Radiographic Evaluation of the Canine and Feline Thorax: Cardiac and Pulmonary Assessment

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Key Takeaways

• Thoracic radiography is the primary imaging modality for cardiac and pulmonary assessment in dogs and cats, requiring systematic evaluation of patient positioning, technique, and breed-specific variations. The Vertebral Heart Score (VHS) is an objective metric for quantifying canine cardiac enlargement, with species-specific reference intervals crucial for accurate interpretation.
• The dorsoventral (DV) projection is preferred for consistent cardiac silhouette evaluation and assessment of pulmonary lobar vessels, while the ventrodorsal (VD) view is better suited for evaluating the caudal vena cava, accessory lung lobe, and pleural effusion. Consistent positioning and inspiratory phase are critical for reliable VHS measurement.
• Left atrial enlargement, a key indicator of degenerative mitral valve disease in dogs, manifests as a caudodorsal cardiac bulge and can elevate or compress the mainstem bronchus; its presence often warrants echocardiographic follow-up. Pulmonary venous distension, identified by a vein diameter exceeding the artery diameter, signifies left-sided volume overload and precedes cardiogenic pulmonary edema.
• Breed-specific VHS reference intervals are essential to avoid misdiagnosis of cardiomegaly, as variations in thoracic vertebral morphology significantly influence the score, particularly in breeds like Corgis. Similarly, age-appropriate reference intervals must be applied to kittens, as their cardiac silhouette is proportionally larger than that of adult cats.
• Referral for echocardiography is indicated when radiographic findings suggest clinically significant cardiac disease that will alter management, such as a VHS above breed-specific limits with pulmonary infiltrates or radiographic left atrial enlargement. Laboratory diagnostics, like NT-proBNP measurement, can supplement radiographic findings when equivocal.

Thoracic radiography remains the first-line imaging modality for evaluating cardiac and pulmonary disease in dogs and cats. This article provides a structured framework for interpreting cardiac silhouette size, chamber enlargement, pulmonary vasculature, and lung patterns in both species. It serves the practicing veterinarian who needs decision criteria for distinguishing normal variation from clinically significant disease, selecting appropriate views, and determining when echocardiography or advanced imaging is warranted. The content addresses the diagnostic question: does this patient have radiographic evidence of cardiac disease, and if so, what is its nature and severity?

Radiographic assessment of the heart requires systematic attention to patient positioning, radiographic technique, and breed-specific variation. A single lateral view cannot fully characterize cardiac size or chamber morphology. The vertebral heart score (VHS) provides an objective, repeatable measurement that has become the standard for quantifying canine cardiac enlargement, while feline assessment relies on similar principles with species-specific reference intervals. Pulmonary evaluation requires integration of vascular caliber, interstitial and alveolar patterns, and distribution of abnormalities to differentiate cardiogenic edema from primary respiratory disease.

At a Glance

Radiographic Physics and Positioning Principles

Image quality determines interpretive accuracy. The cardiac silhouette magnifies with increasing object-to-film distance, so thoracic radiographs must be obtained with the patient in sternal or lateral recumbency with the thorax positioned directly against the cassette or detector. Inspiratory films are essential, as expiration falsely increases cardiac width and pulmonary opacity. A short exposure time minimizes motion blur from cardiac and respiratory movement.

The American College of Veterinary Radiology publishes professional standards for image acquisition and interpretation that emphasize consistent technique across serial studies. Serial comparison requires identical positioning and exposure factors, because changes in patient rotation or phase of respiration can mimic or mask cardiac enlargement.

Lateral Projection Considerations

Right lateral recumbency is preferred for cardiac evaluation in dogs because the heart assumes a more consistent position and the VHS reference values were established using this view. Left lateral recumbency causes the dependent lung lobes to compress and can spuriously increase apparent cardiac size. In cats, either lateral view is acceptable, but consistency within a patient is mandatory for serial monitoring.

Dorsoventral Versus Ventrodorsal Projection

The clinical usefulness of the ventrodorsal versus dorsoventral thoracic radiograph in dogs differs by structure of interest. The VD view is indicated for evaluation of the cranial and caudal mediastinum, the caudal vena cava, and the accessory lung lobe, and in cases of pleural effusion. The DV view is preferred for assessment of a consistent cardiac silhouette, evaluation of the pulmonary lobar vessels, and evaluation of the structures of the dorsal thorax, such as hilar lymph nodes, the caudal dorsal lungs, trachea, mainstem bronchi, and left atrium. For routine cardiac assessment, the DV view provides more reliable vascular and left atrial evaluation.

