Key Role of HRCT in Diagnosing Idiopathic Pulmonary Fibrosis

Introduction

Idiopathic pulmonary fibrosis is a specific form of chronic progressive interstitial pneumonia of unknown etiology. It is a rare disease affecting only the lung tissue with a very poor prognosis. It occurs in adults over 50 years old, with an average survival time from diagnosis of a few years. In recent years, drugs from the group of so-called antifibrotics, which slow down the disease's progression, have helped improve quality and length of life.

However, the key to successful treatment is early diagnosis of the disease, which relies on a combination of clinical and radiological findings. The method of choice within imaging methods is high-resolution chest computed tomography. Hochheger et al. state that the combination of clinical and radiographic findings allows the diagnosis to be determined in approximately 67% of patients. Evaluating changes on HRCT requires significant experience; specialized radiological seminars are held in the Czech Republic for this purpose, and consulting with experienced radiologists through the web application IPFchecker also helps diagnose idiopathic pulmonary fibrosis.

Diagnosis using HRCT

HRCT, as mentioned earlier, represents the basic diagnostic method. The use of this modality in the diagnostic process has greatly reduced the need to perform lung biopsies − for example, Sverzellati states that the examination alone is sufficient for diagnosis in about half of the patients. The method can also be used to assess the progression of the findings, although this approach is not routinely recommended.

The image of idiopathic pulmonary fibrosis is characterized by symmetrical bilateral reticulations, changes in lung architecture, traction bronchiectasis, and honeycomb remodeling. These changes are most pronounced at the lung bases and subpleurally; findings in these locations are among the basic diagnostic criteria. Another change − although nonspecific − associated with idiopathic pulmonary fibrosis is mediastinal lymphadenopathy (nodes typically measuring up to 15 mm), described in more than 70% of patients.

Conversely, the absence of active changes, such as extensive ground-glass opacities, infiltrates, and granulomas, is characteristic of the examination. The presence of ground-glass densities may indicate the presence of potentially reversible acute inflammation, microscopic honeycomb remodeling below the resolution level of HRCT, or complications such as infection or drug reactions. Consolidation and nodules are not characteristic of idiopathic pulmonary fibrosis. When present, it is necessary to investigate complications such as tumors or tuberculosis; pulmonary ossification can also be a rare cause.

Application usage in diagnosis

In the diagnosis of idiopathic pulmonary fibrosis, the free web application IPFchecker can be used as a tool for the early detection of patients. The web application, in addition to a calculator evaluating the possibility of the disease based on clinical findings and HRCT findings, also includes the option to consult HRCT findings with a radiologist from a specialized center.

Conclusion

Idiopathic pulmonary fibrosis is a rare progressive disease of lung tissue with a poor prognosis. Early diagnosis and administration of drugs from the group of antifibrotics can extend life expectancy. The diagnosis is based on a combination of clinical and radiological findings. The basic diagnostic method is HRCT, which, along with the clinical picture, suffices for the diagnosis in nearly three-quarters of patients.

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Sources:
1. Brožík J. HRCT image of idiopathic interstitial pneumonias. Case Studies in Allergology, Pneumology, and ENT 2007; 1: S11−S13.
2. Sverzellati N. Highlights of HRCT imaging in IPF. Respir Res 2013; 14 (Suppl. 1): S3, doi: 10.1186/1465-9921-14-S1-S3. 
3. Hochheger B., Marchiori E., Zanon M. et al. Imaging in idiopathic pulmonary fibrosis: diagnosis and mimics. Clinics (Sao Paulo) 2019 Feb 4; 74: e225, doi: 10.6061/clinics/2019/e225.