Overview of Renal Amyloidosis in Cats

Kidney amyloidosis is a rare disorder of protein metabolism in which abnormal deposits of protein called amyloid is deposited in the kidneys. The cause of kidney amyloidosis remains poorly understood. It is a hereditary condition in certain breeds of cat. It also may occur in other breeds or mixed breeds as a reaction to chronic infections and inflammatory conditions. The term renal and kidney mean the same thing and may be used interchangeably. 

Below is an overview of Feline Amyloidosis followed by in-depth information on the diagnosis and treatment of this condition. 

Most cats with kidney amyloidosis are old at the time of diagnosis (7 years in cats). The disease can occur in any age or breed. It is a hereditary disorder in Abyssinian cats. There is a definite female predilection in Abyssinian cats (females are 1.6 times as likely to be affected compared to males).

Amyloid deposits in the kidney lead to excessive protein loss in the urine and eventual chronic kidney failure. Amyloid may also be deposited in other organs like the liver, spleen and pancreas, causing them to malfunction as well.

What to Watch For

Excessive thirst

Excessive urination

Poor appetite

Weight loss

Intermittent vomiting

Labored breathing due to thromboembolism (blood clots in the lungs)

Ascites (fluid accumulation in the abdomen)

Edema (swelling of the limbs and/or face)

Diagnosis of Renal Amyloidosis in Cats

Complete blood count and chemistry panel

Urinalysis

Urine protein/creatinine ratio

X-rays

Biopsy of the kidney

Treatment of Renal Amyloidosis in Cats

Identify and treat any underlying infectious or inflammatory condition that may have led to the amyloidosis

Manage any concurrent kidney failure

Dimethylsulfoxide (DMSO)

Colchicine

Home Care and Prevention

Manage any concurrent kidney failure as described by the veterinarian with prescription diets, subcutaneous fluids, hormonal therapy to correct anemia and vitamin D therapy. Control hypertension with medication if necessary and minimize risk of thromboembolism (forming blood clots) using low dose aspirin, if prescribed.

There are no specific preventative measures against amyloidosis.

In-depth Information on Renal (Kidney) Amyloidosis in Cats

Kidney amyloidosis is an uncommon disorder of protein metabolism in which a protein called amyloid is abnormally deposited in the kidneys, causing excessive protein loss in the urine.

Kidney amyloidosis is uncommon in cats, except for Abyssinian cats, in which it is familial. Chronic inflammatory diseases can predispose cats to the development of kidney amyloidosis, however only a small percentage of cats with chronic inflammatory conditions develop amyloidosis, thus, other factors must also be important in the development of amyloidosis. These other factors are poorly understood. Most cats with amyloidosis do not have discernible inflammatory or infectious conditions at the time of diagnosis.

Most cats with kidney amyloidosis are old at the time they are diagnosed with the disease. The average age is 7 years. The hereditary form tends to strike earlier; Abyssinian cats are less than 5 years of age on average, at the time of death or euthanasia from the disease.

Amyloid deposits in the kidneys lead to eventual kidney failure. Signs of kidney failure include anorexia, lethargy, and weight loss. Excessive water consumption and urination is another common sign of kidney failure. Occasional vomiting is also seen.
        
Kidney amyloidosis causes excessive protein loss in the urine. One of the proteins lost in the urine is a protein responsible for preventing the blood from clotting. As a result, affected cats are more susceptible to formation of blood clots. These clots tend to lodge in the lungs, causing clinical signs that may not be obvious, ranging from labored breathing to major respiratory distress.

Excessive urinary loss of a protein called albumin may lead to ascites, which is an accumulation of fluid in the abdomen. It may also lead to edema, which is a swelling of the limbs and/or face. Ascites and edema are relatively uncommon occurrences in cats with kidney amyloidosis.

Diagnosis In-Depth

Complete blood count and chemistry panel. These tests do not diagnose amyloidosis directly; however, they give information that may be suggest excessive protein loss from the body, as well as information as to other body systems. Complete blood counts may show changes expected for kidney failure, such as anemia. The chemistry panel usually shows low total protein, low albumin, and often, elevated kidney parameters. High cholesterol is often seen.

Urinalysis. Excessive protein detected on a urinalysis is the hallmark of kidney amyloidosis. Further tests to document the magnitude of the protein loss will be necessary.
        

Urine protein/creatinine ratio. This test confirms that the amount of protein lost in the urine is truly excessive.

X-rays. Kidney size on radiographs can vary in cases of amyloidosis. In cats, kidney size may be small, normal, or larger than normal, making this test not very informative.

Biopsy of the kidney. A kidney biopsy is necessary to make a definitive diagnosis of amyloidosis and distinguish it from other disorders of the kidney that can lead to excessive urinary protein loss.

Therapy In-depth

Treatment of kidney amyloidosis is difficult and often unrewarding, especially if kidney failure has already begun to develop. The principles of therapy are as follows:

Identify and treat any underlying infectious or inflammatory condition that may have led to the amyloidosis.

Manage any concurrent kidney failure – this may require hospitalization and intravenous fluids, or may only require outpatient care. Prescription diets, hormonal supplements, and other dietary supplements may be necessary for treatment.

Experimental therapy such as DMSO or colchicine. Administration of the drug dimethylsulfoxide (DMSO) during the very early stages of the disease has been shown to be an effective treatment; however, most cats present much later in the course of their disease, when DMSO is much less effective.

Colchicine may be beneficial for humans with the disorder in certain circumstances, but it has yet to be studied well in cats.

Follow-up Care for Cats with Amyloidosis

Optimal treatment for your catrequires a combination of home and professional veterinary care. Follow-up can be critical, especially if your cat does not rapidly improve.

Administer all prescribed medication(s) as directed. Alert your veterinarian if you are experiencing problems treating your cat.

Feed special low protein prescription diets as recommended.

Return for frequent re-examination. If therapy has been attempted, your veterinarian will want to monitor the urinary protein loss by performing serial urine protein/creatinine ratios to see if the magnitude of the protein loss is decreasing, as well as serial chemistry panels to see if the circulating protein and albumin levels are rising toward the normal range.