Hyperphosphatemia: Causes, Symptoms, Treatment, Prognosis, Pathophysiology, Prevention
Hyperphosphatemia is a condition characterised by electrolyte imbalance with increased level of phosphate in the blood. On an average the phosphate level should be between the range of 0.81 mmol/L and 1.45 mmol/L. When the level of serum phosphate is higher than 1.46 mmol/L, the condition is known as hyperphosphatemia. Increased level of serum phosphate can be caused as a result of increased phosphate intake or decreased excretion of phosphate. Hyperphosphatemia can also result from shift of phosphate from intracellular space to extracellular space. Hyperphosphatemia is one of the most common causes of morbidity and mortality in individuals with chronic kidney disease and also a common cause of complication in patients with cardiovascular disorders.
Symptoms of Hyperphosphatemia
Clinically speaking, individuals with hyperphosphatemia are generally asymptomatic. They may have symptoms of hypocalcemia such as tetany, muscle cramps, weakness, numbness and tingling sensation. Acute conditions may show hyperreflexia, Trousseau sign, Chvostek sign, and Carpopedal spasm. Other common symptoms of Hyperphosphatemia include:
- Shortness of breath
- Disturbed sleep
- Bone and joint issues
- Seizures and convulsions
- Altered mental status
- Confusion and delirium
- Neuromuscular hyper excitability
Prevalence Rate of Hyperphosphatemia
The occurrence of hyperphosphatemia is not very common among the general population. However, it is a common condition seen in almost 70% of the patients with chronic renal disease. Patients undergoing dialysis are affected by hyperphosphatemia at some point during the treatment. Prevalence rate of Hyperphosphatemia is not related to race and sex of the patient. Risk of developing this condition increases with age, as the risk of developing kidney issues increases with aging.
Prognosis of Hyperphosphatemia
Morbidity associated with hyperphosphatemia results due to the underlying condition and not from hyperphosphatemia directly. If detected early, the condition can be controlled.
Causes and Risk Factors of Hyperphosphatemia
The causes and risk factors of hyperphosphatemia include:
- Kidney diseases
- Patients undergoing treatment with haemodialysis and chemotherapy.
- Cancer (Lymphoma, bone tumor, leukaemia etc.)
- Endocrinological disorders such as hypoparathyroidism and pseudo hypoparathyroidism.
- Trauma and injury
- Immobilization for a prolonged period of time
- Metabolic disorders
- Haematological disorders
- Genetic inheritance
- Ischemic bowel disease.
Pathophysiology of Hyperphosphatemia
There are several mechanisms that control phosphorus homeostasis in the body. Intake of phosphorus should match excretion of phosphorus, i.e. there should be a balance between gastrointestinal absorption and renal excretion and also between cellular release and uptake in other tissues. The condition hyperphosphatemia occurs when there is excessive load of phosphorus through gastrointestinal absorption, cellular release or exogenous administration that exceeds tissue uptake and renal excretion.
This imbalance is caused by 3 major reasons as follows:
- Reduced phosphate excretion
- Excess intake of phosphate
- Abnormal shift of phosphate ion to intracellular space from intracellular space.
- Irrespective of the cause of hyperphosphatemia, the signs and symptoms elicited is the same in all the cases.
Complications of Hyperphosphatemia
- Short Term Complications of Hyperphosphatemia: These include acute hypocalcaemia, tetany, deposition of calcium and phosphate in bone joints, subcutaneous tissues and soft tissues, and chronic kidney disease.
- Long Term Complications of Hyperphosphatemia: Long term complications of hyperphosphatemia are much severe most of which are irreversible. These include renal failure; organ damage; damage to vascular system; bone, skin and heart complication. If present over prolonged period of time, it increases the risk of developing cardio vascular issues. Hyperphosphatemia is one of the causes of mortality in patients with the history of kidney transplant, end stage renal disease and chronic kidney issues.
Diagnosis of Hyperphosphatemia
A thorough physical examination is required for correct diagnosis. This is carried out by an experienced physician. However, it should be noted that this condition may be not show all symptoms clinically and appears asymptomatic in a large number of cases. It is thus important to carry a blood work. Patient may exhibit signs of being hypotensive or hypocalcaemia such as positive Trousseau or Chvostek sign, carpopedal spasm, seizure, hyperreflexia etc. Diagnosis of hyperphosphatemia includes a full chemistry profile as follows:
- Decreased Calcium Level with Increased Phosphate Level: This is commonly associated with renal failure, hypoparathyroidism and pseudohypoparathyroidsm.
- Determining BUN (Blood Urea Nitrogen) and Creatinine Levels: These help in understanding whether hyperphosphatemia is caused by renal failure or not.
- Parathyroid Hormones (PTH) above Normal Limits: This is common in patients with pseudo-hypothyroidism and renal failure.
- Low Levels of Parathyroid Hormones (PTH) with Normal Renal Functions: Common in individuals with primary or acquired hypoparathyroidism.
- Elevated Serum Calcium and Phosphate Levels: This is associated with milk-alkali syndrome and vitamin D intoxication.
- High 25 and 1, 25 Vitamin D with Low Levels of Parathyroid Hormones: Associated with vitamin D intoxication.
- Low Levels of Parathyroid Hormones and Vitamin D: Common with milk- alkali syndrome.
A 24 hour measurement of urinary phosphate is suggested if the definitive cause of hyperphosphatemia cannot be determined.
Imaging studies are not commonly done in this condition; but in case of renal failure, an ultrasonography may be done. In certain cases, a bone density test may be suggested to determine bone loss. Bone biopsy is also done in certain cases. CT scan may be done for studying coronary artery calcification.
Treatment of Hyperphosphatemia
Treatment modality of hyperphosphatemia includes the following:
- Right diagnosis and treatment of the underlying condition.
- Limit Phosphate Intake: Patients diagnosed with hyperphosphatemia are advised to follow a low phosphate diet.
- Increase Excretion of Phosphate: Forced saline diuresis may be considered in certain cases.
Prevention and Precautions of Hyperphosphatemia
Individuals with increased risk of hyperphosphatemia and risk of recurrent episodes of hyperphosphatemia should follow a low phosphate diet. An experienced dietician can assist in planning out a daily diet plan. Certain food should be eliminated such as nuts, meats, dairy products, colas or substituted as needed. Besides following a restricted diet, intake of phosphate binders is important. It is also advised to stay well hydrated and avoid phosphorus containing substances such as enemas, laxatives and other supplements.
Hyperphosphatemia is a condition characterised by increased level of serum phosphate i.e. higher than 1.46 mmol/L. It is caused by increased intake of phosphate by the body and decreased excretion of phosphate leading to an imbalance. Hyperphosphatemia is generally associated with other renal, endocrinological and neurological conditions. In severe cases, it can cause serious complications such as renal failure and cardiovascular complications. Diagnosis includes physical examination with detailed blood work. Treatment modality includes treatment of the underlying condition in addition to phosphate restricted diet.