World Small Animal Veterinary Association Renal Pathology Initiative: Classification of Glomerular Diseases in Dogs.

Evaluation of canine renal biopsy tissue has generally relied on light microscopic (LM) evaluation of hematoxylin and eosin-stained sections ranging in thickness from 3 to 5 µm. Advanced modalities, such as transmission electron microscopy (TEM) and immunofluorescence (IF), have been used sporadically or retrospectively. Diagnostic algorithms of glomerular diseases have been extrapolated from the World Health Organization classification scheme for human glomerular disease. With the recent establishment of 2 veterinary nephropathology services that evaluate 3-µm sections with a panel of histochemical stains and routinely perform TEM and IF, a standardized objective species-specific approach for the diagnosis of canine glomerular disease was needed. Eight veterinary pathologists evaluated 114 parameters (lesions) in renal biopsy specimens from 89 dogs. Hierarchical cluster analysis of the data revealed 2 large categories of glomerular disease based on the presence or absence of immune complex deposition: The immune complex-mediated glomerulonephritis (ICGN) category included cases with histologic lesions of membranoproliferative or membranous patterns. The second category included control dogs and dogs with non-ICGN (glomerular amyloidosis or focal segmental glomerulosclerosis). Cluster analysis performed on only the LM parameters led to misdiagnosis of 22 of the 89 cases-that is, ICGN cases moved to the non-ICGN branch of the dendrogram or vice versa, thereby emphasizing the importance of advanced diagnostic modalities in the evaluation of canine glomerular disease. Salient LM, TEM, and IF features for each pattern of disease were identified, and a preliminary investigation of related clinicopathologic data was performed.

Glomerular filtration rate estimated by 3-sample plasma clearance of iohexol in 118 healthy dogs.

BACKGROUND: Glomerular filtration rate (GFR) decreases in the aging human kidney, but limited data exist in dogs. HYPOTHESIS: There is an effect of age and body size on estimated GFR in healthy dogs. ANIMALS: One hundred and eighteen healthy dogs of various breeds, ages, and body weights presenting to 3 referral centers. METHODS: GFR was estimated in clinically healthy dogs between 1 and 14 years of age. GFR was estimated from the plasma clearance of iohexol, by a compartmental model and an empirical correction formula, normalized to body weight in kilograms or liters of extracellular fluid volume (ECFV). For data analysis, dogs were divided into body weight quartiles 1.8-12.4, 13.2-25.5, 25.7-31.6, and 32.0-70.3 kg. RESULTS: In the complete data set, there was no trend toward lower estimated GFR/kg or GFR/ECFV with increasing age. GFR decreased with age in dogs in the smallest weight quartile only. A significant negative linear relationship was detected between body weight and estimated GFR/kg and GFR/ECFV. Reference ranges in different weight quartiles were 1.54-4.25, 1.29-3.50, 0.95-3.36, and 1.12-3.39 mL/min/kg, respectively. Standardization to ECFV rather than kilogram body weight did not produce substantial changes in the relationships between GFR estimates and age or weight. CONCLUSIONS AND CLINICAL IMPORTANCE: Interpretation of GFR results for early diagnosis of renal failure should take into account the weight and the age of the patient for small dogs.

Determination of extracellular fluid volume in healthy and azotemic cats.

