MR Urography Revealing Renal Physiology: Compensatory Changes in Duplex Kidneys.

OBJECTIVE

To use DCE-MRU to evaluate the physiological differences between duplex kidneys with and without obstructed moieties.

METHODS

Consecutive patients who underwent DCE-MRU studies between January 2019 and March 2021 for evaluation of duplex kidneys were included. The study population consisted exclusively of patients with duplex kidneys (complete ureteral duplication), divided into group A (duplex kidneys with one obstructed moiety, n = 5) and group B (duplex kidneys without obstruction, n = 5). Utilizing prior described techniques, filtration rate (Ft) parameter, which is a measure of renal filtration, was calculated of each renal moiety and compared between the two groups.

RESULTS

Five patients in group A were compared to 5 patients in group B. In group A, the non-obstructed moiety showed relative increased Ft or hyper filtration compared to the normal contralateral side. Those in group B did not show increased Ft.

CONCLUSION

MRU, with its high spatial and temporal resolution and its ability to calculate Ft, provides a non-invasive assessment of renal physiology, and this is the first report of renal compensation occurring within a kidney where one moiety of the kidney demonstrates hyperfiltration, perhaps as a compensation for the stressed obstructive state of the other pole.