Vertebral Heart Score Methodology

The vertebral heart score, originally described by Buchanan and Bücheler, measures cardiac length and width relative to thoracic vertebral body length. On a right lateral radiograph, the long axis of the heart is measured from the ventral border of the left mainstem bronchus to the cardiac apex. The short axis is measured perpendicular to the long axis at the widest point of the cardiac silhouette. These measurements are then transposed onto the vertebral column starting at the cranial edge of the fourth thoracic vertebra, and the number of vertebrae spanned by each measurement is summed.

The vertebral heart scale on CT is correlated to radiographs in dogs, and CT-based VHS measurement shows moderate to high correlation with radiographic values. Cardiac gating may not be necessary when assessing canine heart size on CT, which simplifies advanced imaging protocols. However, radiography remains the clinical standard because of availability, cost, and the extensive reference data established over decades of use.

Breed-Specific Variation

Breed-specific VHS values differ from the original reference value in most cases. The thoracic vertebral length-to-height ratio predicts the vertebral heart score in normal Welsh Corgi Pembroke dogs, with Corgi-specific VHS derived from the right lateral radiograph significantly lower than the reference value. This variation correlates with thoracic vertebral characteriztics, as the ratio of T4 length to height differs significantly among breeds. Shih Tzus have the highest T4 length-to-height ratio and Beagles the lowest among breeds studied. Practitioners must consult breed-specific reference intervals when available, particularly for chondrodystrophic and deep-chested breeds.

Feline Reference Intervals

Reference intervals for radiographic cardiac size in kittens have been established, with a median VHS of 9.5 vertebrae and a 95% reference interval of 8.0 to 10.9 vertebrae. The reference intervals for radiographic, echocardiographic and NT-proBNP values in healthy kittens also report a median cardiac thoracic ratio of 67.2% with a 95% reference interval of 54.4% to 79.8%. These values are higher than adult feline references, reflecting the relatively larger cardiac silhouette in growing animals. Low-grade heart murmurs were appreciated in 29.5% of healthy kittens in this population, emphasizing that auscultatory findings alone do not establish cardiac disease.

Cardiac Chamber Enlargement Patterns

Chamber-specific enlargement produces characteriztic silhouette changes that guide differential diagnosis. Left atrial enlargement is the most clinically significant radiographic finding in dogs with degenerative mitral valve disease, as it distinguishes stage B1 from stage B2 disease and correlates with risk of pulmonary edema.

Left Atrial Enlargement

On the lateral view, left atrial enlargement appears as a caudodorsal bulge of the cardiac silhouette between the caudal vena cava and the mainstem bronchus. Severe enlargement elevates and compresses the left mainstem bronchus, producing a characteriztic "bow-legged" appearance on the DV view. A novel standardized method for determining left atrial enlargement on lateral thoracic radiographs in dogs draws a line from the dorsal border of the tracheal bifurcation to the crossing point of the dorsal border of the caudal vena cava and the most cranial crus of the diaphragm. If part of the left atrium extends dorsally beyond this line, it is considered enlarged. This method moderately correlates with echocardiographic LA:Ao ratio and may facilitate learning for less experienced observers, though it does not outperform subjective assessment by experienced clinicians.

Right-Sided Enlargement

Right atrial and ventricular enlargement produces increased sternal contact on the lateral view and rounding of the right cardiac border on the DV view. These changes are less specific than left atrial enlargement and require correlation with clinical findings, as pericardial effusion and obesity can mimic right-sided cardiomegaly.

Pulmonary Vasculature Assessment

Pulmonary vascular evaluation requires comparison of artery and vein diameters in the same lobar distribution. On the lateral view, the cranial lobar vessels are assessed where the pulmonary artery and vein cross. On the DV view, the caudal lobar vessels are evaluated as they course toward the diaphragm. The vein should not exceed the artery in diameter in either species.

Pulmonary venous distension indicates left-sided volume overload and precedes radiographic pulmonary edema. Arterial enlargement suggests pulmonary hypertension or increased pulmonary blood flow. The DV view is preferred for vascular assessment because the dorsoventral projection provides more consistent pulmonary lobar vessel evaluation than the VD view.

