnoses of kidney stones—they jumped more than fourfold among women and more than twofold among men between 1984 and 2012. The reason women’s numbers seemed to grow much more than men’s is because they started out quite a bit lower 30 years ago.
Why the surge in the prevalence of kidney stones? The increased use of radiological imaging techniques like CT scans and ultrasound at least partly explains the study results. “A lot of stones may be diagnosed as incidental findings done on patients who aren’t having any symptoms,” says Mehrotra. “And those found incidentally are left alone until people start experiencing symptoms.”
“The worst pain ever”
Which brings us back to pain, the most common symptom of a kidney stone on the move. What does passing a kidney stone feel like? It usually begins suddenly and without warning and is classically described as a sharp, shooting pain that extends from the flank around to the abdomen and down into the groin on the side of the kidney stone. As the stone continues to move toward the bladder, shooting pains may be felt in the scrotum or labia.
Typically, the kidney stone pain gets worse, then better, as the ureter constricts and relaxes as it tries to push urine and the stone forward, but it doesn’t go away completely.
Waves of this severe pain, known as renal colic, usually last 20 minutes to an hour. “Most people say it’s the worst pain they’ve ever had, aside from women who’ve birthed children without epidurals that is,” says Mehrotra.
Some people get lucky and have stones that are so small they move out of the body in the urine without them even knowing it or with just mild discomfort, but that’s unusual. “They’d have to be really tiny for that to happen—less than 1 millimeter (.04 inches),” says Mehrotra. “Stones greater than 1 millimeter will definitely be felt.”
In addition to pain, other possible symptoms include:
- Blood in the urine: This will occur for most people who experience stones. It might not be visible or apparent, or it may be tinted red or pink. Bleeding can be unsettling, and usually results from irritation of the ureter.
- Nausea or vomiting: This is mostly due to the severe pain itself or side effects of pain medications—in particular, opioid drugs like Percocet (oxycodone/acetaminophen), says Mehrotra.
- Urination issues: You may experience pain with urination or an urgent need to pee. If you really feel the urge to go, it’s important to rule out an infection, since people with blockages in their urinary tract are more likely to get urinary tract infections (UTIs).
- Fever: The most concerning symptom is fever, which means that you may have an infection in addition to a kidney stone. Another sign of infection: chills and shivering.
When to seek medical attention
Eighty percent of stones that are 4 millimeters or less can be passed on your own, but the same is true for only about 20 percent of those greater than 6 millimeters (1/4 inch). “At that size, you’ll be in a lot of pain and may need some type of surgical intervention to break the stone or make it smaller to get it out,” says Mehrotra.
Since you can’t tell the size of your stones, how do you know if you should head to the hospital or call your healthcare provider (HCP)? If you experience any of the above symptoms the National Kidney Foundation advises that you seek medical attention as soon as possible to confirm kidney stones are the source and to determine their size and number.
The most likely scenario is that you’ll be sent home with pain medication and instructions to drink a lot of water, says Mehrotra. “Staying hydrated is the most important thing to do in order to propel the stone forward,” she explains. If you’re vomiting or too nauseous to keep water down, you may require intravenous fluids or anti-nausea medication. Healthcare providers can also prescribe medication that relaxes the ureter so the stone can pass more quickly with less pain.
If your stone is small, you're able keep food and water down—and you can stand the pain—you can try passing kidney stones at home. Taking over-the-counter acetaminophen or a nonsteroidal anti-inflammatory drug (NSAID) like ibuprofen can help manage pain, but you should avoid NSAIDs if you have heart disease, hypertension, or a history of kidney disease or damage. Speak to an HCP before taking any new medication.
If you don’t pass kidney stones within two days or you have a fever or chills at any time, seek medical attention, says Mehrotra. “Stones that don’t pass on their own may need surgical intervention and a fever or chills could be a sign of an associated UTI, a potentially life-threatening condition which should be treated right away,” she adds. There are a couple of minimally invasive ways a stone can be removed or broken into smaller pieces, including using shock waves or a laser.
For people with recurrent kidney stones or first-timers who may be at risk for additional stones, tests to help determine whether a condition is causing kidney stones may be in order. Your HCP may also have you strain your urine to recover the stone for analysis or ask you to collect your urine for 24 hours after the kidney stone has passed or been removed. Knowing the composition of the stone or the mineral levels in your urine can help determine what predisposes you to stones and plan treatment or dietary changes to help prevent recurrences.
How to prevent kidney stones
The best way to prevent a kidney stone (or a second or third one) is to drink enough fluid—this will dilute your urine so it’s less concentrated with substances that promote the formation of stones. “Hydration is the biggest factor,” says Mehrotra. “All of the things that can end up in high concentration in urine, like calcium and oxalate, can be managed by drinking more water.”
One meta-analysis found that people who produced 2 to 2.5 liters of urine daily were 50 percent less likely to develop kidney stones than those with less output. (It should be noted: you should always speak with your HCP about how much to drink in a day, as some people have their fluids restricted due to medical conditions.)
Staying hydrated is especially important in the summer, since research shows that as daily temperatures increase, so, too, does the number of patients seeking treatment for kidney stones—likely because higher temps contribute to dehydration. A good rule of thumb is that your urine should appear very light yellow to clear if you’re well hydrated; darker urine is more concentrated.
There are a host of dietary moves you can make to help prevent kidney stones, including:
- Get enough calcium. Don't get confused about “calcium” stones: While 80 to 85 percent of stones are made of calcium, consuming enough of this mineral can help prevent the formation of stones, since calcium binds with oxalate before it gets into the kidneys. The recommended daily amount of calcium for adults is between 1,000 milligrams (mg) and 1,200 mg depending on your sex and age. Ideally, you should obtain calcium from food, since calcium from supplements is linked to kidney stones.
- Limit sodium. Your chance of developing kidney stones increases when you eat more sodium, which is a part of salt. Curb sodium consumption to 1,500 mg a day.
- Eat high-oxalate foods with calcium in the same meal. If you’re calcium oxalate stone prone, this lowers your chances one will form. Oxalate-rich foods include spinach, beets, peanuts, rhubarb, chocolate, and sweet potatoes.
- Try the DASH diet. Designed to prevent and regulate high blood pressure, it's also linked to reduced chances of kidney stones.
To help ensure that your experience with kidney stone pain is a one-time event, it’s important to take precautions. Yet research shows that almost half of kidney stone patients didn’t take prescribed medications and 41 percent didn’t follow the nutritional advice that would keep them from recurring. Lower your risk of stones by being proactive.
