Hypercalciuria is the condition of elevated calcium in the urine. Chronic hypercalciuria may lead to impairment of renal function, nephrocalcinosis, and

chronic kidney disease Chronic kidney disease (CKD) is a type of long-term kidney disease, defined by the sustained presence of abnormal kidney function and/or abnormal kidney structure. To meet criteria for CKD, the abnormalities must be present for at least three mo ...

. Patients with hypercalciuria have kidneys that excrete higher levels of

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

than normal, for which there are many possible causes. Calcium may come from one of two paths: through the gut where higher than normal levels of calcium are absorbed by the body or mobilized from stores in the bones. After initial 24 hour urine calcium testing and additional lab testing, a

bone density Bone density, or bone mineral density, is the amount of bone mineral in bone tissue. The concept is of mass of mineral per volume of bone (relating to density in the physics sense), although medicine#Clinical practice, clinically it is measured by ...

scan (DSX) may be performed to determine if the calcium is being obtained from the bones. Hypercalciuria in patients can be due to underlying genetic causes.

Signs and symptoms

There are no clinical signs or symptoms of hypercalciuria itself but elevated calcium in the urine can contribute to accelerated loss of calcium from bone leading to

osteoporosis Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to more porous bone, and consequent increase in Bone fracture, fracture risk. It is the most common reason f ...

. Additionally, hypercalciuria can contribute to

kidney stone Kidney stone disease (known as nephrolithiasis, renal calculus disease, or urolithiasis) is a crystallopathy and occurs when there are too many minerals in the urine and not enough liquid or hydration. This imbalance causes tiny pieces of cr ...

formation which may present with flank or back pain that comes and goes. It can be painful to pass kidney stones and in extreme cases cause kidney damage. Patients that both form kidney stones and have hypercalciuria are at increased risk for bone loss leading to osteoporosis.

Causes

There are a number of causes of hypercalciuria including genetic (idiopathic),

primary hyperparathyroidism Primary hyperparathyroidism (or PHPT) is a medical condition where the parathyroid gland (or a benign tumor within it) produce excess amounts of parathyroid hormone (PTH). The symptoms of the condition relate to the resulting elevated serum calciu ...

, immobilization, pagets disease,

Multiple Myeloma Multiple myeloma (MM), also known as plasma cell myeloma and simply myeloma, is a cancer of plasma cells, a type of white blood cell that normally produces antibody, antibodies. Often, no symptoms are noticed initially. As it progresses, bone ...

, Calcium excess, Vitamin D excess/increased sensitivity, drug-induced hypercalciuria,

sarcoidosis Sarcoidosis (; also known as Besnier–Boeck–Schaumann disease) is a disease involving abnormal collections of White blood cell, inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph n ...

hyperthyroidism Hyperthyroidism is a endocrine disease in which the thyroid gland produces excessive amounts of thyroid hormones. Thyrotoxicosis is a condition that occurs due to elevated levels of thyroid hormones of any cause and therefore includes hyperth ...

Cushing's disease Cushing's disease is one cause of Cushing's syndrome characterised by increased secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary (secondary hypercortisolism). This is most often as a result of a pituitary adenoma (spec ...

, and

renal tubular acidosis Renal tubular acidosis (RTA) is a medical condition that involves an accumulation of acid in the body due to a failure of the kidneys to appropriately acidify the urine. In renal physiology, when blood is filtered by the kidney, the filtrate ...

. Idiopathic hypercalciuria is defined as elevated calcium in the urine without an identifiable cause despite low to normal calcium intake and otherwise normal lab values. In addition to hypercalciuria, these individuals often have associated low bone density. There can be an underlying genetic component that is beyond current genetic testing available. In familial cases it is common that 50% of first degree relatives are affected. Despite a potential genetic component, urine calcium levels can be influenced by dietary items including sodium, protein, and sugars.

Diagnosis

The gold standard to assess for hypercalciuria is 24-hour urine collection to evaluate urine calcium levels over that time period. Normal range is considered 100 to 300 milligrams per day (mg/day) with standard calcium intake. Hypercalciuria is diagnosed when a value over 300 mg/day is identified. Additional laboratory testing is warranted in the setting of hypercalciuria in order to identify a potential underlying cause.

Treatment

Dietary interventions

Patients suffering from low bone density, hypercalciuria, and stone formation should increase daily fluid consumption and focus on a low sodium and low protein diet. Reducing calcium intake to attempt to remedy elevated urine calcium has been shown to further progress bone loss without an effect on urine calcium loss.

Pharmacological interventions

The use of thiazide diuretics has been effective in reducing urine calcium loss and has an activating effect on bone forming cells. Potassium citrate in conjunction with thiazide diuretics is another medication that has been shown to have a positive impact on bone formation but also decrease the crystallization of calcium based stones in the kidneys. Other drugs are used to treat osteoporosis, including bisphosphonates, but have not been shown to have an effect on urine calcium levels.

References

External links

{{Authority control Abnormal clinical and laboratory findings for urine Calcium Inborn errors of metal metabolism