Hypercalciuria is characterized by excessive calcium in the urine. This imbalance often impacts bone health and is a common factor in kidney stone formation. Recognizing this condition is important because it frequently develops without noticeable symptoms, making early awareness and diagnosis valuable.
Understanding Hypercalciuria
Hypercalciuria is the excretion of higher-than-normal levels of calcium in the urine. For adults, this means excreting over 250 milligrams of calcium daily for women or over 300 milligrams for men. Another measure used is over 4 milligrams of calcium per kilogram of body weight daily, useful in pediatric cases.
Calcium plays a role in various bodily functions, including nerve transmission, muscle contraction, and maintaining strong bones and teeth. The kidneys are important for maintaining the body’s calcium balance, filtering calcium from the blood and reabsorbing most of it back into the bloodstream. When this balance is disrupted, hypercalciuria can develop due to increased calcium absorption from the gut, increased release from bones, or reduced kidney reabsorption.
Identifying the Causes
Many factors can contribute to hypercalciuria, from dietary habits to medical conditions and genetic predispositions. A high intake of sodium can increase calcium excretion. Excessive animal protein or high doses of vitamin D supplements can also contribute.
Underlying medical conditions are associated with hypercalciuria. Primary hyperparathyroidism, where the parathyroid glands produce too much parathyroid hormone, can lead to increased calcium. Other conditions like sarcoidosis, certain cancers affecting bone, and renal tubular acidosis can also cause hypercalciuria. Certain medications, such as loop diuretics and high doses of thyroid hormone, can increase urinary calcium excretion.
Hypercalciuria can have a genetic component. However, many cases are classified as idiopathic hypercalciuria, meaning no specific underlying cause is identified. This is the most common type and is often linked to calcium kidney stone formation.
Symptoms and Diagnosis
Hypercalciuria often has no direct symptoms. Its presence is discovered through complications like kidney stones. Kidney stone symptoms include severe pain in the flank or back, blood in the urine, nausea, vomiting, and recurrent UTIs.
Over time, chronic hypercalciuria can contribute to reduced bone density, leading to osteopenia or osteoporosis, which increases fracture risk. Rarely, individuals might experience increased urination, known as polyuria.
Diagnosing hypercalciuria begins with suspicion based on recurrent kidney stones. The primary diagnostic tool is a 24-hour urine collection, which measures the total amount of calcium excreted over a full day. Blood tests evaluate serum calcium, parathyroid hormone (PTH), vitamin D levels, and kidney function to identify underlying causes. Imaging techniques, such as ultrasound or CT scans, may detect kidney stones.
Treatment and Prevention
Managing hypercalciuria focuses on preventing complications like kidney stones and preserving bone health. Dietary adjustments are a first step. Increasing fluid intake, especially water, helps dilute urine and reduce stone-forming substances. Reducing sodium intake and moderating animal protein consumption can decrease urinary calcium excretion. Adequate but not excessive dietary calcium intake is advised for bone health.
Medications are prescribed when dietary changes are not sufficient. Thiazide diuretics, such as hydrochlorothiazide or chlorthalidone, are used because they reduce calcium excreted. Potassium citrate may be given to prevent stone formation by making the urine less acidic, which inhibits calcium crystal growth. In severe cases with significant bone loss, bisphosphonates might be considered, though their use primarily targets bone density rather than directly reducing urinary calcium.
If an underlying medical condition, such as hyperparathyroidism, is identified as the cause, treating that specific condition is important. Regular follow-up appointments and repeat 24-hour urine tests are needed to monitor treatment effectiveness and make adjustments. This ongoing monitoring ensures urinary calcium levels remain within a healthy range, minimizing complications.