A 23 year old nurse presents with a history of blood in her urine and intermittent flank pain for one month. She has no fever and a course of Nitrofurantoin from her GP did not improve her symptoms. She has no loose stools and examination and observations are normal other than some mild abdominal tenderness. On questioning, she mentions that she travelled to Malawi for a placement when she was a student but took Malaria prophylaxis.
Which of these is the most likely diagnosis?