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80th Western Veterinary Conference
V206
Feline Lower Urinary Tract Disease (FLUTD): Making the Most of Nutritional
Management
S. Dru Forrester
Scientific Affairs, Hill’s Pet Nutrition, Inc
Topeka, KS, USA
OBJECTIVES OF THE PRESENTATION
Recognize importance of nutritional management for cats with FLUTD.
Make evidence-based nutritional recommendations for cats with idiopathic cystitis, urolithiasis, and
urethral plugs.
KEY ETIOLOGIC AND PATHOPHYSIOLOGIC POINTS
The 3 most common causes of FLUTD are feline idiopathic cystitis (FIC), urolithiasis (struvite and
calcium oxalate), and urethral plugs (struvite).
KEY THERAPEUTIC POINTS
Feeding moist food and increasing water intake are key components of managing cats with FLUTD.
Increased sodium intake (in therapeutic foods) is an effective method for diluting urine; however, it
should not be used in cats with kidney disease.
Struvite uroliths can be dissolved in 4 weeks using nutritional therapy.
Ideal management for preventing recurrence of calcium oxalate uroliths is unknown; however,
feeding a moist therapeutic food has been shown to decrease risk of recurrence.
OVERVIEW OF THE ISSUE
Feline lower urinary tract disease (FLUTD) is most often caused by feline idiopathic cystitis (FIC),
urolithiasis, or urethral plugs. Based on feline uroliths analyzed at the Minnesota Urolith Center in 2006
(n=10,093), the most common mineral types were struvite (50%), calcium oxalate (39%), and urate (5%).
Urethral plugs are most often composed of struvite ((81–87%). This presentation reviews nutritional
management of cats with the most common causes of FLUTD, including evidence supporting treatment
recommendations.
ADDITIONAL DETAIL
Feline Idiopathic Cystitis
The standard of care for treating cats with FIC includes nutritional management, environmental
enrichment, and behavioral modification. Of all treatments evaluated in a controlled clinical study, the
only one that has been associated with a statistically significant improvement in clinical signs is feeding
moist food. During a 1-year study of cats with FIC, clinical signs recurred less often in cats fed moist food
(Waltham Veterinary Diet Feline Control pHormula in Gel) (11%) compared with cats fed a dry
formulation (39%).1 In a 6-month study evaluating glucosamine versus placebo in cats with FIC, cats in
both groups improved significantly.2 Owners were given client education handouts describing
recommendations for cats with FIC, including feeding moist food. At the beginning of this study, 95% of
cats were fed dry food exclusively or at least half of their daily food was dry. After starting the trial,
however, 36 (90%) owners increased the amount of moist food given to their cats, so that at least 50% of
their daily intake was moist food. In 33 cats (82.5%), owners began feeding moist food exclusively. Mean
urine specific gravity at the beginning of the study was 1.050 and it was significantly lower (1.036) when
reassessed 1 month later (p < 0.01).
Increasing daily water intake and/or switching to a moist food should be part of initial
management of cats with FIC. Feeding moist food has been associated with an increase in daily water
intake and urine volume in cats compared with feeding dry food. It has been recommended that the goal
of increased water intake is to decrease urine specific gravity below 1.030; however, beneficial effects
have been observed in cats with FIC when urine specific gravity decreased from values around 1.050 to
values ranging from 1.032 to 1.041.1,2 Most cats can be switched to a moist food if the change is made
gradually; for some cats this many require a period of several weeks. Failure to make a gradual transition
may result in refusal to eat the moist food or increased stress, which may cause recurrence of clinical
signs. Therefore moist food should initially be offered as an additional option in a second dish next to the
usual food. If the cat will consume the moist food, the dry food offering can be gradually reduced.
Increasing frequency of feeding (dividing the daily amount of food into several meals) also may
help increase daily water intake. In a study of healthy cats, feeding 2–3 meals per day was associated with
a significant increase in total water intake compared with feeding a single meal.3 This has not been
evaluated in cats with FIC; however, it would appear to be a reasonable method to increase water
consumption. Additional methods for increasing water intake such as adding broth to foods, placing ice
cubes in the cat’s water, using unique water bowls, and providing water fountains also may help in some
cases.
