Lung Ultrasonography in the Evaluation of Interstitial Lung Disease in Systemic Connective Tissue Diseases: Criteria and Severity of Pulmonary Fibrosis – Analysis of 52 Patients

Abstract

Objectives: Patients with a diagnosed systemic connective tissue disease require regular monitoring from the point of view of interstitial lung disease. The main aim of this work is a description of the criteria for pulmonary fibrosis and the degree of the severity of the fibrosis during the course of interstitial lung disease through the TLU (transthoracic lung ultrasound).

Materials and Methods: 52 patients with diagnosed diffuse interstitial lung disease were qualified for this research, together with 50 volunteers in the control group. The patients in both groups were over 18 years of age and were of both sexes. The results of the TLU of the patients underwent statistical analysis and were compared to High-Resolution Computed Tomography (HRCT) results.

Results: As a consequence of the statistical analysis, we defined our own criteria for pulmonary fibrosis in TLU: irregularity of the pleura line, tightening of the pleura line, the fragmentary nature of the pleura line, blurring of the pleura line, thickening of the pleura line, artifacts of line B ≤ 3 and ≥ 4, artifacts of Am line and subpleural consolidations < 5 mm. As a result of the conducted research, a scale of severity of pulmonary fibrosis in TLU was devised (UFI – Ultrasound Fibrosis Index), enabling a division to be made into mild, moderate and severe cases.

Conclusions: Transthoracic Lung Ultrasonography (TLU) gives a new outlook on the diagnostic possibilities, non-invasive and devoid of ionising radiation, of pulmonary fibrosis. This research work has allowed to discover two new ultrasound symptoms of pulmonary fibrosis (blurred pleural line and Am lines).

Zusammenfassung

Ziel: Patienten mit Diagnose einer systemischen Kollagenose brauchen eine regelmäßige Überwachung im Hinblick auf eine interstitielle Lungenerkrankung. Das Hauptziel dieser Arbeit ist die Beschreibung der Kriterien für eine pulmonale Fibrose und dem Schweregrad der Fibrose bei einer interstitiellen Lungenerkrankung mittels TLU (transthorakaler Lungenultraschall).

Material und Methoden: 52 Patienten mit Diagnose einer diffusen interstitiellen Lungenerkrankung wurden für diese Untersuchung ausgewählt zusammen mit 50 Freiwilligen einer Kontrollgruppe. Die Patienten beider Gruppen waren über 18 Jahre alt und beiderlei Geschlechts. Das Ergebnis des TLU der Patienten wurde statistisch analysiert und mit der High-Resolution-Computertomografie verglichen.

Ergebnisse: Als Folge der statistischen Analyse definierten wir unsere eigenen Kriterien für Lungenfibrose im TLU: Ungleichmäßigkeit der Pleuralinie, Straffung der Pleuralinie, unvollständige Pleuralinie, Unschärfe der Pleuralinie, Verdickung der Pleuralinie, B-Linien-Artefakte ≤ 3 und ≥ 4, Artefakte der Am-Linie und subpleurale Verdichtungen < 5 mm. Als Ergebnis aus den durchgeführten Untersuchungen wurde eine Skala der Schwere der Lungenfibrose im TLU entwickelt (UFI- Ultraschall-Fibrose-Index), die eine Unterteilung in leichte, moderate und schwere Fälle ermöglicht.

Schlussfolgerung: Der transthorakale Lungenultraschall (TLU) ermöglicht neue Perspektiven der diagnostischen Möglichkeiten bei pulmonaler Fibrose, die nicht-invasiv und ohne ionisierende Strahlen sind. Diese Forschungsarbeit hat die Beschreibung von zwei neuen Ultraschallmarkern bei Lungenfibrose (unscharfe Pleuralinie und Am-Linien) ermöglicht.

