Case history
A 77-year-old Caucasian female was referred to the renal team with a newly elevated plasma creatinine (288 mmol·L−1) associated with a 2-week history of malaise. Urinalysis demonstrated heavy proteinuria and renal biopsy confirmed the diagnosis of myeloma kidney. She was commenced on pulsed dexamethasone therapy (20 mg for 4 days in succession) before commencing thalidomide 50 mg daily. On day 10 of therapy, she was admitted to hospital with gradually progressive breathlessness for the previous 24 h, present at rest but made worse by exertion. She described a dry cough and ill-defined discomfort bilaterally over the thoracic cage. No haemoptysis was reported. Examination revealed reduced oxygen saturations of 85% on room air and a respiratory rate of 20 breaths·min−1. Auscultation of the chest disclosed bilateral scattered crackles. She had a trace of pitting peripheral oedema only and the jugular venous pressure was not elevated.
A plain chest radiograph was taken and is shown in figure 1.
Chest radiograph
Task 1
How would you interpret the chest radiograph?
Answer 1
There are coarse bilateral patchy infiltrates affecting all the visualised lung fields with relative sparing of the right costophrenic angle. The cardiothoracic ratio on this posterioranterior film is preserved. There is no radiological evidence of congestive cardiac failure. The appearances are in keeping with a diffuse interstitial process, with a wide differential diagnosis. Comparison to a plain chest radiograph taken a month earlier shows these to be new abnormalities.
A blood gas analysis was performed. This revealed an oxygen tension (PO2) of 6.93 kPa (52 mmHg) and carbon dioxide tension (PCO2) of 3.06 kPa (23 mmHg) on an inspired oxygen fraction of 0.21 (room air).
Task 2
What is the alveolar-arterial (A-a) gradient and arterial/alveolar (a/A) ratio? How would you interpret these figures? …
