Calcium Phosphate Kidney Stones – Causes

Causes & Reasons for Calcium Phosphate Kidney Stones 

Concretion of mineral salts occurring in the kidneys lead to renal stone disease.  Also known as nephrolithiasis in medical lingo, they originate as microscopic crystals developing into stones over a period of time.

The kidneys are filtering organs of the human system.  They generally perform the function of removing waste mineral matters from the circulatory system and adding them to the urine secreted by the kidneys.  Urine should contain more of water molecules and this depends largely on the amount of water consumed by the individual.  This is because the water present in urine will successfully dissolve the mineral elements, depriving their power of turning into crystals.  However, in the absence of sufficient water molecules, this ultimately will provide a favorable condition within for the development of kidney stones.

Normally urine will contain stone inhibitors like citrates, magnesium, pyrophosphates that will prevent the formation of crystals.  But when dehydration sets in a body, with minimal soluble actions of water, even these inhibitors will fail to stop stone development within the kidneys; especially so, if high levels of calcium, uric acid, or cystine persists in urine.

Usually kidney stones are either of calcium, uric acid, cystine, or struvite types.  Of these, calcium stone is the popular type which again may be of calcium oxalate or calcium phosphate form.  The less common form is the calcium phosphate type with calcium oxalates being more popularly encountered.


Both forms of calcium stones occur when high calcium compounds are found coursing through the bloodstream.  The kidneys are constantly filtering out these calcium elements, which eventually get deposited in urine, thereby increasing urinary calcium levels as well.  Now how does the calcium level increase within, one may wonder?  There are several disease conditions that contribute to this condition, the foremost beings hyperparathyroidism.  Parathyroid is an endocrine gland secreting hormones that help in calcium metabolism.  When there is increased secretion of these hormones, it removes calcium from the bones, causing low calcium in bones and more in the blood and urine.

A high calcium diet may also cause high urinary calcium levels.  Though it is assumed that dietary calcium is well absorbed by the body, the fact remains that only a certain amount on a daily basis is required.  Thus, if calcium intake continues even after the body’s requirement is met, this will eventually spill into the urinary system, increasing their level in urine.

Also gastrointestinal disorders that cause increased intestinal calcium absorption are known to bring about this kidney stone condition.

Renal tubular acidosis is a condition wherein the acid levels in the body increases.  This increase is due to the kidneys failure to filter out acidic equivalent properties from the blood, leading to poor urinary acidification.  The failure may be due to several reasons, but calcium phosphate kidney stones demonstrate an inclination toward increasing its formation in alkaline urine.  Hence, when calcium levels are high and urine pH levels are also high, then there is a higher risk for an individual to develop calcium phosphate crystals.

Bacteria causing urinary infections are also known to alkalinize urine to great levels.  So, a urinary tract infection along with high urinary calcium levels may also be considered as a causative factor for calcium phosphate renal calculus.