1 Department of Radiology and Nuclear Medicine, Faculty of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto-shi, Kyoto-fu 2 Hitachi Medical Corporation Chair of Department of Diagnostic and Interventional Imageology, Faculty of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto-shi, Kyoto-fu 3 Department of Obstetrics and Gynecology, Faculty of Medicine, Kyoto University,54 Shogoin Kawahara-cho, Sakyo-ku, Kyoto-shi, Kyoto-fu, 606-8507, Japan.
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Abstract |
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Key words: ectopic pregnancy/Fallopian tube/MRI/tubal pregnancy
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Introduction |
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Materials and methods |
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The gold standard for the final diagnosis of ectopic pregnancy was a consensus between surgery, serial HCG concentration, D & C, and sonographic findings. Medical records were reviewed in all patients. Among these 37 cases, 18 (aged 2040 years; mean 29) underwent surgery and were confirmed to have ectopic pregnancy. Appropriate high HCG concentrations at initial presentation accompanied by falling concentrations after MTX administration or expectant follow-up were considered as cases of true ectopic pregnancy (n = 14). Four cases who were followed expectantly, had low concentrations of HCG at initial presentation, but who showed adnexal mass on initial sonography, were also considered as cases of true ectopic pregnancy. One patient who was followed expectantly, had low concentrations of HCG at initial presentation and no abnormal findings on sonography, was excluded from the study because these observations could represent either an aborted pregnancy, or a topic or ectopic one. Consequently, 36 cases (aged 2041 years; mean 29) were considered to have ectopic pregnancy and comprised this study. Eighteen patients underwent surgery, and the MR findings of these patients were correlated to the surgical findings to assess the accuracy of MR imaging.
MR imaging was performed with a use of 1.5 T superconductive system (Sigma, General Electric Medical Systems, Milwaukee, Wisconsin, USA), with a body coil. Sagittal T1 and T2-weighted images (WI) and contrast enhanced T1WI with gadopentetate dimeglumine (GD-DTPA) (Magnevist; Schering, Osaka, Japan) (0.1 mmol/kg) were obtained by conventional spin-echo (SE) technique. The parameters for T1WI were 600/20 ms repetition time/echo time (TR/TE) and for T2WI were 2000/7090 ms (TR/TE). Complementary axial images were obtained in six cases. Axial and coronal images were not obtained in all patients due to time constraints in our service. The slice thickness was 5 mm, with a 2.5 mm gap, 256x192 matrix, the number of signals averaged two with a 32 cm field of view.
Prospective reading
MR scans were interpreted knowing the ultrasound and laboratory results. MR imaging findings were prospectively assessed for the presence or absence of dilatation and contrast enhancement of the Fallopian tube, haematoma, gestational sac (GS)-like structure, and ascites. An enhancing tubular structure close to the ovary was diagnosed as Fallopian tube. GS-like structure was defined as a sac-like cystic structure surrounded by a thick enhancing ring, similar to that seen in sonography (Atri et al., 1992).
Each haematoma and GS-like structure was localized as tubal, adnexal or abdominal. Tubal localization of haematoma or GS-like structure was established when they were observed within the enhancing tubular structure (dilated Fallopian tube) or in the uterine cornus (interstitial).
MR imaging was scored to indicate whether a tubal pregnancy was demonstrated, and with what confidence, as follows: (i) diagnostic (definite tubal pregnancy: presence of wall enhancement of dilated Fallopian tube filled with haematoma or GS-like structure), (ii) suspicious [dilated enhancing tube filled with only a non-specific fluid or only presence of haematosalpinx (cylindrical bloody structure without enhancement)], (iii) equivocal (haematoma or GS-like structure without identifiable tubal findings), (iv) questionable (only ascites), (v) negative.
An addendum to this scoring system was the presence of haematoma or GS-like structure in the uterine cornus. According to previously published MR data (Ha et al., 1993; Bassil et al., 1995
; Yamashita et al., 1995
; Hamada et al., 1997
), this finding was considered diagnostic for interstitial pregnancy, and was included in the diagnostic group (i) for tubal pregnancy, even in the absence of identification of Fallopian tube.
The therapeutic options in our institution were expectant management (close observation), medical treatment with MTX, and surgery. The treatment decision followed criteria amply discussed (Ylostalo et al., 1992; Stovall and Ling, 1993
; Falk, 1994
; Leventhal, 1994
; Atri et al., 1996
).
Retrospective reading
In the second portion of this study, MR images of all 18 surgically confirmed cases were retrospectively reviewed by two radiologists (KT and MLK), in conference, to evaluate signal intensity of haematoma (tubal, adnexal, abdominal) and ascites. Signal intensity of the haematoma was classified as high, intermediate, or low. On T1WI, high signal intensity meant signal similar to or higher than the bone marrow, intermediate signal intensity meant signal similar to the myometrium, and low signal intensity meant signal similar to simple fluid. On T2WI, high signal intensity meant signal intense of simple fluid, intermediate signal intensity meant signal similar to outer myometrium, and low signal intensity meant signal similar to signal void or skeletal muscle.
Signal intensity of the ascites was classified as intermediate [if comparable with water (urine)], high (if signal intensity was similar to myometrium) or prominently high (if signal intensity was higher than signal of the myometrium) on T1WI. On T2WI, signal intensity was compared with the signal of urine, and classified as high, intermediate or low.
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Results |
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MR findings of all cases are summarized in Table I. There were 21 (58%) diagnostic (Figure 1 and 2
), two (5%) suspicious (Figure 3
), eight (22%) equivocal (Figure 4
), and five (14%) negative findings. Fallopian tube was identified as an enhancing tubular structure with tubal haematoma in 18 (Figure 1 and 2
) and without tubal haematoma or GS-like structure in two. There were three cases of interstitial pregnancy (two GS-like structure and one haematoma in the uterine cornus) classified as diagnostic for tubal pregnancy. Thus, in total, there were 21 diagnostic findings. Haematomas were observed in 25 (69%) cases, including 19 tubal (including one interstitial), 10 adnexal and nine abdominal. Six (17%) cases had GS-like structure, including three tubal (two being interstitial), two adnexal and one in rudimentary horn. One case had both tubal haematoma and GS-like structure. Ascites was observed in 20 (55%) cases.
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Of 10 patients pregnant after assisted fertilization, three underwent surgery, five MTX treatment and two, expectant management.
Retrospective reading
The results of the evaluation of signal intensity of the haematoma are summarized in Table IV.
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Ascites showed signal intensity higher than that of urine on T1WI in 100% of 13 cases (high intensity in seven cases and predominantly high intensity in six cases). The signal intensity results on T2WI were four intermediate, six high and three low signal intensity.
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Discussion |
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Surgery is still the standard treatment for ectopic pregnancy (Leventhal, 1994); however, there is a recent trend towards treating ectopic pregnancy either medically or not at all (expectant management) (Ylostalo et al., 1992
; Stovall and Ling, 1993
). These medical regimens most often use MTX administered systemically or locally into the ectopic sac or haematosalpinx. Early institution of medical therapy with MTX diminishes the potential risk of rupture, decreases patient morbidity and health care costs, avoiding surgery and hospitalization (Emerson et al., 1992
; Falk, 1994
). This approach requires a highly accurate non-invasive test for the evaluation of patients with suspected ectopic pregnancy.
Endovaginal sonography is the current alternative to diagnostic laparoscopy for the diagnosis of ectopic pregnancy. It has 84.4% sensitivity, 98.9% specificity, 96.3% positive predictive value, and 94.8% negative predictive value for accuracy in the diagnosis of ectopic pregnancy on the basis of observing any adnexal mass except for a simple