Absence of visualization of one or both kidney → bilat. Renal agenesis / severe hypoplasia, pelvic kidney, unilateral renal agenesis or crossed fused ectopia.
A. Bilat. Renal agenesis or severe hypoplasia
1/4000 births
Severe oligohydramnios, pulmonary hypoplasia, Potter faces, & contractures.
Oligohydramnios (if present → pul. Hypoplasia, poor Px)
V. Ureterovesical junction obst.
VI. Ureteropelvic junction obst.
VII. Renal cysts.
Most fetuses with renal cysts
MCDK (Potter type II)
Obst. Uropathy resulting in renal cystic dysplasia (Potter type IV)
Detection of renal cysts → careful search for associated anomaly, esp in absence of features
indicative of urinary tract obst.
Renal dysplasia : irreversible renal damage, functional capacity - depends on extent & severity of
dysplasia.
90% of dysplastic kidney ← result from urinary tract obst. during nephrogenesis.
# Bernstein's classification of renal dysplasia.
Multicystic dysplasia ← usually caused by ureteropelvic atresia.
Focal & Segmental cystic dysplasia ← obst. Or atresia of one of ureters leading from a duplex
kidney
Cystic dysplasia a/w nonatretic urinary tract obstruction ← mc from post. urethral valves
Heredofamilial cystic dysplasia.
A. MCDK (Multicystic Dysplastic Kidney)
Occurs during embryogenesis ← result from atresia of ureteral bud system at level of upper 1/3 of
ureter with concomitant atresia of renal pelvis & infundibulum
Some (usually very minimal) residual urine formation → but functionless
Renal pelvis & ureter : usually atretic & not visible
Typically visualizes as a paraspinous flank mass : numerous cysts of variable sizes without identifiable
communication or anatomic arrangement
Change markedly in size & appearance as gestation progresses : progressive enlargement or diminution
or may initially enlarge, then decrease later in pregnancy.
Bilateral MCKD: oligohydroamnios develop as early as 12weeks
cf. Typical multicystic flank masses : visible after 16weeks.