Psyllium husk powder increases defecation frequency and faecal score, bulk and moisture in healthy cats.

OBJECTIVES: Constipation is the infrequent or difficult emission of hard, dry faeces and is a common digestive condition in cats. Psyllium is a low-fermentable fibre, with soluble and insoluble components and water-holding properties. It forms a mucilaginous gel with water and is used for the symptomatic treatment of constipation in various species. This study evaluated the effect of dietary psyllium on faecal characteristics in cats. METHODS: Healthy neutered adult cats (six female and three male, aged 3.3-4.4 years) were consecutively fed a dry extruded diet containing either 6% psyllium (test) or 6% cellulose (control) for 10 days each. During the last 3 days (the collection days) of both feeding periods, bowel movements and faecal scores were recorded, and faeces were collected to measure wet weight and moisture. The statistical analysis used linear mixed models with diet, day and their interaction as fixed effects and animal as a random term. RESULTS: The test diet was associated with significantly more bowel movements per day over 3 days (P = 0.0052) and on collection day 2 (P = 0.0229) than the control diet. The mean faecal score was higher (softer faeces) over all three collection days (P <0.0001) and on collection days 1, 2 and 3 (P = 0.0011, P = 0.0349, P = 0.0003, respectively) for the test diet vs the control diet; the total faecal wet weight (P = 0.0003) and faecal moisture (%) were also higher (P = 0.0426) for the test diet. Faeces associated with the test diet often had a dry shell and soft interior, which increased the faecal score. CONCLUSIONS AND RELEVANCE: Psyllium promoted more bowel movements and higher faecal moisture and faecal score in healthy cats, consistent with a previous uncontrolled clinical trial in constipated cats. Together, the studies support the use of dietary psyllium for managing cats with constipation.

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.

Echocardiographic, morphometric and biomarker changes in female cats followed from 6 to 24 months of life.

OBJECTIVES: The aim of the study was to evaluate cardiac size and early growth through echocardiographic, body weight (BW), body condition score (BCS), morphometric and biomarker changes in cats followed from 6 to 24 months of age. METHODS: Twenty-four female European shorthair colony cats were evaluated at birth for BW and at 6, 12, 18 and 24 months of age for BW, BCS, head length (HL) and head width (HW), N-terminal pro B-type natriuretic peptide (NT-proBNP), insulin-like growth factor-1 (IGF-1) and echocardiographic measurements. RESULTS: BCS, HW, left ventricular free wall in diastole, left atrium diameter and aortic diameter increased significantly between 6 and 12 months, while BW, HL and interventricular septum in diastole increased significantly between 6, 12 and 18 months, and BW decreased significantly between 18 and 24 months. NT-proBNP decreased significantly between 6 and 12 months. IGF-1 increased significantly between 6 and 12 months but decreased significantly between 12 and 18 months. CONCLUSIONS AND RELEVANCE: This study prospectively evaluated changes in echocardiographic measurements, BW, BCS, HL, HW, IGF-1 and NT-proBNP in cats during the first 2 years of life. Results show a comparable change over time for different variables. These findings contribute to the understanding of a possible relationship between cardiac measures and body size from young age through to adulthood.

Erratum to "Inter-observer variability for cardiac ultrasound measurements in cats repeated at different time points in early adult life" [5C (June 2018) 44-46].

[This corrects the article DOI: 10.1016/j.vas.2018.03.002.].

Association of diet with left ventricular wall thickness, troponin I and IGF-1 in cats with subclinical hypertrophic cardiomyopathy.

