Page 737 - Small Animal Clinical Nutrition 5th Edition

Chapter
37

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Chronic Kidney Disease

S. Dru Forrester
Larry G. Adams
Timothy A. Allen

“When things are investigated, then true knowledge is achieved.”
Confucius

emphasizes the continuum of severity of renal injury of dogs
INTRODUCTION
and cats with documented presence of kidney damage without
Chronic kidney disease (CKD) is the most common disease evidence of azotemia in stage 1 CKD, to progressively more
affecting the kidneys of dogs and cats. It may be recognized by severe CKD with resultant increasing serum creatinine concen-
reduced kidney function or the presence of kidney damage. tration for stages 2 to 4. Furthermore, by using the term “kid-
CKD is defined as kidney damage present for at least three ney disease” and staging the severity of disease, it is possible to
months, with or without decreased glomerular filtration rate facilitate understanding, communication and application of
(GFR) or greater than 50% reduction in GFR persisting for at management guidelines for patients in each stage.
least three months (Polzin et al, 2005). Kidney damage is fur- The goals of this chapter are to provide pathophysiologic
ther defined as either 1) microscopic or macroscopic patholog- concepts and practical nutritional management recommenda-
ic changes detected by histologic or direct visualization of the tions for dogs and cats with CKD. Nutritional management of
kidneys or 2) markers of damage detected by blood or urine patients with CKD includes measures to reduce signs of uremia
tests or imaging studies. In the past, multiple terms were used and slow progression to later stages of disease. There is general
to define the severity of renal functional abnormalities includ- agreement regarding nutritional management of CKD when
ing renal insufficiency, renal failure and uremia. However, there overt signs exist; however, the role of nutritional intervention
has not been uniform agreement on the specific definition of during earlier stages of CKD is less well defined. Thus, in a
renal insufficiency vs. renal failure. Therefore, it has been sense, the question is not whether to use nutritional manage-
recently proposed by the International Renal Interest Society ment but when should it be initiated. Because detection of
(IRIS) to replace these terms with a scheme to classify severity CKD in its early stages is difficult and there appears to be no
of CKD into four stages based on stable serum creatinine con- harm in avoiding nutrient excess (e.g., phosphorus) during ear-
centrations (Table 37-1). Two of the foundational assumptions lier stages, nutritional management should be considered by
inherent in this classification scheme are that the presence of stage 2 CKD and is clearly indicated when serum creatinine
CKD has been confirmed and that azotemia, if present, has exceeds 2 mg/dl (179 µmol/l) (Jacob et al, 2002; Ross et al,
been localized as renal in origin. This classification scheme 2006). Similarly, significant and persistent renal proteinuria,