Types of kidney stones

Types of kidney stones

The underlying cause of kidney stone formation is directly related to its type. The two go hand-in-hand and once identified, enable a doctor to treat these effectively and implement measures for prevention down the line.

The most commonly occurring type of kidney stone consists of calcium and either phosphate (an inorganic chemical, as well as a salt-forming anion of phosphoric acid) or oxalate substances. Other types can include substances such as uric acid, amino acid cysteine and magnesium ammonium phosphate.

Types of kidney stones can be broken down as follows:

  • Calcium stones: These kidney stones usually occur as a direct result of substance intake via foods consumed. The most common variations of calcium stones are made up of calcium oxalate which are natural substances found in foods, but are also produced in the body by the liver. Fruits, vegetables (spinach and beets), nuts (peanuts) and even chocolate contain high levels of oxalate. These stones can also occur as a result of excessive quantities of vitamin D in the system, or following an intestinal bypass surgical procedure as calcium absorption from the gut has been shown to be increased in these circumstances. Metabolic disorders also influence concentration levels of calcium and oxalate in urine. Calcium phosphate stones occur more frequently in those with metabolic conditions, as well as those taking certain anti-seizure medications such as Topamax (topiramate) for the treatment of migraine headaches.
  • Struvite stones: Infections, such as a urinary tract or kidney infection can result in the formation of struvite stones. This variation typically grows quickly, often without much warning or obvious symptoms, and can become fairly large (causing urinary tract obstructions).
  • Uric acid stones: A lack of hydration or instances where more fluid is lost than is replenished (often due to excess or strenuous exercise) can lead to the formation or uric acid stones, making urine excessively acidic as well. A diet that is high in protein (meat, fish and shellfish) or purines (colourless substance in animal proteins) can raise acidity levels and cause these kidney stones. Certain genetic factors, conditions such as gout, or receiving chemotherapy treatment for cancer can result in the formation of these kidney stones.
  • Cystine stones: Hereditary disorders and conditions (such as cystinuria) which prompt the kidneys to excrete excessive amounts of the amino acid cysteine, result in the formation of these kidney stones as cystine (which forms when two cysteine molecules bind together) leaks from the kidneys into urine. The variation is the least common type of kidney stone which can develop.

What are staghorn calculi?

Kidney stones which grow considerably large and virtually fill the kidney collecting system, resembling antlers, are known as staghorn calculi. These types of kidney stones are normally a composite of carbonate, apatite and struvite, and typically occur due to recurrent urinary tract infections (UTIs). Bacteria that occurs as a result of such infections produces ammonia, which primes chemicals in urine to form kidney stones.

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