Published online June 20, 2003, 10.1148/rg.e13
(RadioGraphics 2003;23:e13.)
A more recent version of this article appeared on September 1, 2003
© RSNA, 2003
MR Imaging Diagnosis of Uterovaginal Anomalies: Current State of the Art1
Sahar N. Saleem, MD
1 From the Radio-diagnosis Department, Cairo University Faculty of Medicine, Kasr Al-Ainy Hospital, 4 St 49 Mokattam, Cairo 11451, Egypt. Presented as an educational exhibit at the 2002 RSNA scientific assembly. Received March 21, 2003, revision requested May 15, revision received and accepted June 2. Address correspondence to the author (e-mail: saharsaleem@yahoo.com).
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Abstract
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Uterovaginal anomalies are associated with a high incidence of decreased fertility and multiple obstetric problems. These anomalies are caused by alterations in development or fusion of the müllerian ducts. Uterovaginal anomalies are classified into three types: dysgenesis, vertical or lateral fusion defects, and unusual configurations. Systematic analysis of magnetic resonance (MR) images allows accurate morphologic demonstration and classification of uterovaginal anomalies, thereby indicating the appropriate treatment. The following parameters are recorded in MR images: uterine size, external fundal contour, intercornual distance, zonal anatomy, and presence of uterine or vaginal septa. Associated pelvic lesions or renal anomalies are to be reported. MR imaging allows diagnosis of obstructive uterovaginal anomalies; determining the site of obstruction is imperative for planning the proper surgical approach. MR imaging techniques, including planes, sequences, and the application of more recent advances, are discussed. Pelvic phase-array coils and endovaginal coils provide detailed images and can be problem-solving tools in complex anomalies. MR imaging findings associated with a variety of uterovaginal anomalies are shown. The author suggests a five-step approach for diagnosing uterovaginal anomalies with MR imaging.
© RSNA, 2003
Index Terms: Magnetic resonance (MR), coils • Uterus, abnormalities, 854.1478 • Uterus, MR, 854.121411 • Vagina, abnormalities, 855.14787, 855.14788 • Vagina, MR, 855.121411
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Introduction
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The identification of uterovaginal anomalies is important in the treatment of infertility and symptoms that arise from an obstructed or deformed reproductive tract. Correct diagnosis and classification of uterovaginal anomalies is needed to determine cases requiring interventional therapy (1).
Magnetic resonance (MR) imaging is a useful noninvasive tool for demonstrating pelvic anatomy and pelvic abnormalities, including anomalies of the female genital system (2-4). With the development of new software and improved hardware over the last few years, MR imaging has proved to be a helpful tool in the management of uterovaginal anomalies, particularly complex lesions (5).
The aim of this article is to assess the expanded applications of current state-of-the-art MR imaging in the diagnosis and management of uterovaginal anomalies. The value of MR imaging in accurately demonstrating the morphology of uterovaginal anomalies and assisting in their classification, thereby indicating the appropriate treatment, is discussed. The proper MR imaging technique required to adequately diagnose uterovaginal anomalies is also discussed. The article focuses on the potential value of recent advances in MR technology, such as endovaginal coils, in diagnosing anomalies of the uterovaginal tract.
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Background
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Embryology
The female reproductive system develops from the müllerian ducts, two ducts that originate in embryonal mesoderm lateral to each wolffian duct. The paired müllerian ducts grow in medial and caudal directions. The most cephalad parts of the ducts remain separate and form the fallopian tubes. The lower parts of the ducts fuse (lateral fusion). The midline septum disappears, leaving a single canal: the uterus and upper two-thirds of the vagina. The lower third of the vagina is formed from the ascending sinovaginal bulb, which fuses with the lower müllerian system (vertical fusion) (Fig 1) (6-8). The entirely separate origin of the ovaries from the gonadal ridge explains the infrequent association of uterovaginal anomalies with ovarian anomalies (6). The close developmental relationship of the müllerian and wolffian ducts explains the frequent association of anomalies of the female genital system and urinary tract (6). Renal anomalies associated with uterovaginal anomalies include renal agenesis, ectopic kidney, cystic dysplasia, and a duplicated collecting system. The associated renal anomaly is ipsilateral to the abnormally developed müllerian duct, since both are dependent on adequate development of the mesonephric system (6,9).
