Three-dimensional ultrasound for diagnosing Robert's uterus: a case series.

This retrospective case series study aimed to evaluate the 3D ultrasonographic manifestations of Robert’s uterus and its differential diagnosis. All procedures in this study were performed in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written or verbal informed consent was obtained from the patients for the publication of this case series and any accompanying images. A copy of the written consent is available for review by the editorial office of this journal. This retrospective case series was conducted at the Department of Ultrasound, Gansu Provincial Maternity and Child Care Hospital, a tertiary academic hospital in Lanzhou, Gansu Province, China. Patient recruitment and data collection were performed from January 2020 to December 2025. All patients underwent routine preoperative ultrasound examinations and subsequent hysteroscopic septoplasty at the same institution. Follow-up data were collected at three months postoperatively. Written informed consent for the ultrasound examinations was obtained from all patients as part of routine clinical care. Preoperative ultrasound assessment of patients with suspected uterine anomalies included the following: (I) evaluation of uterine size, endometrial lining, and adnexa using 2D pelvic ultrasound; (II) acquisition of a 3D ultrasound volume dataset of the entire uterus in the sagittal plane; (III) multiplanar reconstruction to obtain a standardized coronal view of the uterus; (IV) assessment of the external uterine contour, including the presence or absence of fundal indentation; (V) evaluation of the intrauterine septum, including its morphology, length, thickness, echogenicity (myometrial vs. fibrous composition), and the distance from the inferior tip of the septum to the internal cervical os; (VI) assessment of whether the uterine cavity was completely separated into two non-communicating chambers; and (VII) evaluation of cervical canal morphology, including the presence of a single or double cervical canal. Patients who underwent surgery were followed up with 2D and 3D ultrasound at three months postoperatively to assess cavity restoration. Among the 10 patients, four presented with primary infertility, four with recurrent first-trimester miscarriage (ranging from one to three pregnancy losses), one with menorrhagia, and one with an incidental finding during a routine examination. All 10 patients underwent hysteroscopic septoplasty under laparoscopic guidance to monitor uterine wall integrity. Surgical findings confirmed the preoperative 3D ultrasound diagnosis in all cases. The inferior limit of the septum was consistent with the 3D ultrasound measurements (with the distance from the septum tip to the internal cervical os ranging from 2 to 16 mm), resulting in a 100% concordance rate. No intraoperative or postoperative complications (e.g., uterine perforation, excessive bleeding, infection, or intrauterine adhesions) occurred in any case. Postoperative 3D ultrasound at three months showed a largely restored uterine cavity with a residual septum of less than 1 cm in all patients ( Table 1 ). Type 1: both hemi-cavities are narrow but patent. Type 2: one hemi-cavity is blind or severely hypoplastic. 3D, three-dimensional. The distance from the septum tip to the internal cervical os varied among patients. Using 3D ultrasound, experts with extensive experience in ultrasound diagnosis measured and delineated the extent of the septum, with each measurement repeated three times. In patients with a septum tip located very close to the internal cervical os (e.g., ≤5 mm), the functional uterine cavity was more severely compromised, and all presented with either infertility or recurrent miscarriage. In contrast, patients with a greater distance between the septum tip and the internal cervical os (e.g., 16 mm in case 10) had a larger residual cavity above the cervix, which was associated with occasional pregnancies, although the outcomes remained poor. These findings suggest that the distance from the septum tip to the internal cervical os may be a crucial factor influencing reproductive outcomes. According to the degree of asymmetry and the status of the smaller hemi-cavity, the cases were classified as Type 1 (both cavities narrow but patent) or Type 2 (one cavity blind or nearly blind). Among the 10 cases, seven were Type 1 and three were Type 2. No Type 3 cases (both cavities blind or absent) were identified. In cases where 3D ultrasound cannot confidently determine the patency of the smaller cavity, supplemental magnetic resonance imaging (MRI) is recommended; however, in this series, 3D ultrasound alone was sufficient and confirmed by surgery. The characteristic 3D ultrasound features of Robert’s uterus (illustrated in Figures 1-4 ) include: Uterine external contour: the fundal contour is typically normal or flat, with no significant indentation (>1 cm), distinguishing it from a bicornuate uterus ( Figure 1 ). Coronal-plane reconstruction: the reconstructed coronal view clearly shows a complete septum extending from the fundus to a variable distance above the internal cervical os. The septum is broad and shows echogenicity similar to the myometrium ( Figure 2 ) . Cavity morphology: the uterine cavity is completely divided into two separate, narrow, triangular, or elongated hemi-cavities that do not communicate ( Figure 3 ). Asymmetry in the size and shape of the two hemi-cavities is often evident (e.g., Case 10, Figure 4A ). Cervical canal: a single, normal cervical canal is visualized, confirming the diagnosis and ruling out a double cervix (such as in a complete septate uterus with double cervix or didelphys) . Case 1. (A) 2D ultrasound image in the sagittal plane showing an apparently normal uterine cavity. (B) 3D ultrasound reconstructed coronal-plane image clearly demonstrating the complete septum dividing the cavity into two separate hemi-cavities, with a flat fundal contour, consistent with Robert’s uterus. 2D, two-dimensional; 3D, three-dimensional. Case 3. (A) 3D ultrasound coronal-plane view showing a complete myometrial septum extending from the fundus to just above the internal cervical os (3 mm above the os). The two hemi-cavities are narrow and triangular. (B) Corresponding hysteroscopic view confirming the thick septum dividing the cavity. The arrow indicates the complete myometrial septum. 3D, three-dimensional. Case 6. The coronal plane on 3D ultrasound demonstrates a thick and complete septum. The two hemi-cavities are distinctly separated. 3D, three-dimensional. Case 10. (A) Preoperative 3D ultrasound in the coronal plane shows a complete myometrial septum, with arrow indicating the normal endometrium. (B) 3D ultrasound image at 3 months after hysteroscopic septoplasty demonstrates a fused uterine cavity with normal morphology, an intrauterine device echo is seen, along with a small fundal indentation (<1 cm). 3D, three-dimensional. The surgical outcomes of all 10 patients who underwent hysteroscopic septoplasty with laparoscopic assistance were monitored. All procedures were completed without complications. Postoperative recovery was uneventful. At three months postoperatively, 3D ultrasound showed restoration of a largely normal uterine cavity in nine patients, while one patient had a minimal residual septum (<5 mm) ( Figure 4B ). No intrauterine adhesions were observed during follow-up. Pathological examination of the resected septum in three cases confirmed benign myometrial tissue with overlying endometrium, consistent with a uterine septum.

