What Are Kidney Stones? 

A kidney stone is a solid mass that forms from substances found in urine. These substances usually dissolve in the urine. When they don’t, or there’s too little fluid, they crystallize and turn into stones. 

The main stone types are calcium, uric acid, struvite, and cystine. Stones also come in different shapes and sizes. They may be smooth or jagged, smaller than a grain of sand or much larger. 

After forming, a kidney stone either stays in the kidney or moves into the urinary tract. Small stones may leave the body through urine. However, larger ones can get stuck in the ureters (tubes that connect the kidneys to the bladder) or urethra (tube that drains your bladder). 

About one in 11 people will ever develop a kidney stone. Many won’t have any symptoms. If the stone blocks urinary flow or causes an infection, it may cause:  

• Sharp pain in your back, side or lower abdomen 
• Blood in your urine that can look red, pink or brown 
• Cloudy or bad-smelling urine 
• Constant need to urinate, painful urination or difficulty urinating 
• Fever or chills 
• Nausea or vomiting 

Diagnosing Kidney Stones 

People without symptoms often discover they have a kidney stone when they have imaging tests for other conditions. If you have symptoms, diagnosis typically involves a review of your medical history and physical exam. 

Your doctor may also order tests, including: 

• Laboratory tests to look for substances in your urine and blood that lead to kidney stones 
• Imaging tests, such as abdominal X-rays or a CT scan, to find kidney stones and measure their size