Prevalence and Distribution
In the general population, the prevalence of uterine anomalies is 0.5% (10) and of vaginal anomalies is 0.025% (11). According to Nahum et al, the distribution of uterine anomalies is 4% hypoplastic, aplastic, or solid; 34% septate; 39% bicornuate; 7% arcuate; 11% didelphic; and 5% unicornuate (10).
Anatomic Considerations
Mayer-Rokitansky-Kuster-Hauser syndrome is due to agenesis of müllerian duct derivatives. The uterus and upper two-thirds of the vagina are absent (12).
Unicornuate uterus results from complete or incomplete arrest of development of one müllerian duct (Fig 2). The other horn (rudimentary) could be absent in 35% of cases, solid noncavitary in 33%, cavitary but noncommunicating with the uterine cavity in 22%, and cavitary communicating with the uterine cavity in 10% (9).
Didelphic uterus results from complete nonfusion of both müllerian ducts (Fig 3). Two uterine bodies and two cervices are present. A longitudinal or transverse vaginal septum may be associated with this anomaly (13).
Bicornuate uterus results from partial nonfusion of the müllerian ducts (Fig 4). Double uterine bodies and a single cervix are present (2). An arcuate uterus is considered a milder form of bicornuate uterus; it has a convex or flat external fundal contour and mild impression on the endometrial cavity (13). Bicornuate bicollis is a variant of bicornuate uterus in which the anomaly is combined with a muscular uterine septum that extends to the external os (14).
Septate uterus results from complete fusion of the müllerian ducts with failure of resorption of the central septum (Fig 5). The septum may be partial or complete and fibrous or muscular (15).
Di-ethyl-stilbestrol (DES)–exposed uterus results when the fetal uterus is exposed to the estrogen analog DES, which causes abnormal myometrial hypertrophy (15).
Classification of Uterovaginal Anomalies
Classification of subtypes of congenital abnormalities of the female reproductive system is important in the treatment of infertility and symptoms arising from obstruction or deformity (10). Many classifications of uterine anomalies exist; for instance, the Buttram and Gibbons classification (16) and the American Fertility Society (AFS) classification (17). We adopted the modified AFS classification by Rock and Adam (18) because it embraces a broader collection of uterine and vaginal anomalies without the conflicting observations or oversimplicity encountered in other classifications. This classification has merit because it correlates anatomic anomalies with embryologic arrests. Accordingly, uterovaginal anomalies are categorized as dysgenesis disorders or vertical or lateral fusion defects. Anomalies are further subcategorized into obstructive or nonobstructive forms, since their treatment differs. Obstructive uterovaginal anomalies require immediate attention because of retrograde flow of trapped mucus and menstrual blood and increasing pressure on surrounding organs, while immediate treatment is not warranted for nonobstructive forms. Because genital tract aberrations do not necessarily follow any defined and consistent pattern, class 4 is a useful addition embracing any possible unusual configurations or combination of defects.
Class 1.—Dysgenesis of müllerian ducts. This class includes agenesis or hypoplasia of the müllerian duct derivatives: the uterus and upper two-thirds of the vagina. The most common form is the Mayer-Rokitansky-Kuster-Hauser syndrome, which is combined agenesis of the uterus, cervix, and upper portion of the vagina.
Class 2.—Disorders of vertical fusion. These anomalies are due to failure of fusion of the müllerian system with the sinovaginal bulb. They include cervical dysgenesis and obstructive and nonobstructive transverse vaginal septa.
Class 3.—Disorders of lateral fusion. This class describes anomalies that result in a duplicated or partially duplicated reproductive tract. The disorders are due to impaired fusion and/or septal resorption of fusing müllerian ducts attempting to form the uterus, cervix, and upper vagina. It includes anomalies due to failure of fusion of the paired müllerian ducts (as in didelphic and bicornuate uteri) and failure of midline septum resorption after fusion (as in septate uterus). Disorders due to lateral fusion defects are further subclassified into (a) the symmetric nonobstructive form seen in five types: unicornuate, bicornuate, didelphic, septate, and DES-related uteri and (b) the asymmetric obstructive form seen in three types: unicornuate uterus with obstructed horn, double uterus with unilaterally obstructed horn, and double uterus with unilaterally obstructed vagina.
