Effect of magnesium-deficient diet on serum and urine magnesium concentrations in healthy cats.

OBJECTIVE: To evaluate the efficacy of using serum total and ionized magnesium (Mg) concentrations and urine Mg concentrations to identify Mg deficiency in cats. ANIMALS: 6 healthy castrated male cats. PROCEDURE: A Mg-replete diet was fed for 37 days, followed by a Mg-deficient diet for 37 days. On days 1, 3, and 7 of the last week of each diet, serum ionized and total Mg concentrations were determined; in addition, urine Mg concentration was determined each day of the last week. Serum total and ionized Mg concentrations were compared with urine Mg concentration, amount of Mg excreted during 24 hours (24-hour urine Mg excretion), ratio of urine Mg concentration to urine creatinine concentration (Umg:Ucr), and urinary fractional excretion of Mg (FEmg) to determine which variable best predicted Mg status. RESULTS: Cats fed Mg-deficient diets had significantly lower serum total and ionized Mg concentrations and 24-hour urine Mg excretion values, compared with cats fed Mg-replete diets. Serum total Mg concentration was the best predictor of Mg status. Twenty-four-hour urine Mg excretion was a repeatable, reliable measurement and had the best correlation with serum total Mg concentration. Serum total Mg concentration also correlated with urine Mg concentration, Umg:Ucr, and FEmg. CONCLUSIONS AND CLINICAL RELEVANCE: Serum total and ionized Mg concentrations can be used to identify cats with dietary-induced Mg deficiencies. Twenty-four-hour urine Mg excretion and urine Mg concentration correlated best with serum total Mg concentration and, therefore, may be the most useful urine variables for identifying Mg deficiency.     

Effects of dietary potassium citrate supplementation on urine pH and urinary relative supersaturation of calcium oxalate and struvite in healthy dogs

OBJECTIVE: To assess the effect of dietary potassium citrate supplementation on the urinary pH, relative supersaturation of calcium oxalate and struvite (defined as the activity product/solubility product of the substance), and concentrations of magnesium, ammonium, phosphate, citrate, calcium, and oxalate in dogs. ANIMALS: 12 healthy adult dogs. PROCEDURE: Canned dog food was fed to dogs for 37 days. Dogs were randomly allocated to 3 groups and fed test diets for a period of 8 days. Study periods were separated by 6-day intervals. During each study period the dogs were fed either standard diet solus (control) or standard diet plus 1 of 2 types of potassium citrate supplements (150 mg potassium citrate/kg of body weight/d) twice daily. Urinary pH, volume and specific gravity, relative supersaturation of calcium oxalate and struvite, and concentrations of magnesium, ammonium, phosphate, calcium, oxalate, and citrate were assessed for each treatment. RESULTS: Mean urine pH was not significantly affected by dietary potassium citrate supplementation, although urine pH did increase by 0.2 pH units with supplementation. Diets containing potassium citrate maintained a higher urine pH for a longer part of the day than control diet. Three Miniature Schnauzers had a significantly lower urinary relative calcium oxalate supersaturation when fed a diet supplemented with potassium citrate, compared with control diet. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary potassium citrate supplementation has limited effects on urinary variables in most healthy dogs, although supplementation results in maintenance of a higher urine pH later in the day. Consequently, if supplementation is introduced, dogs should be fed twice daily and potassium citrate should be given with both meals or with the evening meal only.     

Association between dietary factors and calcium oxalate and magnesium ammonium phosphate urolithiasis in cats.

OBJECTIVE: To identify dietary factors associated with the increase in occurrence of calcium oxalate (CaOx) uroliths and the decrease in occurrence of magnesium ammonium phosphate (MAP) uroliths in cats. DESIGN: Case-control study. ANIMALS: 173 cats with CaOx uroliths, 290 cats with MAP uroliths, and 827 cats without any urinary tract diseases. PROCEDURE: Univariate and multivariate logistic regression were performed. RESULTS: Cats fed diets low in sodium or potassium or formulated to maximize urine acidity had an increased risk of developing CaOx uroliths but a decreased risk of developing MAP uroliths. Additionally, compared with the lowest contents, diets with the highest moisture or protein contents and with moderate magnesium, phosphorus, or calcium contents were associated with decreased risk of CaOx urolith formation. In contrast, diets with moderate fat or carbohydrate contents were associated with increased risk of CaOx urolith formation. Diets with the highest magnesium, phosphorus, calcium, chloride, or fiber contents and moderate protein content were associated with increased risk of MAP urolith formation. On the other hand, diets with the highest fat content were associated with decreased risk of MAP urolith formation. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that diets formulated to contain higher protein, sodium, potassium, moisture, calcium, phosphorus, and magnesium contents and with decreased urine acidifying potential may minimize formation of CaOx uroliths in cats. Diets formulated to contain higher fat content and lower protein and potassium contents and with increased urine acidifying potential may minimize formation of MAP uroliths.     

