RADIOGRAPHIC EVALUATION OF CAUDAL VENA CAVA SIZE IN DOGS

Dilation of the caudal vena cava (CVC) on lateral thoracic radiographs is often interpreted as suggestive of right-sided congestive heart failure. To quantitate the clinical utility of evaluating CVC size as an indicator of right-sided heart disease, we compared the ratio of the diameter of the CVC as measured on a left lateral thoracic radiograph to the descending aorta (Ao), length of the thoracic vertebra above the tracheal bifurcation (VL), and width of the right fourth rib (R4) in 35 dogs with right heart disease and 35 control dogs. Each CVC ratio (CVC/Ao, CVC/VL, CVC/R4) was statistically larger in dogs with right heart disease. Response operating characteristic curves and likelihood ratios were used to determine ratios helpful in identifying dogs with right heart disease. A CVC/Ao > 1.50, CVC/VL > 1.30, or CVC/R4 > 3.50 are strongly suggestive of a right-sided heart abnormality in a patent.     

Ultrasonographic quantitative evaluation of acute and chronic renal disease using the renal cortical thickness to aorta ratio in dogs

The renal cortical thickness (RCT) has been correlated with renal function. Previous studies have also reported that the RCT:Abdominal aorta(Ao) ratio is constant in normal dogs with various physical factors. This multi-center, retrospective, analytical study aimed to determine if there are differences between actual RCT and predicted value of RCT considering physical factors in dogs with acute or chronic renal disease. We also aimed to demonstrate whether the RCT and Ao ratio index would be useful for evaluating renal pathology. A total of 54 dogs with acute or chronic renal disease and 30 normal healthy dogs were included in this study. The RCT was measured at the center of the renal pyramid as the shortest distance perpendicular to the renal capsule from the base of the renal medullary pyramid at three points. The diameter of the Ao was measured just caudal to the branch of the left renal artery in the sagittal plane in systole. The RCT:Ao ratio of chronic kidney disease (CKD) patients was 0.50 ± 0.11 (mean ± standard deviation). The RCT:Ao ratio in normal dogs was 0.67 ± 0.07. The RCT:Ao ratio in patients with acute kidney injury (AKI) was 0.83 ± 0.05. There was a statistically significant difference between normal dogs and dogs with CKD (P < 0.001) and between normal dogs and dogs with AKI (P < 0.001). In conclusion, findings from the current study supported using the RCT:Ao ratio as a non-invasive quantitative method for characterizing kidney pathology in dogs with acute or chronic renal disease.     

Tricuspid annular plane systolic excursion-to-aortic ratio provides a bodyweight-independent measure of right ventricular systolic function in dogs

Objectives

To evaluate whether tricuspid annular plane systolic excursion (TAPSE) can be normalized to aortic valve (Ao) measurements in dogs. To determine TAPSE:Ao reference intervals for healthy dogs and examine diagnostic performance of TAPSE:Ao in dogs with pulmonary hypertension (PH).

COMPUTED TOMOGRAPHIC MEASUREMENT OF THE MAIN PULMONARY ARTERY TO AORTIC DIAMETER RATIO IN HEALTHY DOGS: A COMPARISON TO ECHOCARDIOGRAPHICALLY DERIVED RATIOS