Class 4.—Unusual configurations and combinations of defects.
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MR Imaging Technique for Uterovaginal Anomalies
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Examination Protocol
The sequences that may be used for diagnosis of uterovaginal anomalies are listed in Table 1. The first four sequences are usually sufficient for the diagnosis of most anomalies. These include a large field of view (FOV) coronal T1-weighted sequence for the kidneys and pelvis, a sagittal T2-weighted fast-spin-echo (FSE) sequence, an axial T1-weighted spin-echo sequence, and an oblique long-axis T2-weighted FSE sequence. One or more of the other sequences (5 through 7) may be used if additional data are required. For example, the sequence 5 is used if the extent of uterine septum in the cervix is questionable.
Image Analysis
The following should be assessed in MR images: uterus, vagina, gonads, and associated pelvic lesions and renal anomalies (4).
I. Uterus.
- Size: In the reproductive age group, uterine length normally measures 6–9 cm and the uterine body to cervix ratio is 2:1 when measured in the sagittal plane (3,13).
- Intercornual distance: The distance between the distal ends of the horns is measured in the oblique long-axis images and is normally 2–4 cm (13,15).
- External fundal contour: The external contour of the uterus is normally convex and best detected in long-axis oblique images (3).
- Zonal anatomy: Zonal anatomy is the differentiation between the high-signal-intensity endometrium, the low-intensity junctional zone (inner myometrium), and the intermediate-intensity outer myometrium, as depicted in T2-weighted images (Fig 6). It is normally seen in the reproductive age group (3,13).
- Uterine septum: A uterine septum is looked for; if present, its signal intensity and extent are assessed.
- Intercornual angle: The intercornual angle is the angle between the most medial aspects of the two uterine hemicavities (15,19).
- Obstruction: Distended blood-filled uterus (hematometria) and blood-filled fallopian tubes (hematosalpinx) show the characteristic signal pattern of altered blood and blood products. The level of obstruction is determined (4).
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Figure 6. Normal uterine zonal anatomy in a woman of reproductive age. Sagittal T2-weighted FSE image (repetition time [msec]/echo time [msec]: 4,000/96) obtained with a pelvic phase-array coil shows a normal-size uterus and body-to-cervix ratio. The zonal anatomy, with differentiation between the high-intensity endometrium (E), low-intensity junctional zone (arrow), and intermediate-intensity outer myometrium, is well seen.
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II. Vagina.
The vagina is normally seen as a tube of intermediate signal intensity between the bladder base and urethra anteriorly and the anal canal posteriorly (Fig 7). The direction and extent of a vaginal septum—if present—should be assessed. The obstruction site of a blood-filled vagina (hematocolpos) should be estimated. Any fistulous tracts between the uterovaginal canal and pelvic organs such as the urinary bladder or rectoanal tract should be noted (3,4).
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Figure 7. Normal vagina seen in the axial plane. T2-weighted FSE (4,000/96) image obtained with a pelvic phase-array coil shows the vagina as an intermediate-intensity tube (arrow) between the bladder base (B) anteriorly and the rectum (R) posteriorly.
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III. Gonads.
Both ovaries should be identified. Any associated lesions such as endometriosis or teratoma should be noted.
IV. Associated pelvic lesions or renal anomalies
Any associated pelvic lesions or renal anomalies should be noted (3,4,13).
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MR Imaging Findings in Uterovaginal Anomalies
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Class 1: Dysgenesis of Müllerian Ducts: Hypoplasia, Agenesis.
A hypoplastic uterus is diagnosed on the basis of its small size and reduced intercornual distance (<2 cm). The zonal anatomy may be poorly differentiated in T2-weighted images of infantile uteri (Fig 8) (4,13). In agenesis of the müllerian duct derivatives (Mayer-Rokitansky-Kuster-Hauser syndrome), no identifiable uterine tissue or the upper two-thirds of the vagina could be seen (Fig 9) (12).
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Figure 8. Uterine hypoplasia (class 1). Sagittal T2-weighted spin-echo image (4,000/98) shows a small uterus with poorly developed zonal anatomy (arrow) in an 18-year-old woman with primary amenorrhea.