Effect of diet on struvite activity product in feline urine

Groups of male specific-pathogen-free cats were fed a basal, purified diet (A), with or without 0.45% added magnesium (MgCl2, diet B; MgO, diet C) or 1 of 2 commercial diets (D,E). Urine samples collected for 48 hours after 2 weeks of feeding were analyzed for calcium, magnesium, sodium, potassium, ammonium, sulfate, phosphate, oxalate, and citrate content. Concentrations were used to calculate the negative logarithm of the struvite activity product (pSAP), using a microcomputer-based program for calculation of supersaturation of the urine with crystal solutes. The pSAP value for all samples also was hand-calculated by use of an equation. Consumption of diet B caused a significant (P less than 0.05) increase in urine calcium concentration. Total urine phosphate concentration was lower in urine from cats fed diets A, B, or C than in urine from cats fed diets D or E. For the various diets, urine PO4(-3) was: 5.3 microM for diet A; 6.3 microM for diet C; 0.9 microM for diet E; 36 nM for diet D, and 0.5 nM for diet B. Consumption of diets B and C caused significant increases in urine magnesium concentration (53.1 nM and 49.1 mM, respectively). Ammonium ion concentration was highest in urine from cats fed diets B and D, 116.2 mM and 100.3 mM, respectively. When the pSAP, hand-calculated assuming ionic strength u = 0.2, was regressed on that calculated by use of the microcomputer program, the coefficient of determination was 0.96 (P less than or equal to 0.01).     

Diuretic effects of fenoldopam in healthy cats

Objective: To determine the effect of fenoldopam infusion on urine output, sodium excretion, creatinine clearance, and indirect blood pressure in healthy cats. Design: Prospective study. Setting: Veterinary medical teaching hospital. Animals: Eight purpose‐bred cats, 2–4 years old. Interventions: None. Measurements: Urine output was measured hourly for 12 hours before and after fenoldopam administration. Sodium excretion, modified creatinine clearance, and fractional sodium excretion were measured before and following fenoldopam administration. Urine specific gravity, central venous pressure, and systolic blood pressure were measured every 4 hours during the experiment. Main results: Compared with pre‐infusion values, urine output, sodium excretion, and fractional excretion of sodium increased significantly 6 hours after initiation of fenoldopam infusion. This increase was sustained throughout the observation period. The modified creatinine clearance decreased significantly following 2 hours of fenoldopam infusion, but increased significantly by 6 hours after infusion, the time of peak urine output. Changes in urine specific gravity mirrored changes in fractional sodium excretion, whereas the central venous pressure mirrored changes in modified creatinine clearance. The diuretic effect in cats was prevented when a dopamine receptor blocking agent was administered before fenoldopam infusion. Conclusion: Fenoldopam at a dose of 0.5 μg/kg/min induces diuresis in cats in a delayed manner. This increase appears to be due, in part, to dopamine receptor‐induced natriuresis. Changes in glomerular filtration rate may also occur.     

Azotemia in cats with feline hypertrophic cardiomyopathy: Prevalence and relationships with echocardiographic variables

ObjectivesThe prevalence of renal azotemia in cats with acquired heart disease is not well documented. The aims of this study were therefore (1) to determine the prevalence of azotemia within a hospital population of cats with hypertrophic cardiomyopathy (HCM), and (2) to evaluate the relationship between echocardiographic variables and plasma urea and creatinine.Animals, materials and methods134 client-owned cats were retrospectively studied including 102 cats with HCM and 32 control cats. A complete physical examination, electrocardiography, systolic arterial blood pressure measurement, thoracic radiographs, and echocardiography were performed. Plasma creatinine and urea were determined in all cats. The animal was considered azotemic if plasma creatinine was >1.8 mg/dL and/or urea >65 mg/dL (i.e. BUN> 30 mg/dL).ResultsThe prevalence of azotemia was lower in control cats (25.0%) than in cats with HCM (58.8%) (P = 0.003). No significant differences in plasma urea and creatinine were observed between the HCM and control cats. There was no effect of plasma creatinine and urea on conventional echocardiographic variables in cats with HCM.ConclusionsAzotemia is a frequent finding in cats with HCM but is not dependent on echocardiographic variables.     

