Canine Lung Disease: Diagnostic Imaging and Sampling Techniques

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

Key Takeaways

• Three-view thoracic radiography (right lateral, left lateral, dorsoventral/ventrodorsal) is the initial diagnostic imaging modality for suspected canine lung disease, but its sensitivity is limited by the superimposition of thoracic structures, making lesions smaller than 7-9 mm difficult to detect.
• Computed tomography (CT) offers superior spatial resolution and eliminates superimposition, making it indicated for characterizing suspected metastases, bronchiectasis, or lesions not visible radiographically, particularly when surgical or interventional planning is required.
• Thoracic ultrasound is primarily used for peripheral pulmonary lesions, pleural disease, and mediastinal masses, and ultrasound-guided fine needle aspiration has a high diagnostic yield (approximately 91%) for intrathoracic lesions accessible to the transducer.
• Bronchoalveolar lavage (BAL) is the sampling technique of choice for diffuse interstitial or alveolar patterns, suspected parasitic or inflammatory disease, and is contraindicated in severe respiratory distress or cardiovascular instability; BAL fluid should be processed for cytology and culture within 30-60 minutes.
• Radiographic interpretation requires a systematic approach, evaluating technical quality, extrathoracic structures, pulmonary patterns (alveolar, interstitial, bronchial, vascular), lesion distribution, and extrapulmonary compartments; normal radiographs do not rule out early or subtle parenchymal disease.
• Complications of pulmonary sampling include pneumothorax (especially with fine needle aspiration and blind BAL), hemorrhage, and transient hypoxemia with BAL, necessitating careful patient selection, technique, and post-procedure monitoring.

This article provides a procedural reference for the diagnosis of canine lung disease through imaging and sampling. It is written for practicing veterinarians and veterinary trainees who require a structured approach to selecting, performing, and interpreting thoracic radiography, computed tomography, thoracic ultrasound, and bronchoalveolar lavage. The content focuses on technique, diagnostic yield, and clinical decision-making, and it does not address treatment.

The clinical question this article answers is direct: when a dog presents with suspected pulmonary disease, which diagnostic tool answers which question, and how should the chosen procedure be performed to obtain a diagnostic sample or image? The answer depends on the distribution of disease, the patient's stability, and the differential diagnoses under consideration. Radiography remains the first-line imaging modality, but it has well-defined limitations. Computed tomography provides superior spatial resolution and eliminates superimposition. Ultrasound is reserved for peripheral lesions and pleural disease. Bronchoalveolar lavage recovers cells and pathogens from the airway surface and is the sampling technique of choice for diffuse interstitial or alveolar patterns.

At a Glance

Physiologic and Technical Foundations of Pulmonary Imaging

The lung is an air-filled organ with inherently low soft-tissue attenuation. This property is what makes thoracic radiography feasible, and it is also what limits the modality. Air provides natural contrast against pulmonary vessels, bronchial walls, and parenchymal disease, but the summation of superimposed structures means that a lesion must be large enough or dense enough to alter the composite attenuation of the thorax before it becomes visible. The published literature on human X-ray dark-field imaging demonstrates that conventional attenuation-based radiography lacks sensitivity for early parenchymal disease, a limitation that applies equally to veterinary patients. In that human feasibility study, dark-field radiography detected emphysematous changes that were not apparent on conventional radiographs, highlighting the principle that early or subtle parenchymal disease may be radiographically silent.

The same physical principle governs the interpretation of canine thoracic radiographs. A pulmonary nodule must generally exceed 7 to 9 mm in diameter before it is reliably detected on radiographs, and even then, lesions in the perihilar region or within the cardiac silhouette can be missed. The clinician should therefore treat a normal thoracic radiograph as evidence against advanced disease, not as proof of a normal lung.

Thoracic Radiography

Radiography is the initial imaging study for virtually all dogs with suspected pulmonary disease. The standard study consists of three views: right lateral, left lateral, and dorsoventral or ventrodorsal. The two lateral views are obtained because the dependent lung lobe undergoes relative atelectasis, which can mimic or mask disease. Comparing the two lateral projections allows the radiologist to distinguish true lesions from positional atelectasis.

