MSFinals-0400

MSFinals-0400

A 45-year-old woman presented with abdominal swelling, pain and constipation for 5 days. She also complained of generalised aches and pains and feelings of thirst. She had recently been diagnosed with metastatic breast cancer which had recurred. She has a past medical history of irritable bowel syndrome and hypothyroidism. Her regular medications include paracetamol and thyroxine. Her general practitioner (GP) had started her on codeine yesterday. On examination, she appeared dehydrated and had a soft, but mildly distended, abdomen. Thyroid function tested 2 weeks ago was normal.
What is the most likely cause of her presentation?