Imaging features of Robert’s uterus: Case series of a rare Mullerian duct anomaly

Introduction

Diagnosis of Mullerian duct anomaly (MDA) and its various subtypes can be challenging. Timely and accurate diagnosis is crucial to avoid complications. Robert’s uterus is characterised by an asymmetric uterine septum dividing the endometrial cavity in to two unequal cavities, causing obstruction of one cavity and thus haematometra, haematosalpinx and occasionally endometriosis on the affected side. Patients present with recurrent abdominal pain and severe dysmenorrhoea.

Case 3

A 36-year-old nulliparous woman presented with a long history of left-sided lower abdominal pain and backache which worsened during menstruation. She had a history of hymenoplasty for imperforate hymen and vaginoplasty for cryptomenorrhea due to probable vaginal atresia, performed at 17 years of age. Clinical examination was unremarkable. Ultrasonography carried out elsewhere had shown a left side tubo-ovarian mass and two uterine cavities with left haematometra. She subsequently underwent MRI at our institution (Figure 3) which showed features of Robert’s uterus as illustrated. The MRI also showed a relatively small-sized cervix suspicious of associated dysplasia (Figure 4). She was advised surgery, but was lost to follow-up. OPEN IN VIEWER

Figure 3.

(a) MRI, T2-W coronal images show two uterine cavities with an absent uterine fundal cleft. The myometrial intrauterine septum (black arrow) is demonstrated, the signal intensity of the septum approaching that of the myometrium. (b) T2 axial and (c) T1 axial images show left haematosalpinx (green and red arrows). (d to f) Imaging performed after 1 year shows increase in left haematometra and left haematosalpinx.

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Figure 4.

T2-weighted sagittal MR image of case 3 showing relatively small-sized shortened cervix, s/o dysplastic cervix (black arrow). Note – Left obstructed hemi-uterus with haematometra (white arrow).

Case 4

A 21-year-old woman presented with congestive dysmenorrhoea with aggravation for five years. She gave a history of blood transfusion for excessive menstrual bleeding at 13 years of age. She also had a history of laparoscopic ovarian cystectomy for an endometrioma. Clinical examination was unremarkable. Ultrasonography and subsequent MRI findings are illustrated (Figures 5 and 6) showing features in keeping with Robert’s uterus. She underwent excision of the left obstructed cavity with a left salpingectomy. OPEN IN VIEWER

Figure 5.

(a to c) Ultrasonography shows normal right hemi-uterus (yellow arrow) with small left haematometra (red arrow) and intrauterine septum (black arrow). There was no cleft in the uterine fundus. (d to f) MRI performed after two years of ultrasonography, T2-weighted coronal images (d) show two uterine cavities with an absent uterine fundal cleft. Normal right hemi-uterus and left obstructed hemi-uterus (white arrow) is seen with haematometra. Yellow arrow – external indentation at isthmus, blue arrow – intrauterine septum. (e) T2-weighted and (f) T1-weighted axial images show left haematosalpinx (red arrow).

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Figure 6.

Diagrammatic illustration of case 4.

The salient clinico-radiological findings are summarised in Table 1. The fundal height was measured by drawing an interostial line and measuring the distance from this line to the uterine fundus. Intercornual distance was measured as the distance between the distal ends of the two cavities and the intercornual angle was measured as the angle formed by the two uterine cavities in the long-axis image.

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Table 1.

Salient clinic-radiological features.

	Age (years)	Septum	Side of haematometra/ haematosalpinx	External indentation at isthmus	Associated anomalies	Fundal height	Intercornual distance	Intercornual angle	Endometriosis
Case 1	44	Fibrous	Left	Present	Nil	6.2 mm	3.5 cm	70°	Present
Case 2	18	Myometrium	Left	Present	Nil	5 mm	4 cm	67°	Present
Case 3	36	Myometrium	Left	Cervical dysplasia	Vaginal and cervical dysplasia	13 mm	4.2 cm	77°	Present
Case 4	21	Fibrous	Left	Present	Nil	9 mm	5.3 cm	90°	Present

Discussion

The reported prevalence of MDA varies widely in the literature, ranging from 1 to 5% in the general population^1,2 and 13 to 25% among women with recurrent pregnancy loss.^1–3 Among women who experience challenges in conceiving, infertility or miscarriage, a septate uterus (Figure 7) is a relatively frequent finding, affecting 15.4% of women. ¹ Robert’s uterus is also known as an asymmetric septate uterus, which was first described in 1970. ⁴ The mean age of diagnosis is over 20 years. ⁵ OPEN IN VIEWER

In Robert’s uterus, the inferior part of the septum turns obliquely dividing the endometrial cavity into two, causing obstruction of one of the cavities, while the other cavity communicates normally with the cervix. The obstructed cavity with functioning endometrium releases cyclical secretions, resulting in a haematometra which can extend into the fallopian tube and the adnexal region with formation of a haematosalpinx and endometriomas. Therefore, the classical presentation is with cyclical abdominal pain and dysmenorrhoea.^5–7

Haematosalpinx is a usual finding at presentation and some patients also have associated endometriosis. In a septate uterus, the septum begins from the midline of the uterine fundus and is a result of complete or partial failure of reabsorption of the uterovaginal septum. The other types of septate uterus include partial septum, sometimes referred to as subseptate or complete when the septum extends to the external cervical os. Occasionally, the septum may extend into the vagina. ⁸ The length and tissue composition of the septum can vary. The septum may be composed of varying proportions of fibrous tissue and myometrium and this has implications in the type of surgery performed.^9–11

