Background: Torsion of pedunculated subserosal myoma is a clinically rare but potentially life-threatening disease. In patients with acute abdomen, fibroid pedicle torsion is not a routine differential diagnosis. If not timely identified and treated, fibroid torsion can lead to avascular necrosis and peritonitis. However, relevant publications have so far only been single case reports with a lack of systematic review to summarize clinical features and experience. 

Case presentation: A 48-year-old woman complained of lower abdominal pain for two weeks and was initially treated as acute pelvic inflammatory disease. The patient’s inflammatory indicators returned to normal but abdominal pain persisted. Considering a pelvic mass found by imaging examination and persistent abdominal pain, a diagnostic laparoscopy was performed, which demonstrated torsion of a pedunculated subserosal myoma. The subserosal myoma and the other two fibroids were removed, and the abdominal pain was completely relieved after surgery. Postoperative pathology confirmed uterine leiomyoma with infarction. 

Conclusions: Abdominal pain is the most common symptom of leiomyoma torsion. MRI shows higher accuracy and is highly recommended for preoperative diagnosis of myoma torsion. Regardless of pregnancy status, surgery is the first choice of treatment.

Torsion of pedunculated subserosal myoma is a gynecologic emergency with an incidence of less than 0.25% among surgically diagnosed uterine fibroids[1]. Although the incidence of pedunculated subserosal myoma in torsion is rare and remains largely unknown, it can lead to significant morbidity and potentially be life-threatening[2]. Most cases are diagnosed intraoperatively due to their non-specific symptoms and imaging findings. Therefore, an accurate preoperative diagnosis is challenging and once myoma torsion is suspected, surgical intervention should be considered. To our knowledge, data is limited considering the clinical features of leiomyoma torsion up till now. Herein, we reported a rare case of pedunculated subserosal myoma in torsion with a suspected diagnosis of acute pelvic inflammatory disease. We then reviewed 30 pieces of literature with a total of 34 cases to summarize the clinical characteristics and experience of torsion of pedunculated subserosal myoma.

A 48-year-old woman, gravida 1 para 1 woman came to our hospital in March 2024 complaining of lower abdominal pain for two weeks. She had a one-year history of multiple fibroids. Ten days prior to admission, the patient underwent conservative anti-inflammatory treatment for one week at a local hospital with suspicion of acute pelvic inflammatory disease indicated by elevated inflammatory markers and tenderness on gynecological examination. After treatment, inflammatory indicators returned to normal. However, the patient’s abdominal pain was not significantly relieved which resulted in her referral to our hospital. Gynecological examination revealed an enlarged uterus at 8 weeks gestation and a hard mass on the left side of the uterus with obvious tenderness, measuring about 7 cm. Transvaginal ultrasound revealed multiple fibroids (Figure 1A) and a hypoechoic solid mass measuring 7 × 5 cm closely adhered to the posterior aspect of the uterus with suspicion of leiomyoma degeneration (Figure 1B). 

Figure 1: (A) Transvaginal ultrasound image demonstrating multiple leiomyomas fusing on the anterior wall of the uterus. (B) A solid mass in the posterior wall of the uterus.

An abdominal CT scan revealed a mass on the left side of the uterus, measuring approximately 72 × 46 mm, with an uncertain origin. Pelvic contrast-enhanced MRI showed a mass in the left posterior part of the uterus, measuring 5.0 × 7.6 cm, without clear demarcation from the uterine serous surface. The mass showed mixed-intensity signals on both T1- and T2-weighted imaging with well-defined margin strengthened after enhancement (Figure 2A and B). 

Figure 2: Sagittal T1-weighted (A) and T2-weighted (B) images showed a mass in the left posterior part of the uterus with marginal enhancement.