The radiographic pattern approach remains the foundation of interpretation. Alveolar patterns appear as fluffy opacities with air bronchograms, interstitial patterns as a reticular or nodular increase in opacity, and bronchial patterns as thickened, parallel lines or rings. These patterns are not pathognomonic, but they narrow the differential list and guide the next diagnostic step. For example, a cranioventral alveolar pattern in a dog with fever and productive cough supports bacterial bronchopneumonia, whereas a diffuse miliary interstitial pattern raises concern for fungal disease or metastatic neoplasia.

The MSD Veterinary Manual provides a systematic framework for interpreting thoracic radiographs in dogs, including the pattern-based approach and the recognition of common artifacts. The clinician should also evaluate the extrapulmonary structures on every study, including the pleural space, mediastinum, and thoracic wall, because pulmonary disease frequently coexists with or is caused by disease in these compartments.

Computed Tomography

Computed tomography is indicated when radiography is normal but clinical suspicion for pulmonary disease remains high, when surgical or interventional planning requires precise lesion localization, and when the radiographic findings are ambiguous. CT eliminates the problem of superimposition and provides cross-sectional images with far superior contrast resolution. It is particularly valuable for detecting small pulmonary nodules, characterizing bronchiectasis, and identifying lesions in the perihilar region that are hidden on radiographs.

The decision to recommend CT should be based on how the result will change management. In a dog with a solitary pulmonary mass and no radiographic evidence of metastasis, CT of the thorax is justified to stage the disease before surgery. In a dog with a classic cranioventral alveolar pattern and a good response to empirical antimicrobial therapy, CT is unlikely to alter the treatment plan and may not be cost-effective. The American College of Veterinary Internal Medicine consensus statements on respiratory disease emphasize that advanced imaging should be used when the information gained will influence therapeutic decisions or prognosis.

Thoracic Ultrasound

Ultrasound cannot penetrate aerated lung, so its role in pulmonary imaging is limited to the pleural surface, the peripheral lung, and the mediastinum. When the lung is consolidated or when a mass abuts the thoracic wall, ultrasound can image the lesion directly and guide sampling. In a published series of 75 canine and feline patients with non-cardiac thoracic disease, ultrasound-guided fine needle aspiration was diagnostic in 91% of cases, and the technique was valuable for characterizing mediastinal masses, pleural effusion, and peripheral pulmonary lesions.

The technique requires the operator to identify the lesion in two planes, confirm that it is accessible without traversing aerated lung, and then aspirate using a 22- or 25-gauge needle attached to a syringe. Suction is applied while the needle is moved gently within the lesion, and the sample is expelled onto slides for cytology. The primary risk is pneumothorax, which is more likely when the lesion is small, deep, or surrounded by aerated lung. The operator should therefore limit the number of passes, use the shortest safe needle path, and obtain a post-procedure radiograph or ultrasound to check for pneumothorax in patients with respiratory compromise.

Ultrasound is also the imaging modality of choice for the evaluation of pleural effusion, and it can be used to guide thoracocentesis or the placement of a chest drain. The presence of pleural fluid improves ultrasound transmission and may allow visualization of pulmonary lesions that are not visible radiographically.

Bronchoalveolar Lavage: Indications and Patient Preparation

Bronchoalveolar lavage (BAL) is indicated when cytologic or microbiologic evaluation of the lower airways is expected to change the diagnostic or therapeutic plan. Common indications include chronic cough with radiographic evidence of interstitial or bronchial disease, suspected parasitic infection such as angiostrongylosis, unexplained pulmonary infiltrates, and suspected bacterial pneumonia when transtracheal wash has been non-diagnostic. The procedure is contraindicated in patients with severe respiratory distress, uncontrolled hemorrhage risk, or cardiovascular instability. In animals with significant hypoxemia, preoxygenation and careful monitoring are mandatory.

Patient preparation begins with a thorough physical examination and assessment of respiratory effort. Thoracic radiographs should be reviewed before the procedure to identify the most affected lung lobe and to rule out conditions such as tension pneumothorax or massive pleural effusion that would alter the approach. Sedation is required in most dogs. A protocol combining a benzodiazepine with an opioid or a neuroleptanalgesic agent is commonly used, but the specific choice depends on the patient's cardiovascular status and the clinician's preference. General anesthesia with an endotracheal tube is preferred in dogs with active coughing or those that resist instrumentation. The procedure should be performed with the patient in sternal recumbency whenever possible to maximize retrieval from dependent lung regions.

