Respiratory System - Diffuse Lung Disease and Neoplasms Flashcards

Chronic Obstructive Pulmonary Disease (COPD)

• Definition and Overview: COPD is a common and treatable lung disease characterized by progressive airflow limitation and tissue destruction. It currently stands as the third leading cause of death worldwide.

• Pathophysiology: Chronic inflammation leads to airway narrowing and a decrease in lung recoil. It is associated with structural changes in the lungs resulting from prolonged exposure to noxious particles or gases, with cigarette smoke being the most common culprit.

• Impact: Morbidity and mortality can be decreased through prompt diagnosis and treatment.

• Core Disease Processes: COPD is characterized by two coexisting disease processes that cause the obstructive process:

  • Chronic Bronchitis

  • Emphysema

Chronic Bronchitis

• Definition: A long-term inflammatory condition of the airways characterized by a persistent productive cough.

• Clinical Criteria: The cough must last at least $3$ months per year for $2$ consecutive years without other identifiable underlying causes.

• Pathology: Exposure to lung irritants (primarily smoking) leads to excessive mucus production, resulting in airway obstruction and further inflammation.

• Clinical Manifestations: Persistent productive cough, sputum production, and in severe cases, shortness of breath (SOB), wheezing, and fatigue. It often occurs as part of COPD but can exist independently.

• Imaging Findings:

  • Half of the patients may present with a normal chest radiograph.

  • Demonstrations may include an increase in bronchovascular markings, often referred to as a "dirty chest."

Emphysema

• Definition: A progressive form of COPD characterized by persistent respiratory symptoms and airflow limitation resulting from alveolar or airway damage.

• Pathophysiology: Chronic exposure to noxious gases (mainly cigarette smoke) causes the destruction of alveolar walls, leading to air trapping and impaired gas exchange. This results in lung over-inflation and the formation of large air-filled sacs known as bullae.

• Clinical Manifestations:

  • Shortness of breath (SOB).

  • Chronic cough.

  • Reduced exercise tolerance.

  • Physical sign: Barrel chest.

• Diagnosis: Pulmonary function testing (PFT) via spirometry is the standard. Radiographic studies are not typically indicated for the primary diagnosis but are used to observe complications.

• Imaging (Chest Radiograph):

  • Lung hyperinflation.

  • Flattening of the diaphragm.

  • Increased anterior-posterior (AP) diameter (barrel shape).

  • Elongated, tubular-appearing heart.

• Imaging (CT):

  • Identification of bullae (air-containing cystic spaces), which may be located in subpleural regions.

  • Useful for planning surgical procedures or evaluating patients with malignancy or bronchiectasis.

Asthma

• Definition: A chronic inflammatory respiratory condition characterized by intermittent airflow obstruction and bronchial hyperresponsiveness.

• Pathophysiology: Inflammation causes swelling of the bronchial mucous membranes, excess mucus secretion, and spasm of the bronchial walls.

• Onset and Symptoms: Often presents in childhood. Hallmark symptoms include intermittent dyspnea, cough, and wheezing.

• Triggers:

  • Allergens: House dust, pollen, molds, animal dander, specific fabrics, or foods.

  • Environmental/Physical: Exercise, heat or cold exposure, emotional upset.

  • Infections: Viral infections.

• Imaging:

  • Acute: Increased hyperlucent lung volume, flattening of the diaphragm, and increased retrosternal air space.

  • Chronic: Prominent interstitial markings ("dirty chest").

• Treatment:

  • Bronchodilators.

  • Inhaled steroid drugs.

  • Oral medications to reduce bronchial muscular spasms.

Bronchiectasis

• Definition: A chronic lung disease characterized by the permanent widening (dilatation) of the bronchial airways.

• Pathophysiology: Destruction of the elastic and muscular components of the bronchial wall, often caused by repeated infection leading to bacterial invasion and mucus pooling.

• Clinical Manifestations: Productive cough, dyspnea, intermittent wheezing, hemoptysis, and chest pain (CP).

• Complications: Pneumonia, lung abscess, empyema, septicemia, cor pulmonale, respiratory failure, secondary amyloidosis with nephrotic syndrome, and recurrent pleurisy.

• Imaging:

  • Chest X-ray: Often the initial study; shows coarseness and loss of definition in interstitial markings.

  • CT: More sensitive and specific. Hallmark sign is the "signet-ring sign," produced by multiple dilated bronchi.

• Treatment and Prognosis: Treated with antibiotics. It is rarely curable but is treatable and preventable via vaccination.

Sarcoidosis

• Definition: A multisystem disorder of unknown etiology, most common in young adults and African Americans.

• Pathology: Characterized by noncaseating granulomas in various organs. It is thought to be an exaggerated immune response to an undefined antigen (microbes or environmental factors) in genetically susceptible individuals.

• Major Involvement Sites: Lungs, skin, eyes, and joints.

• Clinical Manifestations: Unexplained dry cough, CP, and SOB; however, many patients are asymptomatic.

• Radiographic Staging:

  • Stage 1: Bilateral hilar lymphadenopathy.

  • Stage 2: Bilateral hilar lymphadenopathy combined with pulmonary infiltrates.

  • Stage 3: Pulmonary infiltrates without bilateral hilar lymphadenopathy.

  • Stage 4: Pulmonary fibrosis.

• Other Imaging Findings: CT is more sensitive for subtle lymphadenopathy. The "donut sign" refers to lymphadenopathy encircling the trachea.

• Treatment: Not indicated for asymptomatic Stage I or II. Corticosteroids are used for significant symptoms or progressive Stages II or III.

