Avian Diagnostic Imaging: Radiography and Ultrasonography in Birds

Radiography and ultrasonography are essential imaging modalities for evaluating companion birds and backyard poultry. This article provides veterinarians with practical guidance on radiographic positioning, normal avian anatomy, common pathological findings, and ultrasonography applications for cardiac, coelomic, and reproductive assessment in parrots, chickens, ducks, and geese. The content focuses on concrete management decisions, observations, and professional escalation criteria based on published evidence.

At a Glance

Core Principles of Avian Diagnostic Imaging

Avian anatomy differs substantially from mammalian anatomy, and these differences directly affect imaging technique and interpretation. Birds have pneumatic bones that communicate with the respiratory system, a fused synsacrum, a keeled sternum, and air sacs that occupy much of the coelomic cavity. The Merck Veterinary Manual provides foundational guidance on avian anatomy and clinical examination for pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Understanding these structural features is necessary before attempting image acquisition or interpretation.

The avian respiratory system includes air sacs that extend into the humerus, femur, vertebrae, and skull in many species. These air-filled structures create natural contrast on radiographs but also complicate ultrasonography because air reflects ultrasound waves. The World Organisation for Animal Health addresses animal health and welfare standards that apply to diagnostic procedures in poultry and companion birds (World Organisation for Animal Health, www.woah.org/en/what-we-do/animal-health-and-welfare). Clinicians must balance diagnostic necessity with patient safety and welfare during restraint and positioning.

Radiography has been used in avian medicine since the 1970s, with early publications describing techniques for positioning and interpretation in birds (Radiography, PubMed, 1973, https://pubmed.ncbi.nlm.nih.gov/4739818). Modern digital radiography systems allow for rapid image acquisition and post-processing adjustments that improve diagnostic quality. Ultrasonography has become more accessible with the availability of high-frequency linear and microconvex probes designed for small patients.

The clinician must recognize that avian patients have higher metabolic rates and oxygen demands than comparably sized mammals. Stress during handling and positioning can lead to rapid deterioration in compromised patients. The imaging protocol should be planned in advance to minimize handling time. All necessary equipment should be prepared before the patient is removed from its enclosure.

Radiographic Positioning and Technique

Patient Preparation and Restraint

Manual restraint is the most common method for avian radiography. The bird should be fasted for two to four hours before imaging to reduce crop and gastrointestinal contents that may obscure coelomic structures. Fasting is especially important in psittacines and poultry species that store food in the crop. The clinician must assess the patient's respiratory status before restraint because birds with respiratory compromise may not tolerate positioning.

Chemical restraint may be necessary for fractious patients or when precise positioning is required. Isoflurane or sevoflurane delivered via mask or induction chamber provides safe anesthesia for most avian species. The Merck Veterinary Manual describes anesthetic protocols for pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Anesthetized birds require monitoring of heart rate, respiratory rate, and body temperature throughout the procedure.

For manual restraint, the clinician should use radiolucent positioning aids such as foam wedges, tape, and sandbags. The bird's head should be positioned in a natural extension to avoid tracheal compression. The wings should be secured with tape placed over the humeral region instead of the carpus to avoid joint injury. The legs should be extended caudally and secured with tape at the tarsometatarsus.

Standard Views

The standard avian radiographic study includes ventrodorsal (VD) and lateral projections. The VD view is obtained with the bird in dorsal recumbency, wings extended laterally and secured with tape, and legs extended caudally. The sternum should be centered over the spine to avoid rotation. The lateral view is obtained with the bird in right or left lateral recumbency, wings extended dorsally, and legs extended caudally. The wings should be positioned so they do not overlap the coelomic cavity.

Orthopedic Diagnostic Imaging in Exotic Pets reviews positioning techniques for avian patients and emphasizes the importance of symmetry in the VD view for evaluating the cardiac silhouette and air sacs (Orthopedic Diagnostic Imaging in Exotic Pets, Veterinary Clinics of North America: Exotic Animal Practice, 2019, https://pubmed.ncbi.nlm.nih.gov/30961896). Asymmetric positioning can create false impressions of cardiomegaly or coelomic masses.

Additional views may be indicated for specific clinical questions. The dorsoventral (DV) view is obtained with the bird in sternal recumbency and may be better tolerated by dyspneic patients. Oblique views are useful for evaluating the coracoid bones, shoulder joint, and elbow joint. The stressed lateral view with the legs pulled caudally improves visualization of the coelomic cavity in large birds.