BACKGROUND: Methods for determining extracellular fluid volume (ECFV) are important clinically for cats. Bromide dilution has been studied in cats to estimate ECFV. Markers of GFR also distribute in ECFV and can be used for its measurement. HYPOTHESIS/OBJECTIVES: The primary objective was to develop a method of determining ECFV from iohexol clearance in cats and evaluate agreement with that determined using bromide dilution. Additional objectives were to compare ECFV between azotemic and nonazotemic cats and evaluate appropriate methods of standardizing ECFV. ANIMALS: Client-owned cats with varying renal function. METHODS: Validation of ECFV determined from slope-intercept iohexol clearance was performed in 18 healthy nonazotemic cats. ECFV was then determined using the validated method and bromide dilution and agreement assessed. Appropriateness of standardization to body weight (BW) and body surface area (BSA) was evaluated. RESULTS: Extracellular fluid volume determined from slope-intercept iohexol clearance and bromide dilution was 0.84 ± 0.32 L and 0.85 ± 0.19 L (mean ± SD), respectively. There were wide limits of agreement between the methods (-0.58 to 0.54 L) and therefore, agreement was considered to be poor. ECFV did not differ significantly between azotemic and nonazotemic cats (P = .177). BSA was found to be the best method for standardizing ECFV measurement in cats. CONCLUSIONS AND CLINICAL IMPORTANCE: This study developed a method for determining ECFV from slope-intercept iohexol clearance which provides simultaneous assessment of renal function and an estimate of ECFV. ECFV does not differ between azotemic and nonazotemic cats, which suggests fluid volume loss or overload is not an important clinical feature in cats with mild chronic kidney disease.

Estimation of glomerular filtration rate in dogs with 99M-Tc-DTPA and iohexol.

The glomerular filtration rates (GFR) of 18 dogs of different breeds were estimated by simultaneously comparing the plasma decay curves of 99M-Tc-diethylenetriaminepentaacetic acid (Tc-DTPA) and the contrast medium iohexol. Nine of the dogs were clinically healthy, and nine had renal disease. After the intravenous injection of the two substances, nine to 12 blood samples were taken during the first six hours and in some cases up to 24 hours. The total clearance of the substances was determined by one- and two-compartment models. Individual GFRiohexol values, estimated by using a two-compartment model in 16 of the dogs, ranged from 39.0 ml min-1 m-2 to 84.3 ml min-1 m-2 and for GFRTc-DTPA from 41.1 ml min-1 m-2 to 106.6 ml min-1 m-2. The GFRiohexol values estimated by using a one-compartment model in the 18 dogs ranged from 4.52 ml min-1 m-2 to 105 ml min-1 m-2 and for GFRTc-DTPA from 5.4 ml min-1 m-2 to 118.9 ml min-1 m-2. The agreement between the two methods was good, as shown by a limits of agreement plot. The ratio of GFRTc-DTPA/GFRiohexol was 1.15 throughout the range of measurement (SD = 0.085). The study indicates that the iohexol method is a valid measure of GFR in the dog. The practical aspects make it a useful tool in small animal practice.

Calculation of urinary enzyme excretion, with renal structure and function in dogs with pyometra.

The urinary enzyme markers of renal damage, alkaline phosphatase (AP), gamma-glutamyl transferase (GGT) and N-acetyl-beta-glucosaminidase (NAG), glomerular filtration rate (GFR) and renal biopsies were studied to evaluate renal status in dogs with pyometra. After ovariohysterectomy, urinary enzymes were measured daily for 12 days in 55 dogs, and again at a later follow-up visit. Thirteen dogs had high levels of at least one enzyme at initial presentation. Seventeen dogs had a transient increase in urinary enzyme values between one and five days after surgery. Enzyme values usually declined to low activities within 12 post-operative days. Renal biopsies demonstrated tubular abnormalities in many dogs. Mean GFR was 2.4 and 2.0 ml min(-1) kg(-1), respectively on day 1 post-operatively and at the follow-up visit 1-4 months later. High urinary enzyme values often reflected extensive lesions in renal proximal tubular cells and sometimes reduced GFR.

Pharmacokinetic aspects of measurement of glomerular filtration rate in the dog: a review.

Glomerular filtration rate (GFR) is estimated by means of clearance, defined as the volume of plasma that has been cleared of a particular substance per unit time. Glomerular filtration rate may be estimated by measuring the renal clearance of a filtration marker using data from both urine and plasma or by plasma clearance using only plasma data. Several alternative pharmacokinetic models are used for the calculation of clearance using various filtration markers with slightly different pharmacokinetic properties. The purpose of this article is to discuss how the choice of marker and pharmacokinetic model may influence estimated GFR values and to elucidate commonly used methods and reported GFR values in the dog.

