The kidneys are very important organs with complex functions. Their main job is to filter the bloodstream and remove waste products produced during metabolism of nutrients. These waste products are eliminated from the body in urine. The kidneys also help regulate the volume and composition of blood.
One of the most common disorders of senior cats is chronic kidney (or renal) insufficiency. In its most severe form, it is called chronic kidney (or renal) failure. The term chronic renal disease (CRD) covers the entire spectrum. Cats now live much longer than in the past due to advances in nutrition and veterinary medicine. After a lifetime of wear and tear, kidney function declines as a cat ages. CRD now accounts for a significant amount of illness and death in senior cats. Fortunately, our understanding of kidney function and CRD has also increased dramatically so that more effective treatment options are available.
Each kidney is composed of thousands of individual functional units called nephrons. There is such an abundance of nephrons that cats can continue to live should damage or disease compromise a kidney or part of both kidneys. Throughout the cat’s life, individual nephrons sustain damage from wear and tear, but enough functioning nephrons remain to provide adequate kidney function. Indeed, two-thirds or more of total kidney function must be lost before most cats will show signs of illness or changes are noted on blood tests. CRD is an ongoing, irreversible disease process that progresses over months to years.
Many signs of CRD are commonly seen in other senior cat diseases too. These include weight loss, poor appetite, lethargy, vomiting, increased thirst, and increased urination. Diseases such as diabetes mellitus and hyperthyroidism may have similar signs so that diagnostic tests are required to differentiate them. As CRD advances, other signs
may appear, such as ulcers in the mouth and bad breath produced by toxic levels of waste
products (uremia). Severe weight loss, dehydration, and low blood potassium levels
(hypokalemia) can contribute to debilitation and weakness. As well, the kidneys produce
a hormone called erythropoietin that stimulates the bone marrow to make new red blood
cells to replace older damaged ones. In some cats with CRD, erythropoietin levels may
fall, the bone marrow may decrease its production of red blood cells, and anemia may
result. Anemia further contributes to weakness and general debilitation. Finally, the
kidneys play a role in regulating blood pressure so that about 1 in 5 cats with CRD will
Cat Health Blog