Robert’s uterus (also known as Robert’s uterine malformation) is a rare and specific subtype of complete septate uterus. Unlike the classic symmetric complete septum, Robert’s uterus features an asymmetric septum that results in one hypoplastic or blind hemi-cavity, while the other hemi-cavity may be relatively normal. It is defined by the presence of a complete, asymmetric muscular septum that divides the uterine cavity into two separate hemi-cavities, extending from the fundus to just above the internal cervical os, while the cervix remains single and morphologically normal. The estimated incidence of Robert’s uterus is less than 1% among all Müllerian anomalies and approximately 5–10% of septate uteri ( 1 ). This anatomical disruption creates an unfavorable environment for implantation and is associated with infertility, early pregnancy loss, and other adverse obstetric outcomes ( 2 ). Conventional two-dimensional (2D) transvaginal ultrasound, limited to sagittal and transverse planes, often fails to provide a comprehensive evaluation of the uterine coronal plane. This limitation makes it difficult to accurately assess the septum’s length, thickness, and, most importantly, its spatial relationship to the internal cervical os, leading to low diagnostic sensitivity and frequent misclassification as a bicornuate or partial septate uterus ( 3 ). Hysteroscopy combined with laparoscopy remains the diagnostic gold standard; however, it is invasive. Three-dimensional (3D) ultrasonography, through volume data acquisition and post-processing, allows reconstruction and visualization of a standardized uterine coronal view. This non-invasive “one-stop” assessment clearly depicts the external uterine contour, cavity morphology, and cervical canal ( 4 ). According to the European Society of Human Reproduction and Embryology-European Society for Gynaecological Endoscopy (ESHRE-ESGE) classification system, Robert’s uterus corresponds to U2bC3V0 (a complete septate uterus with a single cervix and no vaginal anomaly)( 5 ). Dedicated imaging studies on Robert’s uterus are scarce, especially systematic evaluations using 3D ultrasound. This retrospective case series analyzed the 3D ultrasound imaging data of patients with surgically confirmed Robert’s uterus to systematically summarize its sonographic features and clarify the diagnostic value of 3D ultrasound in classification and treatment guidance. We present this article in accordance with the AME Case Series reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2026-0834/rc ).

