Kidney stones (nephrolithiasis) are hard deposits formed from crystallized minerals and salts within the kidney. While historically an adult issue, these painful formations are becoming more common in adolescents, with incidence rates rising sharply in the last two decades. Stones typically form when the urine contains too much of crystal-forming substances (like calcium, oxalate, or uric acid) or lacks enough liquid to prevent crystallization. The factors leading to this mineral imbalance in teens are complex, involving modern lifestyle choices, genetic predispositions, and other health issues.
Unhealthy Diet and Low Fluid Consumption
The most common and modifiable factors contributing to kidney stone formation in teens are related to diet and inadequate fluid intake. Dehydration leads to highly concentrated urine, which dramatically increases the risk of stone formation. Many adolescents do not drink enough plain water, often choosing instead to consume high volumes of sugary sodas and sports drinks that further exacerbate the problem.
High sodium intake, often from processed foods and fast food, is another major contributor to stone risk. When the kidneys work to excrete excess salt, they also increase the amount of calcium released into the urine. This excess urinary calcium then readily combines with other waste products like oxalate to form the most common type of stone, calcium oxalate. Limiting salt is a straightforward strategy for reducing the amount of calcium the body excretes.
Sugary drinks, especially those containing high-fructose corn syrup, also directly promote stone formation. Fructose consumption can increase the absorption and excretion of both calcium and uric acid, leading to a urine chemistry that is ripe for crystallization. The modern diet, which is typically low in stone-inhibiting elements like potassium from fruits and vegetables, creates an environment where stone-forming minerals can easily precipitate.
Genetic and Inherited Risk Factors
While lifestyle factors are prominent, many teenagers who develop kidney stones have an underlying genetic or inherited predisposition that makes them more susceptible. Having a close family member who has had kidney stones significantly increases a teen’s individual risk. These intrinsic factors often cause the body to excrete high concentrations of stone-forming substances regardless of dietary choices.
Hypercalciuria
One of the most frequent inherited metabolic abnormalities is hypercalciuria, characterized by excessive calcium in the urine. The excess calcium can be due to increased absorption from the gut, a defect in the kidney’s ability to reabsorb calcium, or increased calcium release from bone. Hypercalciuria is the prevailing abnormality found in children with an identifiable metabolic cause for their calcium stones.
Rare Genetic Disorders
A rarer but more severe genetic disorder is cystinuria, a condition where the kidneys cannot properly reabsorb the amino acid cystine. Cystine is relatively insoluble at normal urine pH, and its excess concentration leads to the formation of hard cystine stones. Individuals with cystinuria often begin forming stones in childhood and frequently experience recurrence. Primary hyperoxaluria is another group of rare genetic metabolic disorders where the liver produces excessive amounts of oxalate, a precursor to the most common stone type. This overproduction is due to a deficient liver enzyme, which forces the body to excrete massive amounts of oxalate through the kidneys. The resulting high levels of urinary oxalate combine readily with calcium to form stones, often leading to severe and recurrent stone disease.
Contributing Health Issues and Prescription Drugs
Certain medical conditions and necessary medications can unintentionally alter urine chemistry.
Gastrointestinal Disorders
Gastrointestinal disorders like Crohn’s disease or ulcerative colitis can lead to increased stone risk. These conditions cause malabsorption of fat, which then binds to calcium in the gut. This leaves free oxalate to be excessively absorbed and excreted by the kidneys.
Urinary Tract Infections (UTIs)
Chronic or recurrent UTIs are a cause, particularly for the formation of struvite stones. Certain types of bacteria can produce an enzyme called urease, which raises the urine’s pH and creates an environment where struvite crystals readily precipitate. These “infection stones” can grow rapidly and sometimes become quite large.
Prescription Medications
Specific prescription drugs can also increase a teenager’s likelihood of developing stones. Certain medications used to treat conditions such as seizures, like Topiramate, can change the acidity of the urine, which favors the formation of specific stone types. Additionally, some antibiotics, including sulfas and cephalosporins, have been linked to an increased risk of kidney stones.