The “Pseudo-Lung Point” Sign: All Focal Respiratory Coupled Alternating Pleural Patterns Are Not Diagnostic of a Pneumothorax

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In less than two decades since the introduction of the Focused Assessment with Sonography in Trauma (FAST) examination ultrasound has become ubiquitous in the trauma bay. First used for the identification of abdominal and pericardial fluid, its utility has been expanded to include the detection of pneumothorax; the so-called extended FAST.1In our case, a 22-year-old man was a restrained passenger involved in a single-vehicle head on collision. On arrival to the trauma bay, he was hemodynamically stable. An extended FAST examination revealed what appeared to be a lung point when the chest was scanned laterally (Fig. 1). These features are best determined through viewing real-time video sequences (see Video, Supplemental Digital Content 1,; Author: Lawrence Gillman, Videographer: Andrew Kirkpatrick, Length: 6 seconds, and Size: 0.8 MB, which demonstrates the “pseudo-lung point” moving across the screen with respiration). Using M-mode imaging, a distinct respiratory coupled pleural sonographic alternation was seen (Fig. 2). A chest radiograph revealed right rib fractures and a right pulmonary contusion with no evidence of pneumothorax, which was corroborated through computed tomography scan of the chest (Fig. 3).The diagnosis of pneumothorax was one of the first clinical applications of lung ultrasound. The lung point was first described by Lichtenstein in 2000.2 The ability to demonstrate the alternating lung sliding and absence of lung sliding within the same ultrasound field has been touted as being diagnostic of a pneumothorax with 100% specificity.2 This is dramatically emphasized using time-motion (M-mode) ultrasonography where one sees alternating patterns of the “seashore” and “stratosphere” signs.At initial viewing, the ultrasound imaging of our patient revealed an alternating pleural-based pattern of sonographic imagery that was coupled to the respiration that could be considered consistent with a lung point (Fig. 1) in addition to a rhythmic alternation of the expected seashore sign in M-mode (Fig. 2). We have considered this to represent a pseudo-lung point because there was no concomitant stratosphere sign.We believe that this case, therefore, illustrates the need for diligence in interpreting the lung point in the sonographic and clinical context and not as a simple pattern to be memorized. As the physical examination continues to be enhanced by advanced US techniques, it needs to be remembered that these techniques are still adjuncts that defer to the overall clinical acumen of the clinical sonographer interpreting and integrating all historical, physical, and sonographic findings to arrive at a correct diagnosis.

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