Myometrial tissue in uterine septa

May 1998, Vol. 5, No. 2

TheJournal of the American Associationof Gynecologic Laparoscopists

Myometrial Tissue in Uterine Septa Tony G. Zreik, M.D., Robert N. Troiano, M.D., Rola A. D. Ghoussoub, M.D., David L. Olive, M.D., Aydin Arici, M.D., and Shirley M. McCarthy, M.D., Ph.D.

Abstract

Study Objective. To assess the frequency of myometrial tissue in the septa of septate uteri. Design. Retrospective review (Canadian Task Force classification 11-2). Setting. University-affiliated tertiary referral center. Patients. Twenty-nine consecutive women with uterine septa diagnosed by magnetic resonance imaging (MRI). Interventions. The MRI examination was performed with a 1.5 Tesla scanner using high-resolution phased array coils with multiplanar fast-spin echo and Tl-weighted sequences. Of resected septa, tissue was available in four for histologic evaluation for the presence of myometrial tissue. Measurements and Main Results. In 17 women MRI showed a partial septum, all containing myometrium. The 12 patients with complete septum had evidence of myometrium in the upper part of the septum, with fibrous tissue constituting the Iower part. Histology reviewed from four resected septa (2 partial, 2 complete) reported myometrial tissue. Conclusion. Uterine septa are frequently composed of myometrial tissue. (J Am Assoc Gynecol Laparosc 5(2):155-160, 1998)

Mullerian duct malformations are interesting and challenging clinical problems for obstetricians and gynecologists. In particular, bicornuate and septate uteri are associated with specific obstetric complications mandating accurate diagnosis and treatment. The most impressive feature of the septate uterus is early pregnancy wastage occurring in the first half of pregnancy, whereas the bicornuate uterus is associated with an increased frequency of spontaneous pregnancy loss, together with premature labor and abnormal

fetal presentation requiring cesarean delivery. 1'2 As such, women with these anomalies are considered to be poor obstetric performers and potential candidates for surgical repair. 3 Although the bicornuate uterus infrequently requires surgery, laparotomy is required to fuse the uterine horns. In contrast, the septate uterus can be treated successfully with hysteroscopic resection or division of the septum.4-7Both approaches mandate accurate preoperative diagnosis. Furthermore, if the bicornuate

From the Departments of Obstetrics and Gynecology (Drs. Zreik, Olive, and Arici), Surgical Pathology (Dr. Ghoussoub), and Diagnostic Radiology (Drs. Troiano and McCarthy), Yale University School of Medicine, New Haven, Connecticut. Address reprint requests to Tony G. Zreik, M.D., Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology, Yale University School of Medicine, P.O. Box 208063, New Haven, CT 06520-8063; fax 203 785 7134. Presented at the 24th annual meeting of the American Association of Gynecologic Laparoscopists, Orlando, Florida, November 8-12, 1995. CTF II-2: Evidence obtained from well-designed cohort or case-control studies, preferably from more than one center or research group.

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uterus is accurately and noninvasively diagnosed, patients can be spared laparoscopy and its costs in health care dollars. 8' 9 Two diagnostic tools traditionally used to distinguish septate from bicornuate uteri are ultrasonograplay (US) and hysterosalpingography (HSG). Surgery by laparoscopy or laparotomy is considered the gold standard for confirming the diagnosis. However, since both US and HSG have not proved completely reliable in making this differential diagnosis, 1~ and in view of the invasive nature of laparoscopy and its inability to assess the uterine cavity adequately, magnetic resonance imaging (MRI) has emerged as a single, noninvasive, accurate test for the diagnosis of uterine anomalies. 8' 9.11 Infertility and recurrent pregnancy loss traditionally were attributed to the fibrous and avascular nature of septa, 12 but the advent of MRI calls this assumption into question. We undertook this study to assess the frequency of myometrial tissue in the septa of septate uteri. Materials and Methods The patient cohort consisted of 29 consecutive women (mean age 34 yrs, range 25-51 yrs) in whom partial or complete uterine septum was diagnosed by MRI of the pelvis. Clinical diagnoses at the time of referral were infertility (10 patients), recurrent spontaneous abortions (8), vaginal and cervical septa (2), pelvic pain (4), and pelvic mass (5). Of the 17 patients who subsequently underwent hysteroscopic resection of the septa, 4 had tissue submitted for histology; 13 had hysteroscopic incision of the septa and therefore had no specimen submitted for histology. Five women were surgically evaluated by laparoscopy or hysteroscopy, but underwent no corrective surgery. The remaining seven had no surgical intervention. Magnetic resonance imaging was performed with a 1.5-Tesla system (Signa; GE Medical Systems, Milwaukee, WI). Twenty-two patients were imaged with a phased array coil and seven in a body coil. After a fast inversion recovery localizer, axial spin echo T1weighted images were performed with a repetition time (TR) of 600 msec, echo time (TE) 16 msec, field of view (FOV) of 20 to 24 cm, 1 signal average (NSA), matrix size 256 x 160, and section thickness 5 mm with a gap of 1.5 mm. Multiplanar T2-weighted sequences were then performed, including a plane parallel to the long axis of the uterus. Fast spin echo (FSE) T2-

