Mild Pelviectasis
Roya Sohaey, MD
DIFFERENTIAL DIAGNOSIS
Common
Normal, Idiopathic
Trisomy 21 (T21)
Ureteropelvic Junction Obstruction, Early
Less Common
Duplicated Collecting System
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Routine renal views
Axial at level of renal pelvis
Measure anterior-posterior renal pelvis diameter (RPD)
Longitudinal (sagittal or coronal)
Best for renal morphology
Look for calyx distention
Look for ureter distention
Use color Doppler to identify renal arteries
Helpful for small or absent kidneys
Definition of mild pelviectasis (MP)
RPD on axial view
> 4 mm at 14-22 wks
> 5 mm at 22-32 wks
> 7 mm after 32 wks
RPD should be < 1/3 renal diameter
No calyx or ureter distention
Helpful Clues for Common Diagnoses
Normal, Idiopathic
3% of normal fetuses have MP
Often resolves in utero
Look for other anomalies
Trisomy 21 (T21)
1.6x ↑ risk for T21 when finding present
Compare with maternal a priori risk
Look for other T21 markers
Increased nuchal fold
Echogenic bowel
Short femur/humerus
Echogenic intracardiac focus
Ureteropelvic Junction Obstruction, Early
MP can be first sign of ureteropelvic junction (UPJ) obstruction
Unilateral or asymmetric MP
Findings
Progressively ↑ RPD
Calyceal dilatation
Dilatation ends abruptly at UPJ
Helpful Clues for Less Common Diagnoses
Duplicated Collecting System
Separate upper pole and lower pole collecting systems
Variable amount of duplication
Partial: 2 renal pelves fuse proximally
Complete: 2 separate full ureters
Weigert-Meyer rule
Upper pole with ectopic ureter or ureterocele
Ectopic ureter inserts inferior to trigone
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