Case report: Accessory cavitated uterine malformation: A diagnostic dilemma.

A 21-year-old nulliparous female presented to the outpatient department (OPD) with complaints of lower abdominal pain with cyclical dysmenorrhea for a period of 4 years. The pain appeared to be increasing in intensity over time often requiring the use of IV analgesics for its management. The general physical examination was normal. No obvious mass was felt on local examination. However, mild local tenderness was elicited in the hypogastrium. She attained her menarche at 13 years of age and her cycles consisted of normal flow and periodicity. A history of diagnostic laparoscopy was obtained which showed presence of a uterine bulge in the region of the right cornua ( Fig. 3 ). No other significant medical or surgical history was present. On Ultrasonography (USG), a hyperechoic cystic lesion with hypoechoic rim was noted in the uterine corpus within the myometrium on right side around the region of the cornua with showed posterior acoustic enhancement ( Fig. 1 ). The endometrial cavity was seen separately from the lesion. The lesion didn’t have any continuation with the cervix and was within the fundal contour with no separate horn which was confirmed on 3-dimensional ultrasound (3D USG) ruling out unicornuate uterus with rudimentary horn. On 3D imaging, the adjacent endometrial cavity had normal contour unlike unicornuate uterus. Considering the history and imaging findings, strong suspicion of ACUM was made following which magnetic resonance Imaging (MRI) pelvis was advised. Fig. 1 Trans abdominal USG 2D(A) and 3D(B) showing the presence of a well-defined hyper echoic cystic lesion (lei) in the right adnexa surrounded by normal myometrium showing posterior acoustic enhancement. The endometrial cavity (cav) appears normal with presence of both Cornu of normal morphology. Fig 1 – Trans abdominal USG 2D(A) and 3D(B) showing the presence of a well-defined hyper echoic cystic lesion (lei) in the right adnexa surrounded by normal myometrium showing posterior acoustic enhancement. The endometrial cavity (cav) appears normal with presence of both Cornu of normal morphology. MRI showed the presence of a well-defined cavity in right sided myometrium appearing minimally hyperintense on T1 and heterogeneously hyper intense on T2 weighted images with surrounding well defined T2 hypointense rim with intensity similar to junctional zone. The content was showing blooming on susceptibility weighted sequences (hemorrhagic product) ( Figs. 2 A,B and C). A normal uterine cavity was seen adjacent to this lesion on left side continuing with the cervix. Adnexa was unremarkable ( Fig. 2 A). Based on imaging findings, diagnosis of ACUM was made. The patient was then referred to a higher centre for surgical management where hysteroscopy and laparoscopy was converted to a laparotomic excision of the ACUM followed by histopathological examination which confirmed the diagnosis. Fig. 2 T1 (A) and T2 (B) weighted images depicting a well-defined T1 heterogeneously isointense (to muscle) and T2 heterogeneously hyper intense lesion (lei) with internal hypo intense (hemorrhagic) contents in the region of the right uterine myometrium adjacent to the right cornua of the uterus. Note the normal appearing endometrial cavity (cav) with myometrium surrounding the lesion. The T2 hypo intense rim surrounding the cyst is explained by the presence of smooth muscle and stromal components. Gradient image (C) showing foci of blooming in the region of the right uterine cornua suggesting hemorrhagic content. Fig 2 – Fig. 3 Laparoscopic view depicting the uterus (UT) showing a well-defined lesion(CAV) along the region of the right cornua (A). Right ovary (RO) visualized separate from the lesion (B). Fig 3 - T1 (A) and T2 (B) weighted images depicting a well-defined T1 heterogeneously isointense (to muscle) and T2 heterogeneously hyper intense lesion (lei) with internal hypo intense (hemorrhagic) contents in the region of the right uterine myometrium adjacent to the right cornua of the uterus. Note the normal appearing endometrial cavity (cav) with myometrium surrounding the lesion. The T2 hypo intense rim surrounding the cyst is explained by the presence of smooth muscle and stromal components. Gradient image (C) showing foci of blooming in the region of the right uterine cornua suggesting hemorrhagic content. Laparoscopic view depicting the uterus (UT) showing a well-defined lesion(CAV) along the region of the right cornua (A). Right ovary (RO) visualized separate from the lesion (B).

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A relatively recently accepted entity, ACUM forms a potentially treatable cause of chronic pelvic pain and dysmenorrhea in females. A high degree of suspicion must be kept in dealing with young patients presenting with related symptoms with imaging findings complementing the diagnosis. With increasing awareness among health professionals and improvements in imaging modalities, advancements are being made for prompt diagnosis and adequate management of this once (although relatively recently) commonly misdiagnosed entity.