Key words

pleura - thorax - ultrasound - interstitial diseases of the lungs - pulmonary fibrosis

Introduction

Interstitial diseases of the lungs (IDL) constitute a heterogenous group of diffuse parenchyma lung diseases (DPLD), with often unknown etiology and pathogenesis [1] [2]. The common characteristic is the occurrence of inflammatory and fibrous changes, embracing to various degrees the interstitial tissues of the lungs and the air spaces [1] [3]. The incidence of these diseases is 30 – 70 per 100 000 inhabitants annually, which testifies to the seriousness of the clinical problem. Pulmonary fibrosis is the final stage of the majority of the chronic IDL, which causes a reconstruction of the structure of the lungs and the vascular bed and, subsequently, the development of pulmonary hypertension [1]. The classification of IDL is presented on the basis of the most current clinical, pathomorphological and radiological (chest X-ray, HRCT) data [3] [4] [5]. The test which constitutes the gold standard in the diagnosis and differentiation of other causes of fibrosis is a biopsy of the lungs. Because of its invasive nature, lung biopsy is performed in cases in which diagnosis still remains unclear [4] [6], despite earlier tests, according to the algorithm of diagnostic procedure in multiple changes in the lungs.

Lung ultrasonography (LUS) is a non-invasive diagnostic method possessing validation and allowing for the diagnosis of many lung diseases [7]. Owing to insufficient data in the literature on the subject of the value of this diagnostic method in IDL, further research leading to the establishment of ultrasonographic criteria in pulmonary fibrosis and the possibility of monitoring the course of the disease is necessary. The aim of the study was a presentation of the criteria and degree of the severity of pulmonary fibrosis using LUS.

Methods and Materials

Patient group

A total of 64 consecutive patients with diagnosed interstitial lung disease in accordance with the accepted classification of interstitial lung diseases as drawn up by the American Thoracic Society (ATS)/European Respiratory Society (ERS) in 2013, qualified for the research. Patients were of both sexes (20 women, 32 men) with an average age of 50 years (SD 24). The criteria for exclusion included features of infection of the respiratory tract as well as clinical, echocardiographic and radiological features of aggravated left-ventricle failure of the heart. Twelve patients (12/64) were excluded from the study due to lower respiratory tract infections. The largest group of patients with diagnosed IDL consisted of those with a systemic connective tissue disease (57.7 %, 30/52) followed by those with idiopathic pneumonia (30.7 %, 16/52). An open biopsy of the lung was performed on 19 % (10/52) of the patients from the group, and the material obtained underwent histopathological testing. Among the patients with a systemic connective tissue disease, there were mainly those with diagnosed systemic sclerosis (39 %). The research was approved by the Independent Bioethical Commission of Gdańsk Medical University (NKEBN/429/2011).

Control group

Fifty consecutive volunteers of both sexes (16 women, 34 men) with an average age of 47 years (SD 25), without aberrations in anamnesis or in the ECG and X-ray of the chest carried out during periodic testing at workplace (exposure factors were excluded). Exclusion criteria from the control group included persons who presented in anamnesis and/or earlier tests features of left-ventricle cardiac insufficiency and with increased parameters of inflammation. None of the volunteers had been excluded from the study. Lung ultrasonography was performed within 1 – 3 days of the X-ray of the chest. During the LUS, the results of other radiological tests were not known to the person carrying out the ultrasonographic testing.

LUS

The LUS was performed in patients remaining in the sitting and supine position. Each intercostal space available in the tests was assessed. In order to facilitate comparative assessment of lesions in the lungs, they were divided into upper, middle and lower fields. The tests were carried out using the Logiq 7 system (GE Healthcare, WI) with the use of a linear probe (8.0 – 11.0 MHz) and a convex probe (3.5 – 5.0 MHz).

HRCT

Computer tomography of the chest was carried out in the HRCT version in accordance with the standard protocol with the use of a 64-MDct LightSpeed Vct Xt (GE Healthcare Technologies, Wisconsin, USA). During the examination, the patient was in a prone position. The scans were carried out with full inspiration from the apex to the base of both lungs, with a thickness of 1.25 mm and with increments of 10 mm. The HRCT were assessed by two independent radiologists, and the interpretation of doubtful radiological changes was made on the basis of consensus. HRCT was performed in all patients in the study group and the same day as LUS. 

Severity of pulmonary fibrosis

In order to describe the degree of the severity of pulmonary fibrosis, use was made of semi-quantitative methods [8]. On the Warrick scale, the basis is on five basic radiological findings, which are graded from 0 to 5. The extent of the changes is graded from 0 – 3, depending on the number of occupied segments in the HRCT. Thirty points is the maximum obtainable score, and 0 is the minimum (with no radiological changes included in the Warrick scale). Depending on the number of points obtained, the fibrosis is classified as mild (< 8 points), moderate (8 – 15 points) or severe (> 15 points). For practical and clinical reasons, a division of the Warrick scale into the Alveolitis Index (AI) and the Fibrosis Index (FI) was proposed [9]. The AI is separated from the Warrick scale in order to differentiate active changes in the course of IDL. The minimum number of points in the AI is 0 and the maximum is 4. The FI is based on points for changes occurring in the lungs; the maximum number of obtainable points in the FI is 26 ([Table 2]).

