The Early Development of the Fetal Kidney-an in Utero Sonographic Evaluation Between 13 and 22 Weeks' Gestation

Objectives: To establish a nomogram for early fetal kidney development during early gestation.

Methods: The study is a prospective, cross-sectional evaluation of 275 male and female fetuses between 13 and 22 weeks in normal singleton pregnancies. Measurements of fetal kidney length were performed by high resolution transvaginal ultrasonography between 14 and 17 weeks' gestation, and by transabdominal ultrasonography beyond 18 weeks' gestation.

Results: Adequate kidney length measurements were obtained in all 275 normal fetuses as well as in six fetuses with urinary tract anomalies. Kidney length as a function of gestational age was expressed by the regression equation: (square root) kidney length (mm) = -11.66 + 1.52 x gestational age (weeks). The correlation coefficient, r = 0.983 was found to be highly statistically significant (p < 0.0001). The normal mean and the 90% prediction limits were defined. Four cases with single kidney and two cases with posterior urethral valve had kidney length above the 95% upper limit.

Conclusion: The present data offer a normal range of fetal kidney length from early stages of gestation that may allow intrauterine assessment of its development. It may also be helpful in the early prenatal diagnosis of renal abnormalities.