This second trimester was performed for routine assessment of fetal anomalies in a patient with unremarkable history:

The finding is this case is an enormous cystic collection that displaces and deforms the fetus. Further, there is no amniotic fluid. This combination points to a major obstruction of the bladder outlet. Several conditions can cause that such as posterior urethral valve, Urethral meatus agenesis but these usually present with some amniotic fluid. So a more severe condition like Urethral agenesis was suspected. The patient elected to terminate the pregnancy in view of the dismal prognosis and after a drainage tap of the bladder the fetus was delivered:

The pathology confirmed the ultrasound findings (note the absence of external genitalia which is common).