Page 921 - Small Animal Clinical Nutrition 5th Edition

Feline Lower Urinary Tract Diseases 953

cantly decreased urinary calcium and oxalate excretion when
VetBooks.ir treated with EPA for eight weeks. In another study, adminis-
tration of EPA for three months to 88 people with recurrent
urinary stones, primarily calcium oxalate, was associated with
significantly decreased urinary calcium in those with hyper-
calciuria (Yasui et al, 2001).
The recommended range of dietary total omega-3 fatty acids
(i.e., DHA and/or EPA) for managing inflammation associat-
ed with lower urinary tract diseases is 0.35 to 1.0% DM. This
range was extrapolated from levels associated with antiinflam-
matory effects in other species. Additional study is needed to
better define the therapeutic range of omega-3 fatty acids for
managing patients with FIC and calcium oxalate uroliths.

Other Nutritional Factors
Antioxidants Figure 46-17. This graph demonstrates the relationship between
Vitamin E has antioxidant properties that have been shown to urinary pH and urine saturation values for struvite and calcium
oxalate. Data were collected from 21 adult cats (10 healthy and 11
decrease oxidative stress and damage caused by free radicals.
urolith-forming cats) during consumption of a food (Hill’s
Because oxidative stress is often associated with inflammation, Prescription Diet c/d Multicare Feline) formulated to manage both
antioxidants may help create an unfavorable environment for struvite and calcium oxalate uroliths. Mineral type was not available
the development of uroliths. However, this has not been evalu- for uroliths in most cats; however, calcium oxalate was presumed
ated in cats with naturally occurring urolithiasis. most likely due to location (eight cats had nephroliths), radiographic
appearance and results of quantitative analysis for uroliths that were
Vitamin C is also an antioxidant. However, a portion of uri-
removed. Urine constituents (e.g., calcium oxalate, magnesium,
nary oxalate is derived from endogenous metabolism of vita- phosphate) and pH were measured for each cat and used to calcu-
min C. In a controlled study of healthy cats fed differing late values for relative supersaturation (RSS). This was followed by a
amounts of vitamin C ranging from 40 to 193 mg vitamin computer-modeling procedure to predict effect that changing only
C/kg of food for four weeks, there was no significant change urinary pH would have on RSS values. Results were similar for both
healthy and urolith-forming cats; therefore, all data are shown in one
in urinary oxalate excretion (Yu and Gross, 2005). Effects of
graph. Note that as urinary pH increases, urine saturation for struvite
vitamin C supplementation have not been studied in cats with increases; however, as urinary pH decreases over the physiologic
calcium oxalate uroliths. Because cats do not have a dietary range, there is only a slight change in calcium oxalate saturation. In
requirement for vitamin C, supplementation should be avoid- this model, reducing urinary pH from 7.4 to 6.4 decreased struvite
ed in cats at risk for calcium oxalate uroliths (Bartges and saturation by 122 units but only increased calcium oxalate satura-
tion by 0.9 units. (Adapted from Yu S, Gross KL. Dietary manage-
Kirk, 2006). One source of vitamin C that should be avoided
ment of the three most common lower urinary tract diseases in cats.
is cranberry concentrate tablets. In: Proceedings. Hill’s Symposium on Lower Urinary Tract Disease.
Educational Concepts, 2007: 53-57.)
Oxalate
Excessive intake of oxalate is unlikely in dogs and cats eating needed to determine if potassium supplementation benefits cats
most commercial foods but it could occur in pets receiving ex- with calcium oxalate uroliths. Based on current information,
cessive amounts of certain human foods as treats. Foods that dietary potassium intake should exceed 0.65% DM in cats at
contain relatively high amounts of oxalate (e.g., spinach, car- risk for struvite disease and calcium oxalate uroliths. Most com-
rots, liver, sardines) should be avoided in patients with a histo- mercial foods are replete with potassium.
ry of calcium oxalate uroliths. Table 46-18 provides more infor-
mation about the oxalate content in selected human foods. Vitamin B (Pyridoxine)
6
Increases in urinary oxalic acid excretion have been observed in
Potassium kittens fed pyridoxine-deficient foods. However, no studies
Transient negative potassium balance has been reported to occur have evaluated effects of vitamin B in cats with calcium ox-
6
in adult cats receiving long-term dietary acidification (i.e., for alate uroliths (Bai et al, 1989, 1991). No evidence suggests that
struvite urolith prevention) with phosphoric acid and NH Cl; supplementing vitamin B beyond nutritional requirements
4
6
potassium balance returned to normal by the end of both stud- benefits cats with calcium oxalate urolithiasis. Because most
ies (Fettman et al, 1992; Ching et al, 1990). In an epidemiolog- commercially available pet foods are well supplemented with
ic study, cats fed foods with higher amounts of potassium (2.17 vitamin B , it seems unlikely that additional supplementation
6
to 3.20 mg/kcal; 0.87 to 1.28% DM for a food with 4 kcal would be helpful unless the primary food is homemade.
ME/g DM) had decreased risk of calcium oxalate uroliths com-
pared with cats that were eating foods with less potassium (0.95 Vitamin D
to 1.60 mg/kcal; 0.35 to 0.64% DM for a food with 4 kcal Increased vitamin D intake should be avoided because it can
ME/g DM) (Lekcharoensuk et al, 2001a). Additional study is lead to increased intestinal absorption of calcium with subse-