Exposure Settings

Avian patients require lower exposure settings than comparably sized mammals because of their pneumatic bones and air sacs. Digital radiography systems allow for adjustment of kilovoltage peak (kVp) and milliampere-seconds (mAs) based on patient thickness. A general starting point for a medium-sized parrot is 50 to 55 kVp and 2 to 3 mAs. Smaller birds such as budgerigars may require 45 to 50 kVp, while larger birds such as geese may need 60 to 65 kVp. The clinician should evaluate image quality and adjust settings accordingly.

The use of a grid is generally not recommended for birds weighing less than 500 grams because the grid lines may obscure detail and increase radiation dose. For larger birds such as geese and turkeys, a grid may improve image quality. The clinician should select the smallest focal spot available to maximize detail. Exposure time should be as short as possible to minimize motion artifact, ideally less than 0.05 seconds.

Normal Radiographic Anatomy

Skeletal System

The avian skeleton includes several unique features visible on radiographs. The sternum has a prominent keel that is most developed in flying birds. The synsacrum is a fused structure incorporating the caudal thoracic, lumbar, sacral, and cranial caudal vertebrae. The pygostyle is the fused terminal caudal vertebrae that supports the tail feathers. The coracoid bones connect the sternum to the shoulder joint and are visible on both VD and lateral views.

Pneumatic bones appear radiolucent because they contain air sac diverticula. The humerus, femur, and vertebrae are commonly pneumatic in many species. Fractures of pneumatic bones may communicate with the respiratory system and require different management than fractures of non-pneumatic bones. The Merck Veterinary Manual provides information on avian musculoskeletal disorders (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds).

The skull has a distinctive appearance with a large orbit, a beak composed of the premaxilla and mandible, and a cranium that may appear thin on radiographs. The cervical vertebrae are numerous and highly mobile. The thoracic vertebrae are fused in many species. The ribs have uncinate processes that project caudally and overlap adjacent ribs.

Coelomic Cavity

The coelomic cavity contains the heart, lungs, air sacs, liver, gastrointestinal tract, kidneys, and reproductive organs. The cardiac silhouette is visible in the cranial coelom and appears as a rounded opacity. The liver occupies the mid-coelom and extends caudally. The proventriculus and ventriculus (gizzard) are visible in the left lateral aspect of the coelom. The kidneys are located in the dorsal coelom and are partially superimposed on the synsacrum.

Air sacs appear as radiolucent areas surrounding the coelomic organs. The cervical, clavicular, cranial thoracic, caudal thoracic, and abdominal air sacs are visible on well-positioned radiographs. The lungs are fixed in the dorsal coelom and have a honeycomb appearance because of the parabronchial structure.

The normal cardiac silhouette on the VD view has a width approximately 50 to 60 percent of the thoracic width at the level of the heart. The liver has a triangular shape on the lateral view and extends from the heart to the ventriculus. The spleen is a small round or oval structure located between the proventriculus and ventriculus and is not always visible on radiographs.

Gastrointestinal Tract

The crop is visible in the cervical region and may contain ingesta or gas. The proventriculus appears as a tubular structure cranial to the ventriculus. The ventriculus has a thick muscular wall and may contain grit or ingesta. The intestinal tract fills the caudal coelom and varies in appearance depending on the stage of digestion. Cloacal contents are visible in the caudal coelom.

The proventriculus to ventriculus ratio is an important measurement. The normal proventriculus diameter is approximately equal to the ventriculus diameter on the lateral view. The proventricular wall should be thin and smooth. The ventricular wall is thick and may have a layered appearance because of the koilin lining.

Common Pathological Findings on Radiography

Fractures and Orthopedic Conditions

Avian fractures are common in companion birds and backyard poultry. Radiography is the primary imaging modality for fracture diagnosis and classification. The Merck Veterinary Manual describes fracture management in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Common fracture locations include the humerus, radius, ulna, femur, tibiotarsus, and tarsometatarsus.

Open fractures, comminuted fractures, and fractures involving joints have a guarded prognosis. Fractures of pneumatic bones may result in subcutaneous emphysema if the air sac system is disrupted. The clinician should evaluate the fracture site for alignment, apposition, and evidence of healing on follow-up radiographs.

Orthopedic Diagnostic Imaging in Exotic Pets discusses radiographic evaluation of orthopedic conditions in exotic animals, including birds (Orthopedic Diagnostic Imaging in Exotic Pets, Veterinary Clinics of North America: Exotic Animal Practice, 2019, https://pubmed.ncbi.nlm.nih.gov/30961896). Osteomyelitis, septic arthritis, and pathologic fractures secondary to metabolic bone disease are important differential diagnoses.

