Objectives: Intrauterine adhesion (IUA) is mainly caused by intrauterine operations such as pregnancy-related curettage and hysteroscopic surgery, resulting in the trauma to the basal layer of the endometrium. Hysteroscopic adhesiolysis is a crucial step in the comprehensive treatment of IUA, and the most common complication is uterine perforation. More than half of all uterine perforations occur during the hysteroscopy or probe/dilator pass through the internal os. Furthermore, inappropriate surgical procedures may lead to endometrial injury, recurrence or even aggravation of adhesions, and complications such as cervix laceration and false passage formation. This study aims to explore the usage of the hysteroscopic dilatation techniques to dilate the internal os and lower uterine segment, which is via hysteroscopy entering the internal os laterally and swinging, or by directly opening the forceps or scissors and bluntly spreading dissection under direct hysteroscopic vision. By using the hysteroscopic dilatation techniques, we intend to improve the effectiveness and safety of cervical dilation in patients with IUA in the internal os and/or lower uterine segment.

Methods: A total of 282 patients with adhesions in the internal os or lower uterine segment underwent HA in the Third Xiangya Hospital of Central South University from January 2020 to June 2021 were included, ranging from 21 to 46 (33.0±4.8) years old in age and 5 to 12 in the American Fertility Society score. Among them, there were 2 cases of false passage formation caused by traditional dilatation in other hospitals. All patients underwent hysteroscopy with integrated hysteroscopy with 5Fr instrument channel and 4.9 mm outer sheath diameter. The internal orifice of cervix and the lower segment of uterine cavity were dilated under the microscope. After the hysteroscopy entered the uterine cavity, the separation of uterine cavity adhesion and the placement of uterine contraceptive ring or uterine stent into the uterine cavity were performed routinely. Age, surgical records, and surgical videos of all included cases were collected. The success rate of dilation and the incidence of surgical complications were assessed.

Results: In all cases, the hysteroscopys successfully entered into the uterine cavity by using the hysteroscopic dilatation techniques without failure and switching to cervical dilators. In the 2 cases of false passage due to previous cervical dilation, the uterine cavity was identified and found successfully under direct hysteroscopic vision. During the whole surgery, the vision was clear, and no complications (such as cervix laceration, false passage formation, uterine perforation or water intoxication) occurred. One to 3 months postoperative hysteroscopy revealed no significant fibrotic stenosis in the internal os and lower uterine segment.

Conclusions: The hysteroscopic dilation techniques are a strategy for separation methods that is following structural hierarchy anatomy in the mode of "see and treat" for the adhesion in the internal os and uterine cavity under direct hysteroscopic vision. This method not only has ultrasound guidance, but also has the judgment of structural hierarchy anatomy under direct hysteroscopic vision, so there is less chance of anatomical level judgment error. This method makes full use of the hysteroscopic judgement of the experienced hysteroscopic surgeons, so that surgeons can timely find and avoid re-entering the old false passage caused by previous surgery. The adhesions in the internal os and lower uterine segment were separated by the hysteroscopic dilation techniques. In this way, the damage to the endometrium caused by forced insertion of the hysteroscopy can be avoided. Meticulous separation of adhesions and cervical dilation under direct hysteroscopic vision can effectively reduce the occurrence of surgical complications such as false passage formation, cervical laceration, and uterine perforation. The use of mini-hysteroscopy eliminates the need for preoperative cervical preparation, avoiding associated risks and side effects. Moreover, for patients with adhesions in the internal os and lower uterine segment, preoperative cervical preparation is not effective in cervical dilation, while the hysteroscopic dilation techniques are effective, with higher patient acceptance due to the absence of preoperative cervical preparation. For the skilled hysteroscopic surgeons, the hysteroscopic dilation technique is easy to operate and worthy of clinical application.