The relationship between some plasma clearance methods for estimation of glomerular filtration rate in dogs with pyometra.

The purpose of the present study was to compare different pharmacokinetic models for estimation of glomerular filtration rate (GFR) in 50 dogs with pyometra. GFR was estimated by plasma clearance (CLplasma) of iohexol by four 1-compartment methods (CL1c), a 2-compartment method (CL2c), and the trapezoidal method (CLtr). Regression analysis was performed to establish correction formulas for prediction of CLtr from the CL1c values and to find optimal times of sampling. Standardization of clearance values to body weight (kg), body surface area (m2) and extracellular fluid volume (ECFV) was compared by ranking of values. CLtr and CL2c values were similar, whereas CL1c overestimated CLtr. CLtr could be predicted from 2 samples at 2 and 3 hours after injection, using the formula CLtr = 4.52 + 0.84CL1c - 0.00080(CL1c)2 (R2 = .97). Similar relationships were found when sampling at 2 and 4 hours or at 2, 3 and 4 hours after injection, whereas predictions from the 3- and 4-hour estimates were not optimal (R2 = .79). The 2-sample methods for calculating GFR/ECFV generally produced unreliable predictions of the complete curve GFR/ECFV values. For some dogs, the choice of standardization procedure substantially changed the apparent level of renal function relative to other dogs in the study. We conclude that by applying an appropriate correction formula, GFR may be estimated using 2 blood samples at 2 and 3, or 2 and 4 hours after injection of iohexol when renal function is normal or moderately reduced. The method of standardizing the analysis with respect to body size may influence interpretation of the results substantially.

Use of capillary electrophoresis to quantitate carbamylated hemoglobin concentrations in dogs with renal failure.

OBJECTIVE: To evaluate quantification of the amount of carbamylated hemoglobin (CarbHb), using capillary electrophoresis (CE) and a new dynamic capillary coating system to separate hemoglobin derivatives, and to assess the use of CarbHb amounts to evaluate long-term urea exposure and differential diagnoses of azotemia in dogs. ANIMALS: 8 dogs with renal failure, 2 dogs with diabetes mellitus, and 7 control dogs. PROCEDURE: Optimal analytic conditions for separation of CarbHb and other hemoglobin derivatives in blood samples obtained from dogs were determined, using a commercial analysis system developed for the detection of glycohemoglobin Hb A1c (GlycHb) in human blood samples. Relative content of hemoglobin derivatives in blood from 10 dogs with renal failure or endocrine diseases were compared with values for 7 dogs without renal or endocrine diseases. RESULTS: Satisfactory resolution of hemoglobin derivatives was obtained, which permitted identification and quantitation of the amount of CarbHb as a percentage of the total amount of hemoglobin. Normal or increased amounts of GlycHb did not interfere with CarbHb analysis. Dogs with chronic renal failure had considerably higher peak amounts of CarbHb than dogs with acute renal failure, a dog with chronic renal failure that was treated by use of hemodialysis, or dogs without renal disease. CONCLUSIONS AND CLINICAL RELEVANCE: Amounts of CarbHb in blood samples obtained from dogs can be readily quantified by use of capillary electrophoresis. Assessment of the amount of CarbHb can be used to facilitate evaluation of the cause of azotemia in dogs.

Prevalence of murmurs consistent with aortic stenosis among boxer dogs in Norway and Sweden.

The prevalence and severity of cardiac murmurs consistent with subclinical or clinically detectable aortic stenosis among purebred boxer dogs in Norway and Sweden were evaluated. Two hundred and thirty-one boxers, randomly selected or investigated at dog shows, were examined by phonocardiography by two veterinarians and classified on the basis of the characteristics of their murmurs into categories 0 to 4. No murmur was detected in 23 per cent of the dogs, murmurs classified as category 1 were diagnosed in 25 per cent of the dogs, as category 2 in 46 per cent, as category 3 in 7 per cent cent, and two dogs had category 4 murmurs. In 55 per cent of the dogs, primarily those with very soft murmurs, there was some variation in the intensity of the murmur from beat to beat. The prevalence of cardiac murmurs among Norwegian and Swedish boxers was high and similar to the prevalence reported in Great Britain.

