Ultrasound<\/h2>\n\n- Well-defined anterior uterine wall lesion measuring 3.6 \u00d7 2.9 cm<\/strong>, reported as fibroid.<\/li>\n
- Bilateral ovaries appeared normal.<\/li>\n<\/ul>\n
CT Abdomen<\/h2>\n\n- Ill-defined non-enhancing lesion in the anterior uterine wall measuring 3.0 \u00d7 1.2 cm<\/strong>.<\/li>\n<\/ul>\n
Well-defined hypodense intramyometrial lesion in the right uterine cornual region<\/p>\n![\"\"](\"https:\/\/www.kauveryhospital.com\/ima-journal\/wp-content\/uploads\/2026\/07\/when-a-fibroid-isnt-a-fibroid-mri-diagnosis-of-accessory-cavitated-uterine-mass-5-1.jpg\")
<\/figure>\n<\/div>\nMRI Pelvis<\/h2>\n\n- Well-defined T2 hypointense intramyometrial lesion<\/strong> in the right lateral uterine wall measuring 3.7 \u00d7 3.2 \u00d7 4.0 cm<\/strong>.<\/li>\n
- Central T1 hyperintense cavity (15 \u00d7 8.5 mm)<\/strong> with additional punctate T1 hyperintense foci, representing hemorrhagic contents.<\/li>\n
- Lesion closely related to the right round ligament<\/strong>.<\/li>\n
- Normal endmetrial cavity and bilateral ovaries.<\/li>\n<\/ul>\n
![\"\"](\"https:\/\/www.kauveryhospital.com\/ima-journal\/wp-content\/uploads\/2026\/07\/when-a-fibroid-isnt-a-fibroid-mri-diagnosis-of-accessory-cavitated-uterine-mass-3.jpg\")
<\/figure>\n<\/div>\n![\"\"](\"https:\/\/www.kauveryhospital.com\/ima-journal\/wp-content\/uploads\/2026\/07\/when-a-fibroid-isnt-a-fibroid-mri-diagnosis-of-accessory-cavitated-uterine-mass-4.jpg\")
<\/figure>\n<\/div>\n![\"\"](\"https:\/\/www.kauveryhospital.com\/ima-journal\/wp-content\/uploads\/2026\/07\/when-a-fibroid-isnt-a-fibroid-mri-diagnosis-of-accessory-cavitated-uterine-mass-5.jpg\")
<\/figure>\n<\/div>\nMRI Impression<\/h2>\n
Imaging features are highly suggestive of Accessory Cavitated Uterine Mass (ACUM).<\/strong><\/p>\nDifferential Diagnosis<\/h2>\n
\n\n\nDiagnosis<\/strong><\/td>\nDistinguishing MRI Features<\/strong><\/td>\n<\/tr>\n<\/thead>\n\n\nHemorrhagic degeneration of leiomyoma<\/strong><\/td>\nVariable signal intensity; lacks a functional endometrial-lined cavity and characteristic round ligament location.<\/td>\n<\/tr>\n \nCystic adenomyosis<\/strong><\/td>\nThickened junctional zone, diffuse adenomyosis, multiple myometrial cysts.<\/td>\n<\/tr>\n \nCystic adenomyoma<\/strong><\/td>\nSimilar hemorrhagic cystic changes but usually associated with adenomyosis and lacks the typical subserosal\/round ligament location.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nWhy MRI is important<\/h2>\n
The importance of MRI in the diagnosis of ACUM is:<\/p>\n
\n- Showing the central hemorrhagic cavity (T1 hyperintense) surrounded by T2 hypointense myometrium.<\/li>\n
- Confirming no communication to the endometrial cavity.<\/li>\n
- Defining the characteristic location beside the round ligament.<\/li>\n
- Distinguishing ACUM from leiomyoma, adenomyosis, and cystic adenomyoma.<\/li>\n
- Helping in accurate preoperative diagnosis and proper fertility-preserving surgical planning.<\/li>\n<\/ul>\n
Recognition of these characteristic MRI findings helps avoid misdiagnosis, unnecessary interventions and prolonged patient morbidity<\/p>\n
Discussion<\/h2>\n
Accessory Cavitated Uterine Mass (ACUM) is a rare congenital M\u00fcllerian anomaly, an accessory endometrial cavity within the myometrium, most commonly located near the insertion of the round ligament.<\/p>\n
Severe dysmenorrhea and chronic pelvic pain is caused by recurrent hemorrhage due to cyclic bleeding from the functional endometrial lining.<\/p>\n
