Renal amyloidosis in dogs: symptoms, diagnosis and treatment

Renal amyloidosis is an uncommon disease of protein metabolism in which a protein, known as amyloid, abnormally deposits in the kidneys causing excessive urinary protein loss. Among pets, it is more common in dogs and appears to be an inherited disease in Shar Pei dogs. Chronic inflammatory diseases can predispose animals to the development of renal amyloidosis. However, only a small percentage of animals with chronic inflammatory diseases develop amyloidosis.

It follows that the presence of other factors is equally important in the development of this disease. However, the latter are poorly understood. Most dogs with amyloidosis do not have distinguishable inflammatory or infectious conditions at the time of diagnosis. However, several diseases have been observed in some dogs with amyloidosis, such as systemic fungal diseases, chronic bacterial infections, filariasis and cancer.

At the time of diagnosis of the disease, the majority of dogs with renal amyloidosis appear to be of advanced age (average age of 9 years). The hereditary form tends to arise first. At the time of death or euthanasia due to illness, the average age of Shar Pei is 4 years. The Beagle, Collie, Pointers and Walker breeds may be more at risk, while the German Shepherd and the mestizos are less prone to the development of this pathology.

In dogs, amyloid deposits in the kidney can lead to the onset of any kidney failure. Symptoms related to kidney failure include: anorexia, lethargy and weight loss. Excessive water consumption and as much excessive urination are common symptoms of kidney failure. Occasionally, vomiting episodes can also be observed.

Renal amyloidosis causes excessive loss of protein in the urine. One of these proteins helps prevent blood clotting. It follows that affected dogs are more susceptible to the formation of blood clots. These clots tend to settle in the lungs causing clinical signs that may not be evident. These can range from labored breathing to increased respiratory distress.

Excessive urinary loss of a protein known as albumin can lead to the onset of ascites, or the accumulation of fluid in the abdomen. It can also cause edema (swelling of the limbs and / or muzzle). However, ascites and edema are relatively uncommon in dogs with renal amyloidosis.

Symptoms

Symptoms related to canine amyloidosis can include:

• Shortness of breath due to thromboembolism (blood clots in the lungs)

• Ascites (accumulation of fluid in the abdominal cavity)

• Edema (swelling of the limbs and / or muzzle)

• Possible past history of joint swelling and fever in the Shar Pei

Diagnosis

• Complete blood count and biochemical profile. These tests do not directly diagnose amyloidosis. However, they do provide information that may suggest excessive body protein loss, as well as information related to other body systems. The blood count test can reveal changes related to a possible kidney failure, such as the presence of anemia. The biochemical profile usually reveals low total protein levels, low albumin levels and often high kidney parameters. Often, high cholesterol levels can be observed.

• Urine analysis. The excessive presence of protein in the urine is the hallmark of renal amyloidosis. However, further tests will be required to document the extent of the protein loss.

• Ratio of urinary concentrations of creatinine proteins. This test confirms the real excessive amount of protein lost in the urine.

• Radiographs. In the case of amyloidosis, the size of the kidney observable on the radiography may vary. In dogs, the size of the kidney can be small, normal or larger than normal, making this examination not particularly informative.

• Kidney biopsy. It is necessary to reach a definitive diagnosis of amyloidosis and to distinguish the latter from other kidney pathologies that can lead to excessive urinary protein loss.

Treatment

The treatment of renal amyloidosis in dogs is difficult and often not very rewarding, especially in cases where renal failure has already developed. The principles of therapy are:

• Identify and treat underlying infectious or inflammatory conditions which may have led to the onset of amyloidosis.

• Management of concomitant renal failure. This could require hospitalization of the animal and the administration of fluids intravenously or only outpatient treatment. The following may be necessary for treatment: dietary foods only on veterinary prescription, hormonal supplements and other food supplements.

• Experimental therapy such as DMSO or colchicine. It has been shown that the administration of the drug dimethylsulfoxide (DMSO) during the early stages of the disease can be an effective treatment. However, in most dogs the diagnosis occurs when the progression of the disease is at an advanced stage, making this drug much less effective. In some cases, colchicine may be useful for humans suffering from amyloidosis, but its use in dog care has yet to be studied in depth.

What to do at home

The optimal treatment for your dog requires the combination of home and veterinary care. Follow-up can be crucial, especially if the dog does not improve quickly.

• Administer the drug or all drugs prescribed by the veterinarian in the manner recommended. Promptly notify your veterinarian if you experience problems following your treatment.

• Feed the dog with low-protein veterinary prescription diets as recommended by the vet.

• If a therapy has been instituted, the veterinarian will want to monitor the urinary protein loss by carrying out serial tests relating to the ratio of urinary concentrations of creatinine proteins to verify the decrease in the amount of protein loss. Similarly, he will want to perform serial biochemical profiles in order to verify if the circulating protein and albumin levels increase reaching a normal range.