hydrometrocolpos

accumulation of secretions in the vagina and uterus

dilatation of the vagina proximal to a congenital obstruction (e.g., imperforate hymen)
produces a palpable, fixed midline mass
may cause hydronephrosis
AXR: abdominal mass extending from pelvis
US: cystic mass posterior to bladder with scattered echoes due to cellular material and blood

Cf: hydrometros = uterine dilatation only (obstruction at cervix)