Bronchoalveolar Lavage: Technique and Equipment

The equipment required includes a sterile endotracheal tube, a sterile red rubber catheter or commercially available bronchoscopic catheter, a three-way stopcock, sterile saline warmed to body temperature, and collection traps. A bronchoscope allows direct visualization of the airways and targeted lavage of specific lobes, but blind BAL through an endotracheal tube is an acceptable alternative when bronchoscopy is unavailable. The choice between these approaches depends on the suspected disease distribution and the available equipment. For diffuse disease, blind BAL is often sufficient. For focal lesions identified on imaging, bronchoscopic guidance is preferred.

The technique proceeds as follows:

1. Place the patient under general anesthesia or heavy sedation with an endotracheal tube in place.
2. Advance the catheter through the endotracheal tube until resistance is felt, indicating wedging in a distal airway.
3. Infuse warmed sterile saline in aliquots of 10 to 25 mL depending on body weight, with a total volume of approximately 1 to 2 mL per kilogram.
4. Gently aspirate immediately after each aliquot using a syringe or suction trap.
5. Pool the retrieved fluid in a sterile container on ice.
6. Record the volume retrieved and the appearance of the fluid.

The recovery rate of instilled fluid is typically 40 to 70 percent. Lower recovery rates are seen in patients with airway collapse or severe bronchial disease. The first aliquot retrieved is often more representative of bronchial contents, while subsequent aliquots sample more distal alveoli. Some clinicians submit the first aliquot separately for microbiology and pool the remaining aliquots for cytology, although this practice varies. The retrieved fluid should be processed within one hour of collection. Refrigeration is acceptable for short delays, but cells deteriorate rapidly and cytologic quality declines with prolonged storage.

Bronchoalveolar Lavage: Sample Handling and Interpretation

The lavage fluid should be submitted for total nucleated cell count, differential cell count, and cytologic evaluation. A Gram stain and aerobic bacterial culture are indicated when sepsis is suspected. In endemic regions, examination for larvae of Angiostrongylus vasorum is warranted, as BAL fluid can yield active larvae during both acute and chronic phases of infection, and the technique has been shown to be accurate for diagnosis of canine angiostrongylosis Barçante et al., 2008. The cellular composition of BAL fluid in healthy dogs consists predominantly of alveolar macrophages, with smaller numbers of lymphocytes, neutrophils, and eosinophils. An increased neutrophil percentage suggests bacterial pneumonia or aspiration pneumonitis. Eosinophilia raises suspicion for parasitic infection, hypersensitivity, or eosinophilic bronchopneumopathy. The presence of intracellular bacteria within neutrophils supports a diagnosis of bacterial pneumonia, although culture is required for definitive identification and susceptibility testing.

The diagnostic yield of BAL is highest when the procedure is performed before antimicrobial therapy is initiated. If antibiotics have already been administered, culture results may be falsely negative and cytology becomes the primary diagnostic tool. The procedure is generally well tolerated, but complications include transient hypoxemia, bronchospasm, and rarely pneumothorax. Oxygen supplementation should be available during recovery, and patients should be monitored for respiratory rate, effort, and mucous membrane color for several hours after the procedure.

Imaging Interpretation Checklist

A systematic approach to thoracic radiograph interpretation reduces the risk of missing subtle lesions. The following checklist is intended for use with standard three-view thoracic radiographs, which include right lateral, left lateral, and ventrodorsal projections.

Radiographic interpretation checklist:

1. Assess technical quality. Confirm that the film is adequately exposed, the patient is positioned symmetrically, and the inspiratory phase is adequate. A poorly inflated lung can mimic interstitial disease.
2. Evaluate the extrathoracic structures. Examine the trachea for displacement or collapse, the heart for size and shape, and the great vessels for abnormalities.
3. Assess the pulmonary vasculature. Compare the sizes of the pulmonary arteries and veins in the cranial and caudal lung lobes. Enlarged arteries with tortuous courses suggest pulmonary hypertension. Prominent veins suggest left-sided cardiac disease.
4. Characterize the pulmonary pattern. Determine whether the disease is alveolar, interstitial, bronchial, or vascular. Mixed patterns are common and should be described in terms of the dominant component.
5. Identify the distribution of lesions. Note whether the disease is focal, multifocal, or diffuse, and whether it is cranioventral, caudodorsal, or perihilar. Cranioventral alveolar patterns are typical of aspiration pneumonia. Caudodorsal interstitial patterns are seen with hematogenous spread of disease.
6. Evaluate the pleura and mediastinum. Look for pleural effusion, pneumothorax, or mediastinal masses. The presence of pleural fluid can obscure underlying pulmonary lesions and may require drainage before accurate assessment.
7. Compare serial radiographs when available. Interval change is often more informative than a single study, particularly in distinguishing progressive disease from static lesions.

Computed tomography provides superior sensitivity for the detection of pulmonary nodules, bronchiectasis, and subtle interstitial disease compared with radiography. CT is indicated when radiographs are equivocal, when surgical planning is required, or when a normal radiographic study does not correlate with the severity of clinical signs. The use of CT is limited by the need for general anesthesia and the higher cost, but the diagnostic yield frequently justifies these drawbacks in complex cases.

Ultrasonography in Pulmonary Disease

Thoracic ultrasound is most useful for evaluating pleural disease, peripheral pulmonary masses, and guiding sampling procedures. Ultrasound-guided fine needle aspiration of intrathoracic lesions has been reported to yield diagnostic samples in a high proportion of cases, making it a valuable tool when cytologic confirmation is needed Reichle and Wisner, 2000. The technique is limited to lesions that contact the thoracic wall, as air-filled lung reflects the ultrasound beam and prevents visualization of deeper structures. In cattle and other production species, thoracic ultrasound has been used to assess the extent of pulmonary consolidation and pleural disease, and the amount of affected lung tissue provides prognostic information Flöck, 2004. The same principles apply in dogs, although the smaller thoracic volume and the need for heavy sedation or anesthesia in many patients make the technique less commonly performed than in larger species. Ultrasound is particularly helpful in the setting of pleural effusion, where it can identify the presence of lung consolidation, atelectasis, or masses that would be obscured on radiographs.

Complications and Failure Modes

Pulmonary sampling carries recognized risks that vary by technique. Thoracic radiography and CT are non-invasive, their principal failure modes are technical and interpretive instead of patient related. Ultrasound-guided aspiration and bronchoalveolar lavage (BAL) carry direct procedural risk.

Pneumothorax is the most consequential complication of transthoracic fine needle aspiration and of blind BAL in patients with bullous disease or severe emphysema. Detection relies on post-procedure thoracic radiography or ultrasound. In the authors' experience, a single orthogonal radiographic view obtained 15 to 30 minutes after sampling identifies most clinically significant air leaks. Ultrasound can detect pneumothorax immediately by the loss of the normal gliding sign at the pleural interface, a finding described in the veterinary literature on non-cardiac thoracic ultrasound Reichle and Wisner, non-cardiac thoracic ultrasound in 75 feline and canine patients.

Hemorrhage, usually mild and self-limiting, occurs when the sampling path crosses an intercostal vessel or a pulmonary artery branch. Frank hemoptysis is uncommon but warrants immediate cessation of the procedure and patient monitoring. BAL-associated transient hypoxemia is expected and typically resolves within minutes, pre-oxygenation and pulse oximetry during recovery reduce the risk of clinically significant desaturation.

Bacteremia after BAL is rare in immunocompetent dogs but has been reported. Patients with known cardiac disease or coagulopathy should be stabilized before sampling, and the risk-benefit decision documented.

Common Errors and Corrective Actions

Less experienced operators frequently misinterpret the alveolar pattern on radiographs as consolidation when it represents atelectasis from recumbency or sedation. The distinction matters because atelectasis resolves with ventilation, while true consolidation does not. Repeat radiographs after a recruitment breath or repositioning clarify the finding.

Over-reading of the bronchial pattern is another recurring error. Normal end-on bronchi in the hilar region can mimic bronchial disease. Comparison with the contralateral lung and attention to the distribution, focal versus generalized, reduces false positives.