Robert’s uterus is a rare Müllerian anomaly, with an estimated incidence of less than 1% among all uterine malformations ( 6 ). Its distinctive anatomy—a complete asymmetric septum dividing the cavity while preserving a single cervix—often leads to misdiagnosis on conventional 2D ultrasound, which cannot adequately display the coronal plane ( 7 ). 3D ultrasound overcomes this limitation by providing a standardized coronal view that simultaneously shows the fundal contour, the entire septum, and the cervical canal. This study demonstrates that 3D ultrasound has 100% diagnostic accuracy for Robert’s uterus compared with surgical findings, confirming its role as a reliable non-invasive diagnostic tool. A recent systematic review and meta-analysis demonstrated comparable performance of 3D ultrasound to MRI for congenital uterine disorders, further supporting 3D ultrasound as a first-line imaging modality ( 8 ). The 3D ultrasound features of Robert’s uterus are characteristic and distinct from those of other anomalies. A normal or flat fundal contour helps distinguish it from a bicornuate uterus, which exhibits a deep fundal indentation (>1 cm). The complete septum extending above a single internal cervical os distinguishes it from a complete septate uterus with a double cervix (which would show two cervical canals) and from a partial septate uterus (in which the septum does not extend to the internal cervical os) ( 9 ). In our series, the distance from the septum tip to the internal cervical os ranged from 2 to 16 mm, and this parameter appeared to be associated with clinical severity. Patients with a very low septum (close to the internal cervical os) had smaller functional cavities and presented with more severe reproductive impairment, consistent with previous studies suggesting that cavity volume and septal vascularity may influence implantation ( 10 , 11 ). Accurate diagnosis has significant clinical implications. Robert’s uterus is associated with poor reproductive outcomes due to reduced functional cavity volume, possible compromise of endometrial blood supply, and potentially abnormal myometrial contractility ( 12 ). Hysteroscopic septoplasty is the standard treatment for symptomatic patients ( 13 ). Preoperative 3D ultrasound not only confirms the diagnosis but also provides an exact roadmap for surgery, allowing the surgeon to plan the resection endpoint (just above the internal cervical os) and minimize the risk of injury to the cervix or fundus. In our series, all surgeries were successfully guided by 3D ultrasound measurements, and postoperative 3D ultrasound confirmed adequate cavity restoration. These findings are consistent with previous reports highlighting the value of 3D ultrasound in postoperative assessment ( 14 ). Moreover, 3D ultrasound can identify associated findings such as endometrial polyps, adenomyosis, and ovarian pathology, which may coexist and affect fertility ( 15 ). In our study, one patient with menorrhagia was found to have an endometrial polyp on 3D ultrasound, which was confirmed and removed during hysteroscopy. Thus, 3D ultrasound provides a comprehensive pelvic assessment. Literature reports indicate that approximately 20–30% of patients with septate uterus may have associated renal anomalies ( 16 ). Therefore, in patients diagnosed with Robert’s uterus, a renal ultrasound is recommended to rule out unilateral renal agenesis or other anomalies, although no such findings were observed in any of our cases. The limitations of this study include its retrospective design and small sample size, both of which are inherent to the rarity of this condition. Larger prospective studies are needed to further quantify the diagnostic performance of 3D ultrasound and to assess long-term reproductive outcomes after surgery, including pregnancy and live birth rates. In addition, comparative studies with MRI could further establish the role of 3D ultrasound as a first-line modality ( 2 , 17 ).

3D ultrasound plays a crucial role in the accurate diagnosis and classification of Robert’s uterus. It clearly displays the pathognomonic features on the coronal plane, including a complete septum extending above a single internal cervical os with a normal fundal contour. This non-invasive imaging modality is ideal for preoperative planning, surgical guidance, and postoperative evaluation. 3D ultrasound should be routinely used in the workup of suspected uterine anomalies, particularly in women with unexplained infertility or recurrent pregnancy loss.

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