In gynecological clinics, we often encounter young women who are suffering from severe dysmenorrhea. Their pain is real and intense, but sometimes it is classified as a "functional" problem because the imaging report is "normal", causing the true cause to be overlooked. However, behind this diagnostic "fog", there may be a tiny cavity buried deep in the myometrium that "bleeds" alone every month - this is the protagonist we will discuss today: the accessory cavitated uterine mass (ACUM).

This unfamiliar-sounding name is gradually being recognized as one of the important causes of severe secondary dysmenorrhea in young women. It is not only about pain, but also about women's fertility potential. As I emphasized, in the field of diagnosis and treatment of uterine diseases, "seeing" is the beginning of healing. This article will combine an in-depth case study article with relevant medical literature to demystify ACUM and highlight its latest minimally invasive treatment options.

The attached uterus (ACUM) is a congenital Müllerian dysplasia, but it is not extremely rare and has been underappreciated for a long time. It is typically characterized by the formation of an isolated accessory cavity within the myometrium that does not communicate with the main uterine cavity, and the lining of this accessory cavity is covered with functional endometrial tissue.

Because this lining is physiologically active, it periodically proliferates and bleeds with monthly fluctuations in hormone levels, just like a normal endometrium. But the problem is that this accessory cavity is a "dead end" with no outlet for menstrual blood to drain. Over time, old blood accumulates in the cavity, eventually forming a viscous, dark brown "chocolate-like" liquid, which is quite similar to the "chocolate cyst" in endometriosis. This expanding "built-in blood bag" continues to compress and irritate the surrounding myometrium, causing severe, progressively worsening pain, and at this point, the patient's uterine aortament and ovaries may appear to be abnormal on imaging examinations, which greatly increases the difficulty of early diagnosis.

The most important clinical manifestation of ACUM is severe and progressively worsening dysmenorrhea, which is often difficult to relieve with medication. Due to the occult lesions, routine gynecological examinations and ultrasound examinations can easily miss the diagnosis, resulting in long-term unreasonable explanation and effective treatment of patients' pain. In addition to severe pain, some patients may also face infertility.

The biggest challenge in diagnosing ACUM is its "camouflage". It is often hidden in the seemingly "normal" womb. Therefore, accurate imaging evaluation is crucial. While preoperative MRI or 3D ultrasound can provide important clues, based on the experience of the original case, intraoperative sonography plays the role of the "ultimate detective". It can probe the myometrium in real time and dynamically during surgery, accurately locate the location, size and number of lesions, and even find some symmetrically distributed microscopic lesions that cannot be identified by preoperative images, thus providing decisive guidance for completely removing the lesion and avoiding recurrence.

For the treatment of ACUM, surgery has traditionally been relied on. The surgical process of laparoscopic precise resection of ACUM is described in detail in the original case, and several core principles are highlighted:

Complete resection: Avoid rupture of the cyst and prevent contamination of the pelvic cavity with contents.

Thorough dissection: Remove the "satellite" adenomuscular lesions that may be present around the main lesion to reduce the risk of recurrence.

Protect the uterine cavity: The surgical operation is strictly limited to the muscle layer and never enter the uterine cavity to protect the patient's fertility to the greatest extent.

Fine reconstruction: Suturing the uterine muscle wall in layers without dead space and tension to create optimal conditions for the healing of the uterus and future pregnancies.

This radical surgical excision has been proven to be effective, not only relieving pain, but even helping patients get pregnant naturally. However, any surgery means trauma and scarring of the uterus, which in itself can pose long-term risks, such as uterine rupture during pregnancy. As a result, the medical community has been exploring more minimally invasive, less invasive and equally effective treatments. In recent years, thermal ablation therapy and alcohol sclerotherapy have shown great potential in the treatment of ACUM as two promising minimally invasive techniques.

1. Thermal Ablation

Thermal ablation is not a new concept, it has been widely used in the treatment of uterine fibroids and adenomyosis. Its basic principle is to use physical energy (such as radio frequency, high-intensity focused ultrasound, microwave, etc.) to generate high temperature, so that the lesion tissue will coagulate and necrosis, so as to achieve the purpose of "inactivating" the lesion. These techniques have also been tried to treat ACUM due to its pathological similarities to focal adenomyosis.

A 2023 review published in the Journal of Clinical Medicine systematically evaluated the use of radiofrequency ablation (RFA) in the treatment of adenomyosis. The study pointed out that RFA is guided by ultrasound, and the electrode is precisely inserted into the lesion, and the high-frequency current generated heats up the local tissue, resulting in necrosis and atrophy of the lesion. A meta-analysis of more than 15,000 patients showed that for dysmenorrhea caused by adenomyosis, the response rate of different thermal ablation techniques was significant:

High-intensity focused ultrasound (HIFU): 84.2% remission rate

Radiofrequency ablation (RFA): Response rate 89.2%

Microwave ablation (PMWA): Response rate 89.7%

These techniques serve as a minimally invasive means of preserving the uterus, offering an attractive option for ACUM patients looking to preserve their fertility. However, it is worth noting that safety data on pregnancy after ablation treatment are still being collected, especially the potential risk of uterine rupture, which requires full information and careful evaluation of patients.

2. Ethanol Sclerotherapy

Alcohol sclerosing therapy is a more novel attempt. This technique draws on the successful experience of treating ovarian endometriosis cysts. The operation process is to use a puncture needle to suck up the old blood accumulation in the ACUM cavity under ultrasound guidance, and then inject anhydrous alcohol, which uses alcohol to dehydrate and necrosis the functional intimal cells of the cavity lining, thereby destroying its ability to bleed periodically and achieve the purpose of treatment.

In 2020, the Clinical Case Report reported for the first time a successful case of using alcohol sclerosis for the treatment of ACUM. The study emphasized that the biggest advantage of this method is that it completely avoids cutting and suturing the myometrium, so that there is no uterine scarring, which theoretically greatly reduces the risk of uterine rupture in future gestations and creates conditions for patients to prepare for pregnancy quickly and safely.

In the same year, another study published in Ultrasound in Obstetrics and Gynecology provided more data from a single center. In the study, all six patients with ACUM who underwent alcohol sclerosing therapy experienced significant pain relief without any complications. However, studies have also found that some patients' symptoms may recur within 6 months to 5 years after surgery, suggesting that this may be an effective means of controlling symptoms, but its long-term curative effect still needs to be further observed. Researchers believe that alcohol sclerotherapy has great promise as a low-risk intervention, but more research needs to be answered about its optimal operation technique and the value of repeated treatment.

The attached cavity uterus (ACUM) is increasingly recognized by gynecologists as a hidden pain-causing factor. From traditional radical surgery to emerging minimally invasive ablation and sclerotherapy, advances in treatment methods provide patients with more diverse and personalized options. Especially for young women with fertility requirements, how to find the best balance between completely solving pain and protecting uterine function to the greatest extent is a topic that both doctors and patients need to face together. If you are suffering from severe, unexplained dysmenorrhea, it is important to seek the help of a professional doctor to find the most suitable treatment plan for you through accurate diagnosis, say goodbye to pain, and regain health and hope.