Round Opacity Greater than 5 mm in Diameter

CLINICAL DIAGNOSTIC MANUAL

A round opacity larger than 5 mm in diameter, also known as a pulmonary nodule, can be detected on chest X-ray or computed tomography (CT) scans.

This radiological finding can have various causes, ranging from infections and inflammatory processes to malignant neoplasms. Identifying the underlying cause is essential for appropriate patient management, as some of these conditions may require urgent and specific interventions.

Pathology	Clinical Symptoms and Signs	Suspected Diagnosis	Confirmatory Diagnosis
Bronchogenic carcinoma	Persistent cough, haemoptysis, weight loss, chest pain	History of smoking, chronic symptoms	Chest X-ray, chest CT, bronchoscopic biopsy, PET scan
Pulmonary metastasis	Cough, dyspnoea, chest pain, symptoms of primary cancer	History of cancer in another organ, respiratory symptoms	Chest X-ray, chest CT, needle biopsy, PET scan
Round pneumonia	Fever, productive cough, dyspnoea, chest pain	History of acute respiratory infection	Chest X-ray, chest CT, sputum culture
Lung abscess	Fever, productive cough with purulent sputum, chest pain	History of respiratory infection, severe symptoms	Chest X-ray, chest CT, sputum culture, bronchoscopy
Tuberculous granuloma	Persistent cough, fever, night sweats, weight loss	History of tuberculosis exposure, chronic symptoms	Chest X-ray, chest CT, tuberculin test, sputum culture
Rheumatoid nodule	Cough, dyspnoea, chest pain, joint symptoms	History of rheumatoid arthritis, subcutaneous nodules	Chest X-ray, chest CT, pulmonary function tests, rheumatoid serology
Histoplasmosis	Fever, cough, dyspnoea, chest pain	History of exposure to birds or bats, respiratory symptoms	Chest X-ray, chest CT, serological tests, sputum culture
Wegener’s granulomatosis	Fever, cough, dyspnoea, haemoptysis, systemic symptoms	History of vasculitis, multisystem symptoms	Chest X-ray, chest CT, tissue biopsy, ANCA test
Klebsiella pneumonia	High fever, productive cough, purulent or haemoptyic sputum	History of respiratory infection, severe symptoms	Chest X-ray, chest CT, sputum culture
Hydatid cyst	Cough, dyspnoea, chest pain, allergic symptoms	History of exposure to farm animals, respiratory symptoms	Chest X-ray, chest CT, serological tests, abdominal ultrasound
Pulmonary arteriovenous malformation	Dyspnoea, haemoptysis, chest murmurs, cyanosis	History of unexplained cyanosis, respiratory symptoms	Chest X-ray, chest CT, pulmonary angiography, echocardiography
Benign pulmonary tumours	Cough, dyspnoea, chest pain	History of incidental pulmonary nodule, respiratory symptoms	Chest X-ray, chest CT, needle biopsy, imaging follow-up
Other causes	Variable depending on the aetiology, may include cough, dyspnoea, chest pain, fever	Clinical history and relevant background	Chest X-ray, chest CT, specific tests depending on suspected aetiology