Increasing sodium chloride content of food [1.2–1.4% sodium, dry matter basis (DMB)] has been
used as a method to increase water intake and urine volume and cause subsequent urine dilution. At
present, there are differing opinions regarding safety of feeding high-sodium foods to cats. Most foods
formulated for cats with FLUTD contain 0.25–0.5 % sodium and contain 1–1.4 % sodium (Table 1).
According to the most recent information published by the National Research Council (NRC), it is
difficult to suggest a safe upper limit of sodium for healthy adult cats. The NRC has concluded that as
long as unlimited amounts of water are available, it is likely that cats can tolerate reasonably high
concentrations of dietary sodium (1.5% sodium, DMB). The safe upper limit of sodium for cats with
kidney disease and FLUTD is unknown, however.
Long-term consequences of high-sodium foods have not been evaluated in healthy cats or cats with
hypertension and effect of sodium on kidney function remains controversial. Based on information
currently available, feeding high-sodium foods has not been associated with hypertension in healthy cats
or cats with kidney disease (naturally occurring or experimentally induced).4-6 Effects of high-salt (1.2%
sodium, DMB) intake for 3 months were evaluated in cats with mild azotemia due to naturally occurring
chronic kidney disease.5 These cats had progressive increases in BUN, serum creatinine, and serum
phosphorus compared with cats consuming food with 0.4% sodium, DMB. Based on findings to date,
further study is needed to determine the role of sodium in healthy cats and cats with naturally occurring
hypertension and chronic kidney disease. Pending further studies, high-salt foods should not be fed to
cats with kidney disease and renal function should be monitored when high-salt foods are used in cats at
risk for kidney disease.
Treatment with GAGs such as pentosan polysulfate, glucosamine, and chondroitin sulfate has been
suggested in cats with FIC because defects in the GAG layer covering the urinary bladder epithelium may
play a role in the pathogenesis of the disease. Anecdotally, these agents have been mentioned as helpful
in cats with FIC; however, only one has been critically evaluated. In a randomized controlled clinical trial,
administration of 125 mg glucosamine (Cystease® Ceva Animal Health) by mouth once daily was not
associated with any difference in clinical signs compared with cats that received placebo.2 If signs of FIC
persist despite other treatments, GAGs such as pentosan polysulfate (8 mg/kg PO q12h) or a combination
of glucosamine and chondroitin sulfate (250 mg/200 mg PO q24h) may be attempted.
Struvite Uroliths/Urethral Plugs
Nutritional management is an effective method for dissolving feline uroliths. Two therapeutic foods have
been evaluated in cats with struvite uroliths (Hill’s® Prescription Diet® s/d® Feline and Medi-Cal®
Dissolution Formula, Veterinary Medical Diets); mean time required for dissolution of sterile struvite
uroliths using these foods was approximately 1 month.7,8 For cats with suspected struvite uroliths
(usually cats < 7 years old, alkaline urine pH, struvite crystalluria, and/or radiopaque uroliths), it is
appropriate to transition to feeding a canned dissolution food over a 7-day period. Cats should be re-
evaluated every 2–4 weeks by performing urinalysis and abdominal radiographs. Urine pH should
remain acidic and specific gravity should be < 1.040 if canned food is being fed exclusively. Nutritional
management is continued for 1 month beyond radiographic resolution of the urolith. If uroliths do not
dissolve completely or decrease in size within 2 months, different treatment should be considered.
Many veterinarians prefer to remove struvite uroliths because: 1) they believe it is the most effective
treatment, 2) they believe it is less expensive than nutritional management, 3) they believe it controls
clinical signs quicker, and 4) they believe medical dissolution is more likely to cause urethral obstruction
when uroliths decrease in size, especially in male cats. Surgical removal of uroliths has not be critically
evaluated; however, an unpublished retrospective study of 37 dogs and 29 cats with urinary bladder
uroliths revealed that 4 cats (14%) and 8 dogs (22%) had incomplete removal or uroliths by cystotomy in a
veterinary teaching hospital.9 For cats undergoing cystotomy for urolith removal, it is important to
perform diagnostic imaging post-operatively to confirm success or failure of treatment. If nutritional
dissolution is recommended, it is important to monitor cats for signs of obstruction; however, in a study
evaluating cats undergoing dissolution therapy, none of the male cats experienced urethral obstruction.8
Also, dissolution of uroliths may occur in 1–2 weeks in some cats and even when dissolution requires a
longer period, clinical signs often resolve sooner.8 Selection of treatment method should therefore depend
on several factors including clinical expertise, client preferences, patient factors, and evidence for
effectiveness of various treatments.
