Fetal bilateral hyperechogenic kidneys: Prenatal progression and long-term postnatal outcome

To determine the prenatal progression and long-term outcome of fetal bilateral hyperechogenic kidneys (HK).

Retrospective study 2005-2016. Fetal/maternal demographics, scan findings, postnatal diagnoses and outcomes were collected from electronic patient records and post-mortem reports.

Data available for 65 out of 72 fetuses with bilateral HK. Forty-five (69 %) had normal amniotic fluid index (AFI); of these, 23 had isolated HK and all survived the neonatal period. The remaining patients with normal AFI had other renal and multi-system anomalies; diagnoses included 13 trisomies and genetic syndromes - only one patient with suspected bladder outlet obstruction survived. Of 20 pregnancies with reduced AFI, HK were isolated in 5 fetuses, and only one survived (diagnosed with 17q12 microdeletion). The remaining 15 fetuses had multisystem anomalies and none survived; diagnoses included Meckel-Gruber Syndrome and Dandy-Walker malformation. Survival with bilateral HK and oligohydramnios was 5 %. Overall survival was 25/65 (38 %); follow-up data was available for 23 patients. HK resolved in 17 (74 %) and persisted in 6 children, who were followed-up for median 15 years (4-19 years). Of these, 3 patients developed bilateral renal cysts and were diagnosed with HNF1b/17q12 deletion kidney disease (one patient is in CKD2a, whereas the rest have normal renal function). The remaining patients were found to have a PKD1 variant; bilateral renal cysts (lost to follow-up before a genetic diagnosis) and a unilateral hydronephrosis: all have normal renal function.

Isolated HK with normal AFI is associated with survival past the neonatal period and normal renal function in most cases (96 %). As normal kidney function may be due to glomerular hyperfiltration in early childhood to teenage years, long-term follow up is advisable, in particular for those with a genetic diagnosis that predisposes to chronic renal impairment in adulthood (HNF1b, 17q12 deletion in this study). HK in the presence of reduced AFI carries a poor prognosis, with only 5 % survival (this patient had 17q12 deletion related kidney disease). Overall survival in this study was 38 % in the first year and 34 % long-term.