Fetal Renal Pelvis Dilatation
The ureter is a narrow tube which drains urine from the
kidneys to the bladder (refer diagram to the right). Where the
ureter meets the kidney is called the renal pelvis. This normally
measures less than 4mm at the 18-20 week scan.
In 1-2% of pregnancies the renal pelvis of the baby is dilated
to around 4-10mm. In most cases this is a normal variation
which resolves in later pregnancy or shortly after delivery.
In some babies however, the dilatation may be due to reflux
of urine or rarely obstruction of the ureter. Both of these
conditions are treatable.
Where there is reflux, the urine flushes back up the ureters
towards the kidneys each time the baby passes urine. In the
majority of cases this resolves with time as the baby gets
older and the valve mechanism between the bladder and ureters
mature. With some babies however a short course of antibiotics
is needed and only rarely is surgery performed to correct
this problem.
With obstruction, the ureter may be partially blocked anywhere
along its length from the kidney to the bladder. In the vast
majority of babies the obstruction is mild and surgery is
not required.
Therefore, it is important to follow up all babies with
renal pelvis dilatation, in order to identify those who will
require treatment for related problems in the future. In the
majority of babies with renal pelvis dilatation however such
treatment will not be required, and no long term kidney damage
results.
Kidneys and Ureters
Kidneys with Renal Pelvis Dilatation
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