The clinician should evaluate the cortices of long bones for thickness and opacity. Thin cortices with a ground glass appearance suggest metabolic bone disease. Folding fractures, where the bone bends and cracks on the compression side, are characteristic of nutritional secondary hyperparathyroidism. The growth plates should be evaluated for widening or irregularity in juvenile birds.

Respiratory Disease

Respiratory disease is common in birds and often has radiographic manifestations. Air sacculitis appears as thickening or opacity of air sac walls. Pneumonia causes increased opacity in the lung fields. The Merck Veterinary Manual covers respiratory diseases in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Aspergillosis is a common fungal infection that may produce granulomas visible as soft tissue opacities in the air sacs or lungs.

The air sacs should be evaluated for symmetry and clarity. Unilateral air sac opacity may indicate a mass, granuloma, or fluid accumulation. The trachea should be evaluated for narrowing or displacement. Syringeal disease may cause changes in the tracheal lumen at the level of the thoracic inlet.

The lungs should have a uniform honeycomb pattern. Focal or diffuse increased opacity in the lung fields suggests pneumonia or pulmonary edema. The cardiac silhouette may appear enlarged in birds with right-sided heart failure secondary to respiratory disease. The clinician should evaluate the coelomic cavity for evidence of ascites, which may appear as loss of serosal detail.

Reproductive Tract Disease

Egg binding is a common reproductive emergency in female birds. Radiography confirms the presence of an egg in the oviduct and allows assessment of egg size, shape, and shell quality. The Merck Veterinary Manual describes egg binding and other reproductive disorders in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Retained eggs may appear as mineralized opacities in the caudal coelom.

Egg peritonitis occurs when egg material enters the coelomic cavity and causes inflammation. Radiographic findings include loss of coelomic detail, increased soft tissue opacity, and free fluid. Coelomic masses such as ovarian neoplasia may cause displacement of coelomic organs.

The clinician should evaluate the number, size, and position of eggs in the oviduct. An egg that appears larger than normal or has an irregular shape may be difficult to pass. Eggs with thin or absent shells may be associated with calcium deficiency or oviductal disease. Free mineralized material in the coelom suggests egg peritonitis.

Gastrointestinal Disease

Proventricular dilatation disease (PDD) is a viral condition that causes enlargement of the proventriculus and ventriculus. Radiographic findings include a dilated proventriculus with gas or ingesta retention. The Merck Veterinary Manual provides information on PDD in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Contrast studies may be necessary to evaluate gastrointestinal transit time.

Foreign bodies may be visible on radiographs if they are radiopaque. Metallic foreign bodies such as lead or zinc objects are readily visible. Plastic or cloth foreign bodies may not be visible without contrast administration. Gastrointestinal obstruction causes gas distention proximal to the obstruction site.

The clinician should evaluate the crop for distention, delayed emptying, or abnormal contents. The proventriculus should be evaluated for dilation, wall thickening, or abnormal contents. The ventriculus should be evaluated for the presence and amount of grit. The intestinal tract should be evaluated for gas patterns, wall thickness, and evidence of obstruction.

Metabolic Bone Disease

Metabolic bone disease is common in birds fed inappropriate diets. Radiographic findings include decreased bone density, thin cortices, pathologic fractures, and folding fractures. The Merck Veterinary Manual discusses nutritional disorders in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). The keel bone may appear soft or deformed. The cortices of long bones should be evaluated for thickness and opacity.

The clinician should evaluate the skull for evidence of osteodystrophy, which may appear as a thickened or deformed cranium. The vertebrae should be evaluated for compression fractures or deformities. The pelvis may appear narrowed or deformed in severe cases. The growth plates in juvenile birds may appear widened or irregular.

Ultrasonography in Avian Patients

Equipment and Technique

Ultrasonography in birds requires high-frequency probes because of the small patient size and superficial location of coelomic organs. Linear probes with frequencies of 10 to 18 MHz are suitable for most avian patients. Microconvex probes with frequencies of 8 to 12 MHz may be useful for cardiac imaging. The clinician should select the highest frequency that provides adequate penetration for the patient size.

The bird should be positioned in dorsal recumbency for coelomic ultrasonography. Feathers must be parted or plucked over the area of interest. Acoustic coupling gel is applied to the skin. The probe is placed on the ventral coelom and moved systematically to evaluate the liver, gastrointestinal tract, kidneys, and reproductive organs. The heart is imaged through the thoracic inlet or from a ventrolateral approach.

