Radiography: thorax

• The rabbit thorax can be difficult to interpret due to the relatively small lung field proportional to the size of the rabbit.
• Radiography of the thorax can be problematical due to difficulties eliminating movement blur resulting from breathing.
• High output (high mA capability) x-ray machines enable exposure times to be minimized, reducing the risk of movement blur.
• A reasonably high kV, along with high mA capability, will facilitate the use of shorter exposure times and avoid excessive image contrast.
• Close collimation of the primary beam should be practiced at all times.
• The objective is to produce a radiograph which includes the whole area of interest, is correctly exposed and developed, and is free from movement blur and artifacts.
• The film should be clearly marked with the anatomical marker, the patient's identification, the date and the name of the hospital or practice.

Print-off the Owner factsheet Xray and Ultrasound to give to your clients.

Indications

• Tachypnea, dyspnea (open mouth breathing, abdominal effort).
• Sneezing, wheezing.
• Nasal discharge.
• Muffled heart.
• Arrhythmias, heart murmurs.
• Suspicion of thoracic effusion. 
• Abnormal respiratory sounds on auscultation. 
• Gut sounds in thorax. 
• Bilateral exophthalmos.
• Trauma. 
• Dysphagia.
• Lethargy, exercise intolerance.
• Coughing.

Uses

• Lung pathology: bronchitis, lung abscess pneumonia neoplasia, metastasis.
• Assessment of cardiac size and shape.
• Examination of esophagus.
• Demonstration of pleural space pathology.
• Demonstration of mediastinal pathology .
• Distal tracheal pathology, eg stricture Trachea: stricture.
• Detection of fractured ribs , or other rib pathology.
• Confirmation of diaphragmatic herniation may require barium study to aid in the confirmation of diagnosis.
• Screening in rabbits diagnosed with neoplasia, eg uterine adenocarcinoma Uterine adenocarcinoma, mammary neoplasia Mammary gland: carcinoma.
• As an aid for other procedures such as nasogastric tube placement.
• Investigation of chronic weight loss.

Advantages

• Non-invasive, valuable diagnostic tool.
• Certain views may be performed conscious in quiet or sick animals.
• Can be performed under sedation Sedation/general anesthesia Anesthesia: overview when multiple, in depth, views are required.
• Relatively quick and simple where general anesthesia is not required.

Disadvantages

• May require general anesthesia Anesthesia: overview.

Placing dyspneic animals in dorsal or lateral recumbency can compromise respiration in some cases.

Struggling with a non-compliant, eg under-sedated or stressed patient may be detrimental to its condition.

Technical problems

• Incorrect placement of the patient can result in misinterpretation of the radiograph and non-diagnostic images.
• Multiple views should be obtained to allow adequate image assessment:
  • Only the lung away from the plate can be properly assessed as the one near the plate is compressed by pressure due to body weight.
  • Both right-side and left-sided radiographs should be taken to fully assess the lung fields.  

Alternative techniques

• Ultrasonography may occasionally be an alternative but is more often a supplementary procedure .
• CT Computed tomography scanning is extremely useful for respiratory system assessment and can be used independently or in conjunction with radiography for diagnostic purposes.

Time required

Preparation

• Dependent upon the method of restraint (conscious, GA Anesthesia: overview or sedation Sedation).

Procedure

• 10-15 min, or longer, dependent upon skill of radiographer.

Decision taking

Criteria for choosing test

Is the examination appropriate?

• Can you make the diagnosis without it?
• Can it tell you what you need to know?
• Will your management be affected by the radiological findings?

Choosing the right projections

• Right lateral recumbency:
  • Gives information about lung fields, heart size and shape , thoracic skeleton.
• Left lateral recumbency:
  • Both laterals should be performed when looking for subtle changes, eg metastasis in the lungs, due to reduced visibility of soft tissue opacities within the lung fields on the side, which is compressed by the patient's weight.
• Dorsoventral (patient in sternal recumbency):
  • Gives additional information about lung fields , eg lateralization of a lesion seen on a lateral recumbency film, and particularly about heart size and shape.
• Ventrodorsal:
  • Shows accessory lung lobe and reveals more of the caudal lobes medially, but heart falls across to right side so not the projection of choice for assessing cardiac outline.

Ventrodorsal not to be attempted when pleural fluid suspected or severe dyspnea present.

• Horizontal beam lateral view:
  • In very dyspneic patient it may be difficult to position for standard views.
  • Standing lateral view will show caudodorsal area (limbs obscure cranial thorax).

Patients may be restrained in a cardboard box.

Risk assessment

• Suitability for chemical restraint.
• Type of chemical restraint: GA or sedation, balancing patient criteria against any limitations of x-ray equipment.