Diffuse lung disease (DLD), also known as diffuse interstitial lung disease (ILD), is a collective term for a diverse group of pulmonary disorders that primarily affect the interstitium—the connective tissue framework that supports the alveoli¹. The alveoli are the tiny air sacs in the lungs responsible for gas exchange, where oxygen is absorbed into the bloodstream, and carbon dioxide is expelled². In healthy lungs, the alveoli expand fully during inhalation, facilitating efficient oxygenation and carbon dioxide removal. However, in cases of DLD, the interstitium becomes inflamed and stiff, leading to fibrosis (scarring) and thickening of the alveolar walls. These pathological changes progressively impair the ability of the lungs to function, causing significant respiratory dysfunction and reducing overall lung capacity³.

The clinical manifestations of DLD are often nonspecific, which poses challenges for timely diagnosis. Patients frequently present with symptoms such as dyspnea (shortness of breath), a persistent dry cough, and generalized fatigue.

 As the disease advances, the severity of these symptoms escalates, and additional complications may emerge. For instance, cyanosis (bluish discoloration of the skin, lips, or fingernails) may develop due to reduced oxygen levels in the blood⁴. Other signs include clubbing of the fingers, a condition associated with chronic hypoxia, and in some cases, cor pulmonale, which refers to right-sided heart failure resulting from long- term pulmonary hypertension.

Diffuse lung diseases are also characterized by the progression of lung tissue damage, which may include granuloma formation in conditions like sarcoidosis or specific histopathological patterns such as usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP). The presence of such patterns aids in narrowing down potential diagnoses⁶.

Diffuse lung diseases (DLD) encompass a diverse group of conditions that significantly impact pulmonary function, contributing to substantial morbidity and mortality across age groups. These diseases primarily involve the pulmonary interstitium, distal airspaces, or peripheral airways, resulting in impaired gas exchange and progressive respiratory decline. The significance of DLD lies in its wide spectrum of presentations, ranging from acute neonatal disorders to chronic, debilitating conditions in adults, each requiring distinct diagnostic and therapeutic approaches⁷.

Patients undergoing High-Resolution Computed Tomography (HRCT) of the lung will be positioned on a flat examination table that moves in and out of a circular gantry of the CT scanner. Unlike conventional contrast-enhanced CT scans, HRCT does not require intravenous (IV) contrast administration. The patient will be appropriately positioned to ensure optimal imaging of the chest region.

The HRCT scanner is an open system, and the patient will not be enclosed in a tube or confined space. Throughout the procedure, the technologist will maintain continuous visual and auditory communication with the patient.

Patients will be instructed to remain completely still during the scan and may be asked to hold their breath at specific intervals to minimize motion artifacts. The total duration of the procedure will range from 0.5 to 01 second, depending on patient compliance and the scanning protocol.

INCLUSION CRITERIA

Patients fulfilling the following criteria will be included in the study:

1. Male or female patients referred for HRCT lung evaluation.
2. Patients aged above 18 years.

EXCLUSION CRITERIA

Patients meeting any of the following criteria will be excluded from the study:

1. Pregnant women, due to potential radiation hazards to the fetus.
2. Patients diagnosed with lung tumors, as the pathology may interfere with the assessment of lung parenchyma.
3. Patients with tuberculosis (TB), as the disease process and associated lung changes may not align with the objectives of the study

Table 1: Demographic Profile (Age, Gender)

The basic demographic characteristics of the study population. The mean age of the patients was found to be 64.38 ± 13.73 years, suggesting that diffuse lung diseases are predominantly seen in the elderly population. Gender distribution was observed to be equal, with 50% males and 50% females. The demographic data lays a foundational understanding for the epidemiology of diffuse lung disease and highlights the need to consider age and gender factors while classifying and analyzing disease patterns.

Table 2: Clinical Symptom Distribution in Diffuse Lung Disease

The clinical symptomatology associated with diffuse lung disease is outlined. A cough was reported universally among all patients (100%), with 91.66% experiencing frequent cough and 8.33% reporting occasional symptoms. Shortness of breath was present in 98.33% of the cases, further highlighting the respiratory compromise. Additional findings included a history of occupational exposure (31.66%) and a family history of lung disease (45%).

Table 3: Clinical Diagnosis Distribution

The clinical diagnoses made based on HRCT findings and clinical correlation. The most common diagnosis was Usual Interstitial Pneumonia (UIP), accounting for 36.66% of cases, followed by Non-Specific Interstitial Pneumonia (NSIP) (30%), Respiratory Bronchiolitis-associated Interstitial Lung Disease (RB-ILD) (8.33%), and Sarcoidosis (8.33%). Other less frequent diagnoses included Hypersensitivity Pneumonitis (HP), Connective Tissue Disease-Associated ILD (CTD-ILD), Cryptogenic Organizing Pneumonia (COP), and LAM.

