Imaging description

A 16-year-old patient was diagnosed at 22 weeks of gestational age (GA) with a fetus with multicystic dysplastic kidney (MCDK). The contralateral kidney appeared slightly echogenic but otherwise normal on ultrasound (Fig. 77.1a,b). Fetal MRI confirmed large disorganized cortical cysts of different size in the right kidney but also demonstrated the presence of small subcortical cysts in the left kidney (Fig. 77.1c). However, the amount of amniotic fluid remained normal throughout the pregnancy and the patient carried the baby to term. At birth, ultrasound of the kidneys confirmed a right MCDK that got progressively smaller over time (Fig. 77.1d, f), but failed to demonstrate the small subcortical cysts in the left kidney (Fig. 77.1e). A dysplastic appearance of the left kidney with subcortical cysts was only noticed on follow-up ultrasound at the age of 1 year (Fig. 77.1g). The renal function was mildly decreased postnatally.

Importance

Renal cystic dysplasia is usually unilateral and may affect an entire kidney, a segment of a kidney, or a pole of a duplex kidney. Recent studies demonstrate that MCDK and obstructive dysplasia may have a similar pathogenesis, with glomerular cysts being the initial dysplastic event in the kidneys. Early prenatal studies show that MCDK appear as normal kidneys on ultrasound up to 14 weeks of gestational age despite complete obstruction. They are often diagnosed at the routine anatomic scan around 20 weeks of gestational age. Small subcortical cysts in the setting of obstructive dysplasia may appear later in pregnancy or after birth and are often more difficult to diagnose prenatally than MCDK.