Indicators of pulmonary hypertension in dogs examined with thoracic computed tomography (CT) are not well established in the veterinary literature. In humans, the main pulmonary artery to aortic diameter ratio (MPA:Ao) measured via CT, has been shown to be more sensitive than echocardiographic variables for predicting presence and severity of pulmonary hypertension, in some cases. In veterinary literature, the MPA:Ao has been determined echocardiographically to have an upper limit of about 1:1. Measurement of this ratio has not been described in dogs using CT. The objectives of this cross‐sectional, prospective study were to compare echocardiographic measurement of MPA:Ao with that obtained via CT, determine if measurement of MPA:Ao via CT is repeatable and reproducible, and determine the effect of respiration and contrast administration on the measurement of MPA:Ao via CT. Ten healthy dogs without pulmonary hypertension were anesthetized to undergo thoracic CT using three protocols and echocardiography. The MPA:Ao was measured three times by three observers for each of the three CT protocols and compared to echocardiographic measurements. The mean MPA:Ao measured among all observers and CT protocols was 1.108 ± 0.152 (SD). The effect of CT scan protocol on MPA:Ao significantly differed among the three methods (P = 0.0014), where expiratory scans had lower MPA:Ao than inspiratory scans. The ratio measured on inspiratory CT scans consistently overestimated MPA:Ao when compared to echocardiography (bias = 0.226). Findings did not support the echocardiographically derived upper limit of MPA:Ao as an upper limit for determination of main pulmonary arterial enlargement on CT.     

M-mode echocardiographic ratio indices in normal dogs, cats, and horses: a novel quantitative method

A novel method for quantitative echocardiographic interpretations is introduced based on the calculation of ratio indices in which each raw M-mode measurement is divided by the aortic root dimension (Ao). "Aorta-based" indices were calculated with the animal's measured aortic root dimension (Ao(m)) as the length standard. Conversely, "weight-based" indices employed an idealized estimate of aortic dimension (Ao(w)) with a weighted least squares linear regression against the cube root of body weight (Ao(w) = kW(1/3)). Use of these indices circumvented undesirable statistical characteristics inherent in linear regression of echocardiographic dimensions against body weight and, to a lesser extent, body surface area. Compared with the regressions, ratio indices resulted in substantial refinement of the predictive range for each M-mode measurement in dogs, particularly with decreasing body size. Weight-based indices outperformed aorta-based indices in this regard. To refine the predictive range, neither type of index was clearly advantageous in cats compared with the simple average method typically employed for that species. Several of the raw M-mode measurements, however, were correlated with body weight in cats and horses, indicating the need for an appropriate correction for body size in these species. The ratio index method was suitable for this purpose. Summary statistics derived from normal dogs (n = 53), cats (n = 32), and horses (n = 17) are presented for each index, including novel clinical indices calculated from area ratios. The latter were designed to represent body size-adjusted lett ventricular stroke area (ie, volume overload) and myocardial wall area (ie, hypertrophy).     

ULTRASONOGRAPHIC DIAGNOSIS OF PORTOSYSTEMIC SHUNTING IN DOGS AND CATS

The value of ultrasonography was evaluated in 85 dogs and 17 cats presented with a clinically suspected portosystemic shunt (PSS). A PSS was confirmed in 50 dogs and nine cats (single congenital extrahepatic in 42, single congenital intrahepatic in 11, and multiple acquired in six). Six dogs and one cat had hepatic microvascular dysplasia, and 29 dogs and seven cats had a normal portal system. Ultrasonography was 92% sensitive, 98% specific, and had positive and negative predictive values of 98% and 89%, respectively, in identifying PSS, with an overall accuracy of 95%. When a PSS was identified with ultrasonography, extrahepatic, intrahepatic, and multiple acquired PSS could be correctly differentiated in 53/54 patients (98%). The combination of a small liver, large kidneys, and uroliths had positive and negative predictive values of 100% and 51% for the presence of a congenital PSS in dogs. The portal vein/aorta (PV/Ao) and portal vein/caudal vena cava (PV/ CVC) ratios were smaller in animals with extrahepatic PSSs compared with animals with microvascular dysplasia, intrahepatic PSSs and those without portal venous anomalies (P<0.001). All dogs and cats with a PV/Ao ratio of < or = 0.65 had an extrahepatic PSS or idiopathic noncirrhotic portal hypertension. Dogs and cats with PV/Ao and PV/CVC ratios of > or = 0.8 and > or = 0.75, respectively, did not have an extrahepatic PSS. Reduced or reversed portal flow was seen in four of four patients with multiple acquired PSSs secondary to portal hypertension. The presence of turbulence in the caudal vena cava of dogs had positive and negative predictive values of 91% and 84%, respectively, for the presence of any PSS terminating into that vein.     