After dissolution or removal of struvite uroliths, cats should be gradually transitioned to a food
formulated to prevent struvite disease. A dissolution (calculolytic) food is appropriate for initial
management (1–3 months) after relieving urethral obstruction; this should be followed by feeding a
struvite preventive food indefinitely. There are several commercially available foods for struvite
prevention (Table 1); only one (Hill’s® Prescription Diet® s/d® Feline) has been evaluated in cats with
struvite disease. In a randomized, prospective study of cats with urethral plugs, effectiveness of feeding
this food was compared with perineal urethrostomy alone and perineal urethrostomy plus the
calculolytic food.10 During the 1-year study, urethral obstruction was not observed in any group. This
study did not include an untreated control group; however, recurrence rate for urethral obstruction in a
previous study was 35%.11 Bacterial UTI occurred in 40–50% of cats that had perineal urethrostomies but
was not observed in cats managed by calculolytic food alone.
Calcium Oxalate Urolithiasis
The treatment of choice for calcium oxalate urolithiasis is urolith removal, followed by methods to
prevent recurrence. Increased water intake is associated with decreased concentrations of urolith-forming
minerals in urine, and has been recommended to help prevent urolith recurrence. One epidemiologic
study showed that cats fed high moisture foods were less likely to develop calcium oxalate uroliths than
cats fed low moisture (dry) foods.12 In addition to feeding moist food, it may be helpful to feed several
meals per day, add additional water or broth to dry or moist food, and use water fountains or novel
water bowls. Although much information is available regarding risk factors for calcium oxalate uroliths,
the cause remains largely unknown, making ideal preventive recommendations challenging.
There are several commercially available therapeutic foods for prevention of calcium oxalate
uroliths in cats (Table 1). Only one food (Hill’s® Prescription Diet® x/d® Feline) has been evaluated in
cats with naturally occurring calcium oxalate uroliths.13 In a study of 10 cats with confirmed calcium
oxalate uroliths, urine saturation for calcium oxalate was measured prior to beginning the study and after
a feeding trial. Using a crossover design, half of the cats were randomly assigned to continue their regular
food and the other half were fed the therapeutic food; after 8 weeks, the foods were switched and fed for
another 8 weeks. Urine saturation was measured and compared between groups (regular food versus
therapeutic food). Results revealed that hypercalciuria was a consistent abnormality in urolith-forming
cats and calcium oxalate saturation was significantly less in cats fed the therapeutic food compared with
regular food.
In cats with hypercalcemia and calcium oxalate uroliths, feeding increased amounts of fiber and
administering potassium citrate have been recommended. In a report of 5 cats with calcium oxalate
uroliths, hypercalcemia resolved and urolith recurrence was not observed after discontinuing an
acidifying food (or urinary acidifier) and changing to a higher fiber food (Hill’s® Prescription Diet®
w/d® Feline) or adding a fiber supplement.14 Increased fiber may have lowered serum calcium by
binding intestinal calcium, preventing its absorption, and/or decreasing transit time through the small
intestine, where most calcium is absorbed.
Increased urinary citrate may form soluble complexes with calcium, making it unavailable to form
calcium oxalate uroliths. Effects of potassium citrate alone on urinary calcium oxalate saturation or
urolith recurrence have not been evaluated in cats. Potassium citrate is found in one therapeutic food
((Hill’s® Prescription Diet® x/d® Feline) that has been evaluated in cats with calcium oxalate uroliths.13
Potassium citrate (50–75 mg/kg PO q12h with food) should be considered in cats that have recurrent
calcium oxalate uroliths despite using a therapeutic food.