Systematic Cardiac Measurement Protocol

The radiographic cardiac evaluation proceeds in a fixed sequence: assess technical quality, evaluate the cardiac silhouette on the lateral projection, measure vertebral heart score (VHS), compare with breed and species reference intervals, then examine the orthogonal projection for chamber-specific changes. Deviating from this order invites interpretive error, particularly when subjective impression of cardiomegaly is allowed to override objective measurement.

Step 1: Confirm Projection and Patient Factors

The right lateral projection is the standard for cardiac evaluation because it minimizes positional variation of the cardiac silhouette. The dorsoventral (DV) projection provides a more consistent cardiac silhouette than the ventrodorsal (VD) view, and is preferred when the primary question concerns heart size or pulmonary lobar vessels The clinical usefulness of the ventrodorsal versus dorsoventral thoracic. The VD view remains indicated for evaluation of the caudal vena cava, accessory lung lobe, and pleural effusion The clinical usefulness of the ventrodorsal versus dorsoventral thoracic.

Patient positioning must be assessed before any measurement is accepted. Rotation of the thorax on the lateral projection changes the apparent cardiac width and can falsely elevate VHS. Inspiratory phase also matters: a radiograph exposed at end-expiration will show a relatively larger cardiac silhouette because the lungs are less inflated. If the patient is dyspnoeic and only expiratory films are obtainable, the VHS should be interpreted with caution and the limitation recorded.

Step 2: Measure Vertebral Heart Score

The VHS is measured on the right lateral projection. The long axis is drawn from the ventral border of the carina to the cardiac apex. The short axis is drawn perpendicular to the long axis at the point of maximal cardiac width. Both measurements are then transposed to the thoracic vertebral column, starting at the cranial endplate of T4, and the number of vertebrae spanned by each axis is summed.

The original reference value in dogs is 9.7 vertebrae with an upper limit of 10.5. Values above 10.5 indicate cardiomegaly. The VHS measured on computed tomography correlates moderately to highly with the radiographic VHS in dogs, and cardiac gating does not appear necessary for CT-based measurement The vertebral heart scale on CT is correlated to. This supports the use of CT-derived VHS when thoracic CT is performed for other indications and cardiac size is a secondary question.

Breed-specific reference intervals must be applied where they exist. The Corgi-specific VHS derived from the right lateral projection is significantly lower than the original reference value, and the T4 length-to-height ratio differs significantly among breeds Thoracic Vertebral Length-to-Height Ratio, a Promising Parameter to Predict. A Corgi with a VHS of 9.8 may therefore be normal, whereas a Beagle with the same value may be at the upper limit. Consult breed-specific published values when available, and record which reference interval was applied.

Step 3: Apply Species-Specific Intervals

Feline reference intervals differ from canine values. Healthy kittens aged 6 to 16 weeks have a median VHS of 9.5 vertebrae with a 95% reference interval of 8.0 to 10.9 Reference intervals for radiographic, echocardiographic and N-terminal pro B-type. The upper bound of 10.9 is higher than the traditional feline adult cut-off of 10.0, which means a kitten with a VHS of 10.5 may be incorrectly classified as cardiomegalic if adult intervals are applied. The cardiac thoracic ratio in the same kitten population had a median of 67.2% with a 95% reference interval of 54.4% to 79.8% Reference intervals for radiographic, echocardiographic and N-terminal pro B-type. Use age-appropriate intervals in juvenile patients and document the reference source.

Step 4: Evaluate Chamber-Specific Signs

The VHS detects global cardiomegaly but does not localize enlargement. Chamber-specific assessment requires evaluation of the cardiac border contours on both projections.

Left atrial enlargement is the most clinically important chamber assessment in dogs with myxomatous mitral valve disease. On the lateral projection, the left atrium forms the caudodorsal border of the cardiac silhouette. Enlargement produces a bulging, rounded contour dorsal to the tracheal bifurcation and may elevate or compress the mainstem bronchi. A standardized method draws a line from the dorsal border of the tracheal bifurcation to the crossing point of the dorsal border of the caudal vena cava and the most cranial crus of the diaphragm, if the left atrium extends dorsal to this line, it is considered enlarged A Novel Standardized Method for Aiding to Determine Left. This method shows moderate correlation with echocardiographic left atrial to aortic ratio and may facilitate learning, though it is not superior to experienced subjective assessment A Novel Standardized Method for Aiding to Determine Left.