Mycoplasma canis and urogenital disease in dogs in Norway.

Mycoplasmas identified as Mycoplasma canis were isolated from nine dogs with clinical signs of urogenital disease in Norway over a period of 20 months. Some of the dogs had been treated unsuccessfully with antibiotics, and three were euthanased as a result of severe persistent disease. Seven of the dogs had a urinary tract infection, one had chronic purulent epididymitis and one had chronic prostatitis. Overt haematuria was frequently observed among the dogs with cystitis. M canis was isolated in pure culture from seven of the dogs and in mixed culture from the other two. In three cases the mycoplasma was cultivated only from urinary sediment, and it was typically obtained in smaller numbers than would be considered indicative of a urinary tract infection. In contrast with most mycoplasmas, the M canis isolated from all the dogs grew on ordinary blood agar plates used for routine bacteriological cultivation. Specific mycoplasma media were not used and the presence of other Mycoplasma or Ureaplasma species cannot be excluded.

Consensus recommendations for immunosuppressive treatment of dogs with glomerular disease based on established pathology.

The purpose of this report was to provide consensus recommendations for the use of immunosuppressive therapy in dogs with active glomerular diseases. Recommendations were developed based on comprehensive review of relevant literature on immunosuppressive therapy of glomerular disease in dogs and humans, contemporary expert opinion, and anecdotal experience in dogs with glomerular disease treated with immunosuppression. Recommendations were subsequently validated by a formal consensus methodology. The Study Group recommends empirical application of immunosuppressive therapy for dogs with severe, persistent, or progressive glomerular disease in which there is evidence of an active immune-mediated pathogenesis on kidney biopsy and no identified contraindication to immunosuppressive therapy. The most compelling evidence supporting active immune-mediated mechanisms includes electron-dense deposits identified with transmission electron microscopic examination and unequivocal immunofluorescent staining in the glomeruli. For diseases associated with profound proteinuria, attendant hypoalbuminemia, nephrotic syndrome, or rapidly progressive azotemia, single drug or combination therapy consisting of rapidly acting immunosuppressive drugs is recommended. The Study Group recommends mycophenolate alone or in combination with prednisolone. To minimize the adverse effects, glucocorticoids should not be used as a sole treatment, and when used concurrently with mycophenolate, glucocorticoids should be tapered as quickly as possible. For stable or slowly progressive glomerular diseases, the Study Group recommends mycophenolate or chlorambucil alone or in combination with azathioprine on alternating days. Therapeutic effectiveness should be assessed serially by changes in proteinuria, renal function, and serum albumin concentration. In the absence of overt adverse effects, at least 8 weeks of the rapidly acting nonsteroidal drug therapy and 8-12 weeks of slowly acting drug therapy should be provided before altering or abandoning an immunosuppressive trial.

A single sample method for estimating glomerular filtration rate in cats.

