CPD shorts: Accessory and cavitated uterine mass/ malformation (ACUM)

Noorayen Alware takes a closer look at ACUM based around a clinical case study

Published: 01 December 2023 CPD

This CPD activity is based on a clinical case study relating to the findings of accessory and cavitated uterine mass / malformation (ACUM) and the subsequent learning that took place. 

Six key points

1. Accessory cavitated uterine mass or malformation (ACUM) is a rare mullerian anomaly related to dysfunction of gubernaculum, which is often undiagnosed or under-diagnosed with ultrasound. It is sometimes known as a ‘non-communicating accessory uterine cavity’, which helps to define what it is thought to be. It is a cavity (or in some cases more than one cavity) that contains functional endometrial tissue, but does not communicate with the uterus. Currently the European Society of Human Reproduction and Embryology (ESHRE) classify it as class 6 (unclassified malformation), because there have been so few reported cases. There is considerable on-going debate about whether this should be classified as a mass or malformation. 

2. It presents most commonly in nulliparous women and people with a uterus under 30 years of age. 

Common symptoms include:

  • Severe dysmenorrhoea
  • Recurrent pelvic pain
  • Often ipsilateral pain on the side of the mass, but can be central
  • Pain is often unresponsive to analgesia or hormonal therapy

3. Many recent articles have used the diagnostic criteria according to Acién et al (2010) which include:

  • An isolated accessory cavitated mass
  • Normal uterus (endometrial cavity), tubes, and ovaries
  • Surgical case with excised mass and with pathological examination
  • Accessory cavity lined by endometrial epithelium with glands and stroma
  • Chocolate-brown-coloured fluid content
  • No adenomyosis (if uterus removed), but there could be small foci of adenomyosis in the myometrium adjacent to the accessory cavity

4.   Imaging: 

  • If consent is given, a transvaginal ultrasound scan (TVS) is the first-line imaging investigation, hence the importance of being aware of the ultrasound features of ACUM
  • ACUM can be difficult to diagnose transabdominally, so MRI referral is preferred for those who decline or where TVS is contraindicated
  • 3D ultrasound can assist in defining the mass and surrounding uterine structures
  • Transrectal ultrasound has also been used to diagnose ACUM
  • MRI may be needed to differentiate ACUM from other differentials. Pelvic MRI has a high accuracy rate for the diagnosis of ACUM 

5. Ultrasound appearances often include:

  • Well-defined solid mass slightly lateral to the uterus
  • Can be seen along the uterine wall of an otherwise normal uterus
  • A cavity seen within the mass
  • Cystic avascular internal echoes within the cavity that may have similar appearances to an endometrioma 

6. ​Differential diagnoses:

  • Cystic adenomyoma
  • Degenerating fibroid
  • Functional non communicating rudimentary uterine horn
  • Pseudo-broad ligament fibroid.

Reflection prompts:

What is the importance of mentioning differential diagnoses in the report when the appearances are atypical of a Mullerian duct anomaly?

What is the value of sonographer representation at gynaecology multidisciplinary team (MDT) meetings? Is there input into your local MDT? 

If yes: What impact has that had on patient outcomes, sonographer role satisfaction and MDT working?

If no: Is this something that can be pursued? How can you influence this?

How often do you hold/attend departmental CPD sessions to discuss unusual ultrasound cases? If you do not have this in place, are there ways that you can learn from interesting, unusual or complex cases? 

How often do you ask for a second opinion when scanning gynaecology cases. What methods do you use to find out the outcome of complex or unusual cases?

Do you routinely use 3D ultrasound for gynaecology scanning? Which cases do you think 3D will add to the diagnostic accuracy?

Further Reading

Acién, P. Acién, M. Fernández, F. et al (2010) The cavitated accessory uterine mass: a Müllerian anomaly in women with an otherwise normal uterus. Obstetrics and Gynecology. 116(5): 1101–1109. https://doi.org/10.1097/AOG.0b013e3181f7e735 

Acién, P. Bataller, A. Fernández, F. et al (2012) New cases of accessory and cavitated uterine masses (ACUM): a significant cause of severe dysmenorrhea and recurrent pelvic pain in young women. Human Reproduction. 27(3): 683-694. DOI: 10.1097/AOG.0b013e3181f7e735

American Society for Reproductive Medicine (2021) ASRM Mullerian anomalies classification 2021

Betzler, N. Brunes, M. Anfelter, P. et al. (2019) Sonografic features of accessory cavitated uterine mass (ACUM) successfully treated with robotic assisted laparoscopic surgery- a case report. Clinical Obstetrics Gynecology and Reproductive Medicine. 5. DOI:10.15761/COGRM.1000268 

Grimbizis, G. Di Spiezio Sardo, A. Saravelos, S. et al (2016) The Thessaloniki ESHRE/ESGE consensus on diagnosis of female genital anomalies. Human Reproduction. 31(1), 2-7. https://doi.org/10.1093/humrep/dev264 

Iranpour, P. Haseli, S. Keshavarz, P. et al (2021). Pelvic Pain and Adnexal Mass: Be Aware of Accessory and Cavitated Uterine Mass. Case Reports in Medicine, 2021, 6649663. https://doi.org/10.1155/2021/6649663 

Mollion, M. Host, A. Faller, E. et al. (2021) Report of two cases of Accessory Cavitated Uterine Mass (ACUM): Diagnostic challenge for MRI. Radiology Case Reports. 16 (11): 3465-3469. https://doi.org/10.1016/j.radcr.2021.07.071

Naftalin, J. Bean, E. Saridogan, E. et al (2021) Imaging in gynecological disease (21): clinical and ultrasound characteristics of accessory cavitated uterine malformations. Ultrasound Obstetetrics and Gynecology, 57 (5): 821-828. https://doi.org/10.1002/uog.22173

Putta, T. John, R. Simon, B. et al (2021) Imaging Manifestations of Accessory Cavitated Uterine Mass-A Rare Mullerian Anomaly. Indian Journal of Radiology and Imaging. 31 (3): 545-550. doi:10.1055/s-0041-1735504

Rackrow, B. (2022) Accessory cavitated uterine mass: a new müllerian anomaly? Fertility and Sterility. 117 (3): 649 – 650. DOI: https://doi.org/10.1016/j.fertnstert.2022.01.006

Setty, T. Naftalin, J. Jurkovic, D. (2022) Accessory cavitated uterine malformations (ACUMs): an unfamiliar cause of dysmenorrhoea. The Obstetrician & Gynaecologist. 24: 40–49. https://doi.org/10.1111/tog.12787