Dynamic incompetent cervix uteri. Sonographic observations.

In 15 of 56 patients with incompetent cervix, rapid changes in the degree of dilatation of the cervical canal were observed during sonographic examination, with the same degree of bladder distension. In ten of those 15 patients, the canal was seen to be completely closed at some point during the examination. Because of these rapid dynamic changes in the dilatation of the cervical canal, it is necessary to observe the cervical portion of the uterus several times during the sonographic examination, especially in patients suspected to have incompetent cervix. It is possible for the cervical canal to remain closed for several minutes during the examination. Incompetent cervix can go undetected if the cervix is not observed frequently throughout the sonographic examination.