ACUM is often misdiagnosed as a degenerating leiomyoma or cystic adenomyosis due to its rarity and nonspecific imaging on ultrasound and CT.<\/p>\n
MRI is the investigation of choice as it shows the typical hemorrhagic cavity within a well-defined myometrial lesion, confirms the normal native endometrial cavity without communication and accurately shows the characteristic location of the lesion, allowing a confident pre-operative diagnosis and appropriate surgical planning..<\/p>\n
The characteristic combination of a hemorrhagic non-communicating intramyometrial cavity adjacent to the round ligament with an otherwise normal uterus is highly suggestive of ACUM and helps distinguish it from its imaging mimics.<\/strong><\/p>\nConclusion<\/h2>\n
Accessory Cavitated Uterine Mass is a rare but important cause of chronic pelvic pain in young women. This case highlights the limitations of ultrasound and CT, both of which suggested a fibroid, whereas MRI established the diagnosis by demonstrating a characteristic hemorrhagic cavitated lesion adjacent to the round ligament. Familiarity with this entity and its MRI appearance is essential for early diagnosis and appropriate surgical management.<\/p>\n
Learning Points<\/strong><\/p>\n\n- ACUM is a rare congenital M\u00fcllerian anomaly and an important cause of severe dysmenorrhea.<\/li>\n
- Ultrasound and CT frequently misdiagnose ACUM as a leiomyoma.<\/li>\n
- MRI is the gold standard<\/strong> for diagnosis.<\/li>\n
- The hallmark MRI appearance is a T2 hypointense intramyometrial lesion with a central T1 hyperintense hemorrhagic cavity<\/strong> adjacent to the round ligament.<\/li>\n
- Early recognition allows definitive surgical treatment and prevents unnecessary delays in management.<\/li>\n<\/ul>\n
References<\/h2>\n\n- Goel A, Kumar K, Ibrahim D, et al. Accessory and cavitated uterine mass. Reference article, Radiopaedia.org (Accessed on 08 Jul 2026) <\/strong>https:\/\/doi.org\/10.53347\/rID-88261<\/strong><\/a><\/li>\n
- Aci\u00e9n P, Aci\u00e9n M, Mayol MJ, Aranda I.<\/strong> The cavitated accessory uterine mass: a M\u00fcllerian anomaly in women with an otherwise normal uterus.<\/em> Obstetrics & Gynecology.<\/strong> 2010;116(5):1101\u20131109.<\/li>\n<\/ol>\n\n
![\"\"](\"https:\/\/www.kauveryhospital.com\/ima-journal\/wp-content\/uploads\/2024\/04\/d.vijay_.jpg\")
<\/div>\n\nDr. Vijay Thiraviyam R, MBBS,
\nMD Radiology
\nKauvery Hospital, Chennai.<\/a><\/b><\/p>\n<\/div>\n<\/div>\n
CT Abdomen<\/h2>\n\n- Ill-defined non-enhancing lesion in the anterior uterine wall measuring 3.0 \u00d7 1.2 cm<\/strong>.<\/li>\n<\/ul>\n
Well-defined hypodense intramyometrial lesion in the right uterine cornual region<\/p>\n<\/figure>\n<\/div>\nMRI Pelvis<\/h2>\n\n- Well-defined T2 hypointense intramyometrial lesion<\/strong> in the right lateral uterine wall measuring 3.7 \u00d7 3.2 \u00d7 4.0 cm<\/strong>.<\/li>\n
- Central T1 hyperintense cavity (15 \u00d7 8.5 mm)<\/strong> with additional punctate T1 hyperintense foci, representing hemorrhagic contents.<\/li>\n
- Lesion closely related to the right round ligament<\/strong>.<\/li>\n
- Normal endmetrial cavity and bilateral ovaries.<\/li>\n<\/ul>\n<\/figure>\n<\/div>\n<\/figure>\n<\/div>\n<\/figure>\n<\/div>\n
MRI Impression<\/h2>\n
Imaging features are highly suggestive of Accessory Cavitated Uterine Mass (ACUM).<\/strong><\/p>\nDifferential Diagnosis<\/h2>\n