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Figure 9a. Mayer-Rokitansky-Kuster-Hauser syndrome (class 1). (a) Sagittal T2-weighted FSE image (4,000/104) documents the absence of uterine tissues. A concurrent mature pelvic cystic teratoma (MCT) is noted. (b) Axial T2-weighted FSE image (4,000/104) shows absence of vaginal tissue between the bladder (B) and the rectum (R).
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Figure 9b. Mayer-Rokitansky-Kuster-Hauser syndrome (class 1). (a) Sagittal T2-weighted FSE image (4,000/104) documents the absence of uterine tissues. A concurrent mature pelvic cystic teratoma (MCT) is noted. (b) Axial T2-weighted FSE image (4,000/104) shows absence of vaginal tissue between the bladder (B) and the rectum (R).
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Class 2: Vertical Fusion Defect
Transverse vaginal septum.—A transverse vaginal septum could be in a high, middle, or low position. It is more common in the upper vagina (Fig 10) (13).
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Figure 10. Transverse vaginal septum (class 2). Sagittal T2-weighted spin-echo image (4,000/98) shows a transverse septum in the middle of the vagina (arrow), causing dilatation of the proximal vagina (V) and uterus (U) (hematocolpos and hetmatometria).
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Obstructed hymen.—Obstructed hymen is also considered a vertical fusion defect (6). Sagittal MR images document the exact site of vaginal obstruction. Consequent dilatation of the proximal reproductive canal filled with obstructed menstrual blood products is usually noted (Fig 11) (4).
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Figure 11. Obstructed hymen (class 2). Sagittal T1-weighted spin-echo image (500/8) shows a dilated hematometrocolpos. The obstruction is at the level of perineum (arrow).
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Class 3: Lateral fusion defects
A. Symmetric nonobstructive form of lateral fusion defects
Unicornuate uterus.— A unicornuate uterus is banana-shaped and slender, without the usual rounded fundal contour, and is usually laterally deviated. Although the corpus uterus is generally smaller than the nulliparous uterus, the size discrepancy is not great (Fig 12). If present, a solid rudimentary horn can be observed as a soft-tissue mass with signal intensity similar to that of myometrium (2,9,15).
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Figure 12a. Simple left unicornuate uterus associated with right renal agenesis (class 3). (a) Axial T2-weighted FSE image (2,000/120) shows a laterally deviated banana-shaped uterus (arrow). No rudimentary horn could be detected. (b) Coronal T1-weighed spin-echo image (500/8) with large FOV (45cm) shows right renal agenesis.
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Figure 12b. Simple left unicornuate uterus associated with right renal agenesis (class 3). (a) Axial T2-weighted FSE image (2,000/120) shows a laterally deviated banana-shaped uterus (arrow). No rudimentary horn could be detected. (b) Coronal T1-weighed spin-echo image (500/8) with large FOV (45cm) shows right renal agenesis.
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Cervical agenesis—No identifiable cervix in MR images. Hematometria may be seen if there is functioning endometrium in the uterine body (4).
Septate Uterus—The outer fundal contour is convex or flat or has a slight indentation less than 1 cm deep. The intercornual distance is within the normal range. The intercornual angle measures less than 60°. These findings are best seen in oblique long-axis images (Fig 13) (2). The uterine septum may be composed of muscle or fibrous tissue. A muscular septum has intermediate signal intensity with all pulse sequences, isointense to myometrium. A fibrous septum usually has a lower intensity with all sequences. The muscular or fibrotic nature of an intracavitary septum is assessed more on the basis of septal thickness than on signal intensity; the fibrous septum is thin and linear. Mixed muscular and fibrous septa have also been described (13). If the septum reaches the internal os, it is complete (Fig 14); if it terminates above the internal os, it is a partial septum (19).
