Introduction

During pregnancy, routine imaging of the fetal kidney is usual, although it may be prompted by an abnormal amount of amniotic fluid. In the newborn, imaging is performed as follow-up to fetal findings or it is prompted by clinical indications. These include the following:

• in the antenatal period oligohydramnios may signal onset of the Potter sequence;

• pulmonary hypoplasia with need for respiratory support and/or air-leak syndromes;

• features consistent with a syndrome, (trisomy 21; VACTERL; prune-belly syndrome, etc.);

• oliguria – defined in the newborn as < 1 ml/(kghr) of urine aft er the first day of life;

• renal failure – progressive azotemia at or aft er 72 hours of life;

• macroscopic or microscopic hematuria;

• renal masses found on examination or by prenatal ultrasound;

• no or poor urinary stream aft er the first day of life;

• evidence of urosepsis;

• ascites.

Modalities of imaging

The clinical value of newborn urogenital imaging can be separated into two categories. First, imaging can be used to provide detailed anatomical information. Second, imaging is increasingly being used to provide functional information about the kidneys. In the newborn, functional information even from the newer imaging modalities in the first two weeks of life is limited by nephrogenesis ending at 36 weeks gestational age, by a reduced glomerular filtration rate, and by reduced concentration ability.