Causes of Feline Chronic Kidney Disease

AN OVERVIEW OF THE FUNCTION OF THE KIDNEYS

Chronic kidney disease (CKD) is a common problem in cats. Kidneys are essential for normal bodily functions. The kidney is a highly complex and remarkable organ that provides the following functions:

• Filtering 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.
• 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’ 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 can be seen in cats of any age, but is most common in middle to old-aged cats.

CAUSES OF CKD IN CATS

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 toxinthat 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
  
  
• Familial kidney disease: ‘Fancy’ cat breeds have been found to suffer from irreversible hereditary diseases such as amyloidosis and polycystic kidney disease (fluid-filled cysts)
  
  
• Tubulointerstitial disease: This disease – that damages kidney tubules and causes inflammation – is difficult and dangerous to test for and because the cause is often unknown, custom treatment is rarely possible

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 managed to offer a better quality of life.