Causes of Feline Chronic Kidney Disease

OVERVIEW OF THE FELINE KIDNEY

The feline kidneys are paired organs that reside in the dorsal abdomen. One is situated on the left and the other on the right. The kidneys at birth are the same kidneys for the rest of a cat’s life. They don’t regrow, and ‘healing’ of damage is a limited ability for this important organ.

Kidneys are essential for normal bodily functions. The kidney is a highly complex and remarkable organ. During the day, the body makes waste that it cannot use and adds it to blood for transport to the kidney. The kidney then filters the waste products and extra water from the blood so that they can be excreted in the urine. This process eliminates toxins from the body and maintains a proper level of hydration.

Other functions of the kidneys include:

• Regulating electrolytes (such as sodium, potassium, phosphorous, and calcium) in the body.
• Producing and concentrating urine, which is made up of waste, toxins, and extra fluid that the body doesn’t need.
• Producing erythropoietin, a hormone that stimulates the bone marrow to create new red blood cells. Red blood cells carry oxygen throughout the body.
• Producing renin, an enzyme that controls the body’s blood pressure.

CHRONIC KIDNEY DISEASE (CKD)

‘Chronic’ means long-lasting; therefore, chronic kidney disease means that there is a progressive decline in the kidneys’ ability to function over time.  It is not usually until the disease is fairly well advanced and the condition has become severe that signs and symptoms are noticeable. Unfortunately, at this point most of the damage is irreversible. Because the kidneys impact other areas of the body, the changes that occur as a result of chronic kidney disease impact many other bodily systems, as well.

CKD is a common problem in cats. CKD can be seen in cats of any age, but is most common in middle to old-aged cats.

BREED PREDISPOSITIONS

Some breeds reported to be disproportionately affected by CKD include: Maine Coon, Abyssinian, Siamese, Russian Blue, Oriental  shorthair, and Burmese cats.

CAUSES OF CKD IN CATS

There are many possible underlying causes of CKD in cats, ranging from congenital abnormalities and immune-mediated disease to hypertension. Some chronic conditions that are common in cats such as, high blood pressure and hyperthyroidism may cause CKD.

Old age, undiagnosed and untreated health problems, diseases and unidentified causes can all lead to long-standing, irreversible damage to the kidneys.

Most cases of CKD have an unknown underlying cause (idiopathic); however, some causes are well recognised. These may include:

• Kidney stones: Disease, genes or bacterial infection can cause kidney stones to form
• Kidney blockage: Pieces of kidney stones that have fractured or splintered can cause partial or complete blockage in the urine-carrying tube (ureter) that connects kidneys to the bladder
• Kidney tumours: Cancer, for example lymphoma (solid tumour of white blood cells) can affect the kidneys
• Infections: Bacterial infection of the kidneys may lead to sufficient damage to cause CKD
• Toxins: Antifreeze is a toxin that gets lots of attention, but there are many things in and around the house that are dangerous when ingested, for example, true lilies (all parts and even the water it’s in) and various medications (common over-the-counter and prescribed meds)
• Glomerular disease: This refers to inflammation of the glomeruli (individual units within the kidneys that filter the blood). When they are inflamed over a period of time, this can lead to CKD. Infections such as FIP/FeLV or cancer can cause the kidneys’ filtration mechanism (glomerulus) to become inflamed which causes damage that ultimately leads to CKD
• Protein problem: Amyloidosis, caused by chronic inflammation in other body parts, is a disease that can affect kidney function; normal tissue is replaced with protein deposits that can’t be cleared and tissue that suffered damage can’t be replaced
• Tubulointerstitial disease: This disease damages kidney tubules and causes inflammation

Other conditions such as birth defects affecting the kidneys and trauma may also cause CKD. In most cases, causes cannot be identified so treatment is aimed at management of the disease and complications that arise from it.

Chronic kidney disease in cats can be successfully managed to offer a better quality of life.