Leiomyoma degeneration or torsion was first suggested by MRI, meanwhile an ovarian tumor cannot be excluded.  An exploratory laparoscopy was performed considering the pelvic mass and the persistent lower abdominal pain. Moderate adhesions between the posterior wall of the uterus and rectosigmoid colon were found during intraoperative exploration (Figure 3A). After separation of pelvic adhesions, a pedunculated subserosal myoma was identified, which was dark bluish  and twisted 360 degrees along its vascular pedicle (Figure 3B, 3C). Besides, two leiomyomas in the anterior wall of the uterus were found, measuring 5×4 cm and 1×2cm respectively. The subserosal myoma and two intramural fibroids were completely removed intraoperatively (Figure 3D). Pathological examination demonstrated uterine leiomyoma with infarction. Postoperatively, the abdominal pain was disappeared and the patient discharged five days after surgery. On regular follow-up, no recurrence was observed by September 2024.

Figure 3: (A) Moderate adhesions between the posterior wall of the uterus and rectosigmoid colon. (B) A pedunculated subserosal myoma on the posterior wall of the uterine was dark bluish. (C) A twisted pedicle. (D) The end of surgery.

Fibroid torsion is uncommon and rarely diagnosed preoperatively[3]. The pathogenic mechanisms and risk factors associated with the torsion of a subserosal uterine leiomyoma remain unclear. Abdominal pain is the primary complaint among patients, which poses a diagnostic challenge due to the wide range of potential pathological conditions[4]. We conducted a literature search in the PubMed database using the terms "myoma", "fibroid", "leiomyoma", and "torsion" as keywords since the year 2000. This search yielded a total of 30 articles, which included 34 cases of pedunculated subserosal myoma in torsion, identified through screening of the titles and abstracts of records retrieved from 133 gynecological literature sources[1,3,5-32] (Table 1).

Who is more likely to develop myoma torsion?

The incidence of leiomyoma torsion varies among women of different ages. The median age at diagnosis is 37.5 years, ranging from 12 to 62. Among the reported cases, the majority (20 out of 34, 59%) occurred in reproductive-age women (aged 30–49 years), while only 6 out of 34 cases (18%) were observed in perimenopausal and postmenopausal women (aged ≥ 50) with myoma torsion (Table1). Women of reproductive age exhibit the highest incidence of myoma torsion, partly because uterine fibroids are prevalent in this demographic[33].  All cases involved myomas with a maximum diameter greater than 5 cm, averaging 11.6 cm, with the largest being 25 cm in a 45-year-old woman (Table 1). Despite the shrinking of uterine fibroid lesions and decreased estrogen in women at the perimenopausal stage, it is noteworthy that 18% of women aged ≥ 50 years experienced myoma torsion with a median maximum diameter of 9.3 cm. This suggests that myoma torsion may be more related to the size of the myoma rather than hormonal changes. The diagnosis of acute pelvic pain in perimenopausal patients should take into account the physiological changes in the pelvis and the patient's clinical history. It is crucial to continue monitoring postmenopausal women with a history of fibroids, as the onset of menopause does not eliminate the risk of myoma torsion.

How to make accurate diagnosis?

The preoperative diagnosis of pedunculated subserosal leiomyoma in torsion is often challenging[18], due to its non-specific symptoms and signs as well as the absence of definitive laboratory and imaging findings. If left untreated for a prolonged period, it can lead to ischemic gangrene and subsequent peritonitis[10]. All cases presented acute abdominal pain, with nearly half (16/34, 47%) presenting to the emergency department/room for their initial consultation. One case was admitted to the surgical oncology department because of small bowel volvulus induced by myoma torsion. Therefore,  an initial evaluation and differential of the patients must be considered since multiple organ systems contribute to abdominal pain[4]. In addition, most cases (22/34, 65%) showed elevated inflammatory indicators, but only a few cases (6/34, 18%) had a fever (Table 1).

Table 1: Literature review of torsion of pedunculated subserosal myoma.

