Original contribution
Sonographic Appearances in Transudative Pleural Effusions: Not Always an Anechoic Pattern

https://doi.org/10.1016/j.ultrasmedbio.2007.09.009Get rights and content

Abstract

Pleural effusion patterns in sonographic appearances can be subclassified as anechoic, complex nonseptated, complex septated and homogeneously echogenic. Previous studies have suggested that transudates are usually anechoic; however, in daily practice we find frequently that heterogeneous echogenic material is present in transudative pleural effusions. This clinical study was to re-evaluate the sonographic appearances of transudative pleural effusions. A total of 127 patients with transudative pleural effusion that met Light’s criteria ([1] a pleural fluid-serum protein ratio of <0.5, [2] a pleural fluid-serum lactate dehydrogenase [(LDH] ratio of <0.6 and [3] a pleural fluid LDH of less than two thirds of the upper limit of normal for serum LDH) and clinical presentations were enrolled. Results showed that transudative pleural effusions had the following sonographic appearances: an anechoic pattern in 45% (57/127) and a complex nonseptated pattern in 55% (70/127). There was no complex septated or homogenously echogenic pattern. In conclusion, sonographic presentations in transudative pleural effusions are not always in an anechoic pattern. If an afebrile patient without infectious symptoms/signs has bilateral pleural effusion compatible with transudate of Light’s criteria, treat the underlying problems and ignore the complex nonseptated sonographic appearance. (E-mail: [email protected])

Introduction

Pleural effusions may be caused by systemic diseases or local infectious/inflammatory factors. Transudates are caused by systemic factors that alter the balance of the formation and absorption of pleural fluid (i.e., left ventricular failure, cirrhosis and nephrotic syndrome), whereas exudative pleural effusions are often caused by alterations in local factors that influence the formation and absorption of pleural fluid (i.e., pneumonia, cancer and tuberculosis) (Light 2002).

Clinically, transudates indicate limited diagnostic possibilities and generally preclude further diagnostic testing. Transudates have been differentiated easily from exudates using Light’s criteria. Practically, Light’s criteria are the most sensitive for identifying exudates, but have lower specificity than other criteria (sensitivity for exudates 98%; specificity for exudates 83%) (Light 2002).

As reported, sonography is also helpful in determining the nature of pleural effusions (Hirsch et al 1981, Yang et al 1992). Pleural effusion patterns can be subclassified as anechoic, complex nonseptated, complex septated and homogeneously echogenic; transudates are usually anechoic (Yang et al. 1992). However, in daily practice we find frequently that heterogeneous echogenic material is present in transudative pleural effusions. Chian et al. (2004) reported that the etiologies of the echogenic swirling pattern of pleural effusions included liver cirrhosis, nephrotic syndrome and congestive heart failure. The swirling pattern of the sonographic appearance is also a complex nonseptated echogenic presentation, not an anechoic pattern. Because of uncertainty regarding the sonographic appearances of transudative pleural effusions, we collected and analyzed the sonographic evidence of transudative pleural effusions in our hospital. The aim was to re-evaluate the clinical significance of the sonographic appearances of transudative pleural effusions in the hope that the ultrasound image in the differential diagnoses of pleural effusions may be of value.

Section snippets

Enrolled patients

We retrospectively collected and carefully reviewed the medical records of patients who had experienced pleural effusion and received diagnostic thoracentesis between September 2004 and August 2006 (24 mo) in our hospital. The study was approved by our Institutional Review Board. Transudates were defined by meeting Light’s criteria (Light et al. 1972) and clinical presentations (systemic factors that alter the balance of the formation and absorption of pleural fluid). Only the results of the

Demographic data

One-hundred twenty-seven patients with transudative pleural effusion were enrolled in our series. Thirty-four (27%) of the effusions were located on the right side, seven (6%) on the left side and 86 (68%) on bilateral sides. Assessment of the amount of pleural effusion showed massive pleural effusion in eight patients (6%), a moderate amount in 49 patients (39%) and mild pleural effusion in 70 patients (55%).

The etiologies of the transudative pleural effusions were congestive heart failure (n

Discussion

Chest ultrasonography is a useful imaging tool in assessing the problems of peripheral lung tumor, consolidation, abscess, mediastinal mass and pleural effusion (Beckh et al. 2002). For pleural effusions, Yang et al. (1992) classified the sonographic patterns as anechoic, complex nonseptated, complex septated and homogeneous. Homogeneous echogenic effusions were to the result of hemorrhagic effusions or empyema. Recent studies have extended the application of sonographic appearances to the

Conclusions

This is the first large retrospective series studying the ultrasound appearance of transudates that demonstrates that the majority of laboratory-proven transudates are complex rather than anechoic. When the complex nonseptated pattern is seen by ultrasound, our data suggests clinical correlation rather than thoracentesis may be adequate for diagnosis of transudate. Some patients might still consider thoracentesis when the clinical findings do not correlate with transudate. So, if an afebrile

Acknowledgments

This work was supported in part by CMUH grant DMR-96 to 030.

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