\n\n\nDiagnosis<\/strong><\/td>\nDistinguishing MRI Features<\/strong><\/td>\n<\/tr>\n<\/thead>\n\n\nHemorrhagic degeneration of leiomyoma<\/strong><\/td>\nVariable signal intensity; lacks a functional endometrial-lined cavity and characteristic round ligament location.<\/td>\n<\/tr>\n \nCystic adenomyosis<\/strong><\/td>\nThickened junctional zone, diffuse adenomyosis, multiple myometrial cysts.<\/td>\n<\/tr>\n \nCystic adenomyoma<\/strong><\/td>\nSimilar hemorrhagic cystic changes but usually associated with adenomyosis and lacks the typical subserosal\/round ligament location.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nWhy MRI is important<\/h2>\n
The importance of MRI in the diagnosis of ACUM is:<\/p>\n
\n- Showing the central hemorrhagic cavity (T1 hyperintense) surrounded by T2 hypointense myometrium.<\/li>\n
- Confirming no communication to the endometrial cavity.<\/li>\n
- Defining the characteristic location beside the round ligament.<\/li>\n
- Distinguishing ACUM from leiomyoma, adenomyosis, and cystic adenomyoma.<\/li>\n
- Helping in accurate preoperative diagnosis and proper fertility-preserving surgical planning.<\/li>\n<\/ul>\n
Recognition of these characteristic MRI findings helps avoid misdiagnosis, unnecessary interventions and prolonged patient morbidity<\/p>\n
Discussion<\/h2>\n
Accessory Cavitated Uterine Mass (ACUM) is a rare congenital M\u00fcllerian anomaly, an accessory endometrial cavity within the myometrium, most commonly located near the insertion of the round ligament.<\/p>\n
Severe dysmenorrhea and chronic pelvic pain is caused by recurrent hemorrhage due to cyclic bleeding from the functional endometrial lining.<\/p>\n
ACUM is often misdiagnosed as a degenerating leiomyoma or cystic adenomyosis due to its rarity and nonspecific imaging on ultrasound and CT.<\/p>\n
MRI is the investigation of choice as it shows the typical hemorrhagic cavity within a well-defined myometrial lesion, confirms the normal native endometrial cavity without communication and accurately shows the characteristic location of the lesion, allowing a confident pre-operative diagnosis and appropriate surgical planning..<\/p>\n
The characteristic combination of a hemorrhagic non-communicating intramyometrial cavity adjacent to the round ligament with an otherwise normal uterus is highly suggestive of ACUM and helps distinguish it from its imaging mimics.<\/strong><\/p>\nConclusion<\/h2>\n
Accessory Cavitated Uterine Mass is a rare but important cause of chronic pelvic pain in young women. This case highlights the limitations of ultrasound and CT, both of which suggested a fibroid, whereas MRI established the diagnosis by demonstrating a characteristic hemorrhagic cavitated lesion adjacent to the round ligament. Familiarity with this entity and its MRI appearance is essential for early diagnosis and appropriate surgical management.<\/p>\n
Learning Points<\/strong><\/p>\n\n- ACUM is a rare congenital M\u00fcllerian anomaly and an important cause of severe dysmenorrhea.<\/li>\n
- Ultrasound and CT frequently misdiagnose ACUM as a leiomyoma.<\/li>\n
- MRI is the gold standard<\/strong> for diagnosis.<\/li>\n
- The hallmark MRI appearance is a T2 hypointense intramyometrial lesion with a central T1 hyperintense hemorrhagic cavity<\/strong> adjacent to the round ligament.<\/li>\n
- Early recognition allows definitive surgical treatment and prevents unnecessary delays in management.<\/li>\n<\/ul>\n
References<\/h2>\n\n- Goel A, Kumar K, Ibrahim D, et al. Accessory and cavitated uterine mass. Reference article, Radiopaedia.org (Accessed on 08 Jul 2026) <\/strong>https:\/\/doi.org\/10.53347\/rID-88261<\/strong><\/a><\/li>\n