Meta-analysis of normal canine echocardiographic dimensional data using ratio indices

ObjectivesTo investigate the dependence of echocardiographic ratio indices (ERIs) on age, body weight (BW) and breed/study group using individually contributed and published summarized data in dogs.BackgroundERIs allow for narrow prediction intervals of M-mode echocardiographic measurements in generic adult dogs. Breed and age-specific differences have not been examined systematically using ERI methods.Animals, materials and methodsIndividual M-mode measurements were contributed by 15 published investigators from 661 dogs, allowing direct calculation of ERIs and summary statistics for each of these breed/study groups. M-mode ERI summary statistics were estimated from published summaries of 22 additional groups that included 527 adult and 36 growing dogs. Individual two-dimensional (2DE) left atrial (LA) and aortic root (Ao) measurements were contributed from 36 dogs. ERIs were analyzed for dependence on BW, breed/study group and age.ResultsThe majority of variation among ERIs was due to differences in the breed or study technique with comparatively little dependence on BW. Age dependence of ERIs was seen in the early growth phases of young dogs, but expected values for each ERI became static long before maturity, roughly at 10–12 weeks of age. ERIs derived from individual 2DE LA and Ao measurements showed no significant dependence on BW.ConclusionsERIs are well normalized for body size and may be useful for clinical evaluation of individuals, prediction of expected M-mode and 2DE cardiac dimensions, and investigation of age or breed-specific cardiac shape changes.     

Two-dimensional,long-axis echocardiographic ratios for assessment of left atrial and ventricular size in dogs

Introduction

Left ventricular (LV) and left atrial (LA) enlargement affect management and outcome of dogs with cardiac disease. Short-axis, two-dimensional echocardiographic (2DE) images, indexed to the aorta (Ao), are frequently used to identify cardiomegaly. Long-axis images offer complementary views of the left heart.

Association of Plasma N-Terminal Pro-B-Type Natriuretic Peptide Concentration with Mitral Regurgitation Severity and Outcome in Dogs with Asymptomatic Degenerative Mitral Valve Disease

Background: The clinical outcome of dogs affected by degenerative mitral valve disease (MVD) without overt clinical signs is still poorly defined, and criteria for identification of animals that are at a higher risk of early decompensation have not yet been determined.
Hypothesis: N-terminal pro-B-type natriuretic peptide plasma concentration (NT-proBNP) is correlated with mitral regurgitation (MR) severity and can predict disease progression in dogs with asymptomatic MVD.
Animals: Seventy-two dogs with asymptomatic MVD, with or without heart enlargement (International Small Animal Cardiac Health Council: ISACHC classes 1a and 1b), and a control group of 22 dogs were prospectively recruited.
Methods: Severity of MR was quantitatively assessed from the regurgitation fraction (RF) by the proximal isovelocity surface area method. Consequences of MR were evaluated from measurements of the left atrium/aorta ratio (LA/Ao), fractional shortening (FS), end-diastolic and end-systolic left ventricular volumes indexed to body surface area (EDVI and ESVI). The relevance of these echo-Doppler indices and NT-proBNP for prediction of outcome at 12 months was studied.
Results: A significant correlation was found between NT-proBNP and RF, LA/Ao, FS, and EDVI ( P < .05). NT-proBNP was higher in dogs with MVD (ISACHC classes 1a and 1b) compared with the control group ( P = .025 and < .001, respectively). The difference was not significant when only dogs from ISACHC class 1a with RF < 30% were considered. Lastly, NT-proBNP was higher in dogs that underwent MVD decompensation at 12 months ( P < .05).
Conclusions and Clinical Importance: NT-proBNP is correlated with MVD severity and prognosis in dogs with asymptomatic MVD.     

