A 72-year-old woman post-abdominal surgery develops fever and cough on postoperative day 3. Chest X-ray shows a wedge-shaped opacity in the left lower lobe with the apex pointing toward the hilum, elevated left hemidiaphragm, and mediastinal shift toward the left. The clinical picture is suspicious for left lower lobe collapse. Which investigation would be most appropriate to confirm the diagnosis and assess for an obstructing lesion?

Explanation

## Confirming Atelectasis and Excluding Obstruction ### Clinical Context Postoperative atelectasis is common, but the presence of fever and the radiological appearance raise concern for an obstructing lesion (mucus plug, aspiration, malignancy) or underlying infection. The investigation must both confirm atelectasis and assess the bronchial tree. ### Why CT Chest with IV Contrast is Optimal **Key Point:** CT chest with intravenous contrast is the investigation of choice for confirming atelectasis and simultaneously evaluating for an obstructing endobronchial lesion or underlying pathology. **High-Yield:** CT provides: 1. **Confirmation of atelectasis**: Demonstrates volume loss, bronchial crowding, mediastinal shift, and characteristic wedge shape 2. **Assessment of airways**: Visualizes bronchial narrowing, mucus impaction, or endobronchial masses 3. **Evaluation of lung parenchyma**: Detects pneumonia, abscess, or other complications 4. **Mediastinal assessment**: Rules out lymphadenopathy or masses causing obstruction ### Radiological Features on CT Confirming Atelectasis | Finding | Significance | |---------|---| | **Wedge-shaped consolidation** | Characteristic shape of lobar/segmental collapse | | **Bronchial crowding** | Vessels and bronchi compressed together | | **Mediastinal shift** | Toward the collapsed lobe (volume loss) | | **Elevated hemidiaphragm** | Indicates volume loss | | **Air bronchograms** | Typically absent in pure atelectasis | | **Patent bronchus sign** | If visible, suggests no complete obstruction | ### Clinical Pearl In a postoperative patient with fever and suspected atelectasis, CT is superior because it can identify treatable causes: retained secretions (which may respond to physiotherapy/suctioning), aspiration (requiring airway management), or an obstructing lesion (requiring bronchoscopy or intervention). IV contrast enhances vascular and mediastinal structures, improving diagnostic accuracy. ### Why Other Investigations Are Suboptimal **Flexible bronchoscopy with BAL (Option 0):** - Therapeutic in mucus plug obstruction, but not diagnostic - Does not visualize the extent of collapse or rule out external compression - Should be reserved for cases where CT suggests a treatable endobronchial lesion **V/Q scan (Option 2):** - Assesses ventilation-perfusion mismatch; not specific for atelectasis - Does not visualize anatomy or identify obstructing lesions - Rarely used in modern practice for this indication **Transthoracic ultrasound (Option 3):** - Limited by air-filled lungs; poor visualization of parenchyma - Cannot assess airways or mediastinum adequately - Not appropriate for this clinical scenario **Mnemonic: CT CONFIRMS — **C**ross-sectional **T** imaging **C**onfirms **O**bstruction **N**ature **F**inds **I**nternal **R**esolution **M**anagement **S**trategy**