Effects of dietary protein content on renal parameters in normal cats

This study evaluates the effect of dietary protein content on renal parameters in 23 healthy spayed female cats. The objective was to determine if cats eating diets high in protein will have higher serum urea nitrogen (UN) and creatinine values without a detectable change in kidney function, as assessed by urinalysis. A single random cross-over design was used. Cats were fed a standard maintenance diet for at least 1 month prior to the dietary trial. They were fed in two phases. For the first phase, cats were randomly assigned to receive either a high protein [HP=46% metabolizable energy (ME)] or low protein (LP=26% ME) diet. For the second phase, cats were fed whichever diet they were not fed during the phase I period. Blood and urine samples were collected at 2-week intervals for the duration of the study (10 weeks). UN, albumin, alanine aminotransferase and urine specific gravity were significantly higher, and creatinine and phosphorus were significantly lower (P<0.05) when cats were fed the HP diet as compared to when they were fed the LP diet, although none of the mean values were found to be outside of the corresponding reference interval. Dietary intake can result in clinically significant changes in UN and statistically significantly changes in several other biochemical analytes, although all analytes are likely to remain within normal reference intervals. Therefore, an accurate dietary history is necessary to help determine if renal parameters are being influenced by diet in a particular patient.     

Influence of prednisolone on urinary calcium oxalate and struvite relative supersaturation in healthy young adult female domestic shorthaired cats

Prednisolone (10 mg PO q24h) or placebo was administered to healthy cats for 2 weeks in a masked, placebo-controlled, crossover-design study, and 24-hour urine samples were collected. When cats received prednisolone, 24-hour urine pH was lower and 24-hour urine excretion of creatinine, magnesium, phosphate, and potassium was higher than when cats received placebo. No significant difference was found in urinary relative supersaturation for calcium oxalate (CaOx) or struvite between treatment groups. Prednisolone administration did not induce diuresis, nor was it associated with increased calcium excretion or urinary saturation for CaOx in these healthy cats. Results of this study, however, should not be extrapolated to cats that form CaOx uroliths associated with idiopathic hypercalcemia.     

Influence of hydrochlorothiazide on urinary calcium oxalate relative supersaturation in healthy young adult female domestic shorthaired cats

Hydrochlorothiazide (1 mg/kg PO q12h) or placebo was administered to healthy cats for 2 weeks in a masked, placebo-controlled, crossover-design study, and 24-hour urine samples were collected. When cats received hydrochlorothiazide, 24-hour urine volume, ammonia, chloride, creatinine, magnesium, oxalic acid, phosphate, potassium, and sodium were significantly higher than when cats received placebo. Hydrochlorothiazide was associated with significantly lower urinary saturation for calcium oxalate, but no difference was found in 24-hour urine calcium and citrate, urinary saturation for struvite, or blood ionized calcium. Hydrochlorothiazide decreased urinary saturation for calcium oxalate and could be useful in managing cats with calcium oxalate uroliths. Results of this study, however, should not be extrapolated to cats that form calcium oxalate uroliths.     

Serum total and ionized magnesium concentrations and urinary fractional excretion of magnesium in cats with diabetes mellitus and diabetic ketoacidosis