Morphological Assessment of Stage HH38 of the Japanese Quail Heart by Micro-Sonogram describes the use of micro-sonography for evaluating avian cardiac anatomy (Morphological Assessment of Stage HH38 of the Japanese Quail Heart by Micro-Sonogram, Methods and Protocols, 2026, https://doi.org/10.3390/mps9030071). This technique allows detailed assessment of cardiac structures in small birds.

The clinician should use the lowest power output settings that provide adequate image quality. Thermal and mechanical indices should be monitored to avoid tissue heating or cavitation. The examination should be completed as quickly as possible to minimize patient stress and prevent hypothermia from the coupling gel.

Limitations of Avian Ultrasonography

Air sacs are the primary limitation of avian ultrasonography. Air reflects ultrasound waves and prevents visualization of structures deep to air-filled spaces. The clinician must work around air sacs by using acoustic windows that avoid air-filled structures. The liver provides an acoustic window for imaging the caudal coelom. The heart may be imaged through the thoracic inlet or from a parasternal approach.

Patient size is another limitation. Very small birds such as budgerigars and finches have coelomic organs that are difficult to resolve even with high-frequency probes. The clinician should adjust gain and depth settings to optimize image quality. Sedation may be necessary to reduce patient movement during the examination.

The presence of feathers, even when parted, may cause artifact and reduce image quality. Plucking a small area of feathers over the region of interest improves acoustic coupling but may be stressful for the patient. The clinician should balance the need for image quality with patient welfare considerations.

Cardiac Ultrasonography

Echocardiography is used to evaluate cardiac function, chamber size, valve morphology, and pericardial effusion in birds. The Merck Veterinary Manual describes cardiac diseases in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Standard echocardiographic views include the right parasternal long-axis and short-axis views. The left ventricle, left atrium, right ventricle, and aorta should be evaluated.

M-mode measurements of the left ventricle allow assessment of systolic function. Fractional shortening is calculated from the left ventricular internal dimensions in systole and diastole. Valvular regurgitation may be detected with color Doppler imaging. Pericardial effusion appears as an anechoic space surrounding the heart.

The clinician should evaluate the cardiac valves for thickening, prolapse, or vegetation. The pericardium should be evaluated for thickening or effusion. The great vessels should be evaluated for dilation or thrombosis. The heart rate should be recorded and considered when interpreting functional measurements.

Coelomic Ultrasonography

The liver is the largest coelomic organ and is readily visualized on ultrasonography. The normal liver has a homogeneous echotexture and is isoechoic or slightly hypoechoic relative to the spleen. Hepatomegaly appears as an enlarged liver with rounded margins. Hepatic lipidosis causes increased echogenicity. Focal masses or nodules may indicate neoplasia or abscesses.

The gastrointestinal tract can be evaluated for wall thickness, luminal contents, and motility. The proventriculus and ventriculus have characteristic appearances. The proventriculus has a thin wall and may contain fluid or ingesta. The ventriculus has a thick muscular wall and a hyperechoic lining. Intestinal loops should be evaluated for wall thickness and peristalsis.

The kidneys are located in the dorsal coelom and are difficult to image because of overlying air sacs. The normal kidney has a homogeneous echotexture. Renal enlargement or masses may be visible in some patients. The reproductive tract is evaluated in female birds for ovarian follicles, eggs, and oviductal disease.

The spleen is a small round or oval structure located between the proventriculus and ventriculus. The normal spleen has a homogeneous echotexture. Splenomegaly may be associated with infection or neoplasia. The pancreas is difficult to visualize in most avian patients because of its small size and location adjacent to the duodenum.

Contrast Studies

Gastrointestinal Contrast Studies

Gastrointestinal contrast studies are used to evaluate transit time, mucosal integrity, and obstructive lesions. Barium sulfate suspension is administered via crop tube at a dose of 10 to 25 mL/kg body weight. Radiographs are obtained immediately after administration and at intervals of 15, 30, 60, and 120 minutes. The Merck Veterinary Manual describes contrast study techniques in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds).

Normal gastrointestinal transit time varies by species and diet. In psittacines, the crop should empty within one to two hours. The proventriculus and ventriculus fill with contrast and empty into the intestines over two to four hours. Delayed transit may indicate PDD, gastrointestinal obstruction, or ileus. Rapid transit may indicate diarrhea or malabsorption.

