The effect of a therapeutic urinary stress diet on the short-term recurrence of feline idiopathic cystitis.

The aim of this cohort study was to evaluate the effect of a therapeutic urinary stress diet on recurrent clinical signs of lower urinary tract disease in cats with idiopathic cystitis. The effects of feeding a therapeutic urinary stress diet were compared with feeding a non-therapeutic diet for a duration of 5 weeks. The owners selected themselves which food to feed their cat. Of 31 cats with acute non-obstructive idiopathic cystitis, 17 were fed the test food and 14 the control food. An episode of recurrence was defined as a minimum of one day with at least two clinical signs; i.e. stranguria, periuria, haematuria, dysuria and pollakiuria. The number of cats fed the therapeutic urinary stress diet that had an episode of recurrence (5/17) was significantly lower compared with cats that were fed other commercial diets (11/14). The formulation of the foods fed to the participating cats (dry, moist or a combination of both) was not found significant compared with the recurrence of idiopathic cystitis. Apart from type of diet, no other risk factors affected the short-term recurrence of FIC. A prospective clinical trial is needed to confirm these findings.

Concentrations of leptin, adiponectin, and resistin in the serum of obese cats during weight loss.

We monitored changes in serum leptin, adiponectin, and resistin concentrations in obese cats during weight loss. Six naturally developed obese cats were fed low-fat, high-fiber dry food during a 9-week experimental period. Serum leptin, adiponectin, and resistin concentrations were measured at week 0, 4, 8, and 9. Body weight became significantly lower week 4 onward than that at week 0 (P<0.05 or 0.01). At week 9, serum leptin concentrations were significantly lower than those at week 0 (P<0.05). Contrarily, serum adiponectin and resistin concentrations did not significantly differ within the 9 weeks. While serum leptin levels were strongly positively correlated with body weight (r=0.923, P<0.001), serum adiponectin levels were moderately negatively correlated with it (r=-0.529, P<0.01), with serum resistin having a no correlation with body weight. Serum leptin levels might be more closely related with pathogenesis of adiposity than serum adiponectin or resistin in cats.

Nutritional Management of Urolithiasis.

Dietary management of urolithiasis in dogs and cats is designed to dissolve calculi when possible and/or reduce the risk of recurrence. The diet must reduce urine relative supersaturation for the particular salt in order to prevent crystallization. To decrease urinary concentrations of crystal precursors, increasing water intake is essential regardless of the stone type. Altering the amounts of dietary precursors of the stone and controlling urine pH is mostly effective for struvite, urate, xanthine, and cystine, but still subject to controversy for calcium oxalate. The investigation of underlying metabolic disorders and close monitoring of animals at risk is recommended.

Narrative review of therapies for chronic enteropathies in dogs and cats.

BACKGROUND: The optimal medical treatment for chronic enteropathy (CE) in dogs and cats is controversial. Sequential treatment using diet, antimicrobials, and immunosuppressive drugs is the most common strategy used by clinicians. OBJECTIVES: To review the evidence for the effectiveness of dietary, drug, and alternative health interventions for inducing clinical remission in dogs and cats with CE. ANIMALS: Retrospective study of dogs and cats with a diagnosis of chronic enteropathy. METHODS: MEDLINE and Centre for Agriculture and Bioscience International (CABI) databases (1950 to March 2017) were searched for randomized controlled trials (RCTs), observational studies, and case series. The primary outcome was induction of clinical remission. All studies were evaluated using the quality of evidence grading guidelines (I-IV), which assign a score defining the strength and quality of the evidence. RESULTS: Twenty-two studies (11 RCTs in dogs and 2 in cats and 9 cohort studies or case series) met the inclusion criteria for inducing remission of gastrointestinal (GI) signs. Of the 13 RCTs achieving grade I scores, 10 studies (totaling 218 dogs and 65 cats) compared single treatment: diet (n = 3), immunosuppressives (n = 3), antimicrobials (n = 2), anti-inflammatory drugs (n = 1), and probiotics (n = 1). Three case series (grade III) reported clinical remission using an elimination diet fed to 55 cats and use of enrofloxacin to induce remission in dogs with granulomatous colitis (2 studies totaling 16 dogs). CONCLUSIONS AND CLINICAL IMPORTANCE: The current evidence for treatment of CE is much greater in dogs than in cats. There is sufficient strong evidence to recommend the use of therapeutic GI diets, glucocorticoids, enrofloxacin, or some combination of these in dogs with CE. Therapeutic GI diets and glucocorticoids are most useful in cats with CE.