- Aci\u00e9n P, Aci\u00e9n M, Mayol MJ, Aranda I.<\/strong> The cavitated accessory uterine mass: a M\u00fcllerian anomaly in women with an otherwise normal uterus.<\/em> Obstetrics & Gynecology.<\/strong> 2010;116(5):1101\u20131109.<\/li>\n<\/ol>\n\n<\/div>\n\n
Dr. Vijay Thiraviyam R, MBBS,
\nMD Radiology
\nKauvery Hospital, Chennai.<\/a><\/b><\/p>\n<\/div>\n<\/div>\n
Well-defined hypodense intramyometrial lesion in the right uterine cornual region<\/p>\n Imaging features are highly suggestive of Accessory Cavitated Uterine Mass (ACUM).<\/strong><\/p>\n The importance of MRI in the diagnosis of ACUM is:<\/p>\n Recognition of these characteristic MRI findings helps avoid misdiagnosis, unnecessary interventions and prolonged patient morbidity<\/p>\n Accessory Cavitated Uterine Mass (ACUM) is a rare congenital M\u00fcllerian anomaly, an accessory endometrial cavity within the myometrium, most commonly located near the insertion of the round ligament.<\/p>\n Severe dysmenorrhea and chronic pelvic pain is caused by recurrent hemorrhage due to cyclic bleeding from the functional endometrial lining.<\/p>\n ACUM is often misdiagnosed as a degenerating leiomyoma or cystic adenomyosis due to its rarity and nonspecific imaging on ultrasound and CT.<\/p>\n MRI is the investigation of choice as it shows the typical hemorrhagic cavity within a well-defined myometrial lesion, confirms the normal native endometrial cavity without communication and accurately shows the characteristic location of the lesion, allowing a confident pre-operative diagnosis and appropriate surgical planning..<\/p>\n The characteristic combination of a hemorrhagic non-communicating intramyometrial cavity adjacent to the round ligament with an otherwise normal uterus is highly suggestive of ACUM and helps distinguish it from its imaging mimics.<\/strong><\/p>\n Accessory Cavitated Uterine Mass is a rare but important cause of chronic pelvic pain in young women. This case highlights the limitations of ultrasound and CT, both of which suggested a fibroid, whereas MRI established the diagnosis by demonstrating a characteristic hemorrhagic cavitated lesion adjacent to the round ligament. Familiarity with this entity and its MRI appearance is essential for early diagnosis and appropriate surgical management.<\/p>\n Learning Points<\/strong><\/p>\n Dr. Vijay Thiraviyam R, MBBS,<\/figure>\nMRI Pelvis<\/h2>\n
\n
<\/figure>\n<\/figure>\n<\/figure>\nMRI Impression<\/h2>\n
Differential Diagnosis<\/h2>\n
\n\n
\n Diagnosis<\/strong><\/td>\n Distinguishing MRI Features<\/strong><\/td>\n<\/tr>\n<\/thead>\n\n \n Hemorrhagic degeneration of leiomyoma<\/strong><\/td>\n Variable signal intensity; lacks a functional endometrial-lined cavity and characteristic round ligament location.<\/td>\n<\/tr>\n \n Cystic adenomyosis<\/strong><\/td>\n Thickened junctional zone, diffuse adenomyosis, multiple myometrial cysts.<\/td>\n<\/tr>\n \n Cystic adenomyoma<\/strong><\/td>\n Similar hemorrhagic cystic changes but usually associated with adenomyosis and lacks the typical subserosal\/round ligament location.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n Why MRI is important<\/h2>\n
\n
Discussion<\/h2>\n
Conclusion<\/h2>\n
\n
References<\/h2>\n
\n
<\/div>\n
\nMD Radiology
\nKauvery Hospital, Chennai.<\/a><\/b><\/p>\n<\/div>\n<\/div>\n
![\"\"](\"https:\/\/www.kauveryhospital.com\/ima-journal\/wp-content\/uploads\/2025\/08\/dr-malavika.jpg\")
<\/div>\n