ABSTRACT

With refinement in ultrasound technology over the past 15 years, a near epidemic of hydronephrosis identified antenatally has created an unparalleled management dilemma for paediatric urologists. At issue is the concept, still extant despite natural history studies to the contrary,1-3 that hydronephrosis is a pathological process, caused by a partial obstruction that was present in utero and is possibly still present after birth, that damages the kidney or reduces its functional potential. Although not well appreciated among paediatric urologists, a direct challenge to this concept was clearly posed by studies4-12 on the physiology of partial obstruction-induced hydronephrosis and on the physical attributes and behaviour of the partially obstructed renal pelvis. When these are reviewed with a contemporary eye towards hydronephrosis in the newborn, they point to exactly the opposite conclusion: hydronephrosis is not a pathological process but actually a compensating physiologic mechanism by which the renal pelvis protects the kidney from high pressures and renal damage. In fact, hydronephrosis, especially when it involves the already stretchy and distensible pelvis of the infant appears to not only be uniquely beneficial but to paradoxically mislead the unwary in to misdiagnosing obstruction. Herein we present a counterargument which by describing the physiological bases of these beneficial and protective effects of hydronephrosis has important implications for a more contemporary clinical management of this challenging group of patients.