MR Urography Revealing Renal Physiology: Compensatory Changes in Duplex Kidneys

Area of Science:

• Nephrology
• Radiology
• Urology

Background:

• Duplex kidneys, a common congenital anomaly, can present with or without obstruction.
• Assessing renal physiology in duplex kidneys is crucial for management.
• Non-invasive methods for evaluating renal function are highly desirable.

Purpose of the Study:

• To investigate physiological differences between obstructed and non-obstructed moieties in duplex kidneys using DCE-MRU.
• To evaluate the filtration rate (Ft) parameter in duplex kidneys with and without obstruction.
• To identify potential compensatory mechanisms within duplex kidneys.

Main Methods:

• Retrospective analysis of DCE-MRU studies in patients with duplex kidneys (complete ureteral duplication) from January 2019 to March 2021.
• Patients were divided into two groups: Group A (one obstructed moiety, n=5) and Group B (no obstruction, n=5).
• Renal filtration rate (Ft) was calculated for each moiety and compared between groups.

Main Results:

• In Group A, the non-obstructed moiety exhibited increased Ft (hyperfiltration) compared to the contralateral normal kidney.
• Group B (duplex kidneys without obstruction) did not show increased Ft in either moiety.
• This suggests a compensatory hyperfiltration in the non-obstructed part of a duplex kidney with unilateral obstruction.

Conclusions:

• DCE-MRU is a valuable non-invasive tool for assessing renal physiology in duplex kidneys.
• Hyperfiltration in the non-obstructed moiety of an obstructed duplex kidney represents a compensatory response.
• This finding is the first report of such intra-renal compensation in duplex systems, highlighting the kidney's adaptive capacity.