Kidney stones

Synonyms: Renal calculus, Urinary calculus

Medical Specialties: Emergency medicine, Family practice, Urology

Clinical Definition

Kidney stones, or renal calculi, are small, hard ''rocks'' that form when chemicals in urine become so concentrated they form solid crystals. If the stones become large, they can lodge in the urinary tract, leading to blockage, infection and severe pain. Most people affected have a chemical blood abnormality or a urine abnormality that contributes to stone formation.  

In Our Own Words

Kidney stones, hard crystals formed from urinary chemicals and waste, are an all-too common reason for an emergency room visit. The pain may be minor for some individuals, but it can also be excruciating. Abnormal levels of substances in the urine or in the blood are the cause of some kidney stones. Those who drink inadequate amounts of water are susceptible to them.  In fact, people who have undergone surgery for weight loss may also be more prone to certain types of stones.

Unfortunately, having kidney stones increases the risk of getting them again, and also increases the risk of developing chronic kidney disease from urinary obstruction. When a stone forms, a person can sometimes pass it in the urine. If that is not possible, treatment to remove or crush them may be needed.

Relevant Conditions
  • Urinary obstruction
  • Kidney disease
  • Gastric bypass, bariatric surgery
Common Types
  • Calcium
  • Struvite
  • Uric acid
  • Cystine
Side Effects
  • Severe flank pain (lower back, on either side)
  • Blood in urine
  • Nausea, vomiting
  • Fever, chills
  • Fever, chills
Share this article
  • Cleveland Clinic. "Kidney Stones." Urology 2013. Accessed Aug. 2013.
  • Harvard Medical School. "Six ways to keep kidney stones at bay" 2012. Accessed Aug. 2013.
  • National Kidney Foundation. "Kidney Stones" 2013. Accessed Aug. 2013.
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