Kidney Stones

What are Kidney Stones?

How do kidney stones form?   From the blood flowing through them, the kidneys produce urine by removing some fluid and certain salts dissolved in that fluid. When concentration levels of dissolved salts reach the point at which the salts no longer dissolve, they precipitate out of solution and become solid again, forming a solid mass of tiny crystals in the kidney's tubal system (nephrons), called a kidney stone.

Kidney stone characteristics.   Size ranges from that of a grain of sand to a golf ball. Depending on their composition, they may be smooth, round, jagged, spiky or asymmetrical.

What effect do they have?

One or more kidney stones can block urine flow through the ureter (carrying urine from the kidney to the bladder) causing severe pain.   Small stones may not be felt, but larger stones moving through the ureter may cause severe pain. A blockage can build up pressure in the kidney causing swelling (hydronephrosis), which over time can damage the kidney. A blockage further down the ureter can cause the muscular ureter to swell (hydroureter) initiating painful spasms,

What salts are in kidney stones?

Calcium stones (calcium phosphate or calcium oxalate)

~80%  of all kidney stones.   Composed of calcium   +    either phosphate or oxalate. 

Possible dietary causes:

• Calcium PHOSPHATE stones:   high levels of phosphate fertilizers used in growing vegetables;
• Calcium OXALATE stones:   beer, black pepper, berries, broccoli, chocolate, spinach and tea.

High blood calcium levels can result from such as:

•  Renal tubular acidosis.   If the kidneys do not effectively eliminate acid, it builds up in the blood. The kidney may be defective or simply overworked by an overly acid-forming diet.

Acid-Alkaline Balance

•  Primary parathyroidism
•  Sarcoidosis
•  Hyperthyroidism
•  Hyperoxaluria
• Some cancers.    E.g. Multiple myeloma (cancer of bone marrow plasma cells)

Struvite Stones

10% of kidney stones

Composed of magnesium ammonium phosphate

Uric acid stones

~5% of kidney stones

Occur mostly in those having chronic infection in the urinary tract (UTI's).   Specifically caused by bacteria that produce urease, which makes urine more alkaline, allowing struvite to precipitate out of urine and form stones.

Occur with increased blood levels of uric acid.   Digestion produces uric acid and if the acid level in the urine is high, the uric acid may not stay dissolved and solid uric acid particles precipitate out in the urine, which can cling together to form a kidney stone.

About 50% of those with uric acid stones have uric acid deposits in other body parts, called gout.    E.g. big toe joint.

Causes of uric acid stones

• Dietary causes.   Today, excess uric acid in the body is most likely due to excess consumption of fructose in sugars, such as in sodas, candies and sweetened foods. Also, uric acid levels are increased by consumption of alcohol (particularly beer and wine) and purine-rich foods, including offal, red meat and shellfish.
• Medical or disease causes.   Include chemotherapy, certain bone marrow disorders over-producing blood cells, and Lesch-Nyhan syndrome (an inherited disorder).

Cystine stones

~2% of kidney stones

People with cystine stones process dietary amino acids abnormally.   E.g. Cystine is an amino acid

Kidney Stone Symptoms

Crampy, spasmodic bouts of severe pain as stones pass into ureter - pain usually begins in the area between the lower ribs and the hip bone. As the stone nears the bladder, the pain often radiates along the inner thigh. Women may feel the pain in the vulva, while men often feel pain in the testicles.

Nausea/vomiting and frequent/painful urination are common - can feel like you are peeing a combination of sharp broken glass and boiling acid!

Fever and chills - usually resulting from obstruction of the ureter, which allows bacteria to become trapped in the kidney and cause a kidney infection (pyelonephritis).

Who gets Kidney Stones?

~600,000 persons in the U.S. develop kidney stones each year

Men are ~4-5 times more likely to develop them than women.    ~10% of men and 5% of women age 30-50 in U.S. suffer from kidney stones, with first episode at age 20-30.

Up to 2/3 of men who have passed one stone will experience a recurrence.   Average of 9 years between episodes

Kidney stones are 4-5 times more common in whites than in African Americans

How to prevent or dissolve kidney stones?

Kidney Stone Treatment

Kidney Stone Prevention