Accessory Cavitated Uterine Malformation (ACUM) - An Incidental Finding in Early Pregnancy

Sep 29, 2026

Uploaded by Jasmine

Accessory cavitated uterine malformation (ACUM) is a rare, often underdiagnosed Müllerian anomaly. The case report describes an ACUM incidentally detected during first-trimester screening in a woman in her early 30s with mild dysmenorrhoea. Transabdominal ultrasound showed a well-circumscribed intramyometrial cavitated lesion near the left round ligament without communication to the endometrial cavity. The pregnancy proceeded uneventfully to uncomplicated term vaginal delivery, and postpartum imaging showed persistence without change.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages5

Reading Time13 min

AccessFree to download

Abstract

Introduction

Case Presentation

Ultrasound findings (first trimester)

Ultrasound findings (second trimester)

Delivery and postpartum follow-up

Review began 11/09/2025 Review ended 12/04/2025 Published 12/05/2025 © Copyright 2025 Neves et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0. , which permits unrestricted use , distribution , and reproduction in any medium , provided the original author and source are credited. DOI: 10.7759/cureus.98510 Open Access Case Report Accessory Cavitated Uterine Malformation (ACUM) : An Incidental Finding in Early Pregnancy Catarina C. Neves 1, Rodrigo P. Mata 1, Ana Codorniz 1, Fernando Guerreiro 1 1. Obstetrics and Gynecology Department, Unidade Local de Saúde do Algarve-Portimão Unit, Portimão, PRT Corresponding author: Catarina C. Neves, [catarinaneves25@gmail.com](catarinaneves25@gmail.com) Abstract Accessory cavitated uterine malformation (ACUM) is a relatively rare and underdiagnosed Müllerian anomaly. We report an ACUM identified incidentally at first-trimester screening in a woman in her early 30s with a spontaneously conceived pregnancy and a history of mild dysmenorrhoea. Transabdominal ultrasound demonstrated a well-circumscribed intramyometrial cavitated lesion beneath the left round ligament, initially anechoic and later with a small echogenic component, without communication with the endometrial cavity and with normal ovaries. The pregnancy progressed uneventfully and culminated in an uncomplicated term vaginal delivery. Postpartum imaging showed persistence of the lesion without change, and the patient remains asymptomatic under gynaecological surveillance. This case highlights the diagnostic challenge of ACUM in pregnancy and emphasises the need for uniform diagnostic criteria as well as prospective studies to define its natural history, reproductive impact, and optimal management. Categories: Obstetrics/Gynecology Keywords: accessory cavitated uterine malformation, congenital uterine malformation, dysmenorrhoea, early pregnancy, first trimester ultrasound, gynaecological ultrasound Introduction Accessory cavitated uterine malformation (ACUM) is a rare Müllerian anomaly characterised by an isolated, cavitated myometrial lesion, most often near the insertion of the round ligament in women with normal uterine anatomy [1] . Its incidence and prevalence are unknown, and the condition is likely still underdiagnosed [2], as it has only recently been recognised as a distinct clinical entity. Multiple definitions have been proposed over the years to describe this lesion, and various terms have been used in the literature, including adenomyotic cyst, juvenile cystic adenomyosis, myometrial cyst and uterine-like mass [3] . Despite this, ACUM remains unclassified in the current uterine anomaly classifications proposed by the European Society of Human Reproduction and Embryology (ESHRE), the European Society for Gynaecological Endoscopy (ESGE) [4] and the revised American Society for Reproductive Medicine (ASRM) [5] . We report a rare case of an ACUM incidentally identified in early pregnancy, an unusual finding that underscores the diagnostic and imaging challenges of this entity during gestation. Case Presentation A woman in her early 30s, gravida 2 para 1, with a history of an uncomplicated spontaneous vaginal delivery approximately three years earlier, attended a routine first-trimester ultrasound for a spontaneously conceived pregnancy. She reported regular menstrual cycles every 28 days, lasting five days, with normal flow but with mild dysmenorrhoea. She had used a combined oral contraceptive pill for more than 10 years in total to control dysmenorrhoea. The patient had no significant past medical or gynaecological history and was a current smoker, consuming around 10 cigarettes per day. First-trimester ultrasound at 13 weeks and two days of gestation demonstrated a single intrauterine pregnancy with the crown-rump length consistent with gestational age. Combined screening for aneuploidy and early-onset pre-eclampsi

FAQs

What is accessory cavitated uterine malformation (ACUM) and why is it challenging in pregnancy?

ACUM is a rare Müllerian anomaly characterized by an isolated cavitated myometrial lesion. It remains underdiagnosed and poses diagnostic and imaging challenges during gestation, requiring consistent diagnostic criteria and further prospective research.

How was the ACUM lesion identified in this case?

It was incidentally noted on first-trimester transabdominal ultrasound as a well-defined intramyometrial cavitated mass near the left round ligament. Follow-up in the second trimester confirmed persistence with an internal echogenic component.

What were the pregnancy and postpartum outcomes for the patient?

The pregnancy was closely monitored without complications and ended in uncomplicated term vaginal delivery. Postpartum imaging showed the lesion persisted without change, and the patient remained asymptomatic under gynecological surveillance.

Sep 29, 2026

Uploaded by Jasmine