Perinatal and infant outcome in prenatally diagnosed hyperechogenic kidneys.

OBJECTIVE Hyperechogenic kidneys are a relatively rare antenatal finding, but they generate significant parental anxiety due to uncertain prognosis. We report perinatal and infant outcomes in a large cohort of fetuses with antenatal hyperechogenic kidneys. METHODS All cases diagnosed prenatally between 2002 and 2017 with hyperechogenic kidneys were assessed in a large tertiary fetal medicine unit. Hyperechogenicity was defined when kidney parenchyma had greater echogenicity than the liver. Pregnancy, pathology and postnatal outcomes were collected from hospital and general practitioner records up to 1 year of age. Abnormal postnatal renal outcome was recorded if there was elevated creatinine beyond 6 months of age, hypertension or major kidney surgery such as nephrectomy. Severe abnormal renal outcome was defined when dialysis or kidney transplant was required at any stage. RESULTS 316 fetuses were identified, mostly bilateral (97%), at a mean gestation of 21 weeks (range 13-37 weeks). The hyperechogenic kidneys were associated with other renal tract abnormalities in 36%, extra-renal structural abnormalities in 32%, abnormal karyotype in 22% and genetic disease in 15% of cases. 139 fetuses did not survive, with 105 terminations of pregnancy (TOP), 5 intrauterine demise (IUD) and 29 early neonatal deaths (NND). The vast majority had complex pathology: only 4% (6/139) had solely hyperechogenic kidneys, 28% (39/139) had multiple renal tract abnormalities alongside hyperechogenic kidneys and over two thirds had extra renal abnormalities (94/139). 177 of 316 cases survived after the first month of life with outcome data available in 126 cases. Of these 126 babies, we identified 3 groups: half had just isolated hyperechogenic kidneys (60; 48%), 56 had other renal structural abnormalities and 10 had additional extra-renal abnormalities. Considering renal outcome alone, kidney function was abnormal in 13 (21%), 10 (18%) and 0 (0%) infants in these three groups respectively, although concurrent pathology clearly affected global outcome in the more complex cases. A neonatal mortality of 1.64% was observed in the isolated renal hyperechogenicity group. The presence of oligohydramnios or abnormal renal volume were not significantly associated with abnormal renal function OR = 2.32 (99% confidence interval 0.54 - 10.02) and OR = 0.74 (99% confidence interval 0.21 - 2.59) respectively. CONCLUSIONS Hyperechogenic kidneys are often complicated by other renal tract and extra-renal abnormalities, aberrant karyotype and genetic disease, and these factors have more of an effect on overall outcome than kidney echogenicity. Renal outcome is good in isolated hyperechogenic kidneys, with 79% having normal renal function. Importantly, for prognostic counselling, all of the children in our non-selected series with isolated echogenic kidneys and normal amniotic fluid levels had normal renal outcome in infancy. This article is protected by copyright. All rights reserved.