Pneumoconiosis

• Definition: A group of occupational lung diseases caused by inhaled fine particles that trigger an inflammatory reaction and lead to irreversible pulmonary fibrosis.

• Types:

  • Silicosis: The world's most prevalent occupational lung disease. Caused by silicon dioxide (crystalline silica) inhalation (foundry work, sandblasting, mining). Usually presents $10$ to $30$ years after exposure. Imaging shows multiple nodular shadows and hilar node enlargement. End-stage treatment is a lung transplant.

  • Asbestosis: Caused by asbestos fibers (construction, shipping). Hallmark imaging finding is pleural involvement (thickened pleura). Calcified pleural plaques are pathognomonic and develop $20$ years post-exposure. Reticulonodular infiltrates can create "shaggy heart borders."

  • Anthracosis (Coal Miner\'s Lung/Black Lung): Caused by coal mine dust. Characterized by dark-colored lung tissue. Can result in weakened musculature and chronic obstructive disease. TB risk is higher due to impaired macrophage function.

Pulmonary Neoplasms

• Solitary Pulmonary Nodule (SPN):

  • Defined as a round/oval area < 3\,cm ($1.2\,inches$) in the lung.

  • Over half are benign (scars, past infections). Malignant nodules may indicate early lung cancer or metastasis.

  • Imaging: CT shows margins (sharp = benign; irregular = malignant). PET shows metabolic activity for malignancy. CXR signs for benignity include "popcorn calcification" and absence of growth over $2$ years.

• Bronchial Adenoma: Rare, slow-growing, low-grade malignancy of the mucous glands. Symptoms include hemoptysis and recurring pneumonia. Often associated with Cushing syndrome.

• Bronchogenic Carcinoma (Lung Cancer):

  • Leading cause of cancer death in the US. Smoking is the most common cause.

  • Small Cell Lung Cancer (SCLC): Often presents as a hilar mass with striking mediastinal widening. Leading cause of Superior Vena Cava (SVC) obstruction.

  • Non-Small Cell Lung Cancer (NSCLC): Includes adenocarcinoma (most common primary lung cancer), squamous cell, and large cell carcinoma.

  • Clinical Syndromes: Pancoast syndrome (shoulder pain) and Horner syndrome (hand muscle atrophy/bony destruction).

• Pulmonary Metastases: The lung is a common site for hematogenous or lymphatic spread from breast, colorectal, or head/neck cancers.

Vascular Diseases of the Lung

• Pulmonary Embolism (PE):

  • Obstruction of pulmonary arteries by a blood clot, commonly originating as Deep Vein Thrombosis (DVT).

  • Diagnosis: D-dimer blood test, CT pulmonary angiography (modality of choice), or V/Q scan (evaluates ventilation vs. perfusion).

  • Treatment: Anticoagulants, thrombolytics, or IVC filter.

• Septic Embolism: An infected thrombus (often from infective endocarditis) travels to the lungs. Imaging shows peripheral wedge-shaped opacities with cavitation.

• Pulmonary Arteriovenous Fistula (PAVM): A congenital anomaly where there is abnormal communication between pulmonary arteries and veins. CT shows a feeding artery and draining vein (pathognomonic). Gold standard for diagnosis is a pulmonary angiogram.

Miscellaneous Lung Disorders

• Atelectasis: Partial or complete lung collapse. Types include Obstructive (resorptive) from tumors or mucus plugs, and Nonobstructive (compression or surfactant-related). Radiographic signs include platelike horizontal lines and displacement of structures toward the affected side.

• Acute Respiratory Distress Syndrome (ARDS): Life-threatening "stiff" lung condition with diffuse alveolar damage and fluid leakage. mortality is approximately $50\%$. Imaging shows ill-defined consolidation occurring $12$ to $24$ hours after initial insult.

• Intrabronchial Foreign Bodies: 4th leading cause of death in US preschool children. Diagnosis gold standard is bronchoscopy. Expiratory chest films show unilateral over-inflation due to a "check valve" mechanism.

• Mediastinal Emphysema (Pneumomediastinum): Air in the mediastinum. Spinnaker sign (elevated thymus) is seen in pediatric patients. Often caused by alveolar rupture.

• Subcutaneous Emphysema: Air in the skin layer. Hallmark physical sign is crepitation (crackling sound) on palpation. X-ray shows a "fluffy" appearance on thoracic borders.

Disorders of the Pleura

• Pneumothorax: Accumulation of air between parietal and visceral pleura.

  • Tension Pneumothorax: A medical emergency where mediastinal structures shift to the contralateral side.

  • Imaging: Hallmark is the visceral pleural line with absent pulmonary markings peripherally.

• Pleural Effusion: Fluid in the pleural space. Imaging shows a blunted costophrenic angle and the "meniscus sign." Thoracentesis is used for fluid removal.

• Empyema: Presence of purulent fluid (pus) in the pleural space. Often a complication of pneumonia.

• Mediastinal Masses:

  • Anterior: "4 T's" (Thymus, Teratoma, Thyroid, Terrible Lymphoma).

  • Middle: Lymphadenopathy or foregut duplication cysts.

  • Posterior: Characteristically neurogenic in nature.

Disorders of the Diaphragm

• Diaphragmatic Paralysis: Loss of innervation from the phrenic nerve. Fluoroscopy shows "paradoxical movement" during a sniff test.

• Eventration of the Diaphragm: Localized elevation of a weakened, thinned portion of the hemidiaphragm without a break in continuity. Most patients are asymptomatic.