BACKGROUND: Cats with subclinical hypertrophic cardiomyopathy (sHCM) have elevated serum insulin and serum amyloid A concentrations correlating with the degree of cardiac hypertrophy. Diet might affect these and other cardiac variables. OBJECTIVE: Evaluate the effect of a complete, balanced diet with restricted starch and supplemented with eicosapentaenoic acid + docosahexaenoic acid (EPA + DHA) on echocardiographic variables and cardiac biomarkers in cats with sHCM. ANIMALS: Forty-four client-owned cats with sHCM. METHODS: A prospective, randomized, double-blind, multicenter study enrolled cats with end-diastole interventricular septum thickness (IVSd) or left ventricular wall thickness (LVWd) ≥6 mm, or both. Nonsedated, fasted cats were examined at baseline and after 6 and 12 months of Test (restricted starch and EPA + DHA supplements) (n = 23) or Control (unrestricted starch without EPA + DHA supplementation) (n = 21) diet. Assessments included auscultation, body weight, body condition score, echocardiography and blood analysis. Linear and generalized mixed models analyzed diet, time and diet * time interactions (5% significance level). RESULTS: No differences between diet groups were significant for any variable at any timepoint. There were significant decreases in the Test but not Control group in maximum IVSd (P = .03), maximum LVWd (P = .02) and insulin-like growth factor-1 levels (P = .04) after 12 months, and in ultrasensitive cardiac troponin I (cTnI) (P = .001) after 6 months; effect sizes (95% confidence interval) were 0.53 (0.09; 0.99), 0.63 (0.18; 1.09), 0.61 (0.16; 1.07), and 0.37 (-0.06; 0.8), respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Cats with sHCM fed Test diet had significant decreases in echocardiographic variables of sHCM and in cTnI and IGF-1.

Associations among echocardiography, cardiac biomarkers, insulin metabolism, morphology, and inflammation in cats with asymptomatic hypertrophic cardiomyopathy.

BACKGROUND: Insulin, insulin-like growth factor-1 (IGF-1), and inflammation possibly are involved in cats with asymptomatic hypertrophic cardiomyopathy (aHCM). OBJECTIVES: To evaluate echocardiography, morphology, cardiac and inflammatory markers, insulin and IGF-1 in cats with aHCM. ANIMALS: Fifty-one client-owned cats with aHCM. METHODS: Observational descriptive study. Variables (body weight [BW], body condition score [BCS], echocardiography, and serum concentrations of N-terminal pro-B-type natriuretic peptide [NT-proBNP], ultra-sensitive troponin-I [c-TnI], serum amyloid A [SAA], insulin, glucose and IGF-1) were evaluated for significant increases above echocardiography cutoff values and laboratory reference ranges, associations and effect of left atrial (LA) remodeling and generalized hypertrophy. RESULTS: Cats with aHCM had BCS ≥6/9 (P = .01) and insulin (P < .001), NT-proBNP (P = .001) and cTn-I (P < .001) above laboratory reference ranges. Associations were present between NT-proBNP and maximum end-diastolic interventricular septum thickness (IVSd; ρ = .32; P = .05), maximum end-diastolic left ventricular free wall thickness;(ρ = .41; P = .01), LA/Aorta (ρ = .52; P = .001) and LA diameter (LA-max; ρ = .32; P = .05); c-TnI and LA/Aorta (ρ = .49; P = .003) and LA-max (ρ = .28; P = .05); and SAA and number of IVSd regions ≥6 mm thickness (ρ = .28; P = .05). Body weight and BCS were associated with IGF-1 (r = 0.44; P = .001), and insulin (ρ = .33; P = .02), glucose (ρ = .29; P = .04) and IGF-1 (ρ = .32; P = .02), respectively. Concentrations of NT-proBNP (P = .02) and c-TnI (P = .01), and SAA (P = .02), were higher in cats with LA remodeling, and generalized hypertrophy, respectively. CONCLUSIONS AND CLINICAL IMPORTANCE: Results suggest potential implications of insulin, IGF-1, and inflammation in cats with aHCM, but it remains to be confirmed whether these findings represent a physiological process or a part of the pathogenesis and development of disease.

Interactions between thyroid and kidney function in pathological conditions of these organ systems: a review.

Thyroidal status affects kidney function already in the embryonic stage. Thyroid hormones influence general tissue growth as well as tubular functions, electrolyte handling and neural input. Hyper- and hypo-functioning of the thyroid influences mature kidney function indirectly by affecting the cardiovascular system and the renal blood flow, and directly by affecting glomerular filtration, electrolyte pumps, the secretory and absorptive capacity of the tubuli, and the structure of the kidney. Hyperthyroidism accelerates several physiologic processes, a fact which is reflected in the decreased systemic vascular resistance, increased cardiac output (CO), increased renal blood flow (RBF), hypertrophic and hyperplastic tubuli, and increased glomerular filtration rate (GFR). Renal failure can progress due to glomerulosclerosis, proteinuria and oxidative stress. Hypothyroidism has a more negative influence on kidney function. Peripheral vascular resistance is increased with intrarenal vasoconstriction, and CO is decreased, causing decreased RBF. The influence on the different tubular functions is modest, although the transport capacity is below normal. The GFR is decreased up to 40% in hypothyroid humans. Despite the negative influences on glomerular and tubular kidney function, a hypothyroid state has been described as beneficial in kidney disease. Kidney disease is associated with decreased thyroid hormone concentrations caused by central effects and by changes in peripheral hormone metabolism and thyroid hormone binding proteins. Geriatric cats form an animal model of disease because both hyperthyroidism and chronic kidney disease (CKD) have high prevalence among them, and the link between thyroid and kidney affects the evaluation of clinical wellbeing and the possible treatment options.

