[Diagnosis of parenchymal lung diseases. Possibilities and limits of transthoracic sonography]

Role of Contrast-Enhanced Ultrasound in Pulmonary Lesions: 5-Year Experience at a Single Center

Contrast-enhanced ultrasound (CEUS) for the differentiation of benign and malignant peripheral pulmonary lesions has been considered experimental for many years. This study was aimed at evaluating the feasibility of CEUS as a diagnostic modality in this area of discussion. CEUS diagnostic accuracy was explored by comparison with contrast-enhanced computed tomography (CECT). The collective included 449 patients with 449 definitive diagnoses (benign, 178; malignant, 271). Logistic regression analysis of CEUS data revealed that delayed time to enhancement, chaotic pattern of distribution of vessels and mild extent of enhancement were independent risk factors for predicting malignancy. Time to wash-out and homogeneity of enhancement did not differ between the two groups (p > 0.05). Based on histopathology or clinical follow-up as a reference standard, CEUS and CECT had similar diagnostic accuracies of 80.16% and 81.75%, respectively. CEUS is a potentially useful imaging tool for diagnosing peripheral pulmonary lesions.

Ultrasound of the pleurae and lungs

The value of ultrasound techniques in examination of the pleurae and lungs has been underestimated over recent decades. One explanation for this is the assumption that the ventilated lungs and the bones of the rib cage constitute impermeable obstacles to ultrasound. However, a variety of pathologies of the chest wall, pleurae and lungs result in altered tissue composition, providing substantially increased access and visibility for ultrasound examination. It is a great benefit that the pleurae and lungs can be non-invasively imaged repeatedly without discomfort or radiation exposure for the patient. Ultrasound is thus particularly valuable in follow-up of disease, differential diagnosis and detection of complications. Diagnostic and therapeutic interventions in patients with pathologic pleural and pulmonary findings can tolerably be performed under real-time ultrasound guidance. In this article, an updated overview is given presenting not only the benefits and indications, but also the limitations of pleural and pulmonary ultrasound.

Detection of air trapping in chronic obstructive pulmonary disease by low frequency ultrasound

BACKGROUND

Spirometry is regarded as the gold standard for the diagnosis of COPD, yet the condition is widely underdiagnosed. Therefore, additional screening methods that are easy to perform and to interpret are needed. Recently, we demonstrated that low frequency ultrasound (LFU) may be helpful for monitoring lung diseases. The objective of this study was to evaluate whether LFU can be used to detect air trapping in COPD. In addition, we evaluated the ability of LFU to detect the effects of short-acting bronchodilator medication.

METHODS

Seventeen patients with COPD and 9 healthy subjects were examined by body plethysmography and LFU. Ultrasound frequencies ranging from 1 to 40 kHz were transmitted to the sternum and received at the back during inspiration and expiration. The high pass frequency was determined from the inspiratory and the expiratory signals and their difference termed ΔF. Measurements were repeated after inhalation of salbutamol.

RESULTS

We found significant differences in ΔF between COPD subjects and healthy subjects. These differences were already significant at GOLD stage 1 and increased with the severity of COPD. Sensitivity for detection of GOLD stage 1 was 83% and for GOLD stages worse than 1 it was 91%. Bronchodilator effects could not be detected reliably.

CONCLUSIONS

We conclude that low frequency ultrasound is cost-effective, easy to perform and suitable for detecting air trapping. It might be useful in screening for COPD.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01080924.

Emerging roles for transthoracic ultrasonography in pulmonary diseases

As a result of many advantages such as the absence of radiation exposure, non-invasiveness, low cost, safety, and ready availability, transthoracic ultrasonography (TUS) represents an emerging and useful technique in the management of pleural and pulmonary diseases. In this second part of a comprehensive review that deals with the role of TUS in pleuropulmonary pathology, the normal findings, sonographic artifacts and morphology of the most important and frequent pulmonary diseases are described. In particular, the usefulness of TUS in diagnosing or raising suspicion of pneumonia, pulmonary embolism, atelectasis, diffuse parenchymal diseases, adult and newborn respiratory distress syndrome, lung cancer and lung metastases are discussed, as well as its role in guidance for diagnostic and therapeutic interventional procedures. Moreover, the preliminary data about the role of contrast enhanced ultrasonography in the study of pulmonary pleural-based lesions are also reported. Finally, the limits of TUS when compared with chest computed tomography are described, highlighting the inability of TUS to depict lesions that are not in contact with the pleura or are located under bony structures, poor visualization of the mediastinum, and the need for very experienced examiners to obtain reliable results.

Accuracy of transthoracic sonography in excluding post-interventional pneumothorax and hydropneumothorax. Comparison to chest radiography

OBJECTIVE

Transthoracic sonography (TS) has evolved as an important imaging technique for diagnosing pleural and pulmonary conditions. However, the value of TS in either excluding or diagnosing pneumothorax is still under debate. This study was conducted to examine whether TS could replace chest radiography for the diagnosis of post-interventional pneumothorax and hydropneumothorax.