The clinician should evaluate the crop for distention, delayed emptying, or filling defects. The proventriculus should be evaluated for dilation, wall irregularity, or filling defects. The ventriculus should be evaluated for emptying time and the presence of filling defects. The intestinal tract should be evaluated for transit time, wall thickness, and evidence of obstruction.

Myelography

Myelography is used to evaluate the spinal cord in birds with neurologic signs. A myelographic technique for avian species has been described and involves injection of contrast medium into the subarachnoid space (A myelographic technique for avian species, Veterinary Radiology and Ultrasound, 1997, https://pubmed.ncbi.nlm.nih.gov/9238789). The procedure requires general anesthesia and aseptic technique.

Contrast medium is injected at the lumbosacral junction or cervical region. Radiographs are obtained immediately after injection. Myelography allows visualization of spinal cord compression, disc herniation, and spinal masses. The procedure carries risks including seizures, respiratory depression, and contrast reactions.

The clinician should evaluate the spinal cord for compression, deviation, or expansion. The contrast column should be continuous and uniform. Filling defects or obstruction of the contrast column indicate extradural or intradural lesions. The needle insertion site should be evaluated for evidence of hemorrhage or contrast leakage.

Practical Implementation Steps

Step 1: Patient Assessment and Preparation

Before imaging, the clinician should perform a complete physical examination and assess the patient's stability. Birds with respiratory distress, severe anemia, or cardiovascular compromise may not tolerate restraint. The Merck Veterinary Manual provides guidance on physical examination of pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Fasting is recommended for elective imaging but may be contraindicated in debilitated patients.

The clinician should obtain a complete history including signalment, diet, environment, and presenting complaint. Previous imaging studies should be reviewed if available. The patient's body weight should be recorded for accurate dosing of contrast media and anesthetic agents if needed.

Step 2: Equipment Setup

Digital radiography systems should be calibrated and set to appropriate exposure parameters. The grid should be removed for small patients to reduce radiation dose. Ultrasonography equipment should be prepared with the appropriate probe and settings. The clinician should verify that all necessary supplies are available, including tape, positioning aids, and contrast medium if needed.

The imaging area should be prepared with appropriate padding and warming devices to prevent hypothermia. The room temperature should be maintained at 25 to 28 degrees Celsius for small patients. All equipment should be within reach before the patient is positioned.

Step 3: Image Acquisition

Standard radiographic views are obtained with careful attention to positioning. The clinician should evaluate image quality immediately after acquisition and repeat views if necessary. Ultrasonography is performed systematically, with images saved for documentation. The examination should be completed as quickly as possible to minimize patient stress.

The clinician should acquire images in a consistent order to ensure all structures are evaluated. For radiography, the VD view is typically obtained first, followed by the lateral view. For ultrasonography, the liver is evaluated first, followed by the gastrointestinal tract, kidneys, and reproductive organs. The heart is evaluated last if echocardiography is indicated.

Step 4: Image Interpretation

Radiographs and ultrasound images are interpreted in the context of the clinical history and physical examination findings. The clinician should evaluate all visible structures systematically. Normal variants and artifacts should be recognized to avoid misinterpretation. The Merck Veterinary Manual provides reference images for normal avian anatomy (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds).

The clinician should document all findings, including normal structures and abnormalities. Measurements should be recorded for serial comparison. Differential diagnoses should be generated based on the imaging findings. The clinician should correlate imaging findings with clinical signs and laboratory results.

Step 5: Documentation and Communication

Findings should be documented in the medical record with a written report. Images should be stored in the patient's digital file. The clinician should communicate findings to the owner or caretaker and discuss recommended next steps. Referral to a specialist may be indicated for complex cases.

The written report should include the patient identification, date, imaging modality, views obtained, and a description of findings. The report should state the clinical significance of the findings and provide recommendations for further diagnostic testing or treatment. The clinician should note any technical limitations that may affect interpretation.

Records and Measurements

Radiographic Measurements

The cardiac silhouette width can be measured on the VD view and compared to the width of the thoracic cavity. The normal cardiac width is approximately 50 to 60 percent of the thoracic width at the level of the heart. Cardiomegaly is suspected when the cardiac width exceeds 65 percent of the thoracic width. The clinician should consider breed and species variations when interpreting cardiac measurements.

The proventriculus to ventriculus ratio can be measured on the lateral view. The normal proventriculus diameter is approximately equal to the ventriculus diameter. Proventricular dilatation is suspected when the proventriculus diameter exceeds the ventriculus diameter by more than 50 percent. Serial measurements are useful for monitoring disease progression.