Increases in urinary oxalic acid excretion have been observed in kittens fed pyridoxine-deficient
foods; however, there have been no studies evaluating effects of vitamin B6 in cats with calcium oxalate
uroliths. Since most commercially available pet foods are well supplemented with vitamin B6, it seems
unlikely that additional supplementation would be helpful. However, if a cat with calcium oxalate
uroliths is being fed a homemade food, it would be appropriate to supplement with vitamin B6 (2–10
mg/kg PO once daily).
Summary
Nutritional management is an important component of managing the most common causes of FLUTD.
Feeding moist food and using other methods to increase water intake are indicated for cats with FIC,
urethral plugs, and urolithiasis. Feeding therapeutic foods for 1–2 months may be used as the sole
treatment to dissolve struvite uroliths in cats. Foods formulated to prevent struvite urolith or urethral
plug recurrence, are indicated after urolith dissolution or removal of urethral plugs. Treatment of choice
for calcium oxalate uroliths is urolith removal followed by encouraging water intake feeding a
therapeutic food formulated to prevent urolith recurrence. Cats with a history of uroliths or urethral
plugs should be monitored periodically by performing urinalyses and diagnostic imaging to detect
recurrent disease and make changes in the therapeutic regimen as needed.
Table 1. Nutrient information for commercially available foods for managing cats with
FLUTD.*
Compan Food Form Indications† Kcal/k Na Ca Mg P n-3 n-6 Targe
y g as t
fed urine
pH
Hill’s Prescription Mois SP, C, FIC 1,062 0.3 0.7 0.05 0.6 0.9 4.3 6.2–
Diet® c/d™ t 2 2 2 8 6 6.4
Multicare with
Chicken Feline
Hill’s Prescription Dry SP, C, FIC 3,858 0.3 0.7 0.06 0.6 0.6 2.7 6.2–
Diet® c/d™ 3 6 1 5 4 6 6.4
Multicare with
Chicken Feline
Hill’s Prescription Mois SD 1,381 0.4 0.6 0.06 0.4 0.3 4.2 5.9–
Diet® s/d® t 1 2 2 8 4 4 6.1
Feline
Hill’s Prescription Dry SD 4,292 0.4 1.0 0.05 0.7 0.2 3.9 5.9–
Diet® s/d® 0 5 9 7 6 2 6.1
Feline
Hill’s Prescription Mois C/FIC 1,197 0.3 0.6 0.08 0.5 0.1 1.4 6.6–
Diet® x/d® t 7 9 2 3 5 7 6.8
with Chicken
Feline
Hill’s Prescription Dry C 3,794 0.3 0.7 0.07 0.6 0.1 2.7 6.6–
Diet® x/d® 6 6 6 6 6 8 6.8
Feline
Hill’s Prescription Mois SP/C/FIC 934 0.3 0.7 0.06 0.5 0.1 3.4 6.2–
Diet® w/d® t 3 4 3 9 5 8 6.4
Feline
Hill’s Prescription Dry SP/C 3,227 0.3 0.9 0.05 0.7 0.2 2.7 6.2–
Diet® w/d® 0 9 9 7 5 8 6.4
Feline
Iams Low Mois SP/FIC 1,159 0.4 1.2 0.1 1.0 5.9–
pH/S™/Felin t 6 7 0 6.3
e Formula
Iams Low Dry SP 4,286 0.5 1.1 0.08 0.9 0.4 3.3 5.9–
pH/S™/Felin 2 0 4 6 5 6.3
e Formula
Iams Moderate Mois C/FIC 1,159 0.4 1.2 0.10 0.9 6.3–
pH/O™ t 8 3 4 0 6.9
/Feline
Formula
Iams Moderate Dry C 4,235 0.4 1.1 0.08 0.9 6.3–
pH/O™ 8 1 8 6 6.9
/Feline
Formula
Purina ONE® Special Dry SP 4,313 0.2 1.0 0.07 0.9 < 6.3
Care Urinary 9 9
Tract Health
Formula
Purina Pro Plan® Dry SP 4,271 0.2 1.0 0.07 1.0 6.2–
Urinary Tract 6 5 0 1 6.4
Health
Formula Extra
Care
Purina UR URinary® Mois SD/SP/C/FI 1,057 0.6 0.9 0.07 0.9 6.0–
St/Ox Feline t C 2 6 7 6.4
Formula
Purina UR URinary® Dry SD/SP/C 3,441 1.1 1.1 0.07 1.0 6.0–
St/Ox Feline 7 0 8 6.4
Formula
Royal Veterinary Mois SP/FIC 1,350 0.4 1.2 0.08 1.1 6.0–
Canin Diet Control t 4 7 3 6.3
Formula
Royal Veterinary Dry SP 3,933 0.7 0.9 0.06 0.6 6.0–
Canin Diet Control 1 6 5 6.3
Formula
Royal Medi-Cal® Mois SD 847 1.2 1.0 NA 1.0 NA
Canin Dissolution t 7 8 6
Formula
Royal Medi-Cal® Dry SD 4,010 0.3 0.9 NA 0.9 NA
Canin Dissolution 7 7 7
Formula
Royal Veterinary Mois SD/SP/C/FI 1,211 1.0 1.0 0.09 1.3 6.0–
Canin Diet™ Feline t C 2 2 7 6 6.3
Urinary SO™
in Gel
Royal Veterinary Dry SD/SP/C 3,971 1.4 1.0 0.07 0.8 6.0–
Canin Diet™ Feline 0 8 5 6 6.3
Urinary SO
30TM
*Unless indicated, all nutrients expressed on dry matter basis
Na = sodium, Ca = calcium, Mg = magnesium, P = phosphorus,
n-6 = omega-6 fatty acids, n-3 = omega-3 fatty acids
† C = calcium oxalate prevention, FIC = feline idiopathic cystitis, SD = struvite dissolution, SP = struvite prevention
REFERENCES
1. Markwell PJ, et al. Clinical evaluation of commercially available urinary acidification diets in the management of
idiopathic cystitis in cats. J Am Vet Med Assoc 1999;214:361–365.
2. Gunn-Moore DA, et al. Oral glucosamine and the management of feline idiopathic cystitis. J Feline Med Surg
2004;6:219–225.
3. Kirschvink N, et al. Effects of feeding frequency on water intake in cats. J Vet Intern Med 2005;19:476.
4. Buranakarl C, et al. Effects of dietary sodium chloride intake on renal function and blood pressure in cats with
normal and reduced renal function. Am J Vet Res 2004;65:620–627.
5. Kirk CA, et al. Effects of sodium chloride on selected parameters in cats. Vet Ther 2006;7:333–346.
6. Luckschander N, et al. Dietary NaCl does not affect blood pressure in healthy cats. J Vet Intern Med 2004;18:463–
467.
7. Houston DM, et al. Evaluation of the efficacy of a commercial diet in the dissolution of feline struvite bladder
uroliths. Vet Ther 2004;5:187–201.
8. Osborne CA, et al. Medical dissolution of feline struvite urocystoliths. J Am Vet Med Assoc 1990;196:1053–1063.
9. Lulich J, et al. Typing the right knot: urolith prevention. Proc ACVIM Forum 2007.
10. Osborne CA, et al. Perineal urethrostomy versus dietary management in prevention of recurrent lower urinary
tract disease. J Small Anim Pract 1991;32:296–305.
11. Bovee K, et al. Recurrence of feline urethral obstruction. J Am Vet Med Assoc 1979;174:93–96.
12. Lekcharoensuk C, et al. Association between dietary factors and calcium oxalate and magnesium ammonium
phosphate urolithiasis in cats. J Am Vet Med Assoc 2001;219:1228–1237.
13. Lulich JP, et al. Effects of diet on urine composition of cats with calcium oxalate urolithiasis. J Am Anim Hosp
Assoc 2004;40:185–191.
14. McClain HM, et al. Hypercalcemia and calcium oxalate urolithiasis in cats: a report of five cases. J Am Anim Hosp
Assoc 1999;35:297–301.
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