The embryological pathogenesis of Robert’s uterus is not fully understood. ¹² The ESHRE (The European Society of Human Reproduction and Embryology) classification describes this anomaly as a complete septate uterus with partial cervical aplasia (class U2bC3V0).^13,14 However, the cervical aplasia component is not clearly defined and in most cases neither reported in the literature. In our series, the cervix morphology was largely normal. In the American Society of Reproductive Medicine classification system, the description of Robert’s uterus closely fits into class VB (partial septate uterus with or without septate cervix). ¹⁵ There are clear limits in describing this anomaly fully by the existing classification systems. There may be a combination of segmental agenesis of the isthmus at the uterocervical junction along with failure of reabsorption of the uterovaginal septum and an external indentation at the uterocervical junction which, if present, could suggest segmental isthmus agenesis. This finding is demonstrated in three cases in our series. ¹⁶ Case 3 of our series had a relatively small-sized cervix raising suspicion of dysplasia. Clear definitions, criteria and pictorial diagrams will be helpful to differentiate Robert’s uterus from other similar types of obstructive anomalies such as bicornuate (bicorporeal) uterus with an obstructed horn or hemicavity and the unicornuate uterus with functional noncommunicating rudimentary horn.

Robert’s uterus is often misdiagnosed preoperatively. Important diagnostic modalities include ultrasound and MRI. Ultrasound is useful for detection of haematometra and haematosalpinx but lacks specificity and sensitivity in the correct diagnosis of MDA subtypes. With ultrasound, Robert’s uterus is frequently misdiagnosed as a unicornuate uterus with non-communicating rudimentary horn. MRI with its excellent anatomic delineation is the best modality to demonstrate the uterine septum, normal external fundal contour, haematometra and haematosalpinx. At MRI, the uterus usually appears normal in size and the key to differentiating a septate uterus from a bicornuate uterus is the evaluation of the external fundal contour. The presence of a clear fundal cleft (>1 cm) is a highly reliable indicator for fusion anomalies such as bicornuate uterus rather than reabsorption anomalies (septate or arcuate uterus). ¹⁷ Historically, an angle <75° between the uterine horns is reported to be suggestive of a septate rather than bicornuate uterus. But the intercornual angle depends upon the degree of haematometra in Robert’s uterus, as also illustrated in case 4 of our series. The good soft tissue resolution on MRI also helps to determine the tissue composition of the septum. A fibrous septum is T2 hypointense whereas a muscular septum shows a T2 intermediate to high signal intensity, approaching that of the myometrial signal. This differentiation helps to decide the surgical approach and type of surgery performed. A less invasive hysteroscopic transcervical approach or transabdominal approach is chosen based on the morphology and tissue composition of the septum. T1W images show the haematometra and haematosalpinx as T1 bright fluid in the endometrial cavity and dilated Fallopian tube based on the stage of haemorrhage. ⁷

Differential diagnosis

Unicornuate uterus with obstructed non communicating horn (Figure 8) – The main point to differentiate Robert’s uterus from a rudimentary uterine horn is that the former has normal fundal contour that is convex, flat or has a small indentation (<1 cm), but the latter has a deeper fundal cleft >1 cm as in the bicornuate uterus. ¹⁸

Accessory and cavitated uterine mass (Figure 9) – Normal morphology of the uterus, endometrial cavity and ovaries are seen. There is an accessory thick-walled mass usually located in the round ligament or embedded in the lateral wall of the uterus. The centre is T2 hyperintense owing to functioning endometrium and blood products can be seen within the cavity as T1 bright contents. ¹⁹ OPEN IN VIEWER

Figure 8.

MRI T2W coronal image show unicornuate uterus with a well-developed left uterine horn (red arrow). Right horn is rudimentary with a non-communicating endometrial cavity. Left hemi-uterus is communicating with normal cervix (red and blue arrows). Deep fundal cleft is seen (black arrow), the main differentiating finding from Robert’s uterus.

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Figure 9.

ACUM. (a and b) MRI, T2W axial and coronal images shows a thick-walled, non-communicating mass with central cavity embedded along the right lateral wall of a normal uterus just below the insertion of round ligament (green arrow in (a)). Normal morphology of uterus, endometrial cavity and cervix is seen. Round ligament insertion is shown as green arrows in (b). (c) T1W axial image shows haemorrhagic contents (red arrow) in the cavity. (d) T2W coronal image demonstrates normal uterine cornua on the right and fallopian tube (yellow arrow).

Preservation of fertility is an important concern and care must be taken to maintain the integrity of the functional, communicating hemi-uterus and cervix. A few cases have reported successful pregnancy after surgery in these cases. ²⁰ A rare complication of pregnancy in the non-communicating half of the uterus caused by trans-peritoneal migration of sperms has also been reported. ²¹

Conclusion

Early and accurate diagnosis of Robert’s uterus is important in guiding appropriate surgical management and prevent morbidity due to endometriosis. Definitive surgery involves drainage of haematometra and excision of blind non-communicating hemi-uterus, taking care to maintain integrity of a functional communicating hemi-uterus and cervix.