From January 2015 to December 2020, 502 patients with CSP were managed in our department. Finally, 403 patients were included in our study. The flow chart was shown in Fig. 1.
Inclusion criteria: (1) patients had a history of cesarean delivery, (2) had amenorrhea and the blood pregnancy test was positive, (3) gestational age less than 12 weeks, (4) the ultra-sonographic findings met the diagnostic criteria, (5) with intact medical record.
Exclusion criteria: (1) patients associated with uterine fibroids or other gynecological disorders, (2) with acute vaginitis or pelvic inflammatory diseases, (3) with other severe disease such as failure of heart, liver or kidney, (4) with unstable hemodynamics, (5) the histopathology after operation indicated without trophoblastic tissue, (6) had been treated in other hospital.
The information of each patient, including age, body mass index (BMI), gravidity, parity, the number of cesarean delivery (CD), the interval of previous cesarean delivery (PCD), the length (D1), thickness (D2) and width (D3) of uterus and gestational sac, fetal cardiac activity, the types of CSP, the baseline of beta-human chorionic gonadotropin (β-HCG), the value of β-HCG before and 24 hours after pretreatment, hospital expenditure, the value of hemoglobin before and 24 hours after dilatation and curettage (D&C) and severe complications, was collected from the medical records.
The uterine size and gestational sac volume were calculated with the following formula: V = (1/6) × × D1 × D2 × D3. The decline ration of beta-human chorionic gonadotropin (β-HCG) was calculated with the following formula: (the β-HCG level before pretreatment – the β-HCG level 24 hours after pretreatment) / the β-HCG level before pretreatment. The blood loss was showed by the decline of hemoglobin and calculated with the following formula: the value of hemoglobin before D&C – the value of hemoglobin 24 hours after D&C. The severe complications were defined as blood loss ≥ 30 g/L and/or laparoscopy and/or laparotomy and/or hysterectomy and/or blood transfusion.
The classification criteria for CSP[17, 18]: Type I: 1. only a small part of the gestational sac morphed into the niche of cesarean section; 2. the myometrium thickness between the gestational sac and the posterior wall of the bladder was > 3 mm; 3. without or minimal blood flow was detected around the gestational sac (Fig. 2A). Type II: 1. part of the gestational sac morphed into the niche of cesarean section; 2. the myometrium thickness between the gestational sac and the posterior wall of the bladder was ≤ 3 mm; 3. moderate blood flow was detected around the gestational sac (Fig. 2B). Type III: 1. most of the gestational sac implanted into the niche; 2. the myometrium thickness between the gestational sac and the posterior wall of the bladder was < 2 mm; 3. marked blood flow was detected around the gestational sac (Fig. 2C).
High intensity focused ultrasound
Enhanced magnetic resonance imaging (MRI) was used to confirm the size, location and blood supply of gestational sac. Bowel preparation was performed using polyethylene glycol-electrolyte powder. Each patient was shaved the lower abdominal area. A catheter was inserted into bladder to control bladder size and push the bowel away from the acoustic pathway.
The procedure was performed by two experienced gynecologists using the JC200 focused ultrasound tumour therapeutic system (Chongqing HIFU Technology Co., Ltd., Chongqing, China). This system is integrated with real-time monitoring ultrasound (MyLab 70, Esaote, Genova, Italy). Focused ultrasound energy was produced by a 20-cm diameter transducer with frequency of 1.0 MHz, which was located in a reservoir filled with cold degassed and degreased water. Patients were conscious sedation and prone on the HIFU system, with the abdominal wall immerged in the sealed reservoir. During treatment, the focus was placed close to the embedding area of the gestational sac in the center slice at the beginning of the HIFU ablation procedure. Cessation of HIFU ablation occurred when: (1) obvious grey scale change in the target area was observed; (2) blood flow signal of gestational sac embedding area disappeared or was significantly reduced in the colour Doppler. SonoVue was injected 5 min pre- and immediately post-treatment to evaluate the ablation effect. The therapeutic effect was defined as: (1) a non-perfused volume was observed in gestational sac embedding area; (2) blood supply around the gestational sac, especially the embedding area, disappeared or significantly reduced.
Uterine artery embolization
Antibiotic was used with a single dose via venous before UAE. The operation of UAE was performed by two experienced interventional radiologists using digital subtraction arteriography (DSA) (AXIOM-Artis-FA; Siemens AG, Munich, Germany). Patients were supine on the UAE system. Local anesthesia was performed at the right groin area. After anesthesia, catheter was punctured via the right femoral artery using the Seldinger technique. DSA was used to confirm the uterine artery blood flow, the location of the gestational sac and its vessels, then embolized bilateral uterine arteries with absorbable gelatin compressed sponges (1-1.4mm, Ailikang, Hangzhou, China). The operation was ceased after another angiography indicated uterine artery blocked and staining disappeared[21, 22].
Ultrasound-guided suction curettage
An experienced gynecologist performed the procedure 24h after pretreatment. Antibiotic was used 30 min before the surgery. 10 U oxytocin via 500ml intravenous injection drip was routinely used during the operation. The operation was performed under general anesthesia with lithotomy position and suprapubic ultrasonography guidance. A vacuum aspirator (Yuyue, Jiangsu, China) was used to aspirate the whole gestational sac avoiding perforate the previous cesarean scar. The tissues were sent for pathological examination (Video). If intractable uterine hemorrhage happened, an 18-Fr gauge Foley catheter balloon tamponade with 100ml saline was used for 12h (Fig. 3). Additional surgery was performed for uncontrolled bleeding.