The clinician should measure and record the length and width of the liver on the lateral view. The liver should not extend caudally beyond the ventriculus. The distance between the cardiac silhouette and the sternum should be measured on the lateral view. Increased distance may indicate pericardial effusion or coelomic masses.

Ultrasonographic Measurements

Echocardiographic measurements should be obtained from standardized views. The left ventricular internal diameter in diastole and systole is measured from M-mode tracings. Fractional shortening is calculated as (LVIDd - LVIDs) / LVIDd x 100 percent. Normal fractional shortening in birds ranges from 30 to 50 percent depending on species and heart rate.

Liver size can be assessed subjectively or measured from standardized views. The liver length and width should be recorded for serial comparisons. Gallbladder size and wall thickness should be noted. The presence of ascites should be documented and quantified if possible.

The clinician should measure the thickness of the ventricular wall and the proventricular wall. The diameter of the proventriculus should be recorded. The size and number of ovarian follicles should be documented in female birds. The presence and size of coelomic masses should be recorded with measurements in three planes.

Record Keeping

All imaging studies should be documented with the date, patient identification, imaging modality, views obtained, and findings. The clinician should note any technical limitations that may affect interpretation. Follow-up studies should be compared to previous studies to assess disease progression or response to treatment. The Merck Veterinary Manual provides guidance on medical record keeping in veterinary practice (Merck Veterinary Manual, www.merckvetmanual.com/).

The clinician should maintain a log of all imaging studies for quality assurance purposes. The log should include the patient identification, date, imaging modality, and a brief summary of findings. The log should be reviewed periodically to identify trends in disease prevalence or imaging quality.

Common Failure Patterns

Positioning Errors

Rotation is the most common positioning error in avian radiography. A rotated VD view causes asymmetry of the coelomic structures and may create false impressions of cardiomegaly or coelomic masses. The clinician should verify that the sternum is centered over the spine and that the wings and legs are symmetrical. Repeat views should be obtained if positioning is inadequate.

Overlap of the wings over the coelomic cavity is another common error. The wings should be extended dorsally on the lateral view and laterally on the VD view. Tape should be used to secure the wings in position. The clinician should evaluate the image for wing overlap before completing the study.

The legs should be extended caudally and symmetrically on the VD view. Asymmetric leg positioning may cause pelvic rotation and obscure coelomic structures. The head should be positioned in a natural extension to avoid tracheal compression and to allow evaluation of the cervical region.

Exposure Errors

Underexposure causes images that are too light and lack detail. Overexposure causes images that are too dark and may obscure soft tissue structures. Digital radiography systems allow for post-processing adjustment, but optimal exposure settings should be used to minimize radiation dose and maximize image quality. The clinician should adjust exposure settings based on patient size and species.

The clinician should evaluate the image for adequate penetration of the coelomic cavity. The spine should be visible through the coelomic structures on a properly exposed image. The air sacs should appear black, and the soft tissue structures should have visible internal detail. The bones should have visible cortices and medullary cavities.

Artifacts

Motion artifacts occur when the patient moves during image acquisition. Short exposure times and patient restraint reduce motion artifacts. Respiratory motion may cause blurring of the lung fields and cardiac silhouette. Anesthesia reduces motion but may alter respiratory patterns.

Foreign material artifacts include grit in the ventriculus, metal bands, and implanted devices. These artifacts may obscure underlying structures and should be noted in the report. The clinician should evaluate the image for artifacts before completing the study.

The clinician should be aware of common artifacts in ultrasonography, including reverberation artifact from air sacs, acoustic shadowing from bone or grit, and side lobe artifact from strongly reflective surfaces. These artifacts should be recognized and distinguished from true pathology.

Limitations of Avian Diagnostic Imaging

Radiography Limitations

Radiography provides two-dimensional images of three-dimensional structures. Overlap of coelomic organs may obscure pathology. The air sacs provide natural contrast but may also obscure soft tissue structures. Small lesions may not be visible on radiographs. The clinician should recognize that a normal radiograph does not rule out disease.

The Merck Veterinary Manual notes that radiography has limitations in evaluating soft tissue structures in birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Contrast studies and advanced imaging such as computed tomography may be necessary for complete evaluation.

Radiography is limited in evaluating the extent of coelomic masses, the internal architecture of organs, and the presence of small amounts of free fluid. The clinician should use ultrasonography as a complementary modality when soft tissue evaluation is needed. Computed tomography provides superior detail for complex cases but requires general anesthesia and specialized equipment.

