Kidney Stones

• Kidney Stones Overview
• Kidney Stones Causes
• Kidney Stones Symptoms
• When to Seek Medical Care
• Exams and Tests
• Kidney Stones Treatment
• Self-Care at Home
• Medical Treatment
• Next Steps
• Follow-up
• Prevention
• Outlook
• Synonyms and Keywords
• Authors and Editors
• Related Kidney Stones articles:
  Kidney stones - on WebMD
  Kidney stones - on MedicineNet

Kidney Stones Overview

The kidney acts as a filter for blood, removing waste products from the body and helping regulate the levels of chemicals important for body function. The urine drains from the kidney into the bladder through a narrow tube called the ureter. When the bladder fills and there is an urge to urinate, the bladder empties through the urethra, a much wider tube than the urethra.

In some people, the urine chemicals crystallize and form the beginning, or a nidus, of a kidney stone. These stones are very tiny when they form, smaller than a grain of sand, but gradually they can grow to a quarter inch or larger. The size of the stone doesn't matter as much as where it is located.

When the stone sits in the kidney, it rarely causes problems, but should it fall into the ureter, it acts like a dam. The kidney continues to function and make urine, which backs up behind the stone, stretching the kidney. This pressure build up causes the pain of a kidney stone, but it also helps push the stone along the course of the ureter. When the stone enters the bladder, the obstruction in the ureter is relieved and the symptoms of a kidney stone are resolved.