Tracing the flow of your urine in real time

The posterior (back) and anterior (front) images of a Tc-99m DMSA scan of a five-year-old child shows that only the left kidney is present, with no kidney where the right one should be (indicated by the red arrows). The scan also shows the single kidney has a wedge-like defect (white arrowhead), indicating a scar due to a previous infection. — Photos: Dr ALEX KHOO CHEEN HOE

It is fairly easy to record things that move around us, but what about things that move inside of us?

Take urine, for instance – how can we visualise the flow of urine inside us in real time?