Ultrasonography Limitations

Ultrasonography is limited by air sacs, which prevent visualization of structures deep to air-filled spaces. The clinician must work around air sacs to obtain diagnostic images. Patient size limits the resolution achievable with available probes. Very small birds may not be candidates for ultrasonography.

Operator experience is a significant factor in the diagnostic yield of ultrasonography. The clinician should have training and experience in avian ultrasonography before attempting diagnostic examinations. Referral to a specialist may be appropriate for complex cases.

The interpretation of avian ultrasonography requires knowledge of normal anatomy and common artifacts. The clinician should be familiar with the appearance of normal structures and the limitations of the modality. Serial examinations may be necessary to confirm findings or monitor disease progression.

Safety and Regulatory Context

Radiation Safety

Radiography involves ionizing radiation and requires appropriate safety precautions. The clinician should use lead aprons, thyroid shields, and dosimeters. The ALARA (as low as reasonably achievable) principle should guide exposure settings. Pregnant personnel should avoid direct involvement in radiographic procedures.

The World Organisation for Animal Health addresses animal health and welfare standards that apply to diagnostic procedures (World Organisation for Animal Health, www.woah.org/en/what-we-do/animal-health-and-welfare). Radiation safety protocols should be established and followed in all veterinary practices.

The clinician should minimize the number of repeat exposures by optimizing positioning and exposure settings before image acquisition. The area of the patient exposed to the primary beam should be limited to the region of interest. Protective shielding should be used for the patient when possible, particularly for the gonads and thyroid.

Animal Welfare

Patient welfare should be prioritized during imaging procedures. Restraint should be as brief as possible. Anesthesia should be used when necessary to reduce stress. The clinician should monitor the patient throughout the procedure and be prepared to intervene if complications arise.

The Merck Veterinary Manual emphasizes the importance of minimizing stress in avian patients (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). Stress can cause immunosuppression and exacerbate underlying disease. The clinician should assess the patient's stress level and adjust the approach accordingly.

The clinician should monitor the patient's respiratory rate, heart rate, and mucous membrane color throughout the procedure. Signs of distress include open-mouth breathing, vocalization, and struggling. The procedure should be terminated if the patient shows signs of severe distress or respiratory compromise.

Regulatory Considerations

The United States Department of Agriculture Animal and Plant Health Inspection Service (APHIS) oversees regulations related to poultry health and disease surveillance (USDA APHIS, www.aphis.usda.gov/livestock-poultry-disease/avian). Veterinarians working with poultry should be familiar with relevant regulations and reporting requirements.

The World Organisation for Animal Health provides international standards for animal health and welfare (World Organisation for Animal Health, www.woah.org/en/what-we-do/animal-health-and-welfare). These standards apply to diagnostic procedures and disease surveillance in both companion birds and poultry.

The clinician should be aware of reportable diseases in their jurisdiction and follow appropriate reporting protocols. Imaging findings suggestive of reportable diseases should be documented and reported to the appropriate authorities. The clinician should maintain records of all imaging studies for regulatory compliance.

Professional Escalation Criteria

Urgent Escalation

The clinician should seek immediate specialist consultation or referral for the following findings:

• Respiratory distress during or after imaging
• Severe hemorrhage from fracture sites
• Suspected spinal cord compression on myelography
• Cardiac tamponade or severe pericardial effusion
• Anaphylactic reaction to contrast medium
• Seizures or respiratory depression after myelography

The clinician should stabilize the patient before transport to a referral facility. Oxygen supplementation, intravenous fluids, and emergency medications should be administered as indicated. The receiving clinician should be contacted with a summary of the case and the imaging findings.

Routine Escalation

The clinician should consider specialist referral for the following situations:

• Complex fractures requiring surgical stabilization
• Suspected neoplasia requiring biopsy or advanced imaging
• Cardiac disease requiring advanced echocardiography
• Reproductive tract disease requiring surgical intervention
• Cases where imaging findings are inconclusive

The Merck Veterinary Manual provides guidance on when to refer avian patients to specialists (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds). The clinician should maintain a list of referral centers with expertise in avian medicine.

The clinician should provide the referring specialist with copies of all imaging studies, a summary of the clinical history and physical examination findings, and the results of any laboratory tests. The owner should be counseled on the expected costs and outcomes of referral.

Frequently Asked Questions

What are the standard radiographic views for birds?

The standard avian radiographic study includes ventrodorsal and lateral projections. The ventrodorsal view is obtained with the bird in dorsal recumbency, wings extended laterally, and legs extended caudally. The lateral view is obtained with the bird in lateral recumbency, wings extended dorsally, and legs extended caudally. Additional views such as oblique projections may be necessary for specific indications. The Merck Veterinary Manual describes standard radiographic positioning for pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds).

