Transvaginal sonography (TVS) of the fetal urinary tract

Examination of the fetal urinary tract is an integral part of routine sonographic examination in the second trimester of pregnancy. Malformations of the urinary tract are being detected at an ever-increasing rate, mostly because they are associated with two easily visualized sonographic markers: the cystic accumulation of fluid and a change of the amniotic fluid volume. Detailed evaluation of the fetal urinary tract and identification of anomalies were considered to be difficult before the 18th week from the last menstrual period (LMP) before the use of transvaginal sonography (TVS). Transvaginal sonography (TVS), owing to its proximity to the maternal pelvic organs at early gestation, enables earlier determination of both normal and abnormal findings in the fetal urinary system such as: renal agenesis, polycystic and multicystic kidneys, hydronephrosis, and bladder extrophy. The TVS enables earlier and more accurate diagnosis and identification of fetal urinary tract anomalies as compared with abdominal ultrasound.