Electrolyte Disturbance in Dogs

Electrolytes are ionized salts that circulate through the body and play a crucial role in nutrient absorption and cell osmosis. Phosphate (PO4-) is one of these important electrolytes. About 85% of the phosphorus in the body is contained in the bones, but a small amount circulates in the blood stream as phosphate ions. These electrolytes help to control nerve and muscle function, transport oxygen, and regulate the conversion of food into energy. 

Low phosphate levels are rare in dogs since the parathyroid glands and the kidneys work to maintain normal blood levels by reducing phosphate excretion and even reabsorbing phosphorus from the bones if necessary. Intestinal inflammation can reduce absorption however, and, over an extended period of time, low phosphorus diets may weaken an animal’s bones. More commonly, electrolyte imbalance is caused by diseases that affect the kidneys and parathyroid glands, causing abnormally high phosphate excretion. 

Phosphate levels in the blood can also drop suddenly if too much is redistributed into the cells through osmosis. This can happen after an insulin injection, or in refeeding syndrome when starving animals eat large amounts of food too quickly. Severely low levels of phosphate in the blood can disrupt breathing and heart rate, destroy red blood cells, and cause muscle weakness and neurological symptoms. This is most common in diabetic dogs, but it can occur in some other situations as well. Immediate treatment with fluids and phosphate ions can rebalance the electrolytes, but hypophosphatemia is still a significant, diabetes-related cause of death.

Phosphate is an important electrolyte that helps to regulate muscle function and metabolism. Many different electrolytes work together, so low phosphate levels, called hypophosphatemia, can cause serious electrolyte disturbance. In dogs, this occurs with poorly regulated diabetes, as well as some other conditions.

These are some of the symptoms that you might see in your dog. Life-threatening symptoms should be treated as an emergency.

• Difficulty breathing
• Irregular heart rate
• Lethargy
• Muscle weakness
• Muscle pain
• Seizures
• Weak bones, lameness, or fractures (chronic phosphate deficiency)

Types

Normal phosphate levels in the blood are between 2.5-7.7 mg/dl. Types of hypophosphatemia are defined based on severity.

• Mild 2-2.4 mg/dl
• Moderate 1.5-2 mg/dl
• Severe < 1.5 mg/dl

Many different conditions can affect absorption, excretion, and cellular intake of phosphate.

Decreased intestinal absorption

• Vomiting
• Diarrhea
• Phosphate binding drugs
• Vitamin D deficiency
• Intestinal inflammation (IBD)
• Dietary deficiency

Phosphate excretion in the urine

• Diabetes with or without ketoacidosis
• Parathyroid gland disorders (Primary and secondary hyperparathyroidism)
• Cancerous tumors that release parathyroid hormones
• Adrenal gland disorders like Hyperaldosteronism
• Cushing’s disease
• Corticosteroid use
• Kidney defects (Fanconi’s syndrome is most common in Basenjis)
• Hypercalcemia (due malignant tumors or renal failure)
• Diuretic use

Excessive cellular intake

• Insulin injections
• Glucose injections
• Respiratory alkalosis 
• Refeeding syndrome
• Xylitol poisoning (sugar substitute)

Electrolyte levels will be determined with a blood test. This will show the degree of hypophosphatemia, as well as abnormal levels of other electrolytes, especially calcium. The veterinarian will try to identify the underlying cause of the imbalance by testing for other conditions like diabetes and high parathyroid hormone levels. Concurrent symptoms, like vomiting or diarrhea, may help to determine the source of the problem. Other tests could focus on potential infections, autoimmune responses, kidney dysfunction or Cushing’s disease. X-rays or ultrasound could be necessary if a cancerous tumor is causing hormone imbalance, or to identify weak bones or fracture.

The veterinarian will need to know your dog’s medical history including any prior or current medications, especially insulin, diuretics, or corticosteroids. Dietary deficiency is most common with homemade diets, so the vet may ask what type of food your pet normally eats. Any history of starvation or potential poisoning will also be relevant.

Severe hypophosphatemia is treated with intravenous fluids and phosphate ions. If your dog is very ill, this treatment can save his life, so it’s important to get to the veterinarian as soon as possible. Once the condition is stabilized, treatment will focus on the underlying cause. Short-term conditions like refeeding or poisoning will resolve themselves once the life-threatening symptoms are treated. The veterinarian may prescribe medication to regulate diabetes or adjust existing doses to avoid recurrence.

Mild or moderate hypophosphatemia will be treated with supplements or diet change. Dairy products are high in phosphate, so the veterinarian may recommend adding these to your dog’s diet, or switching to a different brand of dog food that provides more complete nutrition. 

Other treatments could be necessary depending on the cause of hypophosphatemia. Diuretics or other drugs that reduce phosphate absorption may need to be eliminated. Your dog may need hormone therapy treatment, or medication to help reduce kidney dysfunction. Cancer might need to be treated with surgery and/or chemotherapy. The necessity for any of these treatments will be evaluated by your veterinarian upon diagnosis.

Hypophosphatemia can be resolved with immediate treatment, but full recovery will depend on the underlying cause. If your dog has diabetes, this will require lifelong management with diet and medication. Many other conditions might need long term medication, so you will need to discuss any potential side effects. Complete recovery is possible in some cases, but it will depend on the diagnosis of a veterinarian.