weighted images were obtained in 22 patients using a phased array coil with a TR of 5000 to 7500, effective TE 117 msec, 20 to 24 cm FOV, 2 NSA, 256 x 256 matrix, echo train length 16, band width 32 kHz, and 5-mm section thickness with a 2.5-mm gap. Conventional spin echo T2-weighted images were obtained in seven patients using the body coil with TR 2500 msec, TE 80 msec, FOV 28 to 30 cm, NSA 2, 256 x 128 matrix, and 7-mm slice thickness with a 2-mm gap. Morphology and signal characteristics of the septa were analyzed and tabulated by an MRI radiologist who was blinded to the operative findings. Uteri were classified as septate if the external uterine contour was convex, flat, or concave up to 1.50 cm. Depth of fundal indentation was measured on the images. Septa were defined as complete if they extended into the uterine cervix, or partial if they were confined to the uterine fundus and body. Since MRI enables tissue characterization, the intervening tissue was defined as myometrial or fibrous depending on its signal characteristics on T2-weighted images. It was considered myometrial if its signal was the same as that of the myometrium (isotense), and fibrous if it was low signal, compared with myometrium (hypotense). Myometrium, exclusive of the junctional zone (inner layer surrounding the endometrium), was used for comparison. 13-15 In three cases (two partial and one complete) resected septal tissue was submitted to histology by the same reproductive endocrinologist who routinely performed resection rather than simple incision of the septa. In one woman with recurrent pregnancy loss with a complete septum noted on MRI, the surgeon, who was blinded to MRI findings, was asked to submit resected tissue for histologic evaluation. Specimens were reviewed by a pathologist who was blinded to MRI and operative findings to determine the presence or absence of myometrial tissue in the specimens. Results Findings on MRI consisted of a partial septum in 17 women (Figure 1). The septum was composed entirely of myometrium in all patients, and was without evidence of a fibrous component. The average length of the septum was 2.6 cm (range 2.0-4.3 cm). External contour was convex in 12 (71%), flat in 3 (18 % ), and mildly concave in 2 (11%) patients. Of the 12 women with complete septa, all had myometrium in the upper portion of the septum that

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FIGURE 1. Partial uterine septum. Axial fast spin echo T2weighled image shows the septal component (arrow) to be isotense and continuous with the myometrium.

FIGURE 3. Adenomyosis within a septum. Coronal fast spin echo T2-weighted image shows diffuse thickening and irregularity of the junctional zone (short arrows), and focal low signal within the septum (long arrow) consistentwith adenomyosis.

was confined to the uterine body, and all images showed the lower portion to be fibrous (Figure 2). Average septum length was 5.7 cm (range 4.3-7.9 cm). Average length of the myometrial component was 2.7 cm and the fibrous component 3.0 cm. External uterine contour was convex in five (42%), flat in five (42%), mad mildly concave in two (16%) women. Five patients had leiomyomas and one a diffuse adenomyosis within the septum itself (Figure 3).

