Cross-sectional echocardiographic characterization of atelectatic lung segments. Differentiation from extracardiac tumors

Atelectasis in the perioperative patient

PURPOSE OF REVIEW

To report the impact of atelectasis on perioperative outcomes. Atelectasis occurs in the dependent parts of the lungs of most patients who are anesthetized. Development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance and development of lung injury. Here, we examine the etiology, contributing factors, consequences, diagnosis and treatment of atelectasis.

RECENT FINDINGS

Atelectasis describes the state of absent air in alveoli attributable to collapse, but recent findings suggest that alveoli are filled with foam and fluid. It is now known that atelectasis plays an important role beyond abnormal gas exchange and that prevention or reversal of atelectasis in some populations of postoperative patients may improve outcome.

SUMMARY

Atelectasis in the presence of preexisting lung disease or limited cardiopulmonary reserve may have significant consequences. Increasing understanding of the underlying nature of atelectasis and its contribution to acute lung injury will improve our approach to the prevention and management of atelectasis.

Alternative imaging of the lung

This article illustrates the roles of ultrasonography, scintigraphy, and computed tomography (CT) as alternative techniques for pulmonary imaging in small animals. The advantages and limitations of each modality, normal anatomic features, and technical considerations will be discussed. Selected applications will be examined and include pulmonary consolidation, neoplasia and other masses, atelectasis, pneumothorax, dystrophic mineralization, diffuse infiltrative disease, and pulmonary embolism. The use of ultrasound and CT-guided interventional procedures will also be briefly discussed.

Two-dimensional ultrasonographic findings of atelectatic lung segments

Thirteen cases with pulmonary atelectasis were examined by two-dimensional sonography in our clinics between October 1990 and April 1993. Patients' ages ranged from 2 to 16 years. Five patients revealed atelectasis with pleural effusion and eight patients had only atelectasis. Two-dimensional sonography showed a solid mass indistinguishable from lung parenchyma in patients with atelectatic lung segment without pleural effusion while atelectatic segment was readily identified in those with pleural effusion. We conclude that sonography is a useful and non-invasive technique in differentiating cardiac from extracardiac masses, because atelectatic lung segment with moderate to large pleural effusion may mimic intrapericardial masses.

Problems and pitfalls in the echocardiographic assessment of pericardial effusion

The echocardiographic diagnosis of pericardial effusions is usually based on visualization of a sonolucent circumcardiac space of varying width. However, potential fallacies in interpretation can arise if sonolucent spaces adjacent to the heart (pleural effusions, ascites, pericardial cysts) are mistaken for pericardial effusions. Loculated pericardial effusions, especially if unusual in location or configuration, can cause diagnostic difficulty on occasion. The differential diagnosis of various "solid" echoes within a pericardial effusion is of clinical relevance, yet not widely discussed. Inflammatory tissue, neoplastic involvement, pus, caseous material, and extravasated blood all have characteristic echocardiographic morphologies. All of the various reported echocardiographic signs of tamponade do not have the same significance, so that caution is necessary not to over- or under-read tamponade. Chamber collapse can be absent in real tamponade in specific situations. On the other hand, "regional" tamponade can occur if loculated pericardial effusions are sufficiently large and high tension; echocardiographic appearances are "atypical" but diagnostically valuable if correctly interpreted. These and certain other unusual variants of tamponade deserve to be better known among echocardiographers not only because of their intrinsic interest, but also to avoid potential pitfalls in the echocardiographic assessment of patients with suspected disease.