MRCP2-4230
A 63-year-old man presents with a persistent cough that has lasted for two months. The cough is unproductive and does not wake him from his sleep. He has also experienced mild breathlessness on exertion, lost some weight, and has a reduced appetite. He has been a smoker of 20 cigarettes a day since he was 18 years old. Additionally, he has been constipated for the past two weeks.
During examination, there were no remarkable findings. He did not have clubbing nor lymphadenopathy. Breath sounds were vesicular with no added sounds. Investigations revealed a haemoglobin level of 126 g/L (130-180), a white cell count of 10.5 ×109/L (4-11), platelets of 160 ×109/L (150-400), serum sodium of 149 mmol/L (137-144), serum potassium of 4.4 mmol/L (3.5-4.9), serum urea of 9.4 mmol/L (2.5-7.5), serum creatinine of 120 µmol/L (60-110), and serum corrected calcium of 3.26 mmol/L (2.2-2.6). The chest x-ray showed right hilar lymphadenopathy.
What is the recommended next investigation?