30th April 2024

A 45-year-old woman presents with a sudden onset of severe left flank pain radiating to her groin, accompanied by nausea but no vomiting.

A 45-year-old woman presents with a sudden onset of severe left flank pain radiating to her groin, accompanied by nausea but no vomiting. She reports a history of similar, though less severe, episodes over the past two months. She has no history of urinary tract infections or haematuria. Her medical history is unremarkable, and she takes no medications. Physical examination reveals left costovertebral angle tenderness.

Investigations:

Urinalysis: No blood, WBCs, or nitrites

Serum creatinine: 90 μmol/L (normal range: 45–90 μmol/L)

Which investigation is most likely to confirm the diagnosis?