ICD-10 Code: J43.9

Emphysema is a pathologic diagnosis representing one of the two main components of COPD (the other being chronic bronchitis). It involves irreversible destruction of alveolar walls and enlargement of air spaces, leading to loss of elastic recoil, airway collapse during expiration, air trapping, hyperinflation, and impaired gas exchange. The primary cause is cigarette smoking (accounts for 80-90% of cases), though alpha-1 antitrypsin deficiency is an important genetic cause in nonsmokers. Pathophysiologic subtypes include: (1) Centrilobular emphysema—affects respiratory bronchioles preferentially, associated with smoking, upper lobe predominant; (2) Panlobular emphysema—uniformly affects entire acinus, associated with alpha-1 antitrypsin deficiency, lower lobe predominant; (3) Paraseptal emphysema—affects distal acinus/alveolar ducts, associated with spontaneous pneumothorax. Code J43.9 is used when "emphysema" is documented without subtype specification. Clinical presentation includes progressive dyspnea on exertion, reduced exercise tolerance, and minimal cough (in pure emphysema without chronic bronchitis). Physical exam shows barrel chest, hyperresonance to percussion, decreased breath sounds, pursed-lip breathing, and use of accessory muscles. Chest imaging reveals hyperinflation, flattened diaphragms, increased retrosternal air space, and bullae. Diagnosis confirmed by spirometry showing irreversible airflow obstruction (post-bronchodilator FEV1/FVC <0.70) with reduced DLCO (diffusing capacity).