BACKGROUND: Validated methods of estimating glomerular filtration rate (GFR) in cats requiring only a limited number of samples are desirable. HYPOTHESIS/OBJECTIVES: To test a single sample method of determining GFR in cats. ANIMALS: The validation population (group 1) consisted of 89 client-owned cats (73 nonazotemic and 16 azotemic). A separate population of 18 healthy nonazotemic cats (group 2) was used to test the methods. METHODS: Glomerular filtration rate was determined in group 1 using corrected slope-intercept iohexol clearance. Single sample clearance was determined using the Jacobsson and modified Jacobsson methods and validated against slope-intercept clearance. Extracellular fluid volume (ECFV) was determined from slope-intercept clearance with correction for the 1 compartment assumption and by deriving a prediction formula for ECFV (ECFV Predicted ) based on the body weight. The optimal single sample method was tested in group 2. RESULTS: A blood sample at 180 minutes and ECFV Predicted were optimal for single sample clearance. Mean ± SD GFR in group 1 determined using the Jacobsson and modified Jacobsson formulae was 1.78 ± 0.70 and 1.65 ± 0.60 mL/min/kg, respectively. When tested in group 2, the Jacobsson method overestimated multisample clearance. The modified Jacobsson method (mean ± SD 2.22 ± 0.34 mL/min/kg) was in agreement with multisample clearance (mean ± SD 2.19 ± 0.34 mL/min/kg). CONCLUSIONS AND CLINICAL IMPORTANCE: The modified Jacobsson method provides accurate estimation of iohexol clearance in cats, from a single sample collected at 180 minutes postinjection and using a formula based on the body weight to predict ECFV. Further validation of the formula in patients with very high or very low GFR is required.

Short- and long-term outcome after perineal urethrostomy in 86 cats with feline lower urinary tract disease.

BACKGROUND: Perineal urethrostomy is a surgical method for alleviating urethral obstruction in cats with complicated or recurrent obstructive feline lower urinary tract disease. However, long-term outcome of perineal urethrostomy in cats with feline lower urinary tract disease has only been described in studies with relatively few cats. OBJECTIVES: The aim of this study was to evaluate the long-term prognosis, recurrent episodes, quality of life and survival times in cats with feline lower urinary tract disease who underwent perineal urethrostomy. MATERIALS AND METHODS: Data was collected from 86 cats from medical records, including 75 cats with at least 6 months survival, whose owners responded by questionnaire-based telephone interviews. RESULTS: Long-term follow-up ranged from 1·0 to 10·4 years. The median survival time for all cats was 3·5 years after surgery. Forty-seven cats were still alive at the time of the study. Five cats (5·8%) did not survive the first 14 days after perineal urethrostomy surgery; another six cats (7·0%) did not survive 6 months. Seventy-five cats (87%) lived longer than 6 months; 45 (60%) of these were asymptomatic after surgery; 8 of 75 cats (10·7%) experienced severe signs of recurrent feline lower urinary tract disease. For 19 cats, data were available for more than 6 years. Among these, 13 cats were still alive at the time of this study. The six non-surviving cats had all been euthanased for diseases unrelated to the urinary tract. Eighty-eight percent of the owners categorised their cat's long-term quality of life as good. CLINICAL SIGNIFICANCE: This study shows that long-term quality of life after perineal urethrostomy in cats with obstructive feline lower urinary tract disease is good (as assessed by owners) and the recurrence rate is low.

Quantitative determination of exo- and endo-iohexol in canine and feline samples using high performance liquid chromatography with ultraviolet detection.

A sensitive and specific high performance liquid chromatography-ultraviolet detection (HPLC-UV) method for quantitative determination of exo- and endo-iohexol in cat and dog serum/plasma is presented. Sample preparation consisted of a protein precipitation step performed by adding 15 µL of trifluoroacetic acid to 100 µL of serum/plasma. Following vortexing and centrifugation, an aliquot of the supernatant was injected onto a polymeric PLRP-S column (250 mm × 4.6 mm i.d., dp: 8 µm, 100 Å), maintained at 30 °C. The mobile phase consisted of water (A) and methanol (B) and a gradient elution (flow-rate: 1.0 mL min(-1), total run-time: 21 min). The UV detector was set at a wavelength of 254 nm. Matrix-matched calibration graphs were prepared for both exo- (0.44-657 µg mL(-1)) and endo-iohexol (0.62-93.0 µg mL(-1)). Correlation and goodness-of-fit coefficients were between 0.9985-0.9999 and 4.44-9.87%, respectively. Limits of quantification and detection were 0.44 and 0.15 µg mL(-1) for exo-iohexol and 0.62 and 0.20 µg mL(-1) for endo-iohexol, respectively. Results for within-day and between-day precision and accuracy fell within the ranges specified. The reported method is simple and cost-effective. It has been successfully used for the analysis of exo- and endo-iohexol in serum/plasma samples of cats and dogs as part of pharmacokinetic studies with iohexol in order to determine plasma clearance of exo- and endo-iohexol. This indicates the usefulness of the developed method for application in the field of veterinary clinical practice and research.

