Risk factors associated with calcium oxalate kidney stone and crystal formation
Hypercalciuria
Approximately 80 percent of all calcium oxalate stones are composed predominantly of calcium compounds. The most common cause of calcium crystal production is excess calcium in the urine (hypercalciuria). Extra calcium is normally removed from the blood by the kidneys and excreted in the urine. In hypercalciuria, excess calcium builds up in the kidneys and urine, where it combines with other waste products to form calcium oxalate stones.
Low levels of urinary citrate, magnesium and high levels of oxalate and sodium along with inadequate urinary volume contribute to calcium crystal formation.
Calcium oxalate stones are composed of calcium that is chemically bound to oxalate (calcium oxalate) or phosphate (calcium phosphate). Of these, calcium oxalate is much more common. The less common calcium phosphate crystals typically occur in patients with metabolic or hormonal disorders such as hyperparathyroidism and renal tubular acidosis.
Increased intestinal absorption of calcium (absorptive hypercalciuria), excessive hormone levels (hyperparathyroidism, hypervitaminosis D), and renal calcium leak (kidney defect that causes excessive calcium to enter the urine) can all cause hypercalciuria.
Prolonged inactivity also increases urinary calcium and may cause calcium oxalate stones. (This is why astronauts in space tend to lose bone mass and form calcium oxalate crystals.)
Renal tubular acidosis
Renal tubular acidosis (inherited condition in which the kidneys are unable to excrete acid) significantly reduces urinary citrate (a natural urinary antacid) as well as total urinary acid levels and can lead to stone formation, usually calcium phosphate.
Substances exist normally in urine that can prevent calcium oxalate crystals from developing. Magnesium, citrate, pyrophosphate and other enzymes all act in the body as a deterrent to crystals forming and attaching to the surface of kidney tubes. Having too little of these substances present in urine can trigger calcium oxalate stones.
Medications and Drugs
Certain medications such as calcium-containing antacids, loop diuretics and glucocorticoids can increase calcium secretion into the urine. Too much vitamin D can also lead to increased calcium.
Hyperparathyroidism
Hyperparathyroidism occurs when too much parathyroid hormone is produced by the body, causing calcium to be pulled from the bones into the blood and subsequently into the urine. This helps to explain the association between calcium oxalate stones and low bone density.
Kidney Disease
Kidney disease can cause high calcium levels in the urine when calcium is not properly absorbed back into the bloodstream.
High Blood Pressure and Obesity
High blood pressure and obesity have also been associated with hypercalciuria.
Genetics
Some people are born with a genetic tendency to secrete excess oxalate into the urine. This condition, hyperoxaluria, is rare; most cases of hyperoxaluria arise from other causes. For one, diets rich in oxalate may place someone at risk for calcium oxalate stones. Oxalate-rich foods include beets, chocolate, nuts, rhubarb, spinach, strawberries, tea and wheat bran. Excessive amounts of vitamin C can also increase oxalate levels, as can inflammatory bowel disease.
Protein Levels
High amounts of dietary protein can lead to increases in both calcium and oxalate levels in the urine. The elevated protein results in lower urine pH — an acidic environment that makes it easier for calcium oxalate crystals to form. It also decreases citrate levels in the urine that help prevent calcium oxalate stones from forming. The risks of kidney crystal formation can often be minimized by paying close attention to diet and good hydration.
Lifestyle factors associated with calcium oxalate stone formation
Exercise
Exercising too much or too little can help lead to calcium oxalate crystals. If you exercise extensively, you must replenish the liquid that you lost through perspiration and evaporation. If you exercise too little and have a sedentary life, the inactivity, and often resulting weight gain, can lead to a higher chance of getting calcium oxalate stones.
Without proper hydration, exercise can contribute to kidney calcium oxalate stones
According to recent studies, being obese or gaining weight may increase the risk of developing calcium oxalate crystals. Researchers found women who weighed more than 220 pounds were 90% more likely to develop calcium oxalate crystals than those who weighed less than 150 pounds.
Men and women who gained more than 35 pounds since they were 21 years old also had a 39% to 82% higher risk of calcium oxalate crystals. Prolonged inactivity increases urinary calcium. (This is why astronauts in space tend to lose bone mass and form calcium oxalate crystals.)]
Stomach Bypass Surgery
Stomach bypass surgery increases the risk of developing crystals. Some studies with the highest level of evidence, performed in non-stone forming patients before and after bypass surgery, cite a number of crystal risk factors, including a 25% increase in urinary oxalate, a 30% decrease in urinary citrate, and reduction in urine volume by half a liter. All these risk factors can lead to kidney stone crystal formation in the kidney.
Other Factors
Sometimes, the underlying cause is a metabolic disorder or kidney disease and certain drugs such as Lasix (furosemide), Topomax (topiramate), and Xenical (orlistat), can also promote calcium oxalate crystals.
Many times, it is a combination of factors that creates an environment favorable to crystal and stone formation but often diet intake is one of the leading causes of stones forming.
Other factors associated with calcium oxalate kidney stone formation
Common diseases and conditions that can cause kidney stones
It is important to know that calcium oxalate stones are more common if you have Inflammatory Bowel Disease (IBD), Ulcerative Colitis or Crohn’s Disease. These conditions affect your body’s ability to absorb fats properly. When fat is not absorbed the right way, the fat binds to calcium and leaves oxalate behind. The oxalate is then absorbed and taken to the kidney, where it can form calcium oxalate crystals.
Similarly, following gastric bypass surgery, your body absorbs less calcium from your digestive system. Because of this, higher levels of oxalate are found in the urinary tract. The build-up of oxalate can form crystals, which can form calcium oxalate stones.
Urinary infections can lead to developing struvite crystals. Struvite crystals can happen when you have certain types of urinary tract infections in which bacteria make ammonia that builds up in your urine. Struvite crystals are made of magnesium, ammonium and phosphate. These crystals can grow quickly and become quite large, sometimes with few symptoms or little warning.
Other diseases and conditions that can cause stones
Other diseases such as Dent (a rare genetic disorder that affects the kidneys) and Hyperparathyroidism (a very high amount of a type of hormone called parathyroid hormone in the blood that causes a loss of calcium… calcium is needed to bind with oxalate and leave the body) can cause calcium oxalate crystals.
Family history and genetics might also be a factor for some people in getting calcium oxalate crystals.