Effects of weight loss with a moderate-protein, high-fiber diet on body composition, voluntary physical activity, and fecal microbiota of obese cats.

OBJECTIVE To determine effects of restriction feeding of a moderate-protein, high-fiber diet on loss of body weight (BW), voluntary physical activity, body composition, and fecal microbiota of overweight cats. ANIMALS 8 neutered male adult cats. PROCEDURES After BW maintenance for 4 weeks (week 0 = last week of baseline period), cats were fed to lose approximately 1.5% of BW/wk for 18 weeks. Food intake (daily), BW (twice per week), body condition score (weekly), body composition (every 4 weeks), serum biochemical analysis (weeks 0, 1, 2, 4, 8, 12, and 16), physical activity (every 6 weeks), and fecal microbiota (weeks 0, 1, 2, 4, 8, 12, and 16) were assessed. RESULTS BW, body condition score, serum triglyceride concentration, and body fat mass and percentage decreased significantly over time. Lean mass decreased significantly at weeks 12 and 16. Energy required to maintain BW was 14% less than National Research Council estimates for overweight cats and 16% more than resting energy requirement estimates. Energy required for weight loss was 11% more, 6% less, and 16% less than American Animal Hospital Association recommendations for weight loss (80% of resting energy requirement) at weeks 1 through 4, 5 through 8, and 9 through 18, respectively. Relative abundance of Actinobacteria increased and Bacteroidetes decreased with weight loss. CONCLUSIONS AND CLINICAL RELEVANCE Restricted feeding of a moderate-protein, high-fiber diet appeared to be a safe and effective means for weight loss in cats. Energy requirements for neutered cats may be overestimated and should be reconsidered.

Use of Purina Pro Plan Veterinary Diet UR Urinary St/Ox to Dissolve Struvite Cystoliths.

The objective of this study was to determine the efficacy of feeding the commercially available diet, Purina Pro Plan Veterinary Diets UR Urinary St/Ox, for the dissolution of struvite cystoliths in cats with naturally occurring disease. Twelve cats with clinical signs of lower urinary tract disease and cystoliths confirmed via radiographs were enrolled. The cats were fed the study diet ad libitum and assessed by abdominal radiographs weekly. Cats with cystoliths that resolved based on radiographs and confirmatory ultrasound examination were considered diet successes. Cats with no change in cystolith size after 2-6 weeks underwent cystotomy for stone removal, aerobic culture and antimicrobial susceptibility testing, and analysis. All cats accepted the study diet, and weight loss was not noted over the course of the study. Total cystolith dissolution was achieved by week 2 for 5 cats, which were presumed to have struvite cystoliths. All other cats underwent cystotomy for stone removal after radiographic evidence of cystoliths were still present at 2 weeks (1 cat with severe signs), 4 weeks (5 cats), or 6 weeks (1 cat). The cystoliths that were surgically removed were calcium oxalate (5 cats) and mixed (2 cats) and would not be expected to dissolve with this diet. Follow-up radiographs from 6 cats fed the diet long term (3 presumed struvite and 3 with other cystoliths removed surgically) were collected from 1 to 6 months after beginning the study and showed no evidence of cystolith recurrence. While larger case numbers are needed, these results suggest that feeding Purina Pro Plan Veterinary Diets UR Urinary St/Ox can successfully dissolve cystoliths that are likely struvite and may lessen the risk of recurrence of struvite and calcium oxalate cystoliths.

Evaluation of clinicopathological features in cats with chronic gastrointestinal signs.

