Kidney Stone Disease

Kidney stones (calculi) are hardened mineral deposits that form in the kidney. They originate as microscopic particles or crystals and develop into stones over time. The medical term for this condition is nephrolithiasis, or renal stone disease.

The kidneys filter waste products from the blood and add them to the urine that the kidneys produce. When waste materials in the urine do not dissolve completely, crystals and kidney stones may form.

Stones may pass out of the kidney, become lodged in the tube that carries urine from the kidney to the bladder (ureter), and cause severe, excrutiating pain that begins in the lower back and radiates to the groin. A lodged stone can block the flow of urine, causing pressure to build in the affected ureter and kidney. Increased pressure results in stretching and spasm, which cause the severe pain.

Causes and Risk Factors for Kidney Stones

Several factors increase the risk for developing kidney stones, including inadequate fluid intake and dehydration, reduced urinary volume, certain chemical levels in the urine that are too high (e.g., calcium, oxalate, uric acid) or too low (magnesium, citrate), and several medical conditions such as reflux, medullary sponge kidney, renal tubular acidosis and urinary tract infections (UTIs). Anything that blocks or reduces the flow of urine (e.g., urinary obstruction, genetic abnormalities) also increases the risk.

Chemical risk factors include high levels of the following in the urine:

• Calcium (hypercalciuria)
  
• Cystine (cystinuria; caused by a genetic disorder)
  
• Oxalate (hyperoxaluria)
  

Signs and Symptoms of Kidney Stones

Small, smooth kidney stones may remain in the kidney or pass without causing pain (called "silent" stones). Stones that lodge in the tube that carries urine from the kidneys to the bladder (ureter) cause the urinary system to spasm and produce pain. The pain is unrelated to the size of the stone and often radiates from the lower back to the side or groin.

A "small" stone (usually 4 mm in diameter or less) has a 90% chance of spontaneous passage. Stones that are 8 mm in diameter or larger usually require medical intervention.

Other symptoms of kidney stones may include the following:

• Blood in the urine (hematuria)
  
• Increased frequency of urination (urinary urgency)
  
• Nausea and vomiting
  
• Pain during urination (stinging, burning)
  
• Tenderness in the abdomen and kidney region
  
• Urinary tract infection (UTI; fever, chills, loss of appetite)
  

Kidney stone complications include kidney damage and scarring, decreased kidney function, obstruction of the ureter, recurrent stones and infections, and renal colic (severe pain that radiates from the kidney region to the abdomen and groin).

If you would like more information on this topic, please contact us.

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