In BAL, the most common technical error is wedging the catheter too far distally, which samples only the most peripheral alveoli and yields a fluid that is predominantly surfactant with few cells. The catheter tip should sit in a segmental bronchus, and the flush volume should be sufficient to reach the alveolar space. A second error is using excessive suction during retrieval, which collapses the airway and reduces yield. Gentle manual aspiration or passive drainage is preferred.

Ultrasound-guided aspiration of a lesion that is not in contact with the chest wall risks pneumothorax. The operator should confirm pleural contact in two planes before advancing the needle. When the lesion is small or deeply located, CT guidance is the safer alternative.

Limitations of Current Evidence

The veterinary literature on pulmonary imaging and sampling is dominated by retrospective case series and expert opinion. Prospective comparative studies are scarce. The ACVIM consensus statements provide structured guidance for several respiratory conditions, but they do not cover every clinical scenario, and the evidence base for specific sampling techniques in dogs remains thinner than in human medicine ACVIM consensus statements.

Ultrasound has recognized limitations. Lesions that do not reach the pleural surface are invisible to the transducer, a constraint documented in bovine thoracic ultrasonography and equally applicable to dogs Flöck, diagnostic ultrasonography in cattle with thoracic disease. The technique is operator dependent, and inter-observer agreement for subtle findings has not been rigorously established.

The role of the lung microbiome in canine pulmonary disease is an emerging area. Human studies suggest that dysbiosis may influence cancer pathogenesis and treatment response, but the translational relevance to dogs is unproven McLean et al., the emerging role of the lung microbiome and its importance in non-small cell lung cancer diagnosis and treatment. Clinicians should not yet base diagnostic or therapeutic decisions on microbiome analysis.

Expert opinion differs on the optimal BAL flush volume and on whether blind BAL is acceptable when bronchoscopic guidance is unavailable. Both approaches appear safe in experienced hands, but no controlled trial has compared diagnostic yield directly.

Referral and Escalation Criteria

Referral to a specialist service is warranted when the primary care clinician cannot obtain a diagnostic sample, when the imaging findings are ambiguous and the differential includes neoplasia, or when the patient requires advanced imaging such as CT with contrast angiography to exclude pulmonary thromboembolism. Interventional radiology or bronchoscopy services should be consulted for lesions that are small, central, or adjacent to major vessels.

Laboratory involvement is indicated for BAL fluid when the clinical suspicion includes infectious agents that require specialised culture media, such as Mycoplasma species, or when cytology reveals an unexpected cell population. Molecular diagnostics, including PCR for Angiostrongylus vasorum, should be requested when the history and cytology are suggestive, as BAL has been shown to recover larvae reliably in infected dogs Barçante et al., cytological and parasitological analysis of bronchoalveolar lavage fluid for the diagnosis of Angiostrongylus vasorum infection in dogs.

Regulatory reporting obligations vary by jurisdiction. In most regions, confirmed cases of notifiable zoonotic or trade-relevant diseases must be reported to the relevant animal health authority. The World Organization for Animal Health maintains the international standards for disease notification, and clinicians should consult the current terrestrial code for their region WOAH terrestrial animal health standards. When in doubt, contact the local veterinary authority before proceeding with further diagnostics or treatment.

Frequently Asked Questions

How do I choose between radiography and CT when cost is a limiting factor for the client?

Three-view thoracic radiography remains the first-line screening test for suspected canine lung disease because it is widely available, inexpensive, and identifies most clinically significant parenchymal, airway, and pleural abnormalities. Reserve CT for cases where radiography is inconclusive, where surgical or radiation planning requires precise lesion localization, or where subtle interstitial disease is suspected. CT is also preferred for evaluating the mediastinum, hilar lymph nodes, and the extent of pulmonary metastases. When CT is not affordable, thoracic ultrasound can characterize peripheral lesions and guide sampling, though it cannot visualize deeper parenchymal disease, as demonstrated in bovine patients where only superficial lung involvement was detectable diagnostic ultrasonography in cattle with thoracic disease.

What alternatives exist when fluoroscopy or CT guidance is unavailable for lung sampling?