Statistics

Statistical analysis was performed using the STATISTICA software (version 9.0; Statsoft). The distribution of variables was assessed with the use of the Kolmogorov-Smirnov and W. Shapiro-Wilk tests. The dependencies between two qualitative variables were assessed with the use of the Chi2 test and a test for the differences between two components of the structure. The Mann-Whitney test was used in order to compare the values of the quantitative features. Assessments of the diagnostic power of the method of LUS and individual assessed parameters were carried out using the receiver operating characteristic (ROC) analysis, with the use of the medical set of the STATISTICA program. Items analysed included sensitivity, specificity, true-positive values, true-negative values, false-positive values and false-negative values in order to differentiate severe cases of pulmonary fibrosis from mild and moderate cases. Qualitative variables – frequency of occurrence – were described with the use of the percentage and number of cases, whereas the quantitative variables were described with the help of the median and the range of the highest and lowest quartiles.

Results

Ultrasound features of pulmonary fibrosis

On the basis of the tests carried out, and taking into account the strong dependence between characteristics of pulmonary fibrosis in LUS and HRCT, an original choice was made of the criteria for pulmonary fibrosis in LUS. Evaluation of pulmonary fibrosis is based primarily on the assessment of changes in the pleural line and artefacts. In the course of ILD, there occur three types of ultrasonographic changes: changes within the pleural line, artefacts and consolidations. Below presents the results of study – the most common features of pulmonary fibrosis and criteria of pulmonary fibrosis in [Table 1].

Table 1 Ultrasound features of pulmonary fibrosis: changes in the pleural line, artefacts and consolidations with the incidence in comparison with the control group. 

pleural line
irregularity	ragged		fragmentary		thickened		blurred
100 % (p < 0.001)	98 % (p < 0.001)		77 % (p < 0.001)		23 % (p < 0.001)		52 % (p < 0.001)
artifacts
single B lines		numerous B lines		white lung		Am lines
23 % (p < 0.05)		69.3 % (p < 0.001)		23 % (p < 0.001)		38.5 % (p < 0.001)
consolidation
small (≤ 5 mm)				large (> 5 mm)
33 % (p < 0.001)				13 % (p < 0.001)

Pleural line

The first characteristics of pulmonary fibrosis occurring in LUS are changes within the pleural line. The irregularity of the pleural line, which occurs in all patients with pulmonary fibrosis, is the finding that occurs the earliest. Irregularity of the pleural line occurred in the tested group bilaterally, most often in the lower fields of both lungs (100 % of patients) ([Fig. 2]). A ragged and fragmentary pleural line was accompanied by B line artefacts, observed ≤ 3 per one scan. A thickened pleural line (thickness ≥ 2 mm) is a finding most often encountered in the lower fields of both lungs in patients with diagnosed systemic sclerosis. A blurred pleural line is encountered in severe cases of pulmonary fibrosis ([Fig. 4]). Statistical analysis showed a significant dependence between the occurrence of a blurred pleural line in LUS and the honeycomb in HRCT in the same patients from the group tested (p < 0.005); sensitivity and specificity of blurred pleural line is respectively 0.59 and 0.82.

Fig. 1 Active interstitial lung disease. a HRCT: ground-glass opacity (black arrow). b LUS: white lung (white arrow).

Fig. 2 Mild pulmonary fibrosis. a HRCT: thickened interlobular septa (black, horizontal arrows). b LUS: irregular (horizontal arrow), rugged (vertical arrow up) and fragmentary pleural line (vertical arrow down).

Fig. 3 Moderate pulmonary fibrosis. a HRCT: thickened intralobular septa (black arrow). b LUS: B lines, irregular pleural line, B lines (white arrows).

Fig. 4 Severe pulmonary fibrosis. a HRCT: honeycomb (black arrow). b LUS: blurred pleural line (white arrow).

