Prenatal Minimally Invasive Procedures for Fetal Lower Urinary Tract Obstruction

Fetal lower urinary tract obstruction (LUTO) is a bladder outlet obstruction (BOO) resultant from congenital urinary tract outflow anomalies. It represents a spectrum of pathologies characterized by dilated fetal bladder and bilateral hydronephrosis that can occur as an isolated defect or be accompanied by other congenital abnormalities in approximately 20% of cases. LUTO is associated with high degree of perinatal mortality and long-term morbidity. The severity of obstruction is highly variable and dependent on the underlying mechanism. Posterior urethral valve (PUV) is the most common cause of LUTO, representing up to 63% of cases. Other causes include urethral atresia, urethral stenosis, and prune belly syndrome. Mild forms of the disease can have favorable outcomes but, when more severe, usually formed early in gestation, it leads to dysplastic kidney changes and eventually oligohydramnios or anhydramnios that may result in secondary pulmonary hypoplasia and renal failure that generates significant postnatal morbidity and mortality. Some prenatal fetal interventions as serial amnioinfusion, percutaneous shunting, and fetal cystoscopy have been attempted and offer variable results to improve the prognosis and mostly to obtain a pulmonary survivor. Usually, these techniques should be adapted case to case, depending particularities and require a multidisciplinary trained team. Prenatal diagnosis of these urological conditions at early stage and its categorization are essential to provide an accurate parental counseling and fetal therapy.