Effect of recombinant human thyroid stimulating hormone on serum thyroxin and thyroid scintigraphy in euthyroid cats.

This study investigated the thyroidal response to administration of recombinant human thyroid stimulating hormone (rhTSH) by means of serum total thyroxine (TT(4)) concentration and pertechnetate uptake by the thyroid gland in six healthy euthyroid spayed female cats. A pertechnetate scan was performed on day 1 to calculate thyroid/salivary gland (T/S) uptake ratio. On day 3, 25 microg rhTSH was injected intravenously. Six hours later the thyroid scan was repeated as on day 1. Blood was drawn for serum TT(4) measurement prior to injection of rhTSH and performance of the pertechnetate scan. Statistically significant differences in mean serum TT(4) concentration, T/S uptake ratio before and 6h after rhTSH administration and T/S uptake ratio between left and right lobes were noted. We can conclude that 25 microg rhTSH increases pertechnetate uptake in the thyroid glands of cats, this should be taken into account when thyroid scintigraphy after rhTSH administration is interpreted.

Immunoassay of urinary retinol binding protein as a putative renal marker in cats.

The presence of low molecular weight retinol binding protein (RBP) in urine reflects tubular damage. Therefore, RBP has been used as a renal marker in humans and dogs. Using an anti-human RBP antibody (Ab), this study first demonstrates feline urinary RBP by Western blot analysis and then evaluates its potential as a renal marker in cats by enzyme-linked immunosorbent assay (ELISA). Urine was taken by cystocentesis, centrifuged and stored at -80 degrees C until analysis. Urinary RBP levels were compared in clinically healthy cats (H), chronic renal failure patients (CRF) and cats with hyperthyroidism (HT). The detection of a band at the same position as the human RBP standard with Western blot analysis, indicated that RBP was present in the urine of CRF and HT patients but minimally present in H cats. The data obtained with ELISA were in accordance with these observations. RBP levels were expressed as RBP:creatinine (RBP:c) ratios following normalisation with urinary creatinine. The functional assay sensitivity was 1.37 microg/l RBP. Parallelism between the trend lines of the human RBP standard curve and the curves obtained from sequentially diluted urine samples indicated that feline RBP was recovered. The mean intra-assay coefficient of variance was 7% and the standardised agreement index revealed satisfactory day-to-day repeatability. The RBP:c ratio in all H cats (n=10) was below the assay sensitivity. The groups of CRF and HT patients had increased mean RBP:c ratios of 1.6+/-0.5x10(-2) microg/mg (mean+/-SEM, n=10) and 1.4+/-0.4x10(-2) microg/mg (n=13), respectively. Both groups showed a large variation in the relative RBP concentrations of individual cats. In conclusion, RBP is demonstrated for the first time in urine from most CRF and HT patients and the validated ELISA allows its evaluation as a putative renal marker in cats.

Interference of iohexol with radioiodine thyroid uptake in the hyperthyroid cat.

Absorbed thyroid dose and effective half-life were determined in 46 hyperthyroid cats after treatment with a low dose (mean 111MBq) of radioiodine intravenously. Thirteen of these cats had received iohexol for glomerular filtration rate (GFR) measurement within 24h before treatment with radioiodine in view of another ongoing study at our institution. Pre-therapy values were obtained for total thyroxine (TT(4)) and for the thyroid to salivary gland ratio with sodium pertechnetate gamma-camera imaging. All cats underwent post-therapy scans at 24, 48 and 120 h for evaluation of radioactive iodine uptake (RAIU) and the effective half-life of radioiodine. The absorbed dose was calculated from the cumulative activity with Olinda software. Both groups were comparable in age, TT(4) and the ratio of thyroid activity to salivary gland activity. Statistical analysis revealed a significant decreased absorbed dose in the thyroid in the iohexol group. This decreased uptake was not accompanied by an decreased effective half-life of the radioiodine. The variation of inter-individual RAIU decreased in this group and more homogenous absorbed doses were obtained. No significant difference in outcome could be demonstrated. However, a tendency towards a higher number of residual hyperthyroidism in the iohexol group was noted (15 versus 6% in control group). This study demonstrates that iohexol interferes with the uptake of radioiodine in the hyperthyroid cat but does not provoke increased turnover. In this study, albeit including a small number of cats, outcome did not seem to be significantly affected.

