Radiology in Pet Birds

Radiology in Pet Birds

• Birds possess a keel bone covering most of their ventrum/coelom
• Most organs in birds are not palpable
• Birds lack a diaphragm, creating a "coelomic mass effect" where issues in one organ system can affect others
  • An impacted egg can cause respiratory distress
• Lungs are embedded in the thoracic spine and do not inflate
  • Air sacs facilitate air movement
  • This makes auscultation challenging
• Radiographs (Rads) are essential for the minimum database in sick birds

Taking Images of Birds

• Most views require heavy sedation or anesthesia
• Birds must not be restrained while wearing lead-lined gloves for safety
• Use tape and sandbags or socks for positioning instead of hands
  • Blue painter's tape is recommended for the wings as it doesn't pull feathers
• Special acrylic positioning tables exist, but are not necessary with good technique

Bird Radiographic Views

• Right Lateral:
  • Wings outstretched
  • Legs pulled caudally and down
  • Scapulas and acetabula should be superimposed without rotation
  • Used to evaluate the syrinx (avian voice box)
  • Achieved on unsedated chickens by interlocking wings
• Ventrodorsal (VD):
  • Wings outstretched
  • Legs pulled caudally
  • Keel superimposed on the spine
  • Collimate over the keel, may cut off wing tips for better detail
  • This provides the best view for evaluating the heart, liver, and airways

Additional Radiographic Views

• Box Shot (Standing DV):
  • The bird stands in a "box" without sedation
  • Has a limited view
  • Proventriculus and ventriculus can be evaluated for Gastrointestinal (GI) foreign bodies
  • Can check for eggs
• H View:
  • An Oblique View
  • Angled 45 degrees to the frontal plane
  • Used to evaluate the shoulder girdle in birds of prey

Cardio-Hepatic Waist

• The heart and liver together form an hourglass silhouette
  • A normal silhouette fits between lines dropped from the points of the shoulders
  • A silhouette that does not fit may indicate cardiomegaly
• Best viewed on a VD radiograph
• A large silhoutte can obscure other organs like the GIT, kidneys, gonads, syrinx, thyroid, and spleen

Evaluating the Respiratory Tract in Birds

• Birds have nine air sacs, some entering bones (pneumatic bones) like the humerus
  • Clear air sacs should not be visible on radiographs
  • Spiderweb-like opacities around the cardio-hepatic waist may indicate air sac inflammation
• The beak and sinuses of the skull are also air-filled

Identifying Structures on a Right Lateral View

• It is important to be able to identify structures 1-9, plus the spleen
• The proventriculus sits at a 45-degree angle to the spine

Generalities of Exotic Pets

• Given the increasing number of exotic pets, baseline knowledge of their care is crucial
• Tiny, sick animals have low stress tolerance, sedation is often necessary (except for lizards and chelonians)
  • Patient safety takes priority over perfect positioning
  • Do not restrain exotics with lead gloves
• Whole-body radiographs are standard
  • Always include VD and R lateral views
  • Add a box shot or standing DV view as needed

Domestic Ferrets

• Obligate carnivores with no cecum
• Have a giant spleen (normal)
• Large lung capacity and respiratory tract
  • They are accustomed to microaerophilic environments due to burrowing, resulting in efficient lungs
• Males have a J-shaped os penis
• Require heavy sedation for good positioning
• Usually need two images to capture the whole body length

Rabbits

• Hindgut fermenters with a large cecum
  • GI problems are common
• They have open-rooted teeth that grow continuously
  • CT is the gold standard for dental imaging
• Small lungs relative to heart size
• Have a persistent thymus in adults
• Excrete chalky, radiopaque urine due to high calcium content
• Multiple shots are often needed to image the entire body

Rabbit Dental Radiographs

• Evaluate the occlusive surface and roots, ideally on a straight lateral view
• Take multiple views (straight and oblique)
• Roots:
  • Should be radiolucent
  • Should not contact bone or enter cavities
• Occlusive surface:
  • Has a zigzag pattern in rabbits

Other Exotics: Chinchillas

• Similar tooth situation to rabbits, but has a flat occlusive surface
• Have huge auditory bullae and big ears
• Hindgut fermenters with an abdomen similar to rabbits

