Presentation
Dilated renal pelvis bilaterally on routine antenatal scan
Patient Data
Polyhydramnios is noted (AFI= 43) – single pocket 13.5 cm AP diameter.
Grade I right hydronephrosis, with dilated calyces, AP pelvic diameter exceeds 7 mm.
Left renal physiological pyelectasis, AP pelvic dilated 5 mm, with no significant calyceal dilatation.
Note: the correct measures of renal pelvices are that on AP diameter only.
Both kidneys are of normal site, size and shape. They show normal parenchymal echo-pattern with good cortico-medullary differentiation. No focal lesions or renal cysts. No stones or masses.
The right kidney shows
- size = 5.0 x 2.4 cm
- parenchymal thickness= 0.9 cm
- AP pelvic dimension 6 mm ~ 1 cm (grade I dilated pelvicalyceal system on full bladder status), suggestive of non-obstructive dilatation.
- the right pelviureteric junction is intact with no ureterocele or incompetence on ultrasound basis
- smooth transition between the renal pelvis and ureter excluding pelviureteric junction obstruction
The left kidney shows
- size = 5.0 x 2.3 cm
- parenchymal thickness= 0.9 cm
- AP pelvic dimension <2 mm (pelvicalyceal system considered not dilated on full bladder status)
- no calyceal dilatation
No intra-abdominal fluid collection could be noted.
Normal sonographic features of the urinary bladder, with echofree lumen and no mural lesions. No stones or masses. Full volume = 33 cc.
Case Discussion
This case shows how to differentiate fetal hydronephrosis from fetal pyelectasis, the latter shows no calyceal dilatation. Postnatal follow-up is recommended in cases of persistent pyelectasis during third trimester.
Mild right non-obstructive pelvicalyceal dilatation, in this case, may be attributed to the immature pelvicalyceal system and follow up is recommended. The postnatal assessment helps to differentiate obstructed cases that need surgery and non-obstructed cases that need follow up.
- if dilatation doesn't extend to the ureter and the renal pelvis is ballooned, then pelviureteric junction obstruction is diagnosed. Note that on empty bladder scan, the mildly dilated ureter can appear normal and diagnosis of PUJ could be falsely appreciated
- if dilatation increases on follow up, we can suspect vesicoureteric reflux disease and special study will be needed to confirm the diagnosis
- if dilatation decreased on serial postnatal studies, then immature pelvicalyceal system with poorly coordinated peristalsis can be the etiology
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