When there is no plan for pregnancy or the patient declines surgery, short-acting oral contraceptives are the typical choices for abnormal uterine bleeding (AUB) as the clinical manifestation. This is a short-term treatment. It can effectively improve the symptoms of AUB but does not heal the defect, so the symptom recurrence and the complications of hormones are still important issues [29].

There are quite a few studies on the application of the LNG-IUS to CSD. Xuyun Zhang et al. [30] performed a prospective evaluation of five methods applied to treat CSD, and the duration of menstruation was similar before and after treatment in the LNG-IUS group. Thus, given this lack of difference, the therapeutic application of the LNG-IUS is inadequate, but the long-term clinical efficacy of the LNG-IUS remains to be determined.

Laparotomy is the traditional surgery for the CSD repair. Because of the large surgical field and ease of operation, it is suitable for CSD with serious adhesions in the pelvic cavity. However, due to its disadvantages regarding the large scale of operative trauma and slow postoperative recovery, it is not the first choice to treat CSD at present.

TVR is performed by dissecting the bladder from the cervix and uterus, exposing the cervix and lower uterine segment to clarify the position of the CSD, resecting the defect and suturing the two layers. TVR is a minimally invasive and effective surgical approach [33]. Zhou et al. [34] suggested that TVR relieved the symptoms of postmenstrual spotting and anatomically corrected the scars. Moreover, the optional timing for TVR is an interval $\le$2.5 years between caesarean sections, and the standard healing criterion for CSD is a thickness of the remaining muscular layer of $\ge$8.5 mm at 6 months. Zhang et al. [35] proposed that TVR has the advantages of lower cost and shorter operation time than LP for correcting the CSD. A novel therapeutic approach for repairing a symptomatic CSD by using vaginal natural cavity transluminal endoscopic surgery [36]. TVR is helpful for anatomic reconstruction of CSD. However, TVR requires the surgeon to be experienced in vaginal procedures, and the bladder peritoneal fold and the anterior wall of the lower uterine segment often develop adhesions after caesarean section, making the surgical field hard to expose. Furthermore, the size of the defect is usually a few millimetres, and it is difficult to locate the position accurately.

Electric resection is performed by placing the hysteroscope and an electric resection ring (or an electric rolling ball) into the uterine cavity, and hysteroscopic electric resection is then performed. HP can remove the upper valve of the CSD by blocking the outflow of menstrual blood [37]. HP contributes to alleviating the clinical symptoms of AUB, but it cannot change the anatomic abnormalities of the CSD [31]. In a retrospective review, Xie et al. [38] reported that the operative efficacy of HP (64.5%) was significantly inferior to that of vaginal surgery (93.5%), whereas patients who underwent HP had a shorter operative time (25 vs. 55 min) and less blood loss (10 vs. 50 mL). Bingqing Lv et al. [39] compared HP combined with LP to HP alone, and the results showed similar pregnancy rates between the two methods (61.5% vs. 73.3%; p = 0.505); however, the interval between the operation and pregnancy was much shorter in the HP group than in the HP combined with LP group (10 vs. 27 months). One study showed that the effective rate of menstrual improvement was 59%–100% [40]. Additionally, Florio et al. [26] stated that bipolar electrocision should be performed when the TRM muscles are not too thin ($\ge$2 mm), and electrical coagulation should be performed if there is no active bleeding in the CSD. Another study also suggested that HP may be considered for patients who do not plan to become pregnant and with TRM $>$3 mm or clinical symptoms [41]. A meta-analysis reported that hysteroscopic remodelling appears to be a treatment choice in the management of symptomatic CSD [42]. Channeled (360°) hysterectomy for symptomatic CSD patients may result in increased TRM, reduced CSD, improved symptoms and high patient satisfaction after the procedure [43]. Currently, whether TRM is a limitation of HP is controversial.

LP has the advantages of a full field of vision, less trauma, shorter operation time and faster recovery. It has been advocated for defects (TRM 3 mm) and patients with symptoms who plan to become pregnant [44]. Based on common practice and expert opinion, Roy Mashiach recommended 2.5 mm as the cut-off value [27]. Conventional LP or robotic-assisted LP can be used by a skilled laparoscopic surgeon to repair the CSD [45]. The reported operation time is 65 $\pm$ 26 min [46], and robotic excision requires 240 minutes [47]. Vervoort et al. [48] reported a prospective cohort study that evaluated the effectiveness of an LP resection for CSD-related symptoms, fertility-related problems, and ultrasound findings in 101 women. In this study, the results showed that postmenstrual spotting and dysmenorrhoea were reduced by the laparoscopic approach, and the TRM was enlarged 6 months after the surgery. Olivier Donnez et al. [44] reported that eight women (44%) became pregnant and performed CS at 38–39 weeks of gestation among the 18 women with infertility. A two-centre observational study reported that CSD repair via robot-assisted laparoscopy is a feasible potential therapy, but further research into this technique is still needed [49].

When the CSD does not protrude from the serosa layer, LP does not directly observe the CSD. Thus, LP alone may not completely resect the scar. LH can solve the problems of the poor location ability of LP and incomplete repair of HP for CSD. During HP, the scope of CSD can be identified by the light transmission of the hysteroscope, and suturing of the CSD can be confirmed after laparoscopic repair [23]. During LP, the bladder can be fully pushed down, and the risk of bladder injury can be minimized. In addition, surgical treatment of other pelvic diseases, such as endometriosis, can be immediately performed [50]. LH is better than LP or HP alone, but the disadvantages of LH are its longer operation time and higher cost.

In addition to some of the specialised procedures for repairing CSD mentioned above, there is another type of repairment of CSD when found in a repeated CS. In repeat lower segment caesarean section (LSCS), we found some women with a significant scar defect in the anterior uterine wall (Fig. 3). One prospective study noted that a modified surgical technique concentrated on identification, mobilisation and location of the retracted myometrial fringes by a unique experienced obstetrician [51]. The purpose of this is to make the recovery of anatomical results consistent. The result showed no diverticula in all cases at three months postpartum on pelvic ultrasound. The mean residual scar thickness was 8.4 mm) [51]. In summary, it makes sense to discover and reconstruct the structure of the lower myometrium while repeating the cesarean section.

Fig. 3.

CSD in repeated CS. The blue arrow points to the CSD. (A) The lower segment of the uterus in late pregnancy after opening the abdominal cavity. (B) Lower segment of the uterus after removal of the fetus following incision of the uterus. CSD, caesarean scar defect. CS, caesarean section.