As the cause of abnormal uterine bleeding, diverticulum has received increasing attention. However, massive bleeding due to diverticulum is rare. Relevant documents are summarized in Table 1. Based on the literature, those cases showed some shared characteristics: 1. sudden and repetitive; 2. caused by abnormal blood vessels in the scar; 3. present several years after caesarean section; 4. hormone therapy was ultimately ineffective. These characteristics were similar to those of uterine arteriovenous malformation (AVM) and pseudoaneurysm. Arteriovenous malformation, which can be caused by poor local healing of the incision after cesarean section, always shows a mass with multiple hypo/anechoic tubular structures on ultrasound. Serpiginous and dilated vessels within the myometrium or parametrium are the typical sign on MRI[7]. Pseudoaneurysm, another vascular abnormality that can be caused by cesarean section, can cause massive bleeding[8]. The typical ultrasound manifestation of pseudoaneurysm is the ‘yin and yang’ sign and to-and-fro arterial blood flow with cyst formation. The sensitivity and specificity of ultrasound for pseudoaneurysm diagnosis can reach 95%[9]. Pseudoaneurysm diagnosis can also be confirmed by MRI, as the typical sign is a round sac with extravasation. However, in our case, no abnormal vessels were observed by ultrasound or MRI. Matsubara et al.[10] believed massive bleeding from diverticulum was caused by atypical pseudoaneurysm. He described an atypical pseudoaneurysm as a capsule that, mainly in the form of a thrombus, completely ruptures and falls off. When it ruptures, the aneurysm structure may no longer exist; at this time, the angiographic evidence shows extravasation, but there is no "obvious" capsule.The detection of atypical pseudoaneurysms by ultrasound indicated a low/high ultrasound mass with rich blood flow signals in the uterus[11]. In our case, ultrasound and MRI showed a diverticulum without abnormal blood flow signals around it, as Tasuku or Chin reported[4,6]. Vascular hyperplasia in the diverticulum is obvious and even extends to the posterior part of the cervix under hysteroscopy, which is a typical manifestation of inflammation. Under hysteroscopy, the ruptured artery was thought to be the reason for bleeding caused by inflammation rather than pseudoaneurysm.
As the literature has reported, complete transabdominal diverticulectomy and repair were used in all patients who wanted to preserve fertility. Wang et al. [3] believed that it was necessary to completely resect the diverticulum to avoid re-exposure of the broken arterial end from the thinned or weakened myometrium. In our case, the patient was treated with hysteroscopic surgery alone. The anatomical defects were corrected by hysteroscopic removal of the diverticulum edge which definitely reduced blood aggregation. The production of inflammatory factors was also reduced by simultaneous cauterization of the diverticulum bottom. The patient's symptoms disappeared, and the disappearance of abnormal blood vessels in the diverticulum during subsequent hysteroscopy certified that the treatment was successful. The thickness of the muscular layer in front of the diverticulum may contribute to the success of the treatment. After surgery, the muscular layer was thickened and was maintained during the subsequent pregnancy and follow-up. This is consistent with the phenomenon reported by Tsuji S et al.[2]. The correction of anatomical defects and the reduction of blood aggregation and inflammatory factors may promote the regeneration of diverticulum fibrotic tissue or eliminate the pressure as a fluid pool in the defect, resulting in the thickening of the residual myometrium, which would reduce the probability of rebleeding and vascular exposure. Given the above considerations, the patient has achieved clinical cure, the cause of bleeding has been resolved, hysteroscopic surgery seems to be sufficient.