Kidney stones affect 5-10% of the developed world’s population. They are exactly the entities they are named after, stones that can form in your kidneys or anywhere in your urinary tract.
Many of us know that kidney stones can be excruciating. However, many of us have no idea how these stones are formed and why they form there? Let’s dig deep to find the answer to one of the web’s most searched questions.
What are the causes of kidney stones?
To find out why kidneys can suddenly start forming rocks, let’s review the human anatomy. Each of the kidneys is made up of 2 million functional units called nephrons. These nephrons are tasked with the removal of waste products, metabolites, electrolytes, and water. These ingredients are filtered by the nephrons and eventually transported back to the blood or discarded into urine as per the body’s need.
To date, there is no exact single cause of kidney stones. Stones can arise due to the cumulative effects of many contributing factors over time. We call such a disease a multi-factorial disease. We know that except for the few complex causes, one of the 4 mentioned horsemen of filtration in the kidneys, i.e., water, electrolytes, waste products, and metabolites, is directly or indirectly responsible for causing kidney stones.
Risk factors of kidney stones:
Several risk factors predispose to stone formation, also known as Urolithiasis in the kidneys. Two of the most common risk factors are family history and genetics. In other words, people who have family members suffering from stones are more likely to develop stones too.
Genetics plays a similar factorial role. Specific inborn errors of metabolism or enzyme deficiencies can lead to the formation of kidney stones. Similarly, people with genetically high calcium and uric levels in their blood are also at risk of developing kidney stones. Even basic genetic traits such as low urine pH, normal bacterial flora, and tendency to reserve extra water may become critical predisposing factors of kidney stones.
Other risk factors include diet, water intake, obesity, certain inflammatory diseases of the digestive tract, and pre-existing diseases of the kidneys or other organs.
Types of stones and their causes:
The actual causes of kidney stones are vast. We can categorize them with each type of stone. The four most common types of kidney stones are
- Calcium Stones
Calcium stones are the most common type of kidney stones seen in patients. These can either be calcium phosphate stones. Calcium stones can arise in a variety of conditions. High sodium in the blood can lead to excess calcium exchange in the renal tubules, leading to mineralization.
Diet rich in yogurt and tomatoes may cause less water intake and allow calcium salts to supersaturate in the tubules leading to stone formation. Apart from these dietary causes, underlying diseases such as hyperparathyroidism, bone diseases, can lead to kidney stones.
2. Struvite Stones
Struvites stones are big, multi-headed stones formed of magnesium ammonium phosphate. These stones can grow big enough to occupy the entire renal pelvis, earning themselves the name staghorn calculi. Struvites, owning to their size and sharp shape, usually manifest as hematuria or blood or blood in the urine. These stones typically arise during or after a bacterial infection.
Certain bacteria can break down urea into nitrogen that can increase the pH of the urine. This alkaline urine can make them cause the precipitation of struvite stones.
3. Uric acid Stones
These almost always arise in patients with high uric acid levels, either in their blood or urine. Frequent intake of a protein-rich diet can lead to high blood uric acid levels. If sustained, this can lead to uric acid stone formation.
Similarly, some drugs like probenecid can increase the risk of uric acid stones as well. Any medicine or diet that lowers urine pH below 5.5 can also contribute to uric acid stones in the kidney. Unlike calcium and struvite stones, which are big and radio-opaque, meaning they seem white on an x-ray, uric acid stones are radiolucent and crystalline.
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4. Cysteine Stones
These stones are almost always associated with an inborn error of reabsorption called Cystinuria. In this condition, the body is missing a transporter to carry the protein Cysteine leading to a buildup in the filtered urine.
Excess filtered cysteine can accumulate and form crystalline cysteine stones that are recurrent and do not respond well to surgery. Like uric acid stones, these stones form at low urinary pH, so conditions like metabolic acidosis can exacerbate it.
Keep in mind that all four stones have a specific pH and arise in exquisite circumstances. Although kidney stones can complicate your health and cause pain, they are also good indicators of your underlying health.
Keep a balance diet, drink enough water, cut down meat consumption once a while, and you will be fine.