Snapshot A 28-year-old female smoker presents to the emergency room with abdominal pain, nausea, and vomiting and was taken to the operating room that day for emergent laparoscopic appendectomy. On postoperative day 1, she reports that her abdominal pain is tolerable and she is eating solid foods. However, she develops some shortness of breath and her oxygen level drops down to 91% on room air. On physical exam, her breath sounds are clear to auscultation but diminished at the right base. A chest radiograph reveals loss of lung volume on the right. Introduction Clinical definition atelectasis is decreased expansion or loss of volume affecting the lungs from the Greek words ateles and ektasis or “incomplete expansion” Epidemiology Incidence very common Demographics more common in older patients Risk factors surgery lung disease malignancy infection tuberculosis smoking ETIOLOGY Pathogenesis deflation of alveoli to minimal or no volume versus a consolidation, in which alveoli are filled with material obstructive atelectasis circulating blood will reabsorb the gas from alveoli due to obstruction between alveoli and trachea i.e., from foreign body, mucus plugs, or tumor nonobstructive atelectasis loss of contact between visceral and parietal pleura, loss of surfactant, or scarring i.e., acute respiratory distress syndrome, pleural effusion, or pneumothorax i.e., postoperative atelectasis general anesthesia and restricted breathing from pain can cause decreased surfactant activity and decreased end-expiratory lung volume Associated conditions pneumonia post-operative or postpartum fever traditionally associated with postoperative fever however, there is controversy regarding whether or not atelectasis actually causes fever infant respiratory distress syndrome Presentation Symptoms may be asymptomatic if the area affected is small shortness of breath chest pain cough Physical exam decreased oxygen saturation respiratory decreased breath sounds dullness to percussion decreased fremitus may have tracheal deviation towards the affected side (with volume loss) associated with severe atelectasis imaging Chest radiography indication evaluate for other lung pathologies like pneumonia or pneumothorax findings opacification of part of the lung loss of volume of the lung ipsilateral shift of mediastinum (with volume loss) Bronchoscopy indication when the etiology of obstructive atelectasis is unclear from chest radiograph or chest CT Studies Diagnostic testing diagnostic approach evaluate initially with chest radiograph evaluate with bronchoscopy only when obstruction is suspected Differential Pneumothorax distinguishing factor physical exam will reveal hyperresonance to percussion trachea may deviate away from the lesion chest radiograph shows pneumothorax DIAGNOSIS Making the diagnosis based on clinical presentation and imaging Treatment Management approach treatment is specific to the underlying cause and aims to re-expand the lung use of incentive spirometry may prevent atelectasis in post-operative patients chest physiotherapy may help Other treatments continuous positive airway pressure or mechanical ventilation for patients with hypoxemic respiratory failure antibiotics for infection dornase alfa (DNase) may help mucus clearance bronchodilators may help mucus clearance and ventilation Complications Pneumonia Empyema Bronchiectasis Respiratory failure