Radiographic evaluation of caudal vena cava size as a useful parameter for the diagnosis of heart disease in dairy cattle

To quantify the radiographic parameters of the caudal vena cava (CVC) in healthy cattle and demonstrate their clinical usefulness, the present study compared the ratios of the diameter of the thoracic CVC to the diameter of the aorta (Ao) and length of the thoracic vertebrae (VL), which are all positioned in the same intercostal space, in 81 healthy control cattle (43 growing, 38 adult) and 10 cattle with heart disease. The average diameter of the CVC (CVCave) was correlated with the size of the Ao and VL in the control cows. Although the diameter and pulsation index of the CVC differed significantly between the growing and adult cows, the ratios of CVC/Ao and CVC/VL were fixed values for both the growing and mature cattle. However, in the cattle with heart disease, the pulsation index of the CVC was significantly lower or there was absence of pulsation due to a dilated CVC, and the ratio of CVCave/Ao and CVCave/VL were significantly higher than those in the healthy cattle.     

Balloon Valvuloplasty for Treatment of Pulmonic Stenosis in English Bulldogs with an Aberrant Coronary Artery

Background: English Bulldogs (EB) with pulmonic stenosis (PS) sometimes have an aberrant coronary artery (CA) type R2A encircling the pulmonary artery (PA). Balloon valvuloplasty (BV) is treatment of choice for severe PS, but is considered to be contraindicated in dogs with aberrant CA. Hypothesis: Conservative BV in EB with aberrant CA is safe and improves clinical signs and quality of life. Animals: Four client‐owned EB with severe PS were retrospectively reviewed/analysed. Methods: Retrospective study: Case records, echocardiography, BV, and follow‐up investigations of EB diagnosed with severe PS and treated with BV were reviewed. The ratios of PA to aortic (Ao) velocity time integral (VTI) were calculated to assess progression/improvement of PS. Results: An aberrant CA was confirmed on angiography in all EB. Conservative BV was performed, using a balloon of the size of the PA annulus or smaller (0.6–1 × PA annulus size). All dogs survived the procedure, but only a mild reduction in pressure gradient was achieved. There was an improvement in PA to Ao VTI in 3 of 4 dogs (P≤ .017), which were free of evidence of congestive heart failure (CHF) 5, 10, and 15 months after BV. One dog that had right‐sided CHF when BV was performed died due to progressive right‐sided CHF within 3 months. Conclusions: Conservative BV in EB might be safe and might improve quality and quantity of life.     

Prediction of first onset of congestive heart failure in dogs with degenerative mitral valve disease: The PREDICT cohort study

ObjectiveTo identify risk factors for first-onset congestive heart failure (CHF) in dogs with degenerative mitral valve disease (DMVD).AnimalsEighty-two dogs with and without CHF secondary to DMVD were retrospectively assigned to a derivation cohort. Sixty-five dogs with asymptomatic DMVD were recruited into a prospective validation cohort.MethodsVariables associated with risk of CHF in dogs were identified in a derivation cohort and used to construct a predictive model, which was then prospectively tested through longitudinal examination of a validation cohort.ResultsLogistic regression analysis of the derivation cohort yielded a predictive model that included the left atrial to aortic root dimension ratio (LA:Ao) and plasma concentration of N-terminal pro-B-type natriuretic peptide (NT-proBNP). When this model was prospectively applied to the validation cohort, it correctly predicted first-onset of CHF in 69.2% of cases. Analysis of the validation cohort revealed that plasma NT-proBNP concentration and indexed left ventricular end-diastolic diameter (LVIDd:Ao) were independent risk factors for development of first-onset CHF in dogs with DMVD (NT-proBNP ≥1500 pmol/L, odds ratio (OR), 5.76, 95% confidence interval (CI), 1.37–24.28, P = 0.017; LVIDd:Ao ≥3, OR, 6.11, 95% CI, 1.09–34.05, P = 0.039).ConclusionsMeasures of left heart size and plasma NT-proBNP concentration independently estimate risk of first-onset of CHF in dogs with DMVD. These parameters can contribute to the management of dogs with DMVD.     

