11th January 2024

A 23-year-old girl presents to the emergency department with acute pain during a gastrointestinal illness.

A 23-year-old girl presents to the emergency department with acute pain during a gastrointestinal illness. She describes the pain as both pleuritic and epigastric in origin and reports vomiting up to 20 times/day for the past 48 hours. She appears clinically unwell with epigastric tenderness and retrosternal discomfort on examination, alongside reduced air entry at the left base. She has a respiratory rate of 28 breaths/min, oxygen saturations 92% on 4L oxygen via nasal cannula, HR 123bpm and blood pressure 80/50mmHg. A chest x-ray shows evidence of a left-sided pleural effusion, and she is transferred to the high-dependency unit, where a diagnostic aspiration is carried out. 

Investigations: 

Pleural fluid protein level: 37g/L 

Pleural fluid LDH level: 463 units/L 

Pleural fluid M, C + S: Negative culture and gram staining, neutrophil predominance. 

Pleural fluid amylase: 160 U/L. 

What is the most likely cause of her pleural effusion?

Select the SINGLE most appropriate option from the list below. Select ONE option only.