Prenatal Ultrasound Diagnosis and Management of Fetal Lower Urinary Tract Obstruction
Low urinary tract obstruction always leads to the damage of the renal parenchyma, which results in considerable worsening of the prognosis. Most of the babies die on in the early neonatal period due to the severe renal insufficiency or lung hypoplasia. It's very important to diagnose this condition prenatally and to distinguish those fetuses that will have poor outcome. Diagnosis is typically made on the basis of sonographic findings of distended bladder, hydronephrosis, and oligohydramnios. In fetuses with posterior urethral valve there appears a "key-hole sign" on the ultrasound at the level of the bladder neck and proximal urethra. Prenatal assessment of fetuses with low urinary tract obstruction and finding candidates for in utero correction includes fetal karyotyping, careful assessment of fetal anatomy and serial fetal urine samples. Fetal vesicoamniotic shunting is a modern method of prenatal surgical correction of the low urinary tract obstruction, but the long-term outcomes of this procedure are still contraversive.