Effect of breed, age, weight and gender on radiographic renal size in the dog

In the adult dog, kidney length has been reported as 2.98 ± 0.44 times the length of L2 on ventrodorsal views and 2.79 ± 0.46 times the length of L2 on lateral radiographs. Our aim was to test the hypothesis that the suggested maximum normal left kidney size is too high, and to evaluate the effect of breed type, gender, weight and age of the dog on kidney size. Abdominal radiographs of 200 dogs with no evidence of concurrent disease that might have an effect on renal size were included in the study. The mean ratio of kidney length to the second lumbar vertebra length was similar to previous reports. For the right lateral view it measured 2.98 ± 0.60 and for the ventrodorsal view 3.02 ± 0.66. Significant differences of this ratio between skull type were present, especially between brachycephalic and dolichocephalic dogs. On the right lateral view brachycephalic dogs had the highest median LK/L2 ratio of 3.1 (3.20 ± 0.40), whereas for dolichocephalic dogs it was 2.8 (2.82 ± 0.50), and for mesaticephalic dogs it was 2.97 (3.01 ± 0.6). A ratio >3.5 was found only in mesaticephalic dogs on the ventrodorsal view. There was a significant difference in the LK/L2 ratio between small (≤10kg) and large breed dogs (>30kg) where small dogs had a significantly higher LK/L2 ratio. There was no statistically significant relation between this ratio and age or gender. The previously reported ratios for kidney size seem valid, but because skull type has an impact on the LK/L2 ratio, a single normal ratio should not be used for all dogs.     

Vestibular, vaginal, and urethral relations in spayed dogs with and without lower urinary tract signs

The purpose of this study was to evaluate the urogenital anatomy in female spayed dogs with and without signs of lower urinary tract disease by using conventional vaginourethrography, computed tomography (CT) vaginourethrography, and uroendoscopy. Nineteen dogs with lower urinary tract disease and 12 normal dogs were evaluated prospectively. Measurements made included vaginal length, vaginal height, vaginal width, vestibule length, vestibule height, vestibule width, vestibulovaginal ratios, cingulum height, cingulum width, cingulum area, urethral length, urethral height, urethral width, angle of urethra to vestibule, and angle of vaginal to vestibule. Group comparisons were made between dogs with and without lower urinary tract disease. Comparisons between conventional vaginourethrography and CT vaginourethrography were made when the same anatomical measurement was made by the 2 imaging modalities. There was no significant difference in all of the measurements (P > .01), including vestibulovaginal ratios and cingulum areas, between dogs with and without lower urinary tract disease. There was a larger proportion of dogs with a vestibulovaginal ratio <0.33 in normal dogs (8 of 12) compared with the clinical dogs (8 of 16). A significant difference between vestibulovaginal ratios or cingulum areas between dogs with and without lower urinary tract disease could not be identified. This suggests that a vestibulovaginal ratio of <0.33 may only be an incidental finding and the term "vestibulovaginal stenosis" may need to be redefined.     