Ultrasound-guided fine needle aspiration is the most practical alternative for peripheral pulmonary lesions and has a reported diagnostic yield of 91% in one series of 56 canine and feline patients non-cardiac thoracic ultrasound in 75 feline and canine patients. Blind or radiographically guided sampling is possible for large, peripherally located lesions but carries higher risk of complications. Bronchoalveolar lavage through a blindly placed endotracheal tube remains a robust option for diffuse disease and requires no specialized imaging equipment. For central lesions, consider referral for CT-guided biopsy instead of attempting blind sampling, as the risk of hemorrhage or pneumothorax increases with lesion depth and proximity to major vessels.

How should I document imaging and sampling findings in the medical record?

Record the number and projection of radiographs, the CT protocol including slice thickness and contrast administration, and the ultrasound transducer frequency and approach. Describe lesions using standardized terms: location by lobe and region, distribution (focal, multifocal, diffuse), pattern (alveolar, interstitial, bronchial, vascular), and margin characteriztics. For BAL, document the volume of fluid instilled and retrieved, the lobe sampled, gross appearance, and cell counts. Note any complications and their resolution. Include the rationale for choosing each modality and how the results altered the diagnostic or therapeutic plan. This documentation supports continuity of care and defensible medical decision-making.

What should I tell an owner when recommending bronchoalveolar lavage?

Explain that BAL retrieves cells and fluid from the lower airways to identify inflammatory, infectious, or neoplastic disease when radiographs are inconclusive or when empirical therapy has failed. Describe the procedure as performed under general anesthesia with a sterile catheter wedged in a bronchus. Mention that the dog may cough mildly afterward and that transient hypoxemia is possible. Note that BAL is highly accurate for certain infections, such as angiostrongylosis, where larvae can be recovered from lavage fluid even before the prepatent period cytological and parasitological analysis of bronchoalveolar lavage fluid for the diagnosis of Angiostrongylus vasorum infection in dogs. Discuss the small risk of pneumothorax or hemorrhage and the need for post-procedure monitoring.

How does the diagnostic approach differ in brachycephalic breeds?

Brachycephalic dogs present unique challenges for pulmonary sampling. Their elongated soft palate, stenotic nares, and everted laryngeal saccules increase the risk of airway obstruction during anesthesia and complicate blind BAL catheter placement. Pre-oxygenation and careful anesthetic management are essential. The laryngeal saccule can deflect the catheter into the esophagus, so confirm catheter position by gentle advancement resistance and, ideally, by thoracic radiography or fluoroscopy. Brachycephalic breeds also have higher rates of aspiration pneumonia, which may produce a cranioventral alveolar pattern that can be confused with other bronchopneumonias. Consider CT before sampling in these patients to define the distribution of disease and to plan a safe approach.

When should I refer a case instead of pursue further diagnostics in general practice?

Refer when the diagnostic question exceeds local capabilities, such as when CT is needed for surgical planning or when bronchoscopy with guided BAL is required for focal disease. Refer also when sampling carries unacceptable risk, including patients with coagulopathies, severe pulmonary hypertension, or large cavitary lesions adjacent to major vessels. If a patient deteriorates despite appropriate therapy and the diagnosis remains unclear, referral for advanced imaging or interventional sampling is warranted. Finally, refer when the owner requests a second opinion or when the clinical picture suggests a rare disease that would benefit from specialist evaluation. The ACVIM consensus statements provide guidance on when specialist input is appropriate for complex respiratory cases.

Related Clinical & Scientific Guides

• Feline Hepatic Lipidosis: Nutritional and Medical Management
• Canine Respiratory Infection: Diagnostic Approach and Treatment
• Canine Respiratory Virus: Diagnostic and Management Considerations

References and Further Reading

• X-ray dark-field imaging of the human lung-A feasibility study on a deceased body.. 2018.
• Non-cardiac thoracic ultrasound in 75 feline and canine patients.. 2000.
• Cytological and parasitological analysis of bronchoalveolar lavage fluid for the diagnosis of Angiostrongylus vasorum infection in dogs.. 2008.
• The emerging role of the lung microbiome and its importance in non-small cell lung cancer diagnosis and treatment.. 2022.
• Diagnostic ultrasonography in cattle with thoracic disease.. 2004.
• An elastase activity reporter for Electronic Paramagnetic Resonance (EPR) and Overhauser-enhanced Magnetic Resonance Imaging (OMRI) as a line-shifting nitroxide.. 2018.
• ACVIM Consensus Statements. Journal of Veterinary Internal Medicine.
• 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.