Differential diagnosis of the nonvisualized fetal urinary bladder by transvaginal sonography in the early second trimester

Objective: To describe the pathologic situations associated with the persistently nonvisualized fetal urinary bladder in the early second trimester. Methods: We analyzed retrospectively 13,458 ultrasound examinations performed between 12–16 weeks’ gestation in search of fetal malformations. Seventy percent of the patients were at low risk and 30% comprised a high-risk group for the detection of fetal anomalies. Results: Seven cases of persistent nonvisualization of the fetal urinary bladder were detected by transvaginal sonography among 13,458 fetuses. In one case bladder exstrophy, and in another bilateral multicystic dysplastic kidneys were diagnosed by postabortal examination. Five cases were associated with bilateral renal agenesis. Conclusion: When one fails persistently to demonstrate the fetal urinary bladder during an examination lasting 30 minutes or longer, urinary tract pathology should be highly suspected. Failure to visualize the bladder may be associated with bladder exstrophy, bilateral renal agenesis, or late onset of bilateral multicystic dysplastic kidneys.