Small animal thoracic radiology: Pulmonary edema vs. pleural effusion (lines and buckets) (Proceedings)


Small animal thoracic radiology: Pulmonary edema vs. pleural effusion (lines and buckets) (Proceedings)

Aug 01, 2010

Pulmonary patterns have the bane of radiology since the beginning (1896 that is). The most difficult concept to teach and the most difficult to learn, yet, the pattern itself is only part of the puzzle. The recognition that the disease is actual within the pulmonary parenchyma and not in the pleural space, extrathoracic structures or the mediastinum is the first step. To this end we will review a basic interpretation paradigm and look at the steps for evaluating the thoracic radiograph in dogs and cats. Technique and positioning are critical in this process and should be the cornerstone for high quality thoracic radiographs. Finally, we will tackle pulmonary patterns with an emphasis on describing what is on the thoracic radiographs and equally important, recognizing anything that is missing.

Objectives of the Presentation

      1. Understand the different radiographic features of pleural effusion and pulmonary edema (cardiogenic and non-cardiogenic).
      2. Recognize potential pitfalls in the interpretation of multicompartmental disease of the thorax (e.g., diseases that involve both the pleural space and the pulmonary parenchyma).
      3. Understand the difference between a lobar sign and pleural fluid within a fissure between lung lobes.
      4. Think in terms of next step and how to get a cytologic diagnosis in as non-invasive a fashion as possible.

Key Etiologic and Pathophysiologic Points

      1. Technical factors including technique, phase of respiration and the positioning of the patient have to be taken into account when interpreting thoracic radiographs.
      2. Radiographic abnormalities are non-specific and one must thing in terms of what the next step would be to reach a definitive diagnosis.
      3. The pathophysiology of many pulmonary diseases do not equate with a specific pulmonary pattern.

Key Clinical Diagnostic Points

      1. One should try to compartmentalize radiographic abnormalities into extrathoracic, pleural, pulmonary and mediastinal (including cardiac), recognizing that any disease can have multicompartmental components.
      2. One should try to determine the anatomic location of pathology within the lung first and foremost and then worry about the pulmonary pattern. Even though there may be several pulmonary patterns, one must identify the dominant pattern in order to evaluate for differentials.
      3. Pleural effusions should always be evaluated using cytology and culture and sensitivity unless post trauma and the effusion (assumed to be hemorrhage) is resolving over several days.