Within- and between-examiner agreement for two thyroid palpation techniques in healthy and hyperthyroid cats.

Thyroid gland palpation is an important aid for diagnosing feline hyperthyroidism in an early stage to prevent development of deleterious complications. Our objectives were to assess within- and between-examiner agreement for two thyroid gland palpation techniques in cats and to correlate palpation results with ultrasonographic thyroid measurements. Nine client-owned hyperthyroid (12.6 +/- 2.4 years) and 10 healthy control cats (7.4 +/- 5.4 years) entered this prospective study. Both thyroid glands of all cats were palpated twice by three blindfolded clinicians with the classic palpation technique [technique 1 (T1)] and the technique described by Norsworthy GD, Adams VJ, McElhaney MR, Milios JA [(2002a) Relationship between semi-quantitative thyroid palpation and total thyroxine concentration in cats with and without hyperthyroidism. Journal of Feline Medicine and Surgery 4, 139-143] [technique 2 (T2)]. A semi-quantitative score from 1 to 6 was assigned to the gland size. After clipping of the ventral cervical region, another palpation session followed by ultrasonography of the thyroid glands was performed. Average weighted kappa-values within- and between-examiners were 0.864 and 0.644 for T1 and 0.732 and 0.532 for T2. T1 did lead to significantly smaller within- (P=0.007) and between-examiner (P=0.048) differences than T2. Significant correlation coefficients (P<0.001) between the palpation scores of both techniques and ultrasonographic thyroid lobe length (T1: 0.43; T2: 0.38) were observed. No significant difference before and after clipping was found (T1: P=0.503; T2: P=0.607). The first time that all cats were palpated by either technique, significant score differences between control and hyperthyroid cats were observed both for T1 (P=0.002) and T2 (P=0.003). Both feline thyroid gland palpation techniques have good within- and between-examiner agreements. Based on this study, the classic palpation technique is preferred.

Inter-observer variability for cardiac ultrasound measurements in cats repeated at different time points in early adult life.

A high degree of accuracy is required when using echocardiography to diagnose hypertrophic cardiomyopathy (HCM) in cats, as variation in measurements of 0.5 mm may affect classification of individuals as 'abnormal'. This study in adult cats examined at different time points inter-observer variability between two Board certified echocardiographers in veterinary cardiology. Twenty-four female European shorthair cats were examined at 12, 18 and 24 months of age by observer 1. Two dimensional (2D) echocardiographic images were collected in conscious cats to measure left ventricular, aortic and left atrial dimensions. Measurements were repeated by observer 2 on stored images, and analysed for effect of time, observer and time-observer interaction. Based on end-diastolic left ventricular wall thickness, cats were diagnosed as 'normal' or 'abnormal'. Linear mixed models (generalized when appropriate) were performed. A significant difference between observers was found for all septal (IVSd) and free wall (LVFWd) thickness measurements and left ventricular internal diameters but not for aortic or left atrial measurements. All measurement coefficients of variation (CV) were < 10%. The CV for IVSd was higher than the CV for LVFWd. There was a significant effect of time on IVSd, aortic measurements and left ventricular internal diameter measurements. No significant time-observer interaction was found for any parameter. Diagnosis of cats as 'abnormal' (>5 mm in cats > 6 kg bodyweight) was significantly different between observers for IVSd but not LVFWd. Caution is warranted when diagnosing as 'abnormal' or interpreting small changes based on IVSd, due to significant inter-observer differences in this measurement.

Quantification of vitamin D3 in commercial dog foods and comparison with Association of American Feed Control Officials recommendations and manufacturer-reported concentrations.