Right-sided enlargement produces increased sternal contact on the lateral projection and a reversed D-shaped cardiac silhouette on the DV or VD projection. The right atrial enlargement displaces the cranial cardiac waist, while right ventricular enlargement widens the cardiac base and increases sternal contact beyond the normal one-third to one-half of the cardiac height.

Left ventricular enlargement lengthens the cardiac long axis, displaces the apex caudoventrally, and increases the angle between the trachea and the cardiac long axis. This is best appreciated on the lateral projection and is often accompanied by elevation of the carina.

Step 5: Integrate Pulmonary Vascular Assessment

Cardiac chamber enlargement cannot be interpreted in isolation. The pulmonary vasculature provides the hemodynamic context. On the lateral projection, the pulmonary artery and vein to the right cranial lung lobe are compared at the level of the fourth rib. On the DV projection, the lobar vessels of the caudal lung lobes are assessed. Arteries and veins should be approximately equal in diameter. Venous distension suggests left-sided congestive heart failure, particularly when accompanied by an interstitial to alveolar pulmonary pattern. Arterial enlargement without venous enlargement raises suspicion for pulmonary hypertension or increased pulmonary blood flow.

The DV projection is preferred for pulmonary lobar vessel evaluation because the vessels are less foreshortened than on the VD view The clinical usefulness of the ventrodorsal versus dorsoventral thoracic. This distinction matters when the clinical question is whether a cough is cardiac or respiratory in origin.

Interpretation Checklist

Documentation Standards

The radiographic report should state the projections obtained, the VHS value with the reference interval applied, the cardiac phase if known, and the specific chamber findings. A normal VHS does not exclude cardiac disease, and the report should say so when chamber-specific changes are present despite a normal score. The report should also note technical limitations such as expiratory phase, rotation, or incomplete lung inflation, because these directly affect the reliability of the measurements.

For serial monitoring, use the same projection and positioning for each recheck. The right lateral projection is preferred for consistency. Changes in VHS of less than 0.5 vertebrae between studies may reflect technical variation instead of true cardiac size change, and this threshold should guide clinical decision-making.

Equipment and Technique Considerations

Digital radiography systems allow windowing and level adjustment that can alter the perceived cardiac border. Standardize window settings for cardiac evaluation instead of relying on default lung windows. A narrow window centerd on the cardiac silhouette improves border detection for VHS measurement. Grid use is appropriate for patients over 10 cm of thoracic thickness, grid cut-off from poor centring will artificially distort the cardiac silhouette and should be excluded before measurement.

Computed tomography provides an alternative when thoracic CT is performed for other indications. The CT-derived VHS correlates with the radiographic VHS, and gating is not required The vertebral heart scale on CT is correlated to. This allows retrospective cardiac size assessment from non-gated thoracic CT studies, which is useful in trauma or oncology staging where cardiac disease was not the primary indication.

Common Errors and Corrective Actions

The most frequent interpretive errors in thoracic radiography stem from measurement technique instead of pattern recognition. A vertebral heart score (VHS) measured from an incorrectly positioned patient or from the wrong vertebral starting point loses its diagnostic value. The long axis must be measured from the ventral border of the left mainstem bronchus to the most ventral aspect of the cardiac apex, and the short axis is measured perpendicular to this at the point of maximal cardiac width. Both axes are then summed and compared against the vertebral column starting at the cranial border of T4. Clinicians who measure the short axis obliquely or who include the caudal vena cava in the long axis will systematically overestimate heart size.

Projection selection errors are equally common. The ventrodorsal view is preferred for evaluation of the caudal vena cava and accessory lung lobe, while the dorsoventral view provides a more consistent cardiac silhouette and better assessment of the pulmonary lobar vessels and left atrium. A clinician who evaluates pulmonary vasculature on a ventrodorsal projection may misinterpret normal vessel foreshortening as pathology. Conversely, evaluating the caudal vena cava on a dorsoventral projection can produce a falsely narrow appearance.

