Hyperphosphatemia is an electrolyte disorder in which there is an elevated level of

phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...

in the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...

. Most people have no symptoms while others develop calcium deposits in the soft tissue. The disorder is often accompanied by low calcium blood levels, which can result in muscle spasms. Causes include kidney failure, pseudohypoparathyroidism, hypoparathyroidism, diabetic ketoacidosis, tumor lysis syndrome, and rhabdomyolysis. Diagnosis is generally based on a blood phosphate level exceeding 1.46 mmol/L (4.5 mg/dL). Levels may appear falsely elevated with high blood lipid levels, high blood protein levels, or high blood bilirubin levels. Treatment may include a phosphate low diet and antacids like

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

that bind phosphate. Occasionally, intravenous normal saline or

kidney dialysis Kidney dialysis is the process of removing excess water, solutes, and toxins from the blood in people whose kidneys can no longer perform these functions naturally. Along with kidney transplantation, it is a type of renal replacement therapy. ...

may be used. How commonly it occurs is unclear.

Signs and symptoms

Signs and symptoms include ectopic calcification, secondary hyperparathyroidism, and renal osteodystrophy. Abnormalities in phosphate metabolism such as hyperphosphatemia are included in the definition of the new chronic kidney disease–mineral and bone disorder (CKD–MBD).

Causes

Hypoparathyroidism: In this situation, there are low levels of parathyroid hormone (PTH). PTH normally inhibits reabsorption of phosphate by the kidney. Therefore, without enough PTH there is more reabsorption of the phosphate leading to a high phosphate level in the blood. Chronic kidney failure: When the kidneys are not working well, there will be increased phosphate retention. Drugs: hyperphosphatemia can also be caused by taking oral sodium phosphate solutions prescribed for bowel preparation for

colonoscopy Colonoscopy () or coloscopy () is a medical procedure involving the Endoscopy, endoscopic examination of the large bowel (colon) and the distal portion of the small bowel. This examination is performed using either a Charge-coupled device, CCD ...

in children.

Diagnosis

The diagnosis of hyperphosphatemia is made through measuring the concentration of phosphate in the blood. A phosphate concentration greater than 1.46 mmol/L (4.5 mg/dL) is indicative of hyperphosphatemia, though further tests may be needed to identify the underlying cause of the elevated phosphate levels. It is considered significant when levels are greater than 1.6 mmol/L (5 mg/dL).

Units

Phosphates in blood exist in a chemical equilibrium of hydrogen phosphate (HPO₄^2–) and dihydrogen phosphate (H₂PO₄^–), which have different

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

es. Phosphate (PO₄^3–) and

phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, ...

(H₃PO₄) are not present in significant amounts. Thus millimoles per liter (mmol/L) are often used to denote the phosphate concententration. If milligrams per decililiter (mg/dL) is used, it often denotes the ''mass of phosphorus'' bound to phosphates, but not the mass of some individual phosphate.

Treatment

High phosphate levels can be avoided with phosphate binders and dietary restriction of phosphate. If the kidneys are operating normally, a saline diuresis can be induced to renally eliminate the excess phosphate. In extreme cases, the blood can be filtered in a process called

hemodialysis Hemodialysis, American and British English spelling differences#ae and oe, also spelled haemodialysis, or simply ''"'dialysis'"'', is a process of filtering the blood of a person whose kidneys are not working normally. This type of Kidney dialys ...

, removing the excess phosphate. Phosphate-binding medications include sevelamer, lanthanum carbonate,

, and calcium acetate. Previously aluminum hydroxide was the medication of choice, but its use has been largely abandoned due to the increased risk of aluminum toxicity.

References

External links

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