Artefacts

As a result of the tests conducted, two types of artefacts were observed to occur in patients with confirmed pulmonary fibrosis: B lines and Am lines.

B line artefacts were observed in 92.3 % and specified three types of the observed line B: single B lines (≤ 3 per one scan), numerous B lines (≥ 4 per one scan), white lung. Single B line artifacts (≤ 3) occurred only in the lower fields. Numerous B line artefacts (≥ 4) were observed in 69.3 % of patients from the group tested, mostly in the lower fields ([Fig. 1]). Together with the progress of pulmonary fibrosis, they were also observed in the middle and upper fields. Furthermore, a significant dependence was observed between the presence of numerous B lines (≥ 4) and the presence of a blurred pleural line. Statistical analysis showed that numerous B line artefacts occur when there is a blurred pleural line in LUS (p < 0.001).

White lung is an ultrasonographic finding in which there can be observed numerous B line artefacts merging into one broad vertical artefact, fulfilling the definition of a B line ([Fig. 1]). In the performed statistical analysis, there was shown a dependence between the frequency of occurrence of white lung syndrome (LUS), depending on the occurrence of the characteristic of ground-glass opacity (HRCT), (p < 0.0001); sensitivity and specificity are respectively 0.95 and 0.99. It can, therefore, be accepted that white lung in LUS corresponds to ground-glass opacity syndrome in HRCT. White lung would enable a differentiated diagnosis of active interstitial changes from those in the course of pulmonary fibrosis.

Am line artefacts – to our knowledge – have not yet been described in literature. Am lines were observed in the same localisation as subpleural cysts and emphysematous bullas in HRCT. An Am line artefact definition is: subpleural, horizontal and numerous reverberation artefacts (arranged in parallel one under the other), arising from pleural line and it is running to the edge of screen, wide at the base and narrow at the top, A line does not disappear ([Fig. 5]). Am line is an artefact which is sonomorphologically close to both A line and B line, presenting in the form of a fusion of these two artefacts. Am line, like the former, is an artefact of reverberation and probably arises as the result of the multiple reflection of ultrasound waves between two border surfaces. The first border surface would be that of the pleural line and the second surface would be the wall of emphysematous bulla or subpleural cyst.

Fig. 5 Am line artefact: broad vertical artifact consisting of numerous horizontal artifacts, arranged in parallel one under the other, ending at the lower edge of the screen (arrows).

A hypothesis concerning the mechanism of the origin of Am lines has not been made yet and requires further research. Because of its sonomorphology, the artefact was called an Am line from the English “Multiple A line”. Where Am lines were observed, subpleural emphysematous bullas occurred in HRCT. However, statistical analysis showed a significant dependence between the occurrence of Am lines in LUS and the honeycomb (p = 0.002) and subpleural cysts (p = 0.00 014) in HRCT; sensitivity and specificity Am line coexisting with blurred pleural line is respectively 0.9 and 0.75.

Consolidations

A division of consolidations has been made on account of their length, measured from the pleural line to the lower edge of the subpleural change, into consolidations of small (≤ 5 mm) and large (> 5 mm). Small consolidations were not visible in the HRCT. They have a circular or oval shape and are hypoechogenic ([Fig. 6-a]). Larger consolidations were observed in both the LUS as well as HRCT. Consolidations are hipoechogenne, usually wedge-shaped, rarely round or oval. Within a few centimeters consolidation observed normal vascular pattern. Using Doppler options (PD-pulsed Doppler and CD-color Doppler), showed a typical flow for the pulmonary and bronchial artery branches ([Fig. 6-b]).

Fig. 6 a LUS: Small consolidation, ≤ 5 mm (vertical arrows). b LUS: Large consolidation, > 5 mm, with normal vascular pattern using doppler options (PD-pulsed doppler and CD-color Doppler) (horizontal arrows).

