Imaging techniques for avian lower respiratory diseases

Abstract

Radiography is the most frequently used imaging technique to assess avian lower respiratory disease. The unique architecture of the avian respiratory system results in variations of radiographic appearances that are markedly different from the traditional pulmonary patterns frequently seen in mammals such as alveolar, bronchial, or interstitial. Alveolar lung disease, the hallmark of pneumonia in mammalian imaging, is not identified in avian lungs because the terminal airways consist of interconnecting bronchi and parabronchi without well-developed smaller compartments. Pathological changes of avian lungs are most commonly recognized radiographically as increased soft-tissue opacity with loss of the normal reticulated pattern. Avian lungs are relatively noncompliant and firmly adhered to the thoracic wall; thus, total lung volume is relatively constant throughout respiration, and conditions such as atelectasis do not occur. This review will address the common radiographic findings associated with avian lower respiratory disease. In addition, the potential applications of computerized axial tomography (CT) and magnetic resonance imaging (MRI) in avian respiratory disease will be discussed.