Foetal renal pelvis dilatation

 Choroid plexus cysts

Choroid plexus cysts (CPCs) are sonographically discrete and small cysts are found in the choroid plexus within the lateral cerebral ventricles of the developing fetus at 14–24 weeks’ gestation. Imaging of the choroid plexus is performed in the transverse plane of the fetal head at the same level that the lateral cerebral ventricle is evaluated (23). The choroid plexus should be inspected bilaterally for the presence of cysts. The probability of a chromosomal abnormality is high when CPCs are associated with any other antenatally detected anomalies, indicating a clear need to offer amniocentesis 

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Figure 4. Sagittal plane of the fetal head shows a choroid plexus cyst.

6.1.1. Summary

Evaluation of the fetal head, including both ventricles and choroid plexus, is considered a part of the routine screening for aneuploidy. Identification of CPCs should be a part of this screening examination. CPCs increase the risk for trisomy 18. Follow-up ultrasound is not necessary for isolated CPCs 

7. Mild pyelectasis

Mild pyelectasis is defined as a hypoechoic spherical or elliptical space within the renal pelvis that measures from 5 mm to 10 mm. The measurement is taken on a transverse section through the fetal renal pelvis using the maximum anterior-to-posterior measurement. Measurements <5 mm are normal, should not be designated as pyelectasis, and should not be reported (25). Pyelectasis may also be referred to as “mild renal pelvic dilatation” or “mild hydronephrosis.” Isolated pyelectasis is seen in 0.7% of fetuses at 16–26 weeks’ gestation. 7.1.1. Summary

Mild pyelectasis is an isolated finding in fetal Down’s syndrome of approximately 2%. In the absence of other risk factors, the chance of Down’s syndrome in the presence of isolated mild pyelectasis remains small and does not justify an invasive diagnostic procedure