How do I interpret the cardiac silhouette on avian radiographs?

The cardiac silhouette is visible in the cranial coelom on the ventrodorsal view. The normal cardiac width is approximately 50 to 60 percent of the thoracic width at the level of the heart. Cardiomegaly is suspected when the cardiac width exceeds 65 percent of the thoracic width. The cardiac silhouette should have smooth, well-defined borders. Irregular borders may indicate pericardial effusion or mass lesions.

What are the indications for avian ultrasonography?

Ultrasonography is indicated for evaluation of cardiac function, coelomic masses, reproductive tract disease, hepatomegaly, and ascites. The procedure is also used to guide needle aspiration or biopsy of coelomic lesions. Ultrasonography is complementary to radiography and may provide additional information about soft tissue structures. The Merck Veterinary Manual describes indications for ultrasonography in pet birds (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds).

How do I perform echocardiography in a bird?

Echocardiography is performed with the bird in dorsal recumbency using a high-frequency probe. The heart is imaged through the thoracic inlet or from a ventrolateral approach. Standard views include the right parasternal long-axis and short-axis views. M-mode measurements of the left ventricle allow assessment of systolic function. Color Doppler imaging is used to evaluate valvular function and blood flow patterns.

What are the limitations of radiography in birds?

Radiography provides two-dimensional images of three-dimensional structures, which may result in overlap of coelomic organs. Small lesions may not be visible on radiographs. The air sacs provide natural contrast but may obscure soft tissue structures. Radiography is limited in evaluating soft tissue structures such as the liver, spleen, and kidneys. Contrast studies or advanced imaging may be necessary for complete evaluation.

How do I diagnose egg binding on radiography?

Egg binding is diagnosed by identifying a mineralized egg in the oviduct on radiography. The egg may be located in the caudal coelom and may appear larger than normal or have an abnormal shape. The clinician should evaluate the egg for shell quality and position. Retained eggs may cause coelomic distention and displacement of coelomic organs. The Merck Veterinary Manual describes radiographic findings in egg binding (Merck Veterinary Manual, www.merckvetmanual.com/exotic-and-laboratory-animals/pet-birds).

What is the role of contrast studies in avian imaging?

Contrast studies are used to evaluate gastrointestinal transit time, mucosal integrity, and obstructive lesions. Barium sulfate suspension is administered via crop tube, and serial radiographs are obtained to track contrast progression. Contrast studies are also used for myelography to evaluate the spinal cord. The clinician should be familiar with normal transit times for the species being evaluated.

When should I refer an avian patient for advanced imaging?

Referral for advanced imaging such as computed tomography or magnetic resonance imaging should be considered when radiography and ultrasonography are inconclusive. Indications include suspected intracranial disease, complex fractures, neoplasia staging, and evaluation of the respiratory system. The clinician should discuss referral options with the owner and provide appropriate documentation of previous imaging studies.

Related Veterinary Guides

• Ducks Vs Chickens
• Backyard Chicken Diseases
• Backyard Poultry Biosecurity
• Feeding Backyard Chickens
• Pet Bird Illness Signs

References and Further Reading

• www.merckvetmanual.com
• www.aphis.usda.gov
• Merck Veterinary Manual. Merck Veterinary Manual.
• Animal Health and Welfare. World Organisation for Animal Health.
• Pigeons (Columba livia) as Trainable Observers of Pathology and Radiology Breast Cancer Images.. PloS one, 2015.
• Radiography.. The Veterinary clinics of North America, 1973.
• Orthopedic Diagnostic Imaging in Exotic Pets.. The veterinary clinics of North America. Exotic animal practice, 2019.
• Progress report: caerulein.. Gut, 1970.
• A myelographic technique for avian species.. Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association, 1997.
• Clinical applications of avian eggshell-derived hydroxyapatite.. Bosnian journal of basic medical sciences, 2020.
• Bioinspiration, Biomimetics, and Bioreplication XIV. Proceedings of SPIE the International Society for Optical Engineering, 2024.
• Morphological Assessment of Stage HH38 of the Japanese Quail (Coturnix japonica) Heart by Micro-Sonogram. Methods and Protocols, 2026.
• Acoustic trapping as a generic non-contact incubation site for multiplex bead-based assays. Analytica Chimica Acta, 2015.

This article is educational and is not a substitute for veterinary diagnosis or treatment. Contact a veterinarian for advice about an individual animal.