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Figure 13a. Septate uterus: incomplete septum (class 3). Multiple images in different planes were obtained in the same patient. The solid red line in the right-lower-corner inset indicates the plane of section. (a) Direct coronal T2-weighted FSE image (5,000/96) shows double uteri but has limited value in evaluation of the fundus. (b, c) Oblique long-axis T2-weighted FSE images (4,000/96) obtained parallel to the long axis of the uterus show the convex external contour of the fundus (arrow in b). The intercornual distance (dotted line) is 3.5 cm. The intercornual angle between the distal ends of the horns is less than 60° (intersecting lines). The uterine septum is thick and isointense to myometrium, which indicates it is muscular. The lower extent of the uterine septum in the cervical canal is unclear (? arrow). (d) Oblique short-axis T2-weighted FSE image (4,000/96) of the cervix obtained perpendicular to the long axis of the uterus (dotted line in inset) shows a single cervical canal. The arrowhead points to normal infolding of the cervix seen in many cases without associated anomalies.
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Figure 13b. Septate uterus: incomplete septum (class 3). Multiple images in different planes were obtained in the same patient. The solid red line in the right-lower-corner inset indicates the plane of section. (a) Direct coronal T2-weighted FSE image (5,000/96) shows double uteri but has limited value in evaluation of the fundus. (b, c) Oblique long-axis T2-weighted FSE images (4,000/96) obtained parallel to the long axis of the uterus show the convex external contour of the fundus (arrow in b). The intercornual distance (dotted line) is 3.5 cm. The intercornual angle between the distal ends of the horns is less than 60° (intersecting lines). The uterine septum is thick and isointense to myometrium, which indicates it is muscular. The lower extent of the uterine septum in the cervical canal is unclear (? arrow). (d) Oblique short-axis T2-weighted FSE image (4,000/96) of the cervix obtained perpendicular to the long axis of the uterus (dotted line in inset) shows a single cervical canal. The arrowhead points to normal infolding of the cervix seen in many cases without associated anomalies.
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Figure 13c. Septate uterus: incomplete septum (class 3). Multiple images in different planes were obtained in the same patient. The solid red line in the right-lower-corner inset indicates the plane of section. (a) Direct coronal T2-weighted FSE image (5,000/96) shows double uteri but has limited value in evaluation of the fundus. (b, c) Oblique long-axis T2-weighted FSE images (4,000/96) obtained parallel to the long axis of the uterus show the convex external contour of the fundus (arrow in b). The intercornual distance (dotted line) is 3.5 cm. The intercornual angle between the distal ends of the horns is less than 60° (intersecting lines). The uterine septum is thick and isointense to myometrium, which indicates it is muscular. The lower extent of the uterine septum in the cervical canal is unclear (? arrow). (d) Oblique short-axis T2-weighted FSE image (4,000/96) of the cervix obtained perpendicular to the long axis of the uterus (dotted line in inset) shows a single cervical canal. The arrowhead points to normal infolding of the cervix seen in many cases without associated anomalies.
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Figure 13d. Septate uterus: incomplete septum (class 3). Multiple images in different planes were obtained in the same patient. The solid red line in the right-lower-corner inset indicates the plane of section. (a) Direct coronal T2-weighted FSE image (5,000/96) shows double uteri but has limited value in evaluation of the fundus. (b, c) Oblique long-axis T2-weighted FSE images (4,000/96) obtained parallel to the long axis of the uterus show the convex external contour of the fundus (arrow in b). The intercornual distance (dotted line) is 3.5 cm. The intercornual angle between the distal ends of the horns is less than 60° (intersecting lines). The uterine septum is thick and isointense to myometrium, which indicates it is muscular. The lower extent of the uterine septum in the cervical canal is unclear (? arrow). (d) Oblique short-axis T2-weighted FSE image (4,000/96) of the cervix obtained perpendicular to the long axis of the uterus (dotted line in inset) shows a single cervical canal. The arrowhead points to normal infolding of the cervix seen in many cases without associated anomalies.
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Figure 14. Complete septate uterus (class 3). Oblique long-axis T2-weighted FSE image (4,000/96) shows a septate uterus with a complete septum extending to the external os. The septum is thin and has low signal intensity, which indicates it is fibrous.
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Bicornuate uterus.—Two uterine bodies and a single cervix are present in bicornuate uterus. The fundal cleft is greater than 1 cm in depth. The cleft is best visualized on oblique long-axis images of the uterus. The intercornual distance is increased (>4 cm) in bicornuate uteri. The tissue separating the two horns usually demonstrates signal intensity identical to that of myometrium with all pulse sequences (Fig 15) (2,13,19). Bicornuate bicollis is a term that describes a bicornuate uterus with double cervices. It can be distinguished from didelphic uterus because some degree of fusion has occurred between the lower uterine segments (15). Arcuate uterus with a convex or flat external contour and a mild impression on the endometrial cavity is considered the mildest form of bicornuate uterus (13).