Breed-specific reference intervals are frequently overlooked. The original VHS reference value of 9.7 vertebrae does not apply uniformly across breeds. Welsh Corgi Pembroke dogs have a breed-specific VHS that is significantly lower than the reference value when measured on the right lateral projection, a difference attributed to thoracic vertebral morphology. Applying a single reference interval to all dogs will misclassify normal individuals as cardiomegalic or fail to detect genuine enlargement in breeds with higher baseline values.

Recognized Complications and Early Detection

The principal complication of radiographic cardiac assessment is misclassification of respiratory disease as cardiogenic pulmonary edema. An enlarged left atrium supports a cardiac cause of pulmonary infiltrates, but the absence of visible left atrial enlargement does not exclude it. The radiographic line method, drawn from the dorsal border of the tracheal bifurcation to the crossing point of the dorsal border of the caudal vena cava and the most cranial crus of the diaphragm, provides a reproducible check that correlates moderately with echocardiographic left atrial to aortic ratio. This method is not superior to experienced subjective assessment, but it offers a structured approach for less experienced observers and for serial monitoring.

A second failure mode is the missed esophageal mass. Caudal esophageal lesions, such as those caused by Spirocerca lupi, can mimic cardiac or pulmonary masses on survey radiographs. Survey dorsoventral projections are more reliable than right lateral projections for detecting these lesions, and pneumoesophagography improves visibility of intraluminal nodules. When a caudal thoracic mass is identified, esophageal origin should be considered before attributing the finding to cardiac disease.

Limitations of Current Evidence

The evidence base for radiographic cardiac assessment has important gaps. Feline reference intervals for VHS were derived largely from adult cats, and kittens aged 6 to 16 weeks have a median VHS of 9.5 vertebrae with a 95% reference interval of 8.0 to 10.9 vertebrae. These intervals differ from adult values, and extrapolation across age groups risks misclassification. The same study demonstrated that cardiac thoracic ratio and echocardiographic parameters correlate with body weight and age, indicating that static reference intervals may be inadequate for growing animals.

Computed tomography-based vertebral heart scoring correlates moderately to highly with radiographic VHS, and cardiac gating may not be necessary for CT assessment of heart size. However, CT is not a substitute for radiography in routine cardiac screening, and the clinical equivalence of these modalities for detecting early cardiac disease remains uncertain. Expert opinion still differs on whether breed-specific VHS intervals should replace the original reference value in general practice, and on the threshold at which radiographic cardiomegaly warrants echocardiographic confirmation.

Referral and Escalation Criteria

Referral for echocardiography is indicated when radiographic findings suggest clinically significant cardiac disease that will alter management. A VHS above the breed-specific reference interval combined with pulmonary infiltrates consistent with edema, or radiographic left atrial enlargement in a dog with suspected stage B2 mitral valve disease, warrants echocardiographic confirmation before initiating long-term therapy. The American College of Veterinary Radiology maintains resources on imaging standards and specialty consultation pathways, and the MSD Veterinary Manual provides species-specific guidance on cardiac disease staging and treatment decisions.

Laboratory involvement is appropriate when radiographic findings are equivocal or when concurrent systemic disease is suspected. N-terminal pro B-type natriuretic peptide measurement can support a cardiac diagnosis when radiographs are inconclusive, particularly in cats where the reference intervals for this biomarker are established in healthy kittens. Regulatory reporting is rarely required for cardiac disease, but clinicians should consult the World Organization for Animal Health terrestrial standards when managing diseases with trade implications and the American Veterinary Medical Association practice resources for professional obligations regarding diagnostic imaging and radiation safety.

Frequently Asked Questions

How should I measure vertebral heart score when the cardiac silhouette overlaps the vertebrae on a poorly positioned radiograph?

Reposition the patient and retake the radiograph. A rotated or obliqued thorax distorts the cardiac silhouette and invalidates VHS measurement. If repeat imaging is not possible, interpret the study with caution and state the limitation in the record. The VHS method depends on consistent positioning, and breed-specific reference intervals may differ from the original standard, as demonstrated in studies of Welsh Corgi Pembroke dogs where vertebral morphology influenced the score Thoracic Vertebral Length-to-Height Ratio, a Promising Parameter to Predict the Vertebral Heart Score in Normal Welsh Corgi Pembroke Dogs. When measurement is unreliable, fall back on subjective chamber assessment and integrate echocardiography if available.

Can I use vertebral heart score on computed tomography images instead of radiographs?