Classification of the degree of severity of fibrosis

The ultrasonographic characteristics of pulmonary fibrosis occur with different frequencies, depending on the degree of severity, as established on the basis of the Warrick scale in HRCT ([Table 2]). Analysis of the test results showed that each significant ultrasonographic finding can occur in each form of pulmonary fibrosis. In connection with this, in the assessment of the degree of the severity of the pulmonary fibrosis, attention was paid to the extent of the observed ultrasonographic findings. Each of the ultrasonographic findings was given points. In order to take into account the extent of the changes observed in LUS, it was decided that to the points given for a particular ultrasonographic finding there would be added points for the number of lung fields in which the given finding occurred. In the created ultrasonographic scale assessing the degree of severity of the fibrosis, descriptions were used analogous to those in the Warrick scale (Fibrosis Index – FI – and Alveolar Index – AI) and the Ultrasound Fibrosis Index (UFI) ([Table 3]). In the case of the Ultrasound Alveolar Index, which, like the Warrick scale, assesses the degree of the progression of the active changes in the lungs, from 2 to 4 points could be obtained. In the case of the Ultrasound Fibrosis Index, 3 to 35 points could be obtained. On the basis of the (UFI) points obtained for each single lung and with reference to the earlier described degree of severity of the pulmonary fibrosis in HRCT (FI), there appeared a statistically significant points dependence for mild, moderate and severe degrees of pulmonary fibrosis in LUS. Mild pulmonary fibrosis occurs when the UFI is 3 – 14 points (FI< 8 points on the Warrick scale) – 24 %, 12/52. Moderate 15 – 20 points (FI 8 – 15 points) – 38 %, 20/52. Severe pulmonary fibrosis in LUS occurs when the patient has 21 – 35 UFI points (FI≥ 15 points) – 38 %, 20/52 ([Table 2]).

Table 2 Semi-quantitative scoring method in HRCT: Warrick et al.

		extent score – segments involved
		1 – 3	4 – 9	> 9
HRCT abnormality	grading	1	2	3
ground-glass opacities	1	2	3	4	alveolar index, max. 4
irregular pleural margin	2	3	4	5	fibrosis index, max. 26
septal or subpleural lines	3	4	5	6
subpleural cyst	4	5	6	7
honeycomb	5	6	7	8

Table 3 Semi-quantitative scoring method in LUS: Buda et al.

		extent score – pulmonary fields
		1	2	3
LUS Abnormality	grading	1	2	3
white lung	1	2	3	4	ultrasound alveolar index, max. 4
irregular pleural line	2	3	4	5	ultrasound fibrosis index, max. 35
B lines (< 3)	3	4	5	6
B lines (≤ 4)	4	5	6	7
blurred pleural line	5	6	7	8
Am lines	6	7	8	9

Discussion

The main aim of the work was the description of the ultrasonographic characteristics of pulmonary fibrosis in the group tested, which was referred to the radiological characteristics of pulmonary fibrosis in HRCT. In the course of ILD, there occur three types of ultrasonographic findings: changes within the pleural line (irregular, rugged, fragmentary, thickened and blurred pleural line), artefacts (single B lines, numerous B lines, white lung and Am lines) and consolidations. In the works quoted, the diagnostics of pulmonary fibrosis is based mainly on an assessment of the pleural line and artefacts.

Numerous and varied findings in the scope of pleural line demonstrate the importance of a detailed assessment of the pleural line. For this purpose, evaluation of the pleural line using a probe liner is necessary. Changes within the pleural line in LUS were observed in many studies [10] [11] [12] [13]. They concerned irregular, fragmentary and thickened pleural line. This study takes into account such US findings as: irregularity, rugged, fragmented, thickened and blurred pleural line. Irregularity, rugged or the fragmentary nature of the pleural line may testify to mild or moderate pulmonary fibrosis. Changes characterised by a blurred pleural line have a particularly significant meaning in the diagnosis of pulmonary fibrosis. In this work, there has been shown a positive correlation between the blurred pleural line in LUS and the honeycomb in HRCT. This has a connection with the description of the degree of severity of pulmonary fibrosis. If the blurred pleural line is extensive (observed in several lung fields), the degree of fibrosis is severe.

A thickened pleural line was observed in two papers [12] [13], in 85 % and 100 % of patients tested, respectively. In this work, the pleural line was thickened in only 23 % of patients of the group tested and this was verified by a conducted measurement of the thickness of the pleural line in HRCT.

The thickened pleural line was predominantly observed in patients with diagnosed systemic sclerosis.

The most frequently occurring artefact is the B line, which by definition is a vertical artefact emanating from the pleural line, running to the edge of the screen and moving with the pleural line [14]. B line artefacts can be found in the numerous pulmonary diseases. B lines are observed in the case of a change in density in the subpleural structures, which are smaller than the length of the ultrasound wave. These structures can be, for example, fluid in the course of cardiogenic/non-cardiogenic pulmonary oedema, ALI/ARDS, viral infections or in the acute phase of ILD, fibrosis of the interlobular septum, and also occupation of the pleura in the course of ILD [15].