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Figure 15. Bicornuate uterus (class 3). Oblique long-axis T2-weighted spin-echo image (4,000/12) shows double uterine bodies and a single cervix. The fundus is deeply notched (arrow) with a large intercornual distance (5.5 cm). The intercornual angle is also large. The ovaries are well displayed bilaterally.
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Didelphic uterus.—Two uterine bodies and two cervices are present in didelphic uterus. The uterine horns are widely splayed with a deep fundal cleft, and the intercornual angle is more than 60°. The endometrial and myometrial zonal widths are preserved (Fig 16). Vaginal septa are most commonly associated with this type of uterine anomaly (2,13,19).
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Figure 16. Didelphic uterus (class 3). Axial T2-weighted spin-echo image (5,000/98) shows fully developed, widely splayed double uteri with two cervices.
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B. Asymmetric obstructive form of lateral fusion defects
Unicornuate uterus with a noncommunicating rudimentary horn.—An obstructed rudimentary horn with functioning endometrium may be distended by blood or blood products. Retrograde menstruation into the fallopian tube may lead to associated hematosalpinx (Fig 17) (13).
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Figure 17. Unicornuate uterus with an obstructed functioning rudimentary horn (class 3). Coronal T2-weighted spin-echo image (4,000/120) shows a right unicornuate uterus (arrow). The obstructed functioning rudimentary horn appears as a blood-filled dumbbell-shaped mass. Its shape corresponds to the obstructed uterine horn (H) and its fallopian tube (T), a hematometrosalpinx. Both ovaries (Ov) are identified; each is related to its ipsilateral uterine horn.
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Unilateral obstruction of a cavity of a double uterus.—This is a unique syndrome consisting of a didelphic obstructed hemivagina and ipsilateral renal agenesis (Fig 18) (20).
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Figure 18a. Double uterus with complete obstructed hemivagina and ipsilateral renal agenesis (class 3). T2-weighted FSE image (3,500/120) were obtained in multiple planes. (a) Coronal view shows right unilateral distention (arrow) of a duplicated uterus with ipsilateral renal agenesis. (b) Axial view documents the asymmetric right uterine cavity. (c) Parasagittal T2-weighted FSE image (3,500/120) obtained in the right uterine cavity shows the obstruction at the level of the proximal vagina.
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Figure 18b. Double uterus with complete obstructed hemivagina and ipsilateral renal agenesis (class 3). T2-weighted FSE image (3,500/120) were obtained in multiple planes. (a) Coronal view shows right unilateral distention (arrow) of a duplicated uterus with ipsilateral renal agenesis. (b) Axial view documents the asymmetric right uterine cavity. (c) Parasagittal T2-weighted FSE image (3,500/120) obtained in the right uterine cavity shows the obstruction at the level of the proximal vagina.
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Figure 18c. Double uterus with complete obstructed hemivagina and ipsilateral renal agenesis (class 3). T2-weighted FSE image (3,500/120) were obtained in multiple planes. (a) Coronal view shows right unilateral distention (arrow) of a duplicated uterus with ipsilateral renal agenesis. (b) Axial view documents the asymmetric right uterine cavity. (c) Parasagittal T2-weighted FSE image (3,500/120) obtained in the right uterine cavity shows the obstruction at the level of the proximal vagina.
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Class 4: Unusual Configurations or Combinations of Vertical and Lateral Fusion Defects
MR imaging can display the morphology of unusual uterovaginal anomalies. An example is a case of didelphic uterus and longitudinal vaginal septum (lateral fusion defect) combined with obstructed hymen (vertical fusion defect) (Fig 19) (4).
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Figure 19a. Didelphic uterus and longitudinal vaginal septum combined with obstructed hymen (class 4). (a) Direct coronal T1-weighted spin-echo image (420/6) shows a markedly distended vagina with altered blood products (hematocolpos); obstruction is at the level of the hymen (arrow). A longitudinal septum (arrowhead) splits the vagina into two compartments, sparing its lowest part, which has a different embryologic origin. (b) Sagittal T2-weighted FSE image (4,000/98) shows that the uterus is connected to each vaginal compartment (only one side is shown).