OBJECTIVE: To determine magnesium (Mg) status in cats with naturally acquired diabetes mellitus (DM) and diabetic ketoacidosis (DKA), evaluate changes in Mg status after treatment for DKA, and correlate Mg status with systemic blood pressure and degree of glycemic control. DESIGN: Case series and cohort study. ANIMALS: 12 healthy cats (controls), 21 cats with DM, and 7 cats with DKA. PROCEDURE: Serum total magnesium (tMg) and ionized magnesium (iMg) concentrations and spot urinary fractional excretion of magnesium (FEmg) were determined, using serum and urine samples obtained from all cats when they were entered in the study and from cats with DKA 12, 24, and 48 hours after initiating treatment. Indirect blood pressure and degree of glycemic control were determined in 10 and 21 cats with DM, respectively. RESULTS: Initially, 2 and 13 cats with DM and 1 and 4 cats with DKA had serum tMg and iMg concentrations, respectively, less than the low reference limit (mean-2 SD) determined for controls. In cats with DKA, serum tMg concentration decreased significantly over time after initiating treatment. Urinary FEmg was significantly higher in cats with DM or DKA, compared with controls. Systemic hypertension was not detected nor was there a correlation between Mg status and degree of glycemic control in cats with DM. CONCLUSIONS AND CLINICAL RELEVANCE: Hypomagnesemia was a common finding in cats with DM and DKA and was more readily identified by measuring serum iMg concentration than tMg concentration. The clinical ramifications of hypomagnesemia in such cats remain to be determined.     

Effects of methimazole on renal function in cats with hyperthyroidism

The purpose of this study was to investigate the effects of methimazole on renal function in cats with hyperthyroidism. Twelve cats with naturally occurring hyperthyroidism and 10 clinically normal (i.e., control) cats were included in this study. All cats initially were evaluated with a history, physical examination, complete blood count, serum biochemistry profile, basal serum total thyroxine concentration, complete urinalysis, and urine bacterial culture. Glomerular filtration rate (GFR) was estimated by a plasma iohexol clearance (PIC) test. After initial evaluation, hyperthyroid cats were treated with methimazole until euthyroidism was achieved. Both groups of cats were then reevaluated by repeating the initial tests four to six weeks later. The mean (+/-standard deviation) pretreatment estimated GFR for the hyperthyroid cats was significantly higher (3.83+/-1.82 ml/kg per min) than that of the control cats (1.83+/-0.56 ml/kg per min). Control of the hyperthyroidism resulted in a significantly decreased mean GFR of 2.02+/-0.81 ml/kg per minute when compared to pretreatment values. In the hyperthyroid group, the mean increases in serum urea nitrogen (SUN) and creatinine concentrations and the mean decrease in the urine specific gravity after treatment were not statistically significant when compared to pretreatment values. Two of the 12 hyperthyroid cats developed abnormally high serum creatinine concentrations following treatment. These results provide evidence that cats with hyperthyroidism have increased GFR compared to normal cats, and that treatment of feline hyperthyroidism with methimazole results in decreased GFR.     

Effect of time of cisplatin administration on its toxicity and pharmacokinetics in dogs.

Cisplatin (90 mg/m2) was administered in a 5-minute bolus IV infusion to dogs at 8 AM (n = 6) or 4 PM (n = 6). Blood and urine samples were collected over a 4-hour period for statistical moment pharmacokinetic analysis. Mean urinary excretion rate of total platinum was increased, whereas mean plasma residence time of ultrafilterable platinum was decreased, in the group treated at 4 PM (PM group), compared with those treated at 8 AM (AM group). Over a 2-week postinfusion-monitoring period, both groups of dogs developed decreases in creatinine clearance, urine/serum osmolality ratio (UOsm/SOsm), specific gravity, and increase in BUN, serum creatinine concentration, urine gamma-glutamyltranspeptidase/urine creatinine ratio (UGGT/UCr), fractional excretion of magnesium, and fractional excretion of phosphate. Urine specific gravity and UOsm/SOsm were significantly decreased, whereas UGGT/UCr and BUN were significantly increased in the AM group, compared with the PM group. The time of administration had a significant effect on the pharmacokinetics of cisplatin, which resulted in significant differences in cisplatin-induced renal toxicosis.     

Evaluation of coagulation markers in the plasma of healthy cats and cats with asymptomatic hypertrophic cardiomyopathy

