A kidney stone also referred to as renal stone or renal calculus (plural calculi) is literally a stone that develops in your kidney(s). You can develop more than one stone in one or both kidneys.

There are different types of kidney stones that develop in your urinary tract. Due to their different composition, the etiology and risk factors vary especially in regards to the foods that you eat and contribute to their formation.

Symptoms of these different kinds of stones are the same, but being different in their composition, treatment criteria may vary slightly, though certain management guidelines are common for all.

Usually, kidney stones start to develop in the kidneys. However, they can originate anywhere in the urinary tract such as in the ureters, urinary bladder and the urethra.

They develop as a result of the buildup of crystals and vary in size from a grain of sugar to the size of a ping pong ball or even bigger. It can cause tremendous pain and discomfort to the patient.

Kidney stones are made up of different chemical composition and this forms the basis of classifying them into different types.

Knowing the type of kidney stone is important because it helps you to determine its cause. Once the cause is identified, it gives you clues on how to reduce your risk and prevent recurrence.

When a kidney stone is passed and collected by straining the urine, the stone is sent to the laboratory for analysis to see what is its composition and know the type of stone it is. This information is then useful to make treatment and preventive recommendations.

Types of kidney stones

Not all kidney stones are made up of the same elements. There are five different types of kidney stones, each with a different composition.

Calcium oxalate stones

Kidney stones made of calcium oxalate crystals are the most common. These types of stones are formed when the urine contains low levels of citrate and high levels of calcium and especially oxalate.

Calcium oxalate stones form when there is too much of oxalate filtered from the blood by the kidneys, there is too little of liquid and the oxalate binds to the calcium while the kidneys are filtering blood and forming urine.

The risk of such stones increases in people who have a diet high in proteins, sodium (salt), sugar and foods high in oxalate. Such foods include beets, potato chips, black tea, peanuts, chocolate, nuts, potatoes, and spinach.

Similarly, conditions that increase calcium levels, such as hyperparathyroidism, increase your risk of developing calcium stones. Nevertheless, you must include the recommended calcium in your diet to prevent stones from developing.

Other causes and risk factors that can make you prone to calcium oxalate kidney stones include:

  • ·         Dehydration
  • ·         High doses of vitamin D
  • ·         Obesity
  • ·         Medical conditions like hyperparathyroidism
  • ·         Gastrointestinal conditions like inflammatory bowel disease and ulcerative colitis
  • ·         Gastric bypass surgery

Calcium phosphate stones

Calcium phosphate stones are a type of kidney stones that often occur simultaneously with calcium oxalate stones though they are less common. They can grow faster and larger than the oxalate stones and they end to occur when the urine becomes too alkaline.

They are caused by excess of calcium and phosphate or too little citrate in the urine. They are difficult to prevent and treat.

A high protein diet can increase your risk to the formation of calcium phosphate stones. To reduce your risk of calcium phosphate stones, follow the diet below:

  • Reduce sodium (salt) in your diet
  • Limit animal proteins
  • It is important that you get enough calcium ideally from plant-based foods. It should not be restricted beyond the daily intake requirement. Urinary calcium levels are normal in most  patients with calcium stones. The reason for maintaining adequate calcium intake is that calcium can block other substances such as oxalate in the digestive tract and prevent formation of oxalate crystals.

Calcium phosphate crystals invade kidney tissue and tissue damage is common as in nephrocalcinosis. This is a kidney disorder in which excess of calcium is deposited in the kidneys.

This type of stone is seen more commonly in metabolic conditions, such as renal tubular acidosis. It may also be linked with the use of certain drugs used to treat migraines or seizures, such as topiramate (Topamax, Trokendi XR, Qudexy XR).

Struvite stones

Struvite stones are made of magnesium ammonium phosphate. These types of stones are less common, found mostly in women and caused by bacterial infection in the upper urinary tract that raises urine pH to neutral or alkaline.

These stones tend to grow rapidly and can become so large as to occupy the entire kidney. If left untreated, they can cause recurrent and severe urinary tract infections, urinary obstruction, and renal failure.

Prevention lies in treating an underlying infection promptly. Acetohydroxamic acid (AHA) can reduce urine pH, alkalinity and ammonia levels in the urine and help dissolve these type of stones.

Uric acid stones

Uric acid stones are quite common and seen more in men than in women. There are various causes and risk factors that can give you this type of stones.

Firstly, they tend to occur in people who chronically do not drink sufficient water, or lose water from the body due to chronic diarrhea, or malabsorption.

Other risk factors include:

  • A diet high in animal protein
  • Family history of uric acid stones
  • Genetic factors
  • Presence of gout
  • Undergoing chemotherapy
  • Diabetes
  • Metabolic syndrome

Foods such as organ meats and shellfish have high concentrations of purines. Purines are a natural chemical compound. Eating high purine foods leads to more production of monosodium urate. This predisposes to uric acid stone formation in the kidneys. Therefore, if you are prone, avoid high purine foods and beverages. These include:

  • All types of alcoholic beverages
  • Some fish and shellfish, including anchovies, sardines, herring, mussels, codfish, and trout
  • Some meats, such as bacon, turkey, veal, and organ meats

Secondly, uric acid stones tend to develop when the urine is highly acidic and the purine-rich diet tends to make the urine more acidic.

The treatment of uric acid stones consists of adequate hydration and making the urine alkaline to achieve pH values between 6.2 and 6.8. This can be effectively done with sodium bicarbonate or potassium citrate, which can dissolve the uric acid stones stones that have formed.

Cystine stones

Cystine stones are rare and develop in families who suffer from a hereditary genetic metabolic disorder called cystinurea.

About 1 in 7,000 people worldwide suffer from cystinuria. Studies indicate that cystine stones first develop mostly in people with cystinuria during their twenties or thirties. However, it can affect people in all age groups including children, teens and older adults.

In this disorder, excessive amounts of cystine, an amino acid, collects in the urine. This can lead to the formation of cystine stones in the kidneys, bladder, and ureters.

These stones occur in both men and women who suffer from cystinuria. They tend to reoccur and are larger than other types of stones.

A person with cystine stones has to treat his cystinuria first. This is done by:

  • Maintaining adequate hydration
  • Eating more fruits and vegetables, which makes your urine less acidic
  • Reducing salt in your diet
  • Medication to make the urine less acidic and preventing the crystals from clumping together.

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