Leeds Fetal Medicine Unit Website

Mild Renal Pelviectasis (Mild Renal Pelvis Dilatation)

Definition	Mild renal pelvis dilatation in the absence of other renal tract abnormalities Acceptable dilatation dependent on gestation <4mm up to 14 weeks <5mm 14-22 weeks <6mm 22-32 weeks <8mm 32-40 weeks
Incidence	1:30 pregnancies after 12 weeks
Diagnosis	Ultrasound
Gestation at diagnosis	12 weeks onwards
Known chromosomal or genetic association	Yes, weak association with Down's syndrome (Trisomy 21) increases likelihood by 1.6 of age related or screeing risk (e.g. If triple test risk of Down's is 1:1000 having mild renal pelvis dilatation increases risk to 1:625) May also be caused by reflux of urine from the bladder
Further investigations	If dilatation less than 10mm and adjusted risk of Down's >1:250 no further investigation in pregnancy, but rescan babies kidneys postnatally. If adjusted risk of Down's <1:250 offer karyotype. If dilatation >10mm rescan baby at 32 weeks.
Differential Diaganosis	Any cause of urine flow obstruction e.g. PUJ obstruction or PUV
Prognosis	Very good if isolated and not associated with Down's syndrome
Recurrance risk	Very Low
Research Studies

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