BACKGROUND: Thrombosis and arterial thromboembolism are frequent complications of feline cardiomyopathy, especially when associated with left atrial enlargement. Markers of activated coagulation may be used to evaluate the coagulation status of cats with hypertrophic cardiomyopathy (HCM) in relation to left atrial size. OBJECTIVES: The objective of this study was to compare plasma concentrations of thrombin-antithrombin complex (TAT), D-dimer, and fibrin degradation products (FDP) between clinically healthy cats and cats with HCM. Prothrombin time (PT), activated partial thromboplastin time (aPTT), and antithrombin activity were also compared and the association between left atrial (LA) size and coagulation results in cats with HCM was evaluated. METHODS: Blood samples from 19 clinically healthy cats and 20 cats with HCM were obtained. All cats with HCM were asymptomatic and had no signs of heart failure. LA diameter and LA to proximal aortic (Ao) diameter ratio (LA:Ao) were determined by echocardiography. RESULTS: Reference intervals for D-dimer and TAT concentrations in plasma of healthy cats were established as 0.09-0.32 microg/mL and 2.0-20.0 microg/L, respectively. TAT, D-dimer, and FDP concentrations were increased in 5, 3, and 2 cats with HCM, respectively. TAT and D-dimer concentrations, and PT and aPTT were not significantly different between groups. Antithrombin activity was significantly decreased in cats with HCM (P=.03) despite marked range overlap. LA and LA:Ao were not correlated with coagulation results. CONCLUSIONS: Laboratory evidence of hypercoagulability was found in 45% of cats with HCM. Left atrial size was not associated with laboratory evidence of hypercoagulability. Association between coagulation markers and risk of thrombosis has yet to be evaluated in cats with HCM.     

Analysis of 8 Sarcomeric Candidate Genes for Feline Hypertrophic Cardiomyopathy Mutations in Cats with Hypertrophic Cardiomyopathy

Background: Hypertrophic cardiomyopathy (HCM) is the most common heart disease in cats. Causative mutations have been identified in the Maine Coon (MC) and Ragdoll breed in the cardiac myosin binding protein C gene (MYBPC3). HCM is thought to be inherited in other breeds.
Hypothesis: That a causative mutation for HCM in the British Shorthair (BSH), Norwegian Forest (NWF), Siberian, Sphynx, or MC cats would be identified in the exonic and splice site regions of 1 of 8 genes associated with human familial HCM.
Animals: Three affected BSH, NWF, Siberians, Sphynx, 2 MC (without the known MC mutation), and 2 Domestic Shorthair cats (controls) were studied.
Methods: Prospective, observational study. Exonic and splice site regions of the genes encoding the proteins cardiac troponin I, troponin T, MYBPC3, cardiac essential myosin light chain, cardiac regulatory myosin light chain, α tropomyosin, actin, and β–myosin heavy chain were sequenced. Sequences were compared for nucleotide changes between affected cats, the published DNA sequences, and control cats. Changes were considered to be causative for HCM if they involved a conserved amino acid and changed the amino acid to a different polarity, acid-base status, or structure.
Results: A causative mutation for HCM was not identified, although several single nucleotide polymorphisms were detected.
Conclusions and Clinical Importance: Mutations within these cardiac genes do not appear to be the only cause of HCM in these breeds. Evaluation of additional cardiac genes is warranted to identify additional molecular causes of this feline cardiac disease.     

Survival of cats with naturally occurring chronic renal failure is related to severity of proteinuria

BACKGROUND: Tubulointerstitial kidney disease is a common cause of illness and death in pet cats and is typically not associated with overt proteinuria. HYPOTHESIS: Proteinuria would be independently related to survival in cats with renal failure, with or without hypertension. ANIMALS: The study included 136 client-owned cats; 28 apparently normal, 14 hypertensive but not azotemic, 66 azotemic but not hypertensive, and 28 both hypertensive and azotemic. METHODS: Cox's proportional hazards model was used to determine the influence of initial plasma creatinine concentration, proteinuria (urine protein-to-creatinine ratio or albumin-to-creatinine ratio), age, and systemic hypertension on the risk of death or euthanasia during the follow-up period. Multivariable linear regression was used to determine the relation between severity of proteinuria and predictive variables, including age, plasma creatinine concentration, systolic blood pressure, sex, and urine specific gravity. RESULTS: Plasma creatinine concentration and proteinuria were very highly related to survival. The hazard ratio (95% confidence intervals) for death or euthanasia was 2.9 (1.4-6.3) and 4.0 (2.0-8.0) for urine protein-to-creatinine ratio 0.2-0.4 and >0.4, respectively, compared with the baseline group with a urine protein-to-creatinine ratio of <0.2 and were 2.4 (1.2-4.8) and 4.9 (2.3-10.2) for an albumin-to-creatinine ratio of 30-82 mg/g and <82 mg/g, respectively, compared with a baseline group with albumin-to-creatinine ratio of <30 mg/g. Treated hypertensive cats did not have reduced survival, although systolic blood pressure, together with plasma creatinine concentration was positively related to the magnitude of proteinuria. CONCLUSIONS AND CLINICAL IMPORTANCE: Despite the relatively low concentrations of proteinuria typical of chronic renal disease in cats, this measurement is of prognostic significance.     

