Myoglobin in Urine in Cats

Your veterinarian may refer to myoglobin in the urine as myoglobinuria or proteinuria. These terms simply mean that proteins typically found in your cat's muscles or bloodstream are spilling over into the urine due to an underlying pathology. Your veterinarian will be concerned about the underlying cause of myoglobin in the urine as well as the potential for myoglobin excretion to damage your cat's kidneys. 

Myoglobin is a protein responsible for the delivery of oxygen to your cat's muscle tissue. In a healthy cat, myoglobin is not released into the bloodstream in large enough quantities to spill over into the urine. However, sometimes muscle damage, tissue death, trauma or toxic substances can cause a rapid increase in serum (blood) myoglobin, resulting in excretion of myoglobin by the kidneys. The most obvious indicator that your cat is suffering from myoglobinuria is a reddish-brown urine color. 

Cats with myoglobin in the urine may exhibit symptoms of muscle breakdown, of which myoglobin is a byproduct, and of acute renal damage. Common symptoms of myoglobinuria include:

• Muscle weakness
• Muscle pain or swelling
• Red, brown or black urine
• Vomiting
• Loss of appetite
• Irregular or rapid heartbeat

If your cat has any of the above symptoms, seek treatment from a veterinary professional immediately. Untreated myoglobin in urine in cats can lead to acute and severe kidney damage. The most common signs of acute kidney damage are:

• Loss of appetite
• Weakness
• Vomiting
• Increased urine output and excessive urination

Myoglobinuria a symptom rather than a condition unto itself. Any condition that leads to the loss of muscle tissue or tissue necrosis can lead to myoglobin in the urine. There are a few common causes of myoglobin in urine in cats, such as:

• Snake bites
• Muscle injury or death of muscle tissue
• Certain toxic agents, such as copper, zinc, onions, and chlorates
• Bacterial infections
• Trauma, such as crush injuries, extreme exercise, severe burns, electrocution, and heatstroke
• Phosphate deficiency
• Certain chronic conditions such as lupus or hemolytic anemia

A cat who presents with suspected myoglobinuria will require a complete physical exam to discover any snake bites, loss of muscle mass or signs of physical trauma. To confirm a diagnosis of myoglobinuria, your veterinarian will collect a urine sample. While red or brown urine color is typically indicative of myoglobinuria, only chemical urinalysis can confirm the presence of myoglobin in the urine culture. 

You can also expect your veterinarian to collect a blood sample from your cat to diagnose the underlying cause of myoglobinuria. The cause of your cat's myoglobinuria can be discovered using a complete blood (CBC) count and blood chemistry profile. These tests may show elevated serum enzymes indicative of muscle death or breakdown. Additional tests may also be ordered if your veterinarian suspects your cat's myoglobinuria is secondary to a snake bite, ingestion of a toxic agent or a mineral deficiency. Depending on the severity of muscle breakdown and amount of myoglobin present in the urine, your veterinarian may also measure renal function. Additional tests may be ordered to determine renal enzyme sufficiency, for example.

The line of treatment your veterinarian selects will depend on the underlying cause of your cat's myoglobinuria. Intravenous fluids will likely be administered, along with antioxidants and vitamins, to restore muscle function and encourage healing, regardless of the cause. 

Additional treatments depend on your cat's specific diagnosis. A snake bite will be treated with anti-venom. Infections will require antibiotic administration. Physical trauma may require hospitalization or surgery. Only your veterinarian is qualified to prescribe and administer treatment for your cat's unique set of circumstances. 

Your cat's prognosis will depend on the extent of muscle or kidney damage. Regardless of the underlying cause of myoglobinuria, your cat will require follow-up examinations and short or long-term treatment. In the event that your cat's myoglobinuria is the result of a snake bite, infection, toxic agent, or other incidental cause, follow-up care is required to ensure a complete and uncomplicated recovery. 

For more complicated etiologies, such as muscle death or renal failure, ongoing administration of nutrition and fluids may be required in the short term to promote healing. Genetic testing may be recommended. Depending on the severity of your cat's condition, lifestyle modifications and close supervision over her activity may be necessary to prevent further damage.