Prenatal compensatory renal growth in unilateral renal agenesis

Objective: To create nomograms of fetal renal compensatory growth in cases of unilateral renal agenesis (URA). Methods: A retrospective study of fetuses with isolated URA diagnosed prenatally, and confirmed postnatal was performed. Results: Seventy-four fetuses with isolated solitary kidney were included in the study. A total of 134 measurements of the kidney's length were performed. Ninety five of them were studied longitudinally (2–6 measurements each). The raw values of the compensatory kidney demonstrated a significant correlation with gestational age (Pearson correlation coefficient 0.901, p < 0.001). A quadratic/cubic regression curve, both, described best this relationship, −26.400 + 3.004*GA, −0.026*GA² (r² = 0.819). The Z score between the mean predicted compensatory kidney's length, per week of gestation, and the mean predicted values of normal kidney length as previously published in the literature, progressively increased during pregnancy (cubic r² = 0.946 and 0.260). Conclusion: Cases of URA show a unique growth pattern of the single kidney from second trimester to term. Postnatal renal function is dependent on adequate intra-uterine compensatory growth; the presented nomograms provide insight into renal prognosis and add paramount information to the multidisciplinary prenatal counseling of the future parents.