Evaluation of Predictors of the Development of Azotemia in Cats

Background: Chronic kidney disease (CKD) is a common condition in geriatric cats. Diagnosis is based on the development of persistent azotemia with inadequate urine concentrating ability. Biomarkers are sought for early identification.
Hypothesis: Clinical variables, urine concentrating ability, proteinuria, and N -acetyl-β- d -glucosaminidase (NAG) index will be predictive of cats at risk of developing azotemia within 12 months.
Animals: Client-owned nonazotemic geriatric (≥9 years) cats.
Methods: Prospective longitudinal cohort study monitoring a population of healthy nonazotemic geriatric cats every 6 months until development of azotemia, death, or the study end point (September 30, 2007). Multivariable logistic regression analysis was used to assess baseline clinical, biochemical, and urinalysis variables, urine protein to creatinine ratio (UP/C), urine albumin to creatinine (UA/C) ratio, and urinary NAG index as predictors of development of azotemia.
Results: One hundred and eighteen cats were recruited with a median age of 13 years. Ninety-five cats (80.5%) had been followed or reached the study end point by 12 months of which 30.5% (29/95) developed azotemia. Age, systolic blood pressure, plasma creatinine concentration, urine specific gravity, UP/C, UA/C, and NAG index were significantly associated with development of azotemia in the univariable analysis ( P ≤ .05). However, in the multivariable analysis, only plasma creatinine concentration with either UP/C (Model 1) or UA/C (Model 2) remained significant.
Conclusions and Clinical Importance: This study demonstrates a high incidence of azotemia in a population of previously healthy geriatric cats. Proteinuria at presentation was significantly associated with development of azotemia although causal association cannot be inferred. Evaluation of NAG index offered no additional benefit.     

Effects of a high-protein diet versus dietary supplementation with ammonium chloride on struvite crystal formation in urine of clinically normal cats

OBJECTIVE: To evaluate the effects of a high-protein diet versus dietary supplementation with ammonium chloride (NH4Cl) on struvite crystal formation in the urine of clinically normal cats by measuring the urine concentration of hydrochloric acid (HCl)-insoluble sediment, urine pH, struvite activity product (SAP), number of struvite crystals in urine, and urine volume. ANIMALS: 23 healthy adult cats. PROCEDURE: Urine was fractionated by centrifugation with subsequent extraction of the sediment with 1 N HCl (study 1). Diets containing either 29% crude protein or 55% crude protein were fed to cats in a crossover trial of 3 weeks/period (study 2). Diets supplemented with either sodium chloride (NaCl) or NH4Cl were fed, by use of a 3 x 3 Latin-square design with 3 wk/period (study 3). In studies 2 and 3, urine samples were collected for the last 7 days of each period. RESULTS: The HCl-insoluble sediment contained Tamm-Horsfall glycoprotein (THP; study 1). The high-protein diet (study 2) and dietary supplementation with NH4Cl (study 3) resulted in a decrease in urine pH, SAP, and the number of struvite crystals in urine. However, the high-protein diet decreased urine concentrations of HCl-insoluble sediment containing THP (study 2), in contrast to the NH4Cl supplementation that increased urine volume without a significant effect on the urine concentration of the HCl-insoluble sediment (study 3). CONCLUSIONS AND CLINICAL RELEVANCE: Our results indicate that compared with dietary supplementation with NH4Cl, the high-protein diet is preferable as a urine acidifier for the prevention of struvite crystal formation in clinically normal cats.     