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Figure 19b. Didelphic uterus and longitudinal vaginal septum combined with obstructed hymen (class 4). (a) Direct coronal T1-weighted spin-echo image (420/6) shows a markedly distended vagina with altered blood products (hematocolpos); obstruction is at the level of the hymen (arrow). A longitudinal septum (arrowhead) splits the vagina into two compartments, sparing its lowest part, which has a different embryologic origin. (b) Sagittal T2-weighted FSE image (4,000/98) shows that the uterus is connected to each vaginal compartment (only one side is shown).
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Table 2 summarizes the MR imaging findings in various uterovaginal anomalies.
Effect of MR Imaging on Treatment of Uterovaginal Anomalies
MR imaging depicts uterovaginal morphology, thus aiding in classification of anomalies. Unicornuate uterus is diagnosed by its characteristic banana shape. Imaging parallel to the long axis of the uterus can accurately visualize the external contour of the fundus. A normal convex fundus differentiates a septate from a bicornuate or didelphic uterus. This differentiation is crucial in treatment, as a septate uterus requires septectomy, while a bicornuate or didelphic uterus does not usually require surgical treatment (2,13).
Through recognition of the lower extent of a uterine septum in the cervical canal and uterine cavity, MR imaging can differentiate didelphic from bicornuate uterus and complete from incomplete septate uterus (19). Prediction of the composition of a uterine septum by means of MR images, through recognition of its signal pattern and thickness, allows better treatment planning. A fibrous uterine septum is amenable to hysteroscopic resection; a uterine septum containing myometrium and its vascularity necessitates a transabdominal metroplasty to ensure adequate hemostasis and entails an inpatient hospital stay of 5–10 days (2).
MR imaging with its high soft-tissue resolution allows accurate determination of the level of obstructive uterovaginal anomaly and permits appropriate repair and drainage (21).
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Recent Advances and Potential Indications of MR Imaging
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Pelvic Phase-Array Coil
The pelvic phase-array coil is formed of multiple coils used simultaneously (Fig 20), allowing a superior signal-to-noise ratio and motion-artifact reduction (22). It allows detailed identification of complex anomalies such as congenital rectovaginal fistulas associated with uterovaginal anomalies (Fig 21) (4). Abnormalities in the genital tract are frequently associated with anorectal or persistent cloacal malformations. Girls with an anorectal malformation usually have a rectovaginal fistula that may terminate anywhere from the fornix to near the hymen (23).
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Figure 20. Pelvic phase-array coil. The anterior (A) and posterior (P) coils are held in opposition by straps around a sponge model.
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Figure 21a. An ectopic anal opening in the vaginal fornix of a septate uterus (same patient in Fig 12). The clinical examination showed absent anus in the perineum, with fecal matter coming from the vaginal opening. (a) Sagittal T2-weighted FSE image (4,000/98) obtained with the body coil shows poor detail in the uterine hemicavity and surrounding tissues. (b) An identical sequence used with the pelvic coil shows more detail at the suggested site of the ectopic anal opening (arrow) in the posterior vaginal fornix. Note the markedly distended colon (C).
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Figure 21b. An ectopic anal opening in the vaginal fornix of a septate uterus (same patient in Fig 12). The clinical examination showed absent anus in the perineum, with fecal matter coming from the vaginal opening. (a) Sagittal T2-weighted FSE image (4,000/98) obtained with the body coil shows poor detail in the uterine hemicavity and surrounding tissues. (b) An identical sequence used with the pelvic coil shows more detail at the suggested site of the ectopic anal opening (arrow) in the posterior vaginal fornix. Note the markedly distended colon (C).
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Endovaginal Coil
The endovaginal coil is a radio-frequency (RF) coil that is inserted into the vagina (Fig 22). Endovaginal MR imaging has been reported to be valuable for evaluation of normal female pelvic anatomy (24). It has potential indications in complex uterovaginal anomalies as a problem-solving tool and allows better assessment of the cervical canal (Fig 23, 24) (4).
