MRCP2-1088

MRCP2-1088

A 49-year-old man presents to the clinic with complaints of fatigue and weakness. He has a history of alcoholism and currently consumes 90 units of beer per week. He is taking regular thiamine and appears to be euvolaemic on examination.

The following are his blood test results:

– Hemoglobin (Hb): 122 g/l
– Platelets: 385 * 109/l
– White blood cells (WBC): 8.5 * 109/l
– Neutrophils (Neuts): 4.6 * 109/l
– Lymphocytes (Lymphs): 2.2 * 109/l
– C-reactive protein (CRP): 8 mg/l
– Sodium (Na+): 128 mmol/l
– Potassium (K+): 3.6 mmol/l
– Urea: 3.2 mmol/l
– Creatinine: 38 µmol/l

A paired serum and urine test shows:

– Serum osmolarity: 271 mOsm/kg (normal range 285-295)
– Urine osmolarity: 50 mOsm/kg (low)
– Urinary sodium: 8 mmol/l (low)

What is the most likely diagnosis?