Food-responsive enteropathy (FRE), idiopathic inflammatory bowel disease (IBD), and alimentary tract lymphoma (AL) are often the remaining differentials for cats presenting with chronic gastrointestinal (GI) signs. Differential diagnosis is further complicated by overlapping clinicopathological features and histopathological changes, however. In this study we describe the clinical presentation of cats with chronic GI signs secondary to FRE, IBD, and AL, and evaluate possible associations between clinical, clinicopathological, ultrasonographic findings and diagnosis. The medical records of client-owned cats with chronic GI signs secondary to FRE, IBD, and AL were reviewed. Univariate and multivariate logistic regression models and receiver-operating characteristic curve (ROC) analysis were used for testing the data. Of the 56 cats included in the study, 22 were diagnosed with FRE (mean age, 70 months ± 49), 17 with IBD (mean age, 101 months ± 40), and 17 with AL (mean age, 122 months ± 45). Cats with FRE were younger and presented more often with diarrhea and less frequently with muscle wasting than cats with IBD or AL. In cats with AL, serum cobalamin levels were lower than in those with FRE or IBD (239 ± 190 ng/L vs. 762 ± 408 ng/L and 625 ± 443 ng/L, respectively) and folate levels were higher than in cats with IBD (18.2 ± 4.2 µg/L vs. 9.1 ± 4.7 µg/L, respectively). Multivariate/ROC curve analysis showed increased values of BUN (sensitivity 100, specificity 29.4, criterion >37 mg/dl) and serum folate (sensitivity 80, specificity 100, criterion >15.6 µg/L) and reduced values of cobalamin (sensitivity 100, specificity 62.5, criterion ≤540 ng/L), which suggested a diagnosis of AL versus IBD. Some clinicopathological features evaluated at diagnosis might suggest AL; however, because differentiating AL from IBD is often difficult, definitive diagnosis should be based on invasive diagnostic workup.

Therapeutic effects of an alpha-casozepine and L-tryptophan supplemented diet on fear and anxiety in the cat.

Objectives This study assessed the anxiolytic effectiveness of a test diet (Royal Canin Feline Calm diet) supplemented with L-tryptophan and alpha-casozepine. Methods Subjects were 24 cats that were classified as mildly or markedly fearful based on the presence of a person in their home room. Three different protocols were used to assess anxiety: (1) evaluation of the response to a human in the cat's home room (home room test); (2) analysis of the response to placement in an empty test room (open-field test); and (3) analysis of the response to an unfamiliar human (human interaction test). All three protocols were first run at baseline, and the results were used to assign the animals to control and test diet groups that showed equivalent fear and anxiety. Both groups were retested on the three protocols after 2 weeks (test 1) and again after 4 weeks (test 2). Results The diet groups differed for two behavioral measures in the open-field test: inactivity duration and inactivity frequency. The control group showed statistically significant increases in inactivity duration between baseline and test 1 and baseline and test 2, while the group fed the test diet showed a marginally not significant decrease in inactivity duration between baseline and test 1 and a not significant decrease for test 2. There was also a significant increase in inactivity frequency between baseline and test 1 in the test diet group and marginally not significant decrease in the control group. There were no differences between groups in the approach of the cats toward people for the home room test and the human interaction test. Conclusions and relevance These results suggest that the test diet reduced the anxiety response to placement in an unfamiliar location, but that fear in the presence of an unfamiliar person was not counteracted by the diet.

Effectiveness of a new dietetic weight management food to achieve weight loss in client-owned obese cats.

OBJECTIVES: The aim of the study was to evaluate weight loss and maintenance parameters in cats fed a novel weight management food and to assess the owner's perception of the cat's quality of life. METHODS: This study was designed as a prospective, uncontrolled/unmasked clinical trial. One hundred and thirty-two overweight/obese, otherwise healthy, client-owned cats were enrolled. Initial evaluation included physical examination, nutritional assessment, ideal body weight determination and weight-loss feeding guidelines development. Follow-up evaluations (monthly for 6 months) encompassed determination of body weight, body condition score, body fat index, muscle condition score and feeding practices. Quality of life assessment by owners included the cat's level of energy, happiness, appetite, begging behavior, flatulence, stool volume and fecal score. RESULTS: Eighty-three percent of the cats lost weight, with an average ± SEM weight loss of 11.0 ± 1.8% over 6 months and an average ± SE weekly weight loss rate of 0.45 ± 0.02%. The mean ± SEM duration of weight loss was 134.0 ± 4.8 days. Fourteen percent of cats achieved an ideal body weight. Seventy-nine percent of cats ate more calories from novel weight management food than the recommended daily energy requirement for weight loss, and the majority of these cats still lost weight. Body condition score and body fat index decreased over time compared with baseline from weeks 12-24 and from weeks 8-24, respectively. Owners perceived an increase in energy and happiness (>week 12) in the cats that lost weight, without changes in appetite or begging behavior. CONCLUSIONS AND RELEVANCE: This study confirmed the effectiveness of the novel weight management food in achieving weight loss in overweight/obese client-owned cats. Owners reported significant improvements in their cat's quality of life without negative side effects.

Comparison of foods with differing nutritional profiles for long-term management of acute nonobstructive idiopathic cystitis in cats.

