Case 1
A 17-year-old female presented in August 2021 with cyclic lower abdominal pain for the past 7 months. She had attained menarche at the age of 16 years. Hence, the pain was clinically diagnosed as primary dysmenorrhea and the patient was given anti-spasmodic medications, but they were not beneficial.
Subsequently, the patient underwent USG followed by MRI of the pelvis. On USG, there was a well-defined round thick-walled cystic lesion along the right lateral wall of the uterus with fine internal echoes. No communication with the uterine cavity could be demonstrated, and a possibility of a non-communicating rudimentary uterine horn was considered. MRI was done for further evaluation, which also demonstrated a well-defined, round, thick-walled peripherally enhancing cystic lesion along the right lateral wall of the uterus, at the site of insertion of the right round ligament. The wall of the cystic lesion appeared isointense to myometrium on T1W and hypointense on T2W sequences, while its contents were hemorrhagic (Fig. 2). It showed no communication with the endometrial cavity or any mass effect on the endometrium. The uterus was otherwise normal, and both horns were well developed. Both ovaries were also normal.
Given the typical radiological appearance and characteristic location of the cavity in an otherwise normal uterus, the diagnosis of ACUM (ESHRE/ESGE U6C0V0) was made. The patient underwent a laparoscopic tumorectomy of ACUM in December 2021 which led to complete symptomatic relief.
ACUM is myometrial-lined cavities located in the anterolateral aspect of the uterus, at the site of insertion of the round ligament, predominantly on the right side [2]. They are usually diagnosed in nulliparous females who are < 30 years of age [2]. According to a recent hypothesis, ACUM is thought to represent a new type of unclassified Müllerian duct, which is congenital in origin due to defective function of the female gubernaculum or ectopic Müllerian remnants [2]. In the appropriate clinical setting, ACUM can be diagnosed if it fulfills the following criteria: (i) an isolated accessory cavitated mass; (ii) a normal uterus (endometrial lumen), fallopian tubes, and ovaries; (iii) an accessory cavity lined by functional endometrium; (iv) blood degradation products in cavity; and (v) absence of adenomyosis in the rest of the uterus, although there could be small foci of adenomyosis in the myometrium adjacent to the accessory cavity [2].
The differential diagnoses of ACUM include:
Rudimentary and cavitated uterine horns seen in other uterine structural anomalies
Visualizing a normal uterus in ACUM as compared to the banana-shaped developed horn in a hemiuterus helps in differentiating between these two entities [6]. Similarly, rudimentary functioning horns in MRKH can be identified easily due to associated aplasia or hypoplasia of the uterus and other Müllerian duct derivatives.
Uterine leiomyoma with cystic or red degeneration
The larger size, multiplicity of lesions, and mass effect on the endometrial cavity usually help in the diagnosis [7]. However, a definite diagnosis may require laparoscopy and histopathology to identify the presence of endometrial lining in ACUM.
Focal cystic adenomyosis
This occurs in older multiparous women between 35 and 40 years, is usually ill-defined, and located away from the junctional zone, with no significant mass effect on the endometrial cavity. The rest of the uterus may show features of focal or diffuse adenomyosis [8]. In cornual ectopic pregnancy, although the location of the lesion may be similar to ACUM, MRI helps in accurately localizing the eccentric position of the gestational sac, surrounded by a thin rim (< 5 mm) of the myometrium and situated more than 1 cm from the lateral wall of the endometrial cavity [9]. Besides, the clinical presentation of secondary amenorrhea and urine pregnancy test positivity easily differentiates between the two conditions.
Case 2
A 14-year-old female presented to our department in February 2022 with primary amenorrhea and severe unresolved cyclic lower abdominal pain for six months. She had normal secondary sexual characteristics and hormonal assays.
The patient initially underwent USG of the pelvis. This showed a well-defined round to oval cystic lesion with thick walls in the right adnexa, along with a tubular cystic lesion with incomplete septation and internal echoes within it. No separate uterine structures could be demonstrated apart from the above-mentioned lesions. Subsequently, the patient underwent MRI, which showed a rudimentary horn in the right hemipelvis, with T1W and T2W hyperintense contents within the lumen, without signal suppression on T1FS images, suggestive of hematometra. A large tubular cystic lesion with incomplete septa was seen in the right adnexa abutting the right ovary, which had similar signal intensity contents, suggestive of hematosalpinx. There was complete aplasia of the cervix and vagina; however, both ovaries were normal (Fig. 3). No renal or lumbosacral vertebral anomalies were evident.
The case was diagnosed as atypical MRKH syndrome with an aplastic cervix, vagina, and a functional rudimentary right horn with hematometra and right hematosalpinx (ESHRE/ESGE U5aC4V4). The patient is currently awaiting laparoscopic removal of the functioning horn.
MRKH syndrome is suspected when a patient presents with primary amenorrhea with normal secondary sexual characteristics due to preserved ovarian function. MRI can demonstrate a spectrum of anomalies ranging from the complete absence of a uterus and upper 2/3rd of the vagina with ectopic ovaries, and rudimentary horns connected to each other by a fibrous cord, to the presence of a rudimentary, hypoplastic uterus with one to three layers of uterine differentiation [5]. The rudimentary uterus is defined as one which does not have conventional differentiation of corpus uteri and cervix uteri [5]. It can be located in the pelvis, mostly being attached to the ovary with a constant caudal relationship [5] and is well depicted on MRI unlike with transabdominal ultrasound.
Case 3
A 16-year-old female presented to us in October 2021 with complaints of non-resolving dysmenorrhea for the past 8 months with normal hormonal assay and secondary sexual characteristics.
Transabdominal USG demonstrated two separate uterine cavities, of which the right uterine cavity was filled with anechoic contents showing fine internal echoes. There was a well-defined tubular anechoic structure with incomplete septation seen in the right adnexa. A provisional diagnosis of hemiuterus with right hematometra and hematosalpinx was made. Subsequently, MRI of the pelvis of the patient revealed a banana-shaped uterus (hemiuterus) with normal zonal differentiation in the left hemipelvis, contiguous with a normal cervix and vagina. A large myometrial-lined cavity was seen in the right hemipelvis, which was connected to the left-sided hemiuterus by a fibrous band. This cavity contained heterogeneously hyperintense contents on T1WSE, T2WSE, and T1WFS (fat saturated) sequences, suggesting hematometra in a non-communicating, functional, rudimentary right horn. Right-sided hematosalpinx was also seen (Fig. 4). Bilateral ovaries were visualized separately and appeared normal.
Hence, the diagnosis of a hemiuterus with a non-communicating, functional, right rudimentary horn with hematometra and right hematosalpinx (ESHRE/ESGE U4aC0V0) was made. Surgical excision of the obstructed horn was done laparoscopically for the patient in January 2022, followed by total relief from the debilitating symptoms.
Hemiuterus results from unilateral uterine development, with a rudimentary (functional) horn (Class U4a) or without rudimentary horn (Class U4b—non-functional or aplastic cavity) [1]. Various other conditions may result in similar clinical presentation, such as endometriosis, adenomyosis, and entities causing vaginal obstruction like obstructed hemivagina with ipsilateral renal anomaly (OHVIRA) syndrome [10]. A high index of clinical suspicion and a simple approach to imaging patients with recurrent cyclic pain enable the radiologist to clinch the diagnosis (Fig. 5).
