Nephrotic syndrome is often developed from renal amyloidosis or severe glomerulonephritis. In the case of glomerulonephritis, the filtering ability of the kidneys is impaired, leading to resultant protein loss of albumin through the urine, creating a state of proteinuria and hypoalbuminemia. This in turn results in issues with hormone levels, electrolyte metabolism, hyperlipidemia, and third-spacing of fluids. Third-spacing could then cause swelling in various parts of the body, hypotension, and reduced heart output.

Nephrotic syndrome is defined as the simultaneous presence of an excessive loss of protein in the urine (proteinuria), high cholesterol levels (hyperlipidemia), low levels of the protein albumin (hypoalbuminemia), and an abnormal accumulation of fluid in areas between functioning cells, or third-spacing of fluids. Usually developing as a complication of kidney disease, this rare condition can be fatal, and should be evaluated immediately.

Symptoms of nephrotic syndrome include:

Additional symptoms related to the conditions that cause nephrotic syndrome, namely glomerulonephritis, proteinuria, hypoalbuminemia, and hyperlipidemia, can include:

Nephrotic syndrome is a rare complication that can develop from the kidney diseases:

These conditions need to be present for nephrotic syndrome to occur:

Often, if nephrotic disease is occurring, your dog has already been diagnosed with a kidney disease, namely glomerulonephritis or amyloidosis. Your veterinarian will perform a physical exam, looking at any symptoms present, and review your dog’s medical history. To diagnose nephrotic syndrome, your veterinarian needs to confirm the presence of abnormal urine protein (proteinuria), hypoalbuminemia, hyperlipidemia, and third-space accumulation of fluids. This can be done with a urinalysis and blood tests to measure protein levels, albumin levels, and cholesterol. Nephrotic syndrome is characterized by an abnormally high level of proteins present in the urine. An ultrasound can be performed to assess the state of the kidneys, and to look for abnormal abdominal fluid accumulation.

Treatment of nephrotic syndrome will attempt to resolve symptoms and treat any underlying cause of the condition.

The abnormal swelling is treated through fluid removal only when the dog is in discomfort or in a life-threatening condition. Care is taken, as repeated fluid removals can result in other conditions, such as hyponatremia and hyperkalemia. Diuretic therapy can be initiated, adjusting the dose to minimize further fluid accumulation until the protein loss is decreased. If the circulating blood decreases in volume or if renal failure is suspected, intravenous fluid therapy may be required. 

If the albumin level decreases below a certain level, anticoagulant therapy is usually prescribed, most commonly with aspirin. Low dose aspirin therapy can also control thromboembolism, or when a blood clot blocks a blood vessel.

HMG-CoA reductase inhibitors, or statins, may be prescribed to lower cholesterol levels to help reduce hyperlipidemia. Generally, no other lipid-lowering drugs are recommended, but your veterinarian may put your dog on a diet specifically formulated for renal conditions that contain modified polyunsaturated fatty acid levels.

Chronic renal failure occurs in 70% of glomerulonephritis, and could cause the treatment to fail. Other reasons therapy may fail to yield positive results include a progression of amyloidosis, failure to identify or treat any underlying cancer or inflammatory disease, or if a fatal thromboembolism occurs.

The rate of recovery for amyloidosis is poor. If the nephrotic syndrome developed due to glomerulonephritis, recovery rates can vary, seeing some dogs recover spontaneously, while in others the disease progresses. If the underlying cause leading to the conditions that created the nephrotic syndrome is treated, leaving little permanent damage, the rate of recovery is much better. Therapy and recovery may also be affected by the high cost involved with the diagnosis and treatment of kidney diseases, and the lack of any specific therapy needed for the underlying cause. 

If the treatment is succeeding, you should see weight gain, a decrease in any swellings, and a decreased amount of protein loss. You will most likely visit your veterinarian often to monitor your dog and adjust treatments as needed.