Whether acquired or congenital, kidney failure is also described as either chronic or acute.
Chronic Kidney Failure
Chronic kidney failure, otherwise known as Chronic Renal Failure (CRF) or Chronic Renal Insufficiency (CRI), is a progressive deterioration of kidney function over a relatively long period of time (typically months to years). As already noted, a cat may lose up to 75% of kidney function before symptoms become noticeable, at which time the cat may appear to have become quite suddenly ill.
Acute Kidney Failure
Acute kidney failure, otherwise known as Acute Renal Failure (ARF) is the sudden shutdown of kidney function, most often as a result of a urinary obstruction, an infectious disease, physical injury or poisoning. Immediate and aggressive veterinary treatment is required for cats suffering from ARF, and in some cases this will successfully reverse the disease. Unfortunately, the outlook is often poor and many cats with ARF will not survive or will be left with residual renal insufficiency.
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