ACUM can be described as a non-communicating, accessory uterine horn present within the myometrium or broad ligament of an otherwise normal appearing uterus on MRI studies [ 3 ]. With less than 60 known reported cases reported by 2022 [ 4 ], ACUM is a relatively rare and yet a potentially treatable cause of chronic dysmenorrhea in young females presenting as severe pain in pelvic region (usually localized to the side of the lesion) with associated dysmenorrhea. Their occurrence have been described in both nulliparous as well as parous women [ 5 , 6 ]. The pathogenesis of the condition has been described in literature including those of metaplasia of the stromal element in long standing endometriosis [ 7 ], the more accepted theory is that of mullerianosis/ Mullerian choriostoma, ie, developmentally misplaced mullerian tissues [ 8 ]. Possibility of glaubernaculum dysfunction causing duplication of the mullerian duct at the level of the round ligament explains its origin and its common location. [ 2 ] Considering its origin as a developmental anomaly, the lesion is currently classified in the U6 category (unclassified uterine malformations) according to the ESHRE consensus of 2013 [ 9 ]. However, according to the new Mullerian anomalies classification (MAC) by American society of reproductive medicine in 2021, it is not included as a type of congenital mullerian anomaly [ 10 ]. This could be explained by the possible lack of adequate literature review [ 11 ]. According to the critical review of the same by Ludwin et.al., [ 11 ] ACUM due to the origin and severe morbidity associated with the condition, this inclusion of this condition in the Mullerian anomalies classification (MAC) is required. The exact diagnostic criteria of ACUM states it to be an accessory cavitated lesion located near the region of the round ligament, having normal ovaries, fallopian tubes and uterus. Post operatively the cavity should have an endometrial lining showing storma and glands, with chocolate brown fluid and absence of adenomyotic changes in the surroundings [ 2 ]. On imaging, USG shows findings of a well-defined cystic lesson in the uterine myometrium which appears separate from the ovary. The echogenicity of the lesion varies with its content, most commonly presenting as ground glass echogenicity owing to its hemorrhagic content [ 3 , 12 , 13 ]. Hysterosalphyngography can be done to rule out possibility of other mullerian anomalies but such anomalies are usually picked up on 2D or 3D USG hence limiting issue in diagnosis of the same. Absence of communication with the endometrial cavity is seen in such cases [ 6 , 12 ]. MRI is the modality of choice which shows presence of a hyper intense lesion/collection on T1/ T1 Fat saturated sequences which can appear as iso to hypo intense on T2 weighted images (WI) in the uterine myometrium. A T2 shading effect may also be observed owing to its hemorrhagic content. Blooming can hence be observed on gradient images. The typical location is around the region on the broad ligament insertion in the uterus corresponding to the location of the uterine cornua. The collection is seen surrounded by a T2 hyperintense rim (endometrial lining) which in turn is surrounded by T2 hypointense rim (corresponding to smooth muscle/stromal elements). The rest of the uterus appears normal without presence of any adenomyotic component [ 10 , 13 ]. The most common imaging differentials include those of a unicornuate uterus with a rudimentary horn (differentiated by presence of normal uterine morphology in ACUM), fibroid with cystic degeneration (differentiated by the presence of hemorrhagic content in ACUM with its characteristic imagining findings as compared to the latter which shows fluid properties on MRI) and cystic adenomyotic changes (which can be differentiated by its nonspecific location, older age group presentation and associated changes involving the endometrium which is normal in ACUM) [ 1 ]. The definitive management is considered to be laparoscopic/ laparotomic enucleation of the lesion with a preferably anterior approach [ 10 ]. While other methods of treatment like USG guided sclerotherapy of the lesion have been tried [ 6 ], its effect of future obstetric outcomes have not been adequately described. However, it still appears to be a possible means of conservative/ minimally invasive means of management in patients who are anxious of the surgical management [ 6 , 9 ].

First described by Oliver in 1912 [ 1 ] and mentioned as a distinct clinical entity by Acién et al. [ 2 ] in 2010, ACUM is described as the presence of an accessory uterine horn in an otherwise normal uterus [ 3 ]. A relatively rare entity, ACUM is a commonly misdiagnosed treatable cause for severe pelvic pain in females. With improving imaging modalities and increasing awareness among health professionals, its acknowledgement as a specific entity is increasing in literature with similar improvements in the management of the same.