METHODS

53 patients (21 females, 32 males; median age 64 years, range 37-94 years), 35 of whom underwent transbronchial biopsy (TBB) and 18 patients who had an ultrasound-guided chest tube placement (U-GCTP) were enrolled in the study. TS was performed three hours after either TBB or removal of a chest tube, followed by postero-anterior chest radiograph (CRX). If any discrepancy between TS, the clinical presentation and the CRX became apparent, either a lateral CRX or a computed tomography (CT) of the thorax was performed. TS was assessed according to the presence of the following criteria: (1) "gliding sign" of the pleural line, (2) comet tail artifacts, (3) reverberation artifacts, (4) air/fluid mirror, (5) hyperechoic reflectors within the pleural effusion and (6) "lung point".

RESULTS

In four out of the 53 patients (7.5%) a post-interventional pneumothorax or hydropneumothorax occurred. One out of the 35 patients (2.9%) developed a pneumothorax after TBB, requiring chest tube placement. Three patients (16.7%) developed a hydropneumothorax due to U-GCTP which was detected by sonography but was missed by postero-anterior CRX in one patient. The sensitivity, specificity and accuracy of TS were 100% in excluding post-interventional pneumothorax/hydropneumothorax.

CONCLUSION

TS is a cost-effective and safe bed-side-method, allowing for an immediate exclusion or diagnosis of post-interventional pneumothorax/hydropneumothorax in patients who have undergone TBB or U-GCTP. Thus, these preliminary results suggest that CXR may only be required in patients with pneumothorax diagnosed by TS in order to assess its extension or to exclude any discrepancy between the TS-result and the clinical presentation.

Transthoracic sonography of diffuse parenchymal lung disease: the role of comet tail artifacts

OBJECTIVE

The value of transthoracic sonography in diffuse parenchymal lung disease is not established. This prospective study was conducted to analyze pleural and parenchymal alterations in patients with diffuse parenchymal lung disease by transthoracic sonography and to compare the results with the findings of a control group.

METHODS

Fifty-three patients with diffuse parenchymal lung disease and 35 control subjects underwent transthoracic sonography for assessment of (1) basal pleural effusion, (2) the presence and number of comet tail artifacts, (3) thickening, (4) an irregular, fragmented pleural line, and (5) subpleural alterations.

RESULTS

Basal pleural effusion was revealed in 37.7% of the patients with diffuse parenchymal lung disease (0% of the control subjects; P < .001), and 98.1% had multiple (>6 per scan) comet tail artifacts (14.3% of the control subjects; P < .001). Only a few artifacts (< or = 6 per scan; P < .001) were shown in 85.7% of the control subjects. All the control subjects had strongly localized comet tail artifacts and no thickened pleural line (84.9% of patients; P < .001). In 98.1 % of the patients, an irregular, fragmented pleural surface could be detected (82.8% of the control subjects; P < .05). Subpleural alterations were found in 37.7% of the patients and in 8.6% of the control subjects (P < .001).

CONCLUSIONS

Diffuse parenchymal lung disease should be considered if multiple comet tail artifacts distributed over the whole surface of the lung together with a thickened and irregular, fragmented pleural line are visible. Transthoracic sonography may reflect the distribution of pleural involvement and may show subpleural alterations.

Sonography of lung and pleura in pulmonary embolism: sonomorphologic characterization and comparison with spiral CT scanning

STUDY OBJECTIVES

Despite the widespread use of lung scanning and angiography, pulmonary embolisms (PEs) remain undiagnosed in the majority of patients, suggesting the need for alternative diagnostic approaches. The present study investigates the clinical utility of transthoracic sonography (TS) for the diagnosis of PE and compares the data obtained with the technique to those obtained by spiral CT (sCT) scanning.

DESIGN

This prospective study was performed using 69 patients with suspected PEs. TS was performed in all patients. In addition, sCT scanning was carried out in 62 patients. Other diagnostic procedures included the estimation of d-dimers, echocardiography, venous duplex sonography of the legs, pulmonary angiography, and ventilation/perfusion scanning. The diagnosis of PE was accepted when there was a conclusive result of these investigations or when an embolus could be visualized on a CT scan.

SETTING

The Department of Pneumology in Friedrich-Schiller-University Hospital (Jena, Germany).

PATIENTS

Sixty-nine patients (27 women and 42 men) with suspected PEs.

RESULTS

A diagnosis of PE was established in 44 patients. Ninety-one peripheral parenchymal lesions (mean, 2.6 lesions per patient; range 1 to 9 lesions per patient) that are associated with PE were detected by TS in 35 patients (80%). Multiple, triangular, hypoechoic, and pleural-based parenchymal lesions with a localized and/or basal effusion were typical of the PEs as shown by TS. In nine patients with central PEs that had been diagnosed by CT scanning, no peripheral lesions could be detected by sonography. One patient with sonographic signs of PEs had a diffuse bronchogenic adenocarcinoma that was diagnosed at autopsy. In another patient with parenchymal lesions, pneumonia was diagnosed by CT scanning. The sensitivity of TS for detecting PEs was 80% (sensitivity of CT scanning, 82%), and the specificity of TS for detecting pulmonary lesions was 92% (specificity of CT scanning, 100%). The positive and negative predictive values of TS for the detection of PEs were 95% and 72%, respectively (positive predictive value for CT scanning, 100%; negative predictive value for CT scanning, 77%). The accuracy of TS was 84% (accuracy of CT scanning, 89%).

CONCLUSIONS

TS is a noninvasive technique that is used for diagnosing parenchymal alterations, and it may serve as an additional method in the strategy for diagnosing PE.