The new finding is an Am line artefact. As in a case of blurred pleural line, it has not been described in literature yet. Am lines were observed in the same localisation as subpleural cysts and emphysematous bullas in HRCT. Statistical analysis showed a significant dependence between the occurrence of Am lines (LUS) and the honeycomb and subpleural cysts (HRCT). This caused the LUS sensitivity and specificity in the diagnosis of pulmonary fibrosis has increased significantly.

Subpleural changes occurring in LUS in the course of pulmonary fibrosis are consolidations, which are airless areas of the lungs, thanks to which they become visible in ultrasonographic tests. Small subpleural consolidations most probably are responsible for atelectasis from the tightening of the neighbouring structures of the pulmonary parenchyma in the course of pulmonary fibrosis [16]. In this work, small consolidations were not visible in the HRCT.

Based on the Warrick scale (HRCT) and established criteria of pulmonary fibrosis (LUS), it was possible to evaluate the severity of pulmonary fibrosis in the study group. As a result created: Ultrasound Alveolar Index (UAI) – indicating the severity of active changes and three-tier Ultrasound Fibrosis Index (UFI) – pointing to severity of pulmonary fibrosis. The ability to assess the severity of pulmonary fibrosis, seems to be very important and may facilitate the monitoring of patients with IDL.

Previously, the imaging diagnostics of pulmonary fibrosis was based on chest X-rays and high-resolution computer tomography (HRCT). For more than ten years, there have been individual publications referring to the possibility of using transthoracic lung ultrasonography (LUS) in diagnostics and in the assessment of the degree of pulmonary fibrosis [11] [12] [13] [17] [18]. The groups tested in most studies were heterogenous from the point of view of the confirmed occurrence of the basic disease [11] [13] [17] [18], and only two tests were carried out on groups of patients with diagnosed interstitial diseases of the lung (IDL) in the course of systemic sclerosis [10] [12].

The main limitation of the study is the lack of a universal scale describing the degree of severity of pulmonary fibrosis in the group of patients tested. In order to describe the degree of severity of pulmonary fibrosis, the Warrick scale was accepted as the optimal choice since it took into account the key radiological findings and their extent. The Warrick scale was originally applied in patients with diagnosed pulmonary fibrosis in the course of systemic sclerosis. However, literature describes the application of similar, modified scales in patients with different types of pulmonary fibrosis [9] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32]. Because of the varied bases for pulmonary fibrosis in the group tested and the lack in literature of a single universal scale which could assess the degree of fibrosis in the population tested, it was accepted that the degree of severity of the fibrosis would be assessed with the use of the Warrick scale. The majority of the group tested consisted of patients with a confirmed diagnosis of a systemic connective tissue disease and idiopathic pulmonary fibrosis. It must also be added that the heterogeneity of the group tested, from the point of view of the type of interstitial lung disease, did not affect the assessment of the characteristics of pulmonary fibrosis in ultrasonographic tests.

Pulmonary fibrosis in LUS is based mainly on an assessment of the pleural line and artefacts.

In HRCT, there are, however, visible morphological changes in the lungs. This fundamental difference between imaging methods directly limits a comparison of test results. On account of the large volume of air in the lungs and the fibrous changes, the lungs generate artefacts and the pulmonary tissues are not normally visible [33]. It can be accepted that this is a limitation of the research method. However, it ensues from the results of the tests carried out in this work that ultrasonographic findings in an indirect way present the changes occurring in the lungs in HRCT.

Conclusions

This study demonstrates two new ultrasound findings of pulmonary fibrosis not yet described in the literature: blurred pleural line and Am lines. Presented are a wide range of ultrasound criteria that can be helpful in the differentiation of pulmonary fibrosis with other diseases involved a lung parenchyma. In addition, individual ultrasound findings with an assessment of the extent of lung lesions, allow for more accurate assessment of the severity of pulmonary fibrosis. Transthoracic Lung Ultrasonography (LUS) gives a new outlook on the diagnostic possibilities, non-invasive and devoid of ionizing radiation, of pulmonary fibrosis. The future direction for LUS could be monitoring of patients with IDL.

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