Other Exotics: Guinea Pigs

• These are hindgut fermenters
• Their abdomen very similar to rabbits

Chelonians

• CT scan is generally the best choice due to the shell's density
• Views:
  • Dorsoventral (DV): Best for assessing the reproductive tract, counting eggs, and evaluating shell density
    • Reptile eggs are leathery and less dense than avian eggs
  • Lateral View: Positioning is critical to avoid visceral superimposition
    • Use a horizontal X-ray beam for best image quality
  • Cranio-caudal (A-P): Best for assessing the lungs
    • Again, horizontal beam preferred

Thorax Overview

• The Thorax has 3 divisions:
  • Pleural space: Between the parietal and visceral pleura
    • Parietal Pleura: Lines the thoracic wall
    • Visceral Pleura: Lines the actual lungs
    • It is a potential space and should not have anything in a healthy animal
  • Mediastinum: The space between the right and left pleural sacs
    • Extends from the thoracic inlet to the diaphragm
    • Not a closed cavity as the cranial mediastinum communicates with the retroperitoneal space
  • Thoracic wall and viscera

Pleura

• Normal pleura are not visible on radiographs
• Pleural lines (fissures) may be visible and normal if not pronounced, representing divisions between lung lobes
  • These will be really pronounced with pathology like pleural effusion

Mediastinum Details

• The mediastinum lies between the R and L pleural sacs and is not a closed cavity
• Although usually in the center, it deviates from the midline in 3 places
• Cranioventral reflection: Between the R cranial lobe and the cranial part of the L cranial lobe
• Caudoventral reflection: Between the accessory lobe of R lung and the L caudal lobe
  • Can appear thicker if the patient is overweight
• Vena cava

Mediastinal Organs Visible on X-Ray: Important list!

• Heart
• Trachea
• Cd vena cava
• Aorta
• Esophagus
• Thymus in young animals
• Organs not visible on X-ray: Cr vena cava, aortic arch branches, and lymph nodes

Esophagus

• As the Esophagus has a soft tissue opacity it can be hard to detect
• The Esophagus lies dorsal to the trachea
  • Enlargement can cause ventral displacement of the trachea
• Normal esophageal air is found at the thoracic inlet and heart base
• Normal esophageal fluid is found in the cd mediastinum
• The esophageal stripe sign is a sign of esophageal gas
• The Esophagus has two sphincters, one at each end

Thoracic Wall and Ribs

• Examination of the thoracic wall is often overlooked but is important
• Ribs should be mineralized in all animals, with variable mineralization degrees in the costal cartilages
• Younger animals may not show cartilage mineralization on radiographs
• Older animals show bulky and opaque cartilage due to abundant mineralization
• Exuberant calcifications may occur at the costochondral junction; mistaken for tumors, infection, or lung nodules

Skin Nodules on X-Ray

• An additional reminder to take multiple views and to assess the entire patient, not just internal structures

The Diaphragm

• Structure:
  • Separates the thorax and abdomen
  • Has a dome-shaped center and right and left crus
• Openings:
  • Aortic hiatus
  • Esophageal hiatus
  • Foramen for the caudal vena cava (located on the right crus)
• Laterality Determination:
  • Dependent crus is usually positioned more cranially
  • R lateral: R and L crus are more parallel, caudal vena cava does not superimpose
  • L lateral: R and L crus are more divergent, caudal vena cava superimposes over the L crus

DV (Dorsoventral) vs VD (Ventrodorsal)

Patient Preparation and Background

• Echocardiogram (ECHO) is an ultrasound of the heart
• Procedure:
  • Shave the patient:
    • Dogs: R side, 4–6 intercostal spaces; L side, fourth intercostal space
    • Cats: R side, 3–5 intercostal spaces; L side, fourth intercostal space
  • Apply alcohol or gel
  • Place patient on an echocardiology table

Cardiac Views

• R parasternal long axis view
• R parasternal long axis ventricular outflow view (aka 5 chamber view)
• Parasternal transverse (short axis views)

Doppler Echocardiography

• Color Flow Doppler:
  • Shows the direction of blood flow
  • Color indicates direction:
    • Blue = Away from the transducer (BART)
    • Red = Toward the transducer
• Spectral Doppler:
  • Shows both velocity and direction of blood flow
  • Position relative to Baseline indicates direction
    • Below baseline = Away from the transducer
      • E.g., Aorta and main pulmonary artery
    • Above baseline = Toward the transducer
      • E.g., Mitral and tricuspid valves