OBJECTIVE To quantify vitamin D3 (VitD3) concentrations in commercial dog foods and compare those concentrations with Association of American Feed Control Officials (AAFCO) recommendations and manufacturer-reported concentrations. DESIGN Cross-sectional study. SAMPLE 82 commercial dog foods. PROCEDURES Samples of commercially available dog foods were obtained from owners of healthy dogs in the Guelph, ON, Canada, area and owners of dogs that were patients at the Ontario Veterinary College Health Sciences Centre's Mona Campbell Centre for Animal Cancer. For each food, the VitD3 concentration was determined by high-performance liquid chromatography-tandem mass spectrometry, and adherence to AAFCO and National Research Council recommendations was assessed. Analyzed VitD3 concentrations were compared with manufacturer-reported VitD3 concentrations and between wet and dry foods, among AAFCO nutritional adequacy statements (nutrient profiles vs feeding trials and adult maintenance vs all life stages), between foods sold only by veterinarians and those sold over the counter, and between small and large manufacturers. RESULTS The analyzed VitD3 concentration was below both AAFCO and National Research Council recommendations for one sample and below the assay detection limit for another. Analyzed VitD3 concentrations did not differ significantly from manufacturer-reported VitD3 concentrations or between wet and dry foods, among foods with different AAFCO nutritional adequacy statements, between foods sold only by veterinarians and those sold over the counter, or between foods produced by small and large manufacturers. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that manufacturer-reported VitD3 concentrations were accurate and that dog owners can be confident that VitD3 intake is adequate for AAFCO-compliant commercial dog foods.

A critical review of food-associated factors proposed in the etiology of feline hyperthyroidism.

Since the first description of feline hyperthyroidism (HT) in 1979, several studies have been undertaken to define the etiology of the disease. Epidemiologic studies, after investigating non-food- and food-associated factors, suggest a multifactorial etiology. However, in the absence of prospective cohort studies that can confirm a cause-and-effect relationship between HT and associated risk factors, no causative factor for HT has been identified to date. Feline HT resembles toxic nodular goiter in humans, with autonomously functioning upregulated iodide uptake systems. Contribution of the diet to HT development remains controversial. The purpose of this paper is to review critically the reported food-associated risk factors for HT.

Simplified methods for estimating glomerular filtration rate in cats and for detection of cats with low or borderline glomerular filtration rate.

OBJECTIVES: Diagnosis of early feline chronic kidney disease (CKD) is challenging. Glomerular filtration rate (GFR) is the best overall indicator of kidney function, but multisample plasma clearance methods to determine GFR are labour intensive, time consuming and stressful for feline patients. This study aimed to develop simplified methods to detect decreased GFR in cats. METHODS: Data from a nine-sample combined plasma exogenous creatinine-iohexol clearance test of 73 cats were used. Limited sampling strategies were developed by comparing all sampling time combinations with the complete nine sampling times set and selecting the best sampling time combinations based on maximum relative error. By regression analysis, the ability of routine blood (serum creatinine, serum urea) and urine (urine specific gravity, urinary protein:creatinine ratio) variables to predict GFR or identify cats with low or borderline GFR was examined. Cut-off clearance marker concentrations to predict low or borderline GFR was determined at three time points after marker injection. All procedures were analysed for three clearance markers (exo-iohexol, creatinine, endo-iohexol). RESULTS: For reliable estimation of GFR, at least three blood samples for clinical purposes and five blood samples for research purposes are required. Regression formulae based on routine variables did not reliably predict GFR, but accurately identified cats with low (sensitivity 96.5-98.2%; specificity 60-91.3%) or borderline (sensitivity 91.1-96%; specificity 76.5-81.8%) GFR. Clearance marker concentrations exceeding given marker cut-off concentrations also identified cats with low or borderline GFR with high sensitivities and specificities. CONCLUSIONS AND RELEVANCE: These simplified methods will facilitate the detection of early kidney dysfunction in cats. Early diagnosis allows timely therapeutic intervention, and future studies must reveal whether this improves the long-term outcome of cats with CKD.

Thyroid stimulation with recombinant human thyrotropin in healthy cats, cats with non-thyroidal illness and in cats with low serum thyroxin and azotaemia after treatment of hyperthyroidism.