EFFECTS OF DIET AND AGING ON RENAL MEASUREMENTS IN UNINEPHRECTOMIZED GERIATRIC BITCHES

Under controlled, but varied dietary conditions among geriatric, uninephrectomized Beagle bitches (dogs) observed for 4 years, renal size increase as assessed radiographically and ultrasonographically occurred at variable rates, but on a seemingly continuous basis. The maximum observed mean renal linear parameter increase found was approximately 15%. However, a 10 and 15% increase is a more representative expectation among the 4 parameters (sonographic length, radiographic length, sonographic width, radiographic width) under consideration. The rate of renal size increase was rapid during the first 2 to 3 months following uninephrectomy. Thereafter, the rate of increase was slow, but occurred to varying degrees in both the length and width as assessed radiographically or ultrasonographically. The mechanism creating the size change was hypertrophy, not hyperplasia. Within limits of the 3 diets used in the study, no significant diet effect was found on the rate or degree of long term compensatory hypertrophy. Radiographically and ultrasonographically measured renal length had the greatest correlation with each other as well as with post mortem measurements and are, therefore, the recommended parameter for imaging assessment of compensatory hypertrophy. When the prenephrectomy, radiographic renal lengths and widths were normalized as a ratio of the second lumbar vertebral body length (L2) measured from ventrodorsal radiographs, the diet group means across dogs (approximately three L2 lengths for renal length; two L2 lengths for renal width) were in the middle of the respective previously published normal radiographic ranges for mature dogs (e.g. 2.5 L2 < or = length < or = 3.5 L2; 1.58 L2 < or = width < or = 2.38 L2 lengths). Even after the hypertrophic changes occurred, the radiographic group mean lengths and widths across dogs were still within the specified normal ranges, although toward the upper end of the respective range. This information provides background for clinical interpretation of potential compensatory hypertrophy that may be encountered following uninephrectomy for spontaneous disease in aged dogs. In addition, it appears that available radiographic renal linear ranges for normal mature dogs are applicable to geriatric dogs as well.     

COMPUTED TOMOGRAPHIC CHARACTERISTICS OF THE CISTERNA CHYLI IN DOGS

Previous lymphangiographic studies have investigated the use of computed tomography (CT) for characterizing the thoracic duct and its tributaries in dogs. However, there is limited published information on the appearance of the canine cisterna chyli using CT. The objective of this retrospective study was to describe the features of the canine cisterna chyli in pre‐ and post‐contrast abdominal CT studies. The presence, location, shape, maximum width, size compared with the aortic diameter (Ao:cisterna chyli ratio) and mean attenuation of the cisterna chyli were recorded from archived abdominal CT scans of 30 dogs. Breed, age, sex and neutering status were also noted. A cisterna chyli was identified in 26 of the dogs (87%). In 22 cases a cisterna chyli could be reliably identified prior to intravenous contrast administration and in all 26 cases in postcontrast images. The cisterna chyli was most commonly located right dorsolateral to the abdominal aorta between L1 and L4. Shape varied on transverse images from crescent‐like to globular and maximum diameters ranged from 5 to 9 mm. The Ao:cisterna chyli ratio varied between 0.29 and 0.71 (mean value—males: 0.32; females: 0.38). On pre‐contrast images the mean Hounsfield units were 21.3HU (range: –3.8 to 64.25). Mild enhancement of the cisterna chyli post‐contrast was observed in 24 dogs (80%). Findings supported the use of pre‐ and post‐contrast abdominal CT as a non‐invasive method for assessing qualitative and quantitative characteristics of the canine cisterna chyli.     

QUANTITATIVE AND QUALITATIVE COMPUTED TOMOGRAPHIC CHARACTERISTICS OF BRONCHIECTASIS IN 12 DOGS

Bronchiectasis is an irreversible dilatation of the bronchi resulting from chronic airway inflammation. In people, computed tomography (CT) has been described as the noninvasive gold standard for diagnosing bronchiectasis. In dogs, normal CT bronchoarterial ratios have been described as <2.0. The purpose of this retrospective study was to describe quantitative and qualitative CT characteristics of bronchiectasis in a cohort of dogs with confirmed disease. Inclusion criteria for the study were thoracic radiography, thoracic CT, and a diagnosis of bronchiectasis based on bronchoscopy and/or histopathology. For each included dog, a single observer measured CT bronchoarterial ratios at 6 lobar locations. Qualitative thoracic radiography and CT characteristics were recorded by consensus opinion of two board‐certified veterinary radiologists. Twelve dogs met inclusion criteria. The mean bronchoarterial ratio from 28 bronchiectatic lung lobes was 2.71 ± 0.80 (range 1.4 to 4.33), and 23/28 measurements were >2.0. Averaged bronchoarterial ratios from bronchiectatic lung lobes were significantly larger (P < 0.01) than averaged ratios from nonbronchiectatic lung lobes. Qualitative CT characteristics of bronchiectasis included lack of peripheral airway tapering (12/12), lobar consolidation (11/12), bronchial wall thickening (7/12), and bronchial lumen occlusion (4/12). Radiographs detected lack of airway tapering in 7/12 dogs. In conclusion, the most common CT characteristics of bronchiectasis were dilatation, a lack of peripheral airway tapering, and lobar consolidation. Lack of peripheral airway tapering was not visible in thoracic radiographs for some dogs. For some affected dogs, bronchoarterial ratios were less than published normal values.     

