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Understanding Kidney Stones

What Are Kidney Stones?

Kidney Stones

Kidney stones are small, hard crystals or deposits that form inside your kidneys when salts and other minerals in your urine bond together. Stones often vary in shape and size, with some growing to be quite large.

Some stones stay in the kidneys causing little to no symptoms, and others may pass through the urinary tract, causing painful symptoms as the deposit move down the ureter (the thin tube that leads to the bladder). Some people are able to pass the stone without surgical intervention, but in some cases, surgery to remove the stone may be necessary.

4 Types of Kidney Stones

Kidney stones are common - affecting upwards of 500,000 men and women every year in the U.S. according to the American Urological Association. They come in all shapes and sizes, ranging from a grain of sand to a golf ball.

Anyone who has experienced a large kidney stone knows the severe pain that can come along with one, but did you know there are different types of stones?

  1. Calcium-oxalate stones - These are the most common type of kidney stone and is typically caused by foods with salt or oxalates (byproducts of certain foods), certain medications and even your genetics.
  2. Struvite stones - These affect women more than men. These stones can grow to be very large and may occur with a kidney infection. Surgical removal of these stones is often indicated.
  3. Uric acid stones - These stones are made of uric acid, a waste product that is passed out of the body through the urine. They may be caused by eating too much animal protein such as red meat and are more common in people with conditions such as gout and inflammatory bowel disease.
  4. Cystine stones - These are very rare, caused by a genetic kidney disease called cystinuria.

Symptoms of Kidney Stones

Symptoms of kidney stones range from little to no pain to extreme pain and discomfort, depending on the size of the stone(s). Very small kidney stones may cause no symptoms at all and small or medium sized stones can cause minor pain. Very large stones can result in severe pain that may land you in the emergency department.

When a kidney stone has passed into the urinary tract, symptoms may include:

  • Severe pain, usually located in the side or the back; pain may spread to the abdomen and the groin area as well
  • Urinary symptoms such as painful urination, urinary urge, and frequent need to urinate
  • Blood in the urine and/or foul smelling urine
  • Nausea and/or vomiting
  • Fever, if the stone has caused an infection

Diagnosing a Kidney Stone

Kidney Stone

Patients who present with symptoms of a kidney stone either in their doctor's office or in the emergency department (due to extreme pain from a large stone) will have one of several diagnostic tests performed to confirm the diagnosis. For large kidney stones, tests most commonly performed include: CT scan, Ultrasound or plain radiography.

Who Is at Risk for Developing Kidney Stones?

While anyone can produce kidney stones, certain people are more at risk for developing stones than others. Causes and risk factors for kidney stones include:

  • A family history of stone disease, especially in first degree relatives.
  • Dehydration - Lack of fluids can cause salts and other minerals in the urine to stick together to cause kidney stones.
  • Certain diets - Diets high in protein, salt, oxalates (such as spinach, chocolate, nuts), excess vitamin C or D can increase your risk of developing kidney stones.
  • Certain medical conditions - Gastric conditions such as inflammatory bowel disease, Crohn's disease and chronic diarrhea affect the way the body absorbs water, calcium and oxalates, which increases levels of stone-forming substances in the urine.
  • Metabolic diseases (such as hyperparathyroidism or gout).
  • Obesity has been linked to higher incidences of stone formation.

Metabolic Disorders that Cause Kidney Stones

It’s important to identify the reason why your body makes kidney stones so you can learn how to prevent future stones from forming. Once your acute stone episode has passed or after you have healed from your procedure(s), your provider will shift focus to stone prevention.

In some cases, the underlying cause of your stone disease (called a metabolic disorder) can be completely treated and your risk of recurrent stones eliminated.

In most cases, stone disease cannot be cured; but recurrence can be greatly reduced if you follow a well designed stone prevention plan.

A patient-specific stone prevention plan will be developed once you complete the recommended testing. Testing usually consists of an at home 24-hour urine collection and specialized blood tests.

Common metabolic disorders include:

  • Hypercalciuria—Elevated calcium in the urine. This is NOT caused by consuming a normal calcium diet. Testing will reveal the underlying disorder as there are several causes.
  • Hyperoxaluria—Elevated oxalates in the urine. This is generally caused by consuming foods high in oxalates. Oxalates are found in foods such as spinach, peanuts, and some teas. Patients who have bowel disease (such as Crohn’s disease or ulcerative colitis) and also patients who have undergone gastric bypass surgery are especially at risk.
  • Hypocitraturia—Low levels of citrate in the urine. Citrate is also known as citric acid and is the most potent known stone inhibitor that prevents the formation of crystals in the urine. Citrate is found in high concentrations in citrus fruits such as lemons and oranges. Some patients have low levels of citrate in their urine that may need medication or supplements to adequately treat.
  • Gouty diathesis—Uric acid stones. These stones generally form due to acidic urine. This disorder has been associated with gout; however, the disorder that causes kidney stones is distinct. This is a curable form of stone disease and treatment focuses on alkalinizing the urine (minimizing the acidity of the urine).

Dietary Risks for Kidney Stones

  • Over-consumption of salt— This leads to elevated levels of calcium in the urine.
  • Under-consumption of magnesium— Magnesium is another potent stone inhibitor.
  • Over-consumption of proteins— Once thought to be primarily linked to red meat, over-consumption of any protein can lead to an environment in the kidney that promotes the formation of stones.