A 39-year-old man presents with a history of poor urine output over the past 2 days. Other
than bloody diarrhoea about a week ago, he has no other significant history. There were
several other patients who had presented with bloody diarrhoea in the last 24 h and who had
attended the same eatery that he had attended. He takes no regular medications.
On examination, his blood pressure is 150/90 mmHg, with a heart rate of 110 bpm.
Which would be useful for establishing the cause of his acute kidney disease kidney disease?