Comparisons of 3‐, 2‐Dimensional,and M‐Mode Echocardiographical Methods for Estimation of Left Chamber Volumes in Dogs with and without Acquired Heart Disease

Background: Real‐time 3‐dimensional echocardiography (RT3D) is a recent technique based on volumetric scanning, eliminating the need for geometric modeling of the cardiac chambers and minimizing the errors caused by foreshortened views. Hypothesis: Estimations of left ventricular (LV) end‐diastolic (EDV) and end‐systolic volume (ESV), and left atrial (LA) size, differ depending on the echocardiographic technique of estimation. Animals: Fifty‐one dogs with acquired heart disease and 34 healthy control dogs. Methods: Prospective observational study by M‐mode (Teichholz method), Simpson's modified 2‐dimensional (2D) method, and RT3D methods for estimation of LV volumes. LA size was evaluated by 2D and RT3D methods. Results: RT3D showed good agreement with 2D for EDV and ESV, whereas Teichholz method overestimated LV volumes in comparison with the other 2 methods by approximately a factor 2. There were no statistically significant differences among the 3 methods in estimating ejection fraction. Comparison between RT3D assessment of LA end‐systolic volume per kilogram (LAs/kg) and LA to aortic ratio (LA/Ao) measured by 2D relative to each other showed that the RT3D method underestimated LAs/kg at lower values, and overestimated it at higher values. The difference between methods increased with increasing LA size. Conclusions and Clinical Importance: There was good agreement between RT3D and 2D methods of estimating EDV and ESV, whereas the Teichholz method overestimated LV volumes by approximately a factor 2. In comparison with RT3D, LA/Ao underestimated LA size, especially when LA was enlarged.     

Progression of chronic renal disease in the dog

Progressive loss of nephron function may be caused by persistence of factors that initiated renal disease. However, newer studies suggest that nephron damage is self-perpetuating once renal mass is reduced to some critical level. Original theories on mechanisms of self-perpetuated nephron injury focused on intraglomerular hypertension and glomerular hypertrophy, but several other factors have now been incriminated, including tubulointerstitial responses, proteinuria, and oxidative stress. Studies of dogs with surgically reduced renal mass (remnant kidney model of chronic renal disease) have allowed investigation of the self-progression theory in this species. Use of this model eliminates pre-existing renal disease as a confounding factor. Data from these studies indicate that self-perpetuated renal injury is initiated when mild azotemia is induced (plasma creatinine concentration = 2 to 4 mg/dL). Thus, with naturally occurring renal disease(s), it is likely that self-perpetuated nephron damage is occurring before or at the time when most cases of chronic renal disease are diagnosed. In dogs with remnant kidneys, loss of renal function often occurs at a linear rate over time, but non-linear patterns are common as well. The reciprocal of plasma creatinine concentration, which has been used to monitor rate of progression, is only a fair marker of renal function when compared to GFR. Thus, clinical results from creatinine measurements on cases of naturally occurring disease should not be interpreted too stringently. In remnant kidney dogs, the magnitude of proteinuria (UPC ratio) was not predictive of the rate in decline of GFR, casting doubt on importance of proteinuria in causing progression of renal disease. However, progressive increases in UPC may be a marker of an accelerated rate of renal injury. Self-perpetuation of renal injury in dogs could be the sole mechanism by which naturally occurring renal diseases progress. When more information is available on the rate of progression of naturally occurring diseases, it may become apparent whether factors initially inciting renal damage have an additive effect on rate of progression.