All four women (2 partial, 2 complete septa) in whom histology was available had a history of infertility or recurrent pregnancy loss. The MRI showed one partial septum to be 3.1 cm long and 0.6 cm deep, with a mild concavity of the external contour (Figure 4). The second partial septum was 2.1 cm long with a flat external uterine contour. Of the complete septa, one had an upper myometrial component measuring 3.2 cm long and a lower fibrous component measuring 2.9 cm on MRI (Figure 5). The external contour was concave with a depth of 0.8 cm. The other complete seprum had an upper myometrial portion measuring 3.0 cm and lower fibrous portion measuring 2.1 cm, with a flat external uterine contour. At hysteroscopy or laparoscopy, the diagnosis of septate uterus was confirmed in all four women. Histology confirmed the presence of endometrium and myometrium in the resected tissue, together with areas of coagulation artifact (Figure 6). Discussion

With its ability to demonstrate both internal and external uterine morphology, MRI is well suited for the diagnosis of uterine anomalies. In fact, it is highly accurate, and less expensive and invasive than laparoscopy.]6 In a study of 29 women who underwent MRI

FIGURE 2. Complete uterine septum. Axial T2-weighted image shows the signal intensity of the upper septal segment (long arrow) consistent with myometrium. The lower segment (short arrow) demonstrates a markedly hypotense signal intensity consistent with fibrous tissue.

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FIGURE 6. Resected tissue shows endometrium (E), myometrium (M), and areas of coagulation artifact (C). (Hematoxylin and eosin; magnification 40 x.)

fibrous. It identified a muscular septal component in 10 of 10 women, compared with 7 of 7 by EVS. Pathologic specimens available in five patients with septate uteri showed smooth muscle in the septum. An earlier study n attempted to differentiate bicornuate from septate uteri by examining axial images for the signal intensity of the tissue intervening between the endometrial junctional zone complexes. The authors defined medium-intensity tissue or tissue isointense with myometrium as representative of myometrial tissue and therefore indicative of a bicornuate uterus. A low-intensity band consistent with fibrous tissue was considered representative of a septate uterus, based on the traditional assumption that septa are composed of fibrous tissue.

FIGURE 4. Partial uterine septum prior to resection. Coro-

nal fast spin echo T2-weighted image shows myometrium within the septum (arrow).

for investigation of mullerian duct anomalies, MRI correctly diagnosed all anomalies as well as associated gynecologic disease. ~7The relative accuracy of MRI, endovaginal sonography (EVS), and HSG in classifying mullerian duct anomalies was assessed in 26 patients. 8 For MRI and EVS, accuracy was 100% and 92%, respectively. All 20 HSG studies were interpreted as abnolrnal, but accuracy was only 29% with the reader blinded to findings on physical examination. In addition, MRI characterized septal tissue as myometrial or

FIGURE 5. Complete uterine septum before surgical resection. (A) Axial fast spin echo T2-weighted image shows the upper segment of the septum to consist of myometrial tissue (iong arrow) and (B) the lower segment to be consistent with fibrous tissue (short arrow).

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4. Valle RF, Sciarra JJ: Hysteroscopic treatment of the septate uterus. Am J Obstet Gyneco1156:834-842, 1986

Although that comparison between MRI and histology had only four patients, and more patients are necessary for definitive conclusion, we believe that the commonly held assumption that septa are fibrous is misleading. The most reliable criterion in separating a septate from a bicomuate uterus is the contour of the fundus, with a convex, flat, or mildly concave fundus being representative of a septate and a deep notch of a bicomuate uterus. Review of the literature reveals no extensive authoritative work on the actual composition of uterine septa. Unfortunately, most of the literature lacks any histologic documentation, although smooth muscle in uterine septa was shown on histologic examination, and blood vessels can be disorderly in the subendometrial myometrium of uterine septa. TMInadequacies in myometrial vascularization may have a significant bearing on outcome of pregnancy, 19and "the composition of uterine septal tissue is anything but constant. ''16 In septal tissue biopsies obtained at the time of Tompkins metroplasty, the amount of connective tissue was less and the amount of muscle tissue (muscle interlacing with vessels) more in the septum than in the wall of the uterus. 2~ Demonstration of a muscular component in the uterine septum is important not only for diagnostic purposes, but may prove significant in the operative management of these patients. Although considered poorly vascularized, 18bleeding has been reported at hysteroscopic resection of the septum 21 and traditionally was considered the end point of hysteroscopic treatment. In fact, many endoscopists consider bleeding as a physiologic marker for completion of the procedure, thinking that the relatively fibrous, bloodless septum has given way to uterine wall myometrium,5,6 rather than a myometrial septal component being present. Our finding that septa are frequently composed of myometrium raises interesting issues regarding their evaluation and treatment.