Evaluation of kidney injury in dogs with pyometra based on proteinuria, renal histomorphology, and urinary biomarkers.

BACKGROUND: Proteinuria is a feature of pyometra-associated renal dysfunction, but its prevalence and clinical relevance are not well characterized. OBJECTIVES: To define which subset of dogs with pyometra has clinically relevant kidney injury by quantification of proteinuria; light, immunofluorescence, and electron microscopic examination of kidney biopsy specimens; and measurement of urinary biomarkers. ANIMALS: Forty-seven dogs with pyometra. Ten clinically healthy intact bitches of comparable age. METHODS: Prospective study. Routine clinicopathological variables including urinary protein to creatinine ratio (UPC) were analyzed. Validated assays were used to quantify urinary biomarkers for glomerular (urinary albumin, urinary immunoglobulin G, urinary C-reactive protein, urinary thromboxane B(2)) and tubular function (urinary retinol-binding protein, urinary N-acetyl-ß-d-glucosaminidase). Kidney biopsy specimens from 10 dogs with pyometra and dipstick urine protein concentrations of 2+ or 3+ were collected during ovariohysterectomy. Urinalysis was repeated within 3 weeks after surgery in 9 of the 10 dogs. RESULTS: UPC (median, range) was significantly higher in dogs with pyometra (0.48, 0.05-8.69) compared with healthy bitches (0.08, 0.02-0.16) (P < .01). Twenty-two of 47 dogs with pyometra had UPC>0.5, 12 had UPC>1.0, and 7 had UPC>2.0. Glomerulosclerosis and tubulointerstitial nephritis were common kidney biopsy findings in proteinuric dogs with pyometra. Dogs with glomerulosclerosis (5/10), either global or focal and segmental, had UPC>1.0 at ovariohysterectomy and afterward. Dogs with structural glomerular and tubular changes mostly had urinary biomarker to creatinine ratios above the 75th percentile. CONCLUSION: Dogs with pyometra and UPC>1.0 or high ratios of urinary biomarkers appear likely to have clinically relevant renal histologic lesions and require monitoring after ovariohysterectomy. Future studies should evaluate the role of pyometra-associated pathogenic mechanisms in causing or exacerbating focal and segmental glomerulosclerosis in dogs.

Glucosuria in Norwegian elkhounds and other breeds during dog shows.

Clinically healthy Norwegian elkhounds were tested for glucosuria by urine dipstick analysis and the results were compared with a group of dogs of other breeds during 15 dog shows. Fifty-two of 187 Norwegian elkhounds (27.3 per cent) and 15 of 202 dogs of other breeds (7.4 per cent) were glucosuric during the dog shows; the difference was statistically significant. Two of the glucosuric elkhounds and one non-glucosuric elkhound developed signs of kidney disease during the year of the study.

Disseminated Mycobacterium celatum (type 3) infection in a domestic ferret (Mustela putorius furo).

A 4-year-old male ferret (Mustela putoriusfuro) had a 6-month history of weight loss and gradual development of depression and coughing. Necropsy findings included pale gray tissue around the distal trachea, multiple nodules in the lungs, a single nodule in the stomach wall, gray foci in the liver, and enlarged lymph nodes. Histologic examination revealed multifocal to coalescing granulomatous inflammation in the trachea, lungs, stomach, liver, and lymph nodes, with acid-fast bacteria in epithelioid cells and macrophages. The acid-fast bacteria were identified as Mycobacterium celatum (type 3) using DNA sequence analysis of the 16S ribosomal DNA gene. M. celatum is a recently described mycobacterium isolated mainly from immunocompromised humans. This is the first report of M. celatum infection in an animal.