The most important consideration in dealing with fetal hydronephrosis is the overall welfare of the mother and the child, then one should consider the outcome for the kidneys and the bladder.
What the Paediatric Urologist needs to know is if and when intervention is needed. While we await research that enables us to understand fetal hydronephrosis to the level that we can talk of preservation of the renal functioning unit, the nephron, we can look at the cruder markers of renal decline to suggest early intervention.
Most importantly, we need to know the changes over time. And, the specifics of the renal parenchyma, the calyces, the pelvis, ureters and bladder and features of specific pathology, such as the key-hole sign or the presence of a ureterocele. There are also signs of severity, such as oligohydramnios and the eggshell sign, which assist the clinician to consider intervention and its timing.
The various signs that help define the renal pathology and the severity of impact on the renal prognosis will be presented.