Table 4: HRCT Findings Pattern among Smokers and Non-Smokers

Conversely, traction bronchiectasis and tree-in-bud patterns were observed more frequently among non-smokers, with traction bronchiectasis affecting over 93% of non-smokers compared to 81.82% of smokers. Tree-in-bud appearance, typically linked with endobronchial spread of infection or inflammatory bronchiolitis, was slightly more common in non-smokers. Additionally, non-smokers demonstrated a higher incidence of free pleural fluid, albeit in small numbers. This radiological evaluation underscores the differing pathological mechanisms in smokers versus non-smokers and supports the hypothesis that smoking contributes to distinct morphological lung changes. The comparative HRCT assessment aids in better classification and etiological understanding of diffuse lung diseases, aligning with the study’s objective of pattern- based differentiation using imaging.

The present cross-sectional observational study was conducted to evaluate the role of High- Resolution Computed Tomography (HRCT) in the diagnosis and classification of Diffuse Lung Diseases (DLDs) among 60 patients at a tertiary care hospital in rural central India. The findings of this study reaffirm the pivotal role of HRCT in the early detection, accurate classification, and management       planning              of various            DLD       subtypes⁸.

In our study, the mean age of the study population was 64.38 ± 13.73 years, indicating a higher prevalence of DLD in the elderly, consistent with prior studies such as those by Raghu et al. (2011) and Wells et al. (2008), who observed a similar age predilection in idiopathic interstitial pneumonias. Gender distribution was equal, which contrasts with certain previous reports that suggested a slight male predominance, possibly reflecting regional or population-specific differences^9-10.

Cough and shortness of breath were the most commonly reported symptoms, present in nearly all patients (100% and 98.33% respectively), aligning with established literature where these symptoms are considered hallmark clinical features of DLDs. Additionally, a significant proportion of patients (31.66%) reported occupational exposure and 45% had a family history of lung disease, emphasizing the multifactorial etiology of interstitial lung disorders, as highlighted by   previous   works   (Lynch   et   al.,   2005;   Soares   et   al.,   2013)¹¹.

High-Resolution Computed Tomography (HRCT) has proven to be an invaluable tool in the evaluation and classification of diffuse lung diseases. Through this cross-sectional observational study involving 60 patients at a tertiary care hospital in rural central India, HRCT successfully identified a broad spectrum of pulmonary pathologies. The predominant age group affected was the elderly, with an equal gender distribution. Clinical symptoms like persistent cough and dyspnea, along with risk factors such as smoking and occupational exposure, were consistently correlated           with       HRCT    findings.

1. American Thoracic Society/European Respiratory Society. International Multidisciplinary Consensus Classification of the Idiopathic International Pneumonias. Am J Respir Crit Care Med. 2002;165:277-304.
2. Flaherty KR, King TE, Jr, Raghu G, Lynch JP, III, Colby TV, Travis WD, Gross BH, Kazerooni EA, Toews GB, Long Q, et al. Idiopathic interstitial pneumonia: what is the effect of a multidisciplinary approach to diagnosis? Am J Respir Crit Care Med. 2004;170:904–910.
3. Nicholson AG, Addis BJ, Bharucha H, Clelland CA, Corrin B, Gibbs AR, Hasleton PS, Kerr KM, Ibrahim NBN, Stewart S, et al. Inter-observer variation between pathologists in diffuse parenchymal lung disease. Thorax. 2004;59:500–505.
4. Thomeer M, Demedts M, Behr J, Buhl R, Costabel U, Flower CDR, Verschakelen J, Laurent F, Nicholson AG, Verbeken EK, et al. Idiopathic Pulmonary Fibrosis International Group Exploring N-Acetylcysteine I Annual (IFIGENIA) Study Group. Multidisciplinary interobserver agreement in the diagnosis of idiopathic pulmonary fibrosis. Eur Respir J. 2008;31:585–591.
5. Poonam Vohra, Evaluation of diffuse lung diseases by high resolution computed tomography of chest: International Journal of Research in Medical Sciences /VOL. 5 NO. 4 (2017): APRIL 2017
6. Nishino Mizuki, A Practical Approach to High-Resolution Computed tomography of Diffuse Lung Disease”: https://pubmed.ncbi. nlm.nih .gov/23410907/
7. Brett M. Elicker, The role of high-resolution computed tomography in the follow-up of diffuse lung disease: European Respiratory Review 2017 26: 170008; DOI: 10.1183/16000617.0008- 2017.
8. Wells AU, Desai SR, Rubens MB. et al. Idiopathic pulmonary fibrosis: a composite physiologic index derived from disease extent observed by computed tomography. Am J Respir Crit Care Med. 2003;167(7):962–9.
9. Best AC, Meng J, Lynch AM. et al. Idiopathic pulmonary fibrosis: physiologic tests, quantitative CT indexes, and CT visual scores as predictors of mortality. Radiology. 2008;246(3):935–40.
10. Sumikawa H,Johkoh T,ColbyTV. et al. Computed tomography findings in pathological usual interstitial pneumonia: relationship to survival. Am J Respir Crit Care Med. 2008;177(4):433–9.
11. Talmadge E. King. Clinical Advances in the Diagnosis and Therapy of the Interstitial Lung Diseases. Jr.Am J Respir Crit Care Med 2005; 172: 268- 279.