Why are kidney stones so painful?

Intermountain Healthcare
A kidney stone forms if chemicals concentrated in your urine form a crystal in your kidney, and the crystal grows over time. It's not always clear why this happens. A stone isn't usually painful while it's still in your kidney.

When the stone leaves your kidney, it travels down your ureter so it can leave your body. Some stones are tiny and pass through without causing symptoms. But because the ureter is such a small tube (about 1/8 of an inch wide), a kidney stone can get stuck and block the ureter. If this happens, urine backs up and flows back to the kidney.

The pressure on the kidney caused by the backflow of urine -- combined with spasms in the ureter as your body tries to clear the stone -- can cause intense pressure and pain in the lower back, side, groin or all three. In fact, kidney stone pain is one of the most severe types of pain physicians treat. Kidney stones can also cause sweating, nausea, and vomiting. You might see blood in your urine. And if the stone causes an infection, you can experience fever and chills.

Once the stone passes out of your ureter and into your bladder, you usually don't have any problem passing it the rest of the way out of your body. The urethra is at least twice as wide as the normal ureter, so the stone doesn't usually block it.

Continue Learning about Kidney Stones

Kidney Stones

Referred to as "silent stones," kidney stones often do not cause any symptoms. The first indication of a kidney stone is often a sudden feeling of extreme pain as the stone blocks the flow of urine. Kidney stones are one of the mo...

st painful urologic disorders and one of the most common disorders of the urinary tract.Most kidney stones - which are hardened masses that develop from crystals that separate from the urine in the urinary tract - are passed out of the body without surgical intervention by a doctor. A less common type of kidney stone, called a struvite or infection stone, is caused by infection in the urinary tract. Doctors are not always able to diagnose the cause of a kidney stone, which is why it's important to learn how to prevent them in the fist place. A person who has had a kidney stone in the past may likely form another one.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.