Patient had severe right upper lobe pneumonia and developed hypoxic respiratory failure requiring  invasive ventilatory support in ICU. Subsequently patient developed hydropneumothorax requiring chest drain insertion. Sputum culture showed growth of Strep pyogenes. 

Hydropneumothorax is defined as concurrent presence of pneumothorax and hydrothorax. It classically shows an air-fluid level on erect CXR. One of the main differential diagnosis to consider is pyopneumothorax, also commonly known as infected hydropneumothorax. The main differentiating features distinguishing pyopneumothorax from hydropneumothorax is he presence of thick pleural lining. Further imaging investigations can also be undertaken to differentiate the two conditions such as ultrasound and CT.