Systemic Toxicity Associated With Doxorubicin Administration in Cats

The systemic toxicity of doxorubicin, 30 mg/m² body surface area (BSA) every 21 days to a cumulative dose of 300 mg/m², was evaluated in six cats. Appetite, body weight, and the presence of vomiting and/or diarrhea were monitored throughout the study. Renal function was monitored by measuring serum blood urea nitrogen (BUN) and creatinine concentrations, urine specific gravity, and creatinine clearance before each treatment. Electrocardiograms and echocardiograms were also done before each treatment. The cats were killed 3 weeks after the last treatment, and complete necropsies were performed. Partial or complete anorexia occurred in all cats with significant weight loss occurring after a cumulative doxorubicin dose of 150 mg/m² BSA. Mild vomiting and diarrhea that required no treatment also occurred sporadically in all cats. Echocardiographic changes consistent with doxorubicin-induced cardiomyopa-thy occurred in four cats after cumulative doses of 170 to 240 mg/m² BSA. Clinical heart disease and electrocardiographic changes were not observed. Subsequent histological examination revealed myocyte vacuolization and myocytolysis in all six hearts. Renal dysfunction, characterized by increasing azotemia with progressively more dilute urine, was detected in two cats. Mean creatinine clearance values also decreased significantly throughout the study. At necropsy, all cats had histological evidence of renal disease. (Journal of Veterinary Internal Medicine 1993; 7:309–317. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

Retrospective case-control study of the effects of long-term dosing with meloxicam on renal function in aged cats with degenerative joint disease

Medical records (2005-2009) of a feline-only practice were searched for cats with degenerative joint disease (DJD) treated using meloxicam. DJD was diagnosed by the presence of at least two of the following: (i) altered mobility (observed by the owner), (ii) abnormal physical findings, (iii) characteristic radiographic changes. The primary study cohort consisted of cats older than 7 years that had received meloxicam for variable intervals in excess of 6 months, and for which complete records were available. These cats were subdivided according to whether detectable chronic kidney disease (CKD) was present ('renal group'), or not ('non-renal group'), and, for the 'renal group', according to the cat's IRIS category. Serum biochemistry, urinalysis (including urine specific gravity [USG]), body mass and condition score were monitored regularly. Progression of CKD in the 'renal group' and 'non-renal group' of cats was compared to two groups of age- and IRIS-matched control cats not receiving meloxicam (from the same clinic, over the same time period). The study was thus a case-control design, with two study groups. Thirty-eight cats with DJD receiving long-term meloxicam therapy met the inclusion criteria. Of these, 22 cats had stable CKD at the start of treatment (stage 1, eight cats; stage 2, 13 cats; stage 3, one cat). No cats initially had an elevated urinary protein to creatinine ratio. The remaining 16 cats initially had normal renal analytes and adequately concentrated urine. The median age of the 'renal' and 'non-renal' meloxicam groups was 15.5 and 13.4 years, respectively. The median treatment duration was 467 days in the 'renal group' and 327 days in the 'non-renal group'. After titration (to the lowest effective dose), the median maintenance dose was 0.02 mg/kg/day in both groups (range 0.015-0.033 mg/kg/day). There was no difference in sequential serum creatinine concentration or USG measurements between the 'non-renal group' treated with meloxicam compared to control cats not treated with meloxicam. There was less progression of renal disease in the 'renal group' treated with meloxicam compared to the age- and IRIS-matched cats with CKD not given meloxicam. These results suggest that a long-term maintenance dose of 0.02 mg/kg of meloxicam can be safely administered to cats older than 7 years even if they have CKD, provided their overall clinical status is stable. Long-term meloxicam therapy may slow the progression of renal disease in some cats suffering from both CKD and DJD. Prospective studies are required to confirm these findings.     

Thyroid enlargement and its relationship to clinicopathological parameters and T(4) status in suspected hyperthyroid cats

To relate thyroid size to routine blood parameters and T(4) status the ventral neck of 161 cats with clinical signs consistent with hyperthyroidism was examined by two independent observers using a semi-quantitative palpation system. Thyroid gland size of each side was scored from 0 (non-palpable) to a maximum of 6 (>25 mm). In 127 of the 161 cats, at least one thyroid gland was palpable. The palpation score was significantly correlated with the T(4) concentration. The 17 hyperthyroid cats had significantly higher palpation scores than the 110 euthyroid cats. Euthyroid animals with a palpation score >or=3 were significantly older, had higher body weights, lower alkaline phosphatase, alanine aminotransferase, phosphate, and urine specific gravity, but higher lipase and creatinine concentrations than hyperthyroid cats. Our study demonstrates that although no reliable conclusion on the functional status of the thyroid can be drawn based on its size the likelihood of hyperthyroidism increases with increasing size of the gland.