MSFinals-5021

MSFinals-5021

A 55-year-old male presents to your clinic for a follow-up of his irritable bowel syndrome (IBS). He reports feeling generally well and has not experienced any episodes of diarrhoea for the past 4 months. His medical history includes hypertension and anxiety, and he takes a daily dose of lisinopril, omeprazole and sertraline. Laboratory investigations are ordered as part of this follow-up, and the results are as follows:

Na+ 138 mmol/L (135 – 145)
K+ 4.3 mmol/L (3.5 – 5.0)
Bicarbonate 24 mmol/L (22 – 29)
Urea 5.6 mmol/L (2.0 – 7.0)
Magnesium 0.48 mmol/L (0.7 – 1.0)
Creatinine 101 µmol/L (55 – 120)
Phosphate 0.82 mmol/L (0.8 – 1.4)

What is the most likely cause of these laboratory findings?