Yes, with appropriate caution. A method for measuring VHS on sagittal CT reformatted images has been described in dogs, and cardiac gating may not be necessary for assessment of overall heart size on CT The vertebral heart scale on CT is correlated to radiographs in dogs. Correlation with radiographic VHS was moderate to high in that exploratory study. CT is not a first-line screening tool for cardiac size in general practice, but when thoracic CT is performed for another indication, the VHS can be reported as an incidental cardiac assessment. Reference intervals for CT-derived VHS are not yet established across breeds, so interpret findings conservatively.

What reference intervals should I apply for kittens instead of adult cats?

Use kitten-specific intervals. Healthy kittens aged 6 to 16 weeks have a median VHS of 9.5 vertebrae with a 95% reference interval of 8.0 to 10.9, and a median cardiac thoracic ratio of 67.2% Reference intervals for radiographic, echocardiographic and N-terminal pro B-type natriuretic peptide values in healthy kittens. Applying adult feline cutoffs to kittens risks misclassifying normal growth as cardiomegaly. Low-grade heart murmurs were present in nearly 30% of the kittens in that reference population, so a murmur alone does not confirm cardiac enlargement. Recheck radiographs after skeletal maturity if uncertainty persists.

Which projection should I choose when I need to evaluate both the heart and the pulmonary vessels?

The DV view provides a more consistent cardiac silhouette and better evaluation of the pulmonary lobar vessels, while the VD view is preferred for the caudal vena cava, accessory lung lobe, and pleural effusion The clinical usefulness of the ventrodorsal versus dorsoventral thoracic radiograph in dogs. For a combined cardiac and pulmonary vascular assessment, obtain a right lateral view plus a DV view. If pleural effusion is suspected, the VD view may be more informative. In dyspneic patients, the DV view is safer and usually sufficient for initial assessment. Document which projection was used, because VHS and vessel interpretation differ between views.

How do I document cardiac measurements so that serial comparisons remain meaningful?

Record the projection, patient position, and the exact vertebral bodies used as the reference for VHS measurement. Note whether the study was inspiratory or expiratory, since lung inflation changes cardiac appearance. Store the measurements in the medical record with the radiologist or interpreting clinician identified. When comparing serial studies, compare like with like: right lateral to right lateral, DV to DV. The American College of Veterinary Radiology resources provide professional standards for image labeling and reporting that support consistent documentation. If a measurement is borderline or technically compromised, state that explicitly instead of presenting a false-precision value.

How should I explain radiographic cardiac findings to a client who declines echocardiography?

Explain that radiographs show the size and shape of the heart and the condition of the lung fields, but they do not measure heart function or valve mechanics directly. Describe what the radiographs show in plain terms, for example an enlarged left atrium or evidence of pulmonary edema, and explain why that matters for treatment decisions. State that echocardiography is the reference standard for confirming chamber enlargement and functional assessment, and that radiographic findings can support but not replace that information. Reference the MSD Veterinary Manual as a source of background reading if the client wants more detail. Document the declined referral and the discussion in the record.

Related Clinical & Scientific Guides

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• Ultrasound-Guided Drainage of Abscesses in Small Animals
• Radiographic Monitoring of Total Hip Replacement in Dogs

References and Further Reading

• The vertebral heart scale on CT is correlated to radiographs in dogs.. 2021.
• Reference intervals for radiographic, echocardiographic and N-terminal pro B-type natriuretic peptide values in healthy kittens.. 2021.
• The clinical usefulness of the ventrodorsal versus dorsoventral thoracic radiograph in dogs.. 2006.
• Thoracic Vertebral Length-to-Height Ratio, a Promising Parameter to Predict the Vertebral Heart Score in Normal Welsh Corgi Pembroke Dogs.. 2023.
• A Novel Standardized Method for Aiding to Determine Left Atrial Enlargement on Lateral Thoracic Radiographs in Dogs.. 2023.
• Pneumoesophagography and the appearance of masses in the caudal portion of the esophagus in dogs with spirocercosis.. 2012.
• American College of Veterinary Radiology Resources. American College of Veterinary Radiology.
• MSD Veterinary Manual, Professional Edition. MSD Veterinary Manual.
• American Veterinary Medical Association Practice Resources. American Veterinary Medical Association.

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This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.