This study investigated the recombinant human thyrotropin (rhTSH) stimulation test in healthy cats (group 1), cats with non-thyroidal illness (group 2) and cats with low serum total T(4) (TT(4)) and azotaemia after (131)I treatment (group 3). Serum TT(4) responses and thyroidal pertechnetate uptake after administration of 25 microg rhTSH IV were assessed. Baseline serum TT(4) was significantly lower in group 3 compared with group 1, but not between other group pairs. Serum TT(4) increased significantly in groups 1 and 2 but not in group 3 after rhTSH administration. Post-rhTSH serum TT(4) concentrations differed significantly between groups 1 and 3 and groups 2 and 3, but not between groups 1 and 2. Thyroid/salivary gland uptake ratio (T/S uptake ratio) differed only significantly between groups 1 and 3. Stimulation with rhTSH is valuable to differentiate euthyroidism from iatrogenic hypothyroidism in cats.

Pre- and posttreatment ultrasonography of the thyroid gland in hyperthyroid cats.

Ultrasonography is useful for assessing the morphology of the thyroid gland in hyperthyroid cats. Our aim was to describe the ultrasonographic changes of the thyroid gland in hyperthyroid cats after 131I therapy. Ultrasonography was performed in 15 hyperthyroid cats at initial presentation and 6 months after 131I using a multifrequency linear transducer set at 12 MHz. The following criteria were evaluated: length, width, height, volume, shape, homogeneity, and vascularity, using Power Doppler. Pretreatment, 10 cats had bilaterally abnormal thyroid lobes, four cats one abnormal lobe with the contralateral lobe being normal or reduced in size, and one cat with one normal lobe and one lobe not visible. Six months after 131I therapy, there was a reduction in median volume from 819 to 210 mm3, reduced rounding, reduced heterogeneity, and decreased vascularity. In conclusion, ultrasonography may be used to monitor thyroid changes in order to assess 131I treatment response. Further studies are necessary to determine whether ultrasonography could contribute to the detection of a relapsing course of hyperthyroidism.

Determination of optimal sampling times for a two blood sample clearance method using (51)Cr-EDTA in cats.

Estimation of the glomerular filtration rate (GFR) is a useful tool in the evaluation of kidney function in feline medicine. GFR can be determined by measuring the rate of tracer disappearance from the blood, and although these measurements are generally performed by multi-sampling techniques, simplified methods are more convenient in clinical practice. The optimal times for a simplified sampling strategy with two blood samples (2BS) for GFR measurement in cats using plasma (51)chromium ethylene diamine tetra-acetic acid ((51)Cr-EDTA) clearance were investigated. After intravenous administration of (51)Cr-EDTA, seven blood samples were obtained in 46 cats (19 euthyroid and 27 hyperthyroid cats, none with previously diagnosed chronic kidney disease (CKD)). The plasma clearance was then calculated from the seven point blood kinetics (7BS) and used for comparison to define the optimal sampling strategy by correlating different pairs of time points to the reference method. Mean GFR estimation for the reference method was 3.7+/-2.5 ml/min/kg (mean+/-standard deviation (SD)). Several pairs of sampling times were highly correlated with this reference method (r(2) > or = 0.980), with the best results when the first sample was taken 30 min after tracer injection and the second sample between 198 and 222 min after injection; or with the first sample at 36 min and the second at 234 or 240 min (r(2) for both combinations=0.984). Because of the similarity of GFR values obtained with the 2BS method in comparison to the values obtained with the 7BS reference method, the simplified method may offer an alternative for GFR estimation. Although a wide range of GFR values was found in the included group of cats, the applicability should be confirmed in cats suspected of renal disease and with confirmed CKD. Furthermore, although no indications of age-related effect were found in this study, a possible influence of age should be included in future studies.

Comparison of plasma clearance of exogenous creatinine, exo-iohexol, and endo-iohexol over a range of glomerular filtration rates expected in cats.

The study investigated plasma clearance of exogenous creatinine (PECCT), exo-iohexol (PexICT) and endo-iohexol (PenICT) in six healthy cats, four cats with chronic kidney disease (CKD) and six hyperthyroid (HT) cats to assess potential differences in glomerular filtration rate (GFR) measurement over a wide range of GFR values. The PECCT, PexICT and PenICT were performed in a combined protocol. There was a significant difference between PexICT and PenICT and PECCT in healthy cats. Differences between clearance techniques are suggested to be correlated to range in GFRs and should be taken into account when GFR is measured.