Abbreviations: P = pregnant; ER = emergency department/room; GE = gynecology emergency; OB-GYN = obstetrics and gynecology; LT = laparotomy; LA = laparoscopy; MT = myomectomy; HT = hysterectomy; BOT = bilateral oophorectomy; BSO =bilateral salpingo-oophorectomy; ROT = right oophorocystectomy; NA = not available

Pelvic inflammatory disease and adnexal mass are the major differential diagnoses, but it is noteworthy that pregnancy status and obstetric causes should be considered[4,34]. Imaging modalities are essential for narrowing the differential diagnosis in patients with gynecologic emergencies[35]. In women presenting with pelvic pain, ultrasonography (US) is the most frequently utilized initial imaging modality[36]. However, it does not demonstrate superior accuracy in preoperative diagnosis[37]. The presence of the stalk was confirmed via ultrasound in a limited number of cases (5/30, 16.7%) (Table 2). 

Table 2: Imaging modalities used for cases.

Abbreviations: US = ultrasonography; CT = computed tomography; MRI = magnetic resonance imaging; NA= not available.

Conversely, computed tomography (CT) and magnetic resonance imaging (MRI) are preferred for supplementary imaging, particularly for gastrointestinal and urogenital etiologies of pelvic pain, and are especially recommended in cases of clinically suspected ovarian torsion with inconclusive ultrasound findings. MRI offers the inherent advantage of excellent soft-tissue contrast resolution allowing for the better characterization of the abnormalities[38-40]. The detection rate of pedicle for CT was 42.9% (6/14), while 81.8% (9/11) for MRI. MRI showed higher sensitivity and specificity. However, about half of all cases (41%, 14 /34) were absent of a specific pedicle in preoperative imaging examination (Table 2). Vascular pedicles are critical for the diagnosis of torsion of the leiomyoma[41], but can be challenging to detect with imaging techniques if the pedicle is thin and short[42]. Although atypical clinical symptoms and imaging modalities do not permit a precise preoperative diagnosis, they still play an important role in the detection of torsion of pedunculated subserosal myoma. Once preoperative imaging findings reach an accurate diagnosis, immediate surgical intervention is indicated, and failure to operate can lead to necrosis and sepsis[7]. Exploratory surgery should be considered even when a direct vascular pedicle is invisible, as evidenced by our case, which showed the mass in contact with the uterus. Furthermore, it can identify the source of the mass and provide early treatment for undetected malignancies[1]. 

What should physicians pay attention to? 

Pain occurs in approximately 30% of patients with leiomyomas typically resulting from acute degeneration and is the most common complication of pregnancy[10,43,44]. Fibroid torsion has been reported in 6 cases during pregnancy. Conservative management is the first choice and most commonly used approach for pregnant patients with red degeneration[43]. However, torsion of pedunculated subserous myoma necessitates surgical intervention, and if left untreated, it is even life-threatening due to myoma necrosis, infection, resultant inflammatory peritoneal reaction, and peritonitis[17]. Therefore, it is important to consider torsion when masses are discovered in pregnant patients with severe abdominal or pelvic pain[45].  Surgery is the primary treatment option for torsion of pedunculated subserosal leiomyoma. In 13 cases, a laparoscopic approach was chosen, while laparotomy was performed in 17 cases. It is essential  to carefully choose the appropriate surgical approach, especially in pregnant women. In our case, the patient was treated with anti-inflammatory therapy for one week for suspected pelvic inflammatory disease. Following this treatment, inflammatory indicators decreased back to normal values; however, the abdominal pain persisted, albeit with a decrease in intensity. Ultimately, the real cause of the patient's abdominal pain (torsion of pedunculated subserosal myoma) was finally identified by diagnostic laparoscopy. It is suggested that dynamic monitoring and assessment during clinical diagnosis and treatment is very important. In conclusion, torsion of pedunculated subserosal myoma is a rare condition. The most common symptom of leiomyoma torsion is abdominal pain. It’s difficult to distinguish from other common surgical and gynecologic acute abdomen. MRI shows higher accuracy and is highly recommended for preoperative diagnosis of myoma torsion. Regardless of pregnancy status, surgery is the first choice of treatment.

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