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Figure 22. Endovaginal MR coil. The RF coil loop is fixed inside an inflatable balloon mounted on a plastic rod. Fifty milliliters of air are usually sufficient to inflate the balloon inside the vagina.
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Figure 23a. Cervical agenesis diagnosed with an endovaginal MR coil. (a) Coronal T1-weighted image (420/6) obtained with the body coil shows double uteri (R and L) ; the left one is functioning and blood-filled. The cervix could not clearly identified (?). (b) Coronal T1 weighted image after insertion of endovaginal MR coil (C) documents cervical agenesis. The cervix is replaced by a transverse band of low signal intensity (fibrous) connecting the double uteri (arrow) (class 4).
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Figure 23b. Cervical agenesis diagnosed with an endovaginal MR coil. (a) Coronal T1-weighted image (420/6) obtained with the body coil shows double uteri (R and L) ; the left one is functioning and blood-filled. The cervix could not clearly identified (?). (b) Coronal T1 weighted image after insertion of endovaginal MR coil (C) documents cervical agenesis. The cervix is replaced by a transverse band of low signal intensity (fibrous) connecting the double uteri (arrow) (class 4).
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Figure 24a. Incomplete septate uterus diagnosed with endovaginal MR coil. (a) Oblique long-axis T2-weighted FSE image (4,000/96) obtained with a pelvic phase-array coil shows a septate uterus. The lower extent of the uterine septum in the cervical canal is not clear. (b) Oblique long-axis T2-weighted FSE image image (3,600/98) obtained after insertion of endovaginal MR coil documents a single cervical canal (arrow), thus demonstrating an incomplete septate uterus.
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Figure 24b. Incomplete septate uterus diagnosed with endovaginal MR coil. (a) Oblique long-axis T2-weighted FSE image (4,000/96) obtained with a pelvic phase-array coil shows a septate uterus. The lower extent of the uterine septum in the cervical canal is not clear. (b) Oblique long-axis T2-weighted FSE image image (3,600/98) obtained after insertion of endovaginal MR coil documents a single cervical canal (arrow), thus demonstrating an incomplete septate uterus.
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High-resolution MR Imaging of the Vagina
This new technique combines the pelvic phase-array coil with the endocavitary coil (25). It allows better assessment of the uterovaginal canal and associated fistulas.
MR Hysterography
With use of the pelvic phase-array coil, axial fast spin-echo images (9,000/288) of interleaved 3-mm-thick sections can be obtained with fat saturation. Images can be processed with use of maximum-intensity-projection algorithms to construct MR hysterograms. The estimated time is less than 3 minutes. This technique is currently used to demonstrate uterine cavity anatomy and to assess fallopian tube patency without use of ionizing radiation (26). It could have potential future indications in assessment of uterine cavity features in complex uterovaginal anomalies (eg, communication between double uteri).
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Conclusions
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MR imaging is an excellent modality for detecting uterovaginal anomalies with its multiplanar capabilities and high soft-tissue resolution. MR imaging helps identify the morphology of uterovaginal anomalies and aids in their classification and treatment. Imaging parallel to the long axis of the uterus is especially useful for visualizing the external contour of the uterine fundus. Accurate MR evaluation of uterine septum extension and composition is crucial in the treatment of double uteri. MR imaging can determine the level of obstruction in obstructive uterovaginal anomalies, which is important for surgical planning. Recent advances in the technology of MR imaging allow its use as a problem-solving tool in the diagnosis of uterovaginal anomalies. A five-step approach for diagnosing uterovaginal anomalies with MR imaging is suggested in Figure 25.
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Figure 25. Flowchart of a suggested five-step approach for disgnosing uterovaginal anomalies with MR imaging.
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Figure 1. Development of the uterovaginal canal. Two paired müllerian ducts (yellow lines) grow medially and caudad. Both ducts fuse in the midline to form the uterus and the upper two-thirds of vagina (lateral fusion). The lower third of vagina is formed by fusion of the ascending sinovaginal bulb (red lines) with the müllerian system (vertical fusion). The septum disappears, leaving a single uterovaginal canal.
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Footnotes
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Abbreviations: DES= di-ethyl-stilbestrol,
FOV= field of view,
FSE= fast spin echo.
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References
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Abstract
Introduction