. Israel R, March CM: Hysteroscopic incision of the septare uterus. Am J Obstet Gynecol 149:66-73, 1984 . Daly DC, Walters CA, Soto-Albors CE, et al: Hysteroscopic metroplasty: Surgical technique and obstetric outcome. Fertil Steril 39:623-628, 1983 . Chervenak FA, Neuwirth RS: Hysteroscopic resection of the uterine septum. Am J Obstet Gynecol 141:351-353, 1981 . Pellerito JS, McCarthy SM, Doyle MB, et al: Diagnosis of uterine anomalies: Relative accuracy of MR imaging, endovaginal sonography,and hysterosalpingography. Genitourin Radiol 183:795-800, 1992 . Schwartz LB, Panageas E, Lange R, et al: Female pelvis: Impact of MR imaging on treatment decisions and new cost analysis. Radiology 192:55-60, 1994 10. Mintz MC, Thickman DI, Gussman D, et al: MR evaluation of uterine anomalies. AJR 148:287-290, 1987 11. Reuter KL, Daly DC, Cohen SM: Septate versus bicornuate uteri: Errors in imaging diagnosis. Radiology 172:749-752, 1989 12. Fedele L, Dorta M, Brioschi D, et al: Pregnancies in septate uteri: Outcome in relation to site of implantation as determined by sonography. AJR 152:78t-784, 1989 13. Scoutt LM, Flynn SD, Luthringer DJ, et al: Junctional zone of the uterus: Correlation of MR imaging and histologic examination of hysterectomy specimens. Radiology 179:403-407, 1991 14. McCarthy S, Scott G, Majumdar S, et al: Uterine junctional zone: MR study of water content and relaxation properties. Radiology 171:241-243, 1989 15. Brown HK, Stoll BS, Nicosia SV, et al: Uterine junctional zone: Correlation between histologic findings and MR imaging. Radiology 179:409-413, 1991

References

1. Semmens JP: Congenitaldefects of the reproductivetract: Clinical implications. Contemp Obstet Gynecol 5:95-102, 1975

16. Fedele L, Dorta M, Brioschi D, et al: Magnetic resonance evaluation of double uteri. Obstet Gynecol 74:844-847, 1989

2. Green LK, Harris RE: Uterine anomalies. Frequency of diagnosis and associated obstetric complications. Obstet Gyneco147:427429, 1976

17. Carrington BM, Hricak H, Nuruddin RN, et al: Mullerian duct anomalies: MR imaging evaluation. Radiology 176:715-720, 1990

3. Musich JR, Behrman SJ: Obstetric outcome before and after metroplasty in women with uterine anomalies. Obstet Gyneco152:63-66, 1978

18. Candiani GB, Fedele L, Zamberletti D, et al: Endometrial patterns in malformed uteri. Acta Eur Fertil 14:311-318, 1983 159

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19. Burchell RD, Creed F, Rasonlpour M, et al: Vascular anatomy of the human uterus and pregnancy wastage. Br J Obstet Gynaecol 85:698-706, 1978

21. Azmodeh O, Moghadami-Tabrizi N, Dabirashrafi H, et al: Uterine hemorrhage after hysteroscopic excision of the septum with miniscissors. Abstract presented at the 24th annual meeting of the American Association of Gynecologic Laparoscopists, Orlando, FL, November 8-12, 1995

20. Dabirashrafi H, Bahadori M, Mohammad K, et al: Final report about new concepts of pathology of the septum in septate uterus. Abstract presented at the 24th annual meeting of the American Association of Gynecologic Laparoscopists, Orlando, FL, November 8-12, 1995

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