OBJECTIVE: To evaluate the effect of nutrition on recurrent clinical signs of lower urinary tract (LUT) disease in cats with idiopathic cystitis. DESIGN: Randomized, controlled, masked clinical trial. ANIMALS: 31 cats with acute nonobstructive idiopathic cystitis. PROCEDURES: Cats were assigned to receive 1 of 2 foods (a cystitis prevention or control food) that differed in mineral (calcium, phosphorous, and magnesium), antioxidant, and fatty acid profiles. Owners documented LUT signs daily for up to 1 year. The primary endpoint was the number of recurrent episodes in which a cat had multiple (≥ 2 concurrent) LUT signs within a day (defined as multiple-sign day). Consecutive days in which a cat had multiple LUT signs were considered as a single episode. RESULTS: 4 cats fed prevention food and 2 cats fed control food were excluded from analysis because of noncompliance, gastrointestinal signs, food refusal, or owner voluntary withdrawal. The proportion of cats fed prevention food that had ≥ 1 recurrent episode of multiple-sign days (4/11) was not significantly lower than that of cats fed control food (9/14). However, cats fed prevention food had significantly lower mean incidence rates for recurrent episodes of multiple-sign days (0.7 episodes/1,000 cat-days) and episodes of hematuria (0.3 episodes/1,000 cat-days), dysuria (0.2 episodes/1,000 cat-days), and stranguria (0.2 episodes/1,000 cat-days) as single LUT signs, compared with cats fed control food (5.4, 3.4, 3.1, and 3.8 episodes/1,000 cat-days, respectively). Significantly fewer cats fed prevention food required analgesics (4/11), compared with cats fed control food (12/14). CONCLUSIONS AND CLINICAL RELEVANCE: Foods with differing nutritional profiles appeared to impact mean incidence rates of recurrent feline idiopathic cystitis-associated signs.

Assessment of protein and amino acid concentrations and labeling adequacy of commercial vegetarian diets formulated for dogs and cats.

OBJECTIVE: To determine measured crude protein (CP) and amino acid (AA) concentrations and assess labeling adequacy of vegetarian diets formulated for dogs and cats. DESIGN: Cross-sectional study. SAMPLE: 13 dry and 11 canned vegetarian diets for dogs and cats. PROCEDURES: Concentrations of CP and AAs were determined for each diet. Values were compared with the Association of American Feed Control Officials (AAFCO) Dog and Cat Food Nutrient Profiles. Product labels were assessed for compliance with AAFCO regulations. RESULTS: CP concentration (dry-matter basis) ranged from 19.2% to 40.3% (median, 29.8%). Minimum CP concentrations for the specified species and life stage were met by 23 diets; the remaining diet passed appropriate AAFCO feeding trials. Six diets did not meet all AA minimums, compared with the AAFCO nutrient profiles. Of these 6 diets, 1 was below AAFCO minimum requirements in 4 AAs (leucine, methionine, methionine-cystine, and taurine), 2 were below in 3 AAs (methionine, methionine-cystine, and taurine), 2 were below in 2 AAs (lysine and tryptophan), and 1 was below in 1 AA (tryptophan). Only 3 and 8 diets (with and without a statement of calorie content as a requirement, respectively) were compliant with all pet food label regulations established by the AAFCO. CONCLUSION AND CLINICAL RELEVANCE: Most diets assessed in this study were not compliant with AAFCO labeling regulations, and there were concerns regarding adequacy of AA content. Manufacturers should ensure regulatory compliance and nutritional adequacy of all diets, and pets fed commercially available vegetarian diets should be monitored and assessed routinely.

Effects of two calculolytic diets on parameters of feline mineral metabolism.

OBJECTIVES: To evaluate the influence of two feline calculolytic diets on selected parameters of mineral metabolism. MATERIALS AND METHODS: Two dry commercial diets designed for struvite urolith dissolution were evaluated in 14 cats. The study was designed as a two-sequence, four-period crossover protocol with a baseline period, two 60-day "run-in" periods in which calculolytic diets (Diet 1 and Diet 2) were fed and one 30-day "wash-out" period. Data are expressed as median (range). RESULTS: Feeding the calculolytic diets for two months did not alter plasma concentrations of calcium, phosphorus, magnesium and parathyroid hormone. A significant (P < 0.05 in each case) decline in calcitriol was observed after administering both diets from 236.4 (122.4-429.6) to 170.4 (108.0-394.3) pmol/L (Diet 1) and from 278.4 (153.6-492.0) to 177.1 (87.6-392.4) pmol/L (Diet 2). Cats fed Diet 1 showed a significant increase in urine calcium concentration (from 0.3 (0.2-0.5) to 0.4 (0.3-0.7) mmol/L). Magnesium concentration in urine was significantly increased with both diets, from 1.4 (0.1-1.7) to 1.5 (1.3-2.4) mmol/L (Diet 1) and from 1.1 (0.4-1.9) to 2.0 (0.1-3.1) mmol/L (Diet 2). CLINICAL SIGNIFICANCE: Both diets resulted in an increased urinary concentration of magnesium, through different mechanisms: urine acidification (Diet 1) and increased sodium load (Diet 2).

Survey of dietary and medication practices of owners of cats with chronic kidney disease.

The objective of this study was to describe the dietary and medication patterns of cats with chronic kidney disease (CKD). In this prospective, cross-sectional descriptive study, owners of cats with CKD were asked to complete a web-based survey. The study was advertised on CKD-, pet-, veterinary- and breed-associated websites and list serves. Owners of 1089 cats with CKD participated in the study. The mean reported age of the cats with CKD was 13.7 ± 4.2 years. Forty percent (430/1089) of cats had concurrent diseases, with hyperthyroidism, heart disease and inflammatory bowel disease being the most common. Veterinarian recommendation was the most common reason reported (684/1032; 66%) for diet selection, and 51% (556/1089) of owners fed a veterinary therapeutic diet formulated for kidney disease as some component of the diet. Many owners (466/1079; 43%) reported that their cats had an abnormal appetite; of these owners, 52% responded that their cats had a poor appetite or required coaxing to eat 5-7 days per week. Forty-seven percent and 51% of cats were receiving subcutaneous fluids and oral medications, respectively; however, most cats (811/1036; 78%) were not receiving phosphorus-binding medications. Fifty-six percent and 38% of cats received commercial cat treats and dietary supplements, respectively. Anorexia or hyporexia is a common problem in cats with CKD and may lead to cats being fed suboptimal diets for their disease. This information may be useful for treating or designing nutritional studies for cats with CKD.

Effects of an iodine-restricted food on client-owned cats with hyperthyroidism.

The objective of this prospective, multicentre, non-controlled, open-label study was to evaluate the effects of an iodine-restricted food on circulating total thyroxine (TT4) concentrations and clinical parameters in client-owned cats with hyperthyroidism. Two hundred and twenty-five cats were enrolled in the study and adapted to the iodine-restricted food. Data from physical examinations, questionnaires completed by veterinarians and owners, and circulating concentrations of TT4, urea and creatinine were recorded at weeks 0, 4 and 8. The study group included 136 female and 89 male cats (median age 15 years, range 4-21 years). Group 1 (n = 113) had been on previous anti-thyroid medication, while group 2 (n = 112) consisted of newly diagnosed cats. No differences were found between the two groups at any time point. Circulating TT4 concentrations had decreased (P <0.0001) at week 4 and did not change significantly from week 4 to week 8. Circulating TT4 concentration was within the reference range in 56/88 cats at week 4 and in 51/68 cats at week 8. Clinical parameters (vomiting, polyuria, polydipsia, hyperactivity, polyphagia, weight loss, hair coat quality, and quality of life) had improved (P <0.0001) by week 4. Circulating creatinine concentration decreased (P = 0.001) from week 0 to week 4. Side effects associated with feeding the iodine-restricted food were not observed. In conclusion, in client-owned cats with hyperthyroidism an iodine-restricted food is a valuable management option to normalise circulating TT4 concentrations, and improve clinical signs of hyperthyroidism within 4 weeks. This applies to newly diagnosed cats, as well as to previously diagnosed cats receiving anti-thyroid drugs.

A survey of Southeastern United States veterinarians' preferences for managing cats with diabetes mellitus.

This study evaluated primary practitioners' perceptions of managing feline diabetics. Surveys distributed during local continuing education events achieved a response rate of 46% (90/195). A mean of 74% feline diabetics required chronic insulin; 26% were transient diabetics. Choice of insulin was most influenced by duration of action: human recombinant protamine zinc insulin was ranked first (42%) and glargine second (27%). Dietary management was always/usually recommended by 97% respondents, with prescription or proprietary low-carbohydrate, high-protein diets recommended in 93% responses. More recent graduates (P=0.0419), those who worked in larger practices (P=0.0315), and those who saw more transient diabetics (P=0.0288) were more likely to recommend dietary change. In-house blood glucose curves (BGCs) were the most popular method of assessing glycemic control, while at-home BGCs were least popular, although their use correlated positively with annual diabetic caseload (r=0.43, P=0.0239). Owners mishandling insulin was cited as the most common cause of poor glycemic control, while clinical signs of acromegaly were rarely recognized.

Evaluation of canned therapeutic diets for the management of cats with naturally occurring chronic diarrhea.

Dietary therapy plays an important role in the management of most gastrointestinal disorders. This study was designed to test the efficacy of a new therapeutic diet for cats with diarrhea, compared to the top selling brand. Sixteen adult cats with chronic diarrhea were grouped and assigned to diet X (Hill's Prescription Diet i/d Feline) or diet Y (Purina Veterinary Diets EN Gastroenteric Feline Formula). Following baseline evaluations, cats were fed their assigned test diet for 4 weeks. Fecal scores (FS; 7=very watery; 1=extremely dry and firm) were recorded daily during the last week on each diet. Each cat was then switched to the alternate test diet and the procedure was repeated. Fifteen cats completed the study. Both therapeutic diets resulted in a significant improvement in average FS and diet Y also resulted in significantly better results compared with diet X. Average FS improved at least one unit in 40% of the cats while fed diet X and in 67% of the cats while fed diet Y, resulting in normal stools (average FS≤3) in 13.3% of cats fed diet X and 46.7% of cats fed diet Y. This study confirms the value of dietary change in the management of chronic diarrhea in cats.

Effect of citrus polyphenol- and curcumin-supplemented diet on inflammatory state in obese cats.

Among obesity-associated disorders, low-grade inflammation has been described. The putative therapeutic properties of citrus and curcumin polyphenols could be associated with their anti-inflammatory properties. Two diets supplemented either with hesperidin (0.05 %) and naringin (0.1 %) from citrus extract or with highly bioavailable curcumin from Curcuma longa extract (0.09 %) were fed to eight obese cats for two 8-week periods (cross-over study design) while maintaining animals in an obese state. Plasma acute-phase protein (APP; α1-acid glycoprotein (AGP), serum amyloid A and haptoglobin) levels were assessed before and at the end of each test period. TNF-α, IL-1ß, IL-2, IL-4, IL-5, IL-10, IL-12, IL-18, transforming growth factor-ß, interferon (IFN)-γ mRNA levels were determined in peripheral blood mononuclear cells (PBMC) by real-time PCR. Compared with pre-study values, supplementation with citrus polyphenols resulted in lower plasma AGP and haptoglobin concentrations, while that with curcumin resulted in lower plasma AGP concentration. There were no differences between the supplementations. TNF-α, IL-1ß, IL-4, IL-5, IL-10, IL-12, IL-18, transforming growth factor-ß, mRNA levels remained unaffected by either dietary supplementation. In contrast, IFN-γ and IL-2 mRNA levels were lower at the end of the citrus and the curcumin supplementation, respectively. There were no differences between the supplementations. The present study results show a slight effect of citrus and curcumin supplementation on inflammatory markers expressed by PBMC, and a decreased concentration of APP, which are mainly expressed by the liver. This would confirm that hesperidin and naringin or highly bioavailable curcumin extract have beneficial effects, targeted in the liver and could improve the obesity-related inflammatory state.

A diet with a struvite relative supersaturation less than 1 is effective in dissolving struvite stones in vivo.

Magnesium ammonium phosphate (struvite) is one of the most common minerals found in feline uroliths. Previous studies have shown the efficacy of acidifying calculolytic diets (inducing urine pH < 6.5), in dissolving struvite stones in cats. Recent work in our laboratory found that wet and dry test diets induce a struvite urinary relative supersaturation (RSS) < 1 and that the urine of healthy cats fed the dry test diet dissolved feline struvite stones in vitro. The objective of the present study was to demonstrate the efficacy of those test diets on naturally occurring struvite urocystoliths in cats. A total of twenty-one cats were used, of which seventeen completed the study. Of the seventeen cats, eight were fed the wet test diet and nine the dry test diet. Uroliths dissolved in a median of 18 (10-55) d. In the remaining four cats, uroliths failed to dissolve and were removed surgically. Quantitative analysis showed that these uroliths contained either calcium oxalate or calcium phosphate. The present study demonstrates that diets that induce a struvite RSS < 1 result in struvite stone dissolution in vivo.