Prenatal Sonographic Diagnosis of Unilateral Fetal Renal Agenesis

Abstract

The fetal urinary tract lends itself to prenatal sonographic evaluation. Kidneys may be identified from as early as 12 weeks to 14 weeks, and are seen clearly by approximately 18 weeks to 20 weeks. 1 Green and Hobbins, while recently discussing abdominal ultrasound examination of the first trimester fetus with current improving technology, found that in 60% of cases kidneys can be visualized by 10 weeks menstrual age (MA), while 98% will be seen at 11 weeks and 100% will be visible by 12 weeks. 2 Moreover, the bladder can be identified in 50% of cases by 12 weeks, MA. 2 As a result of these reports, normograms have been established for assessing fetal kidney size in normal gestation. 1–3 When, in early gestation, one kidney is not seen but a normal kidney and appropriate amniotic fluid are visualized, we have not routinely brought the patient back for rescan to visualize the second kidney. We present a unique case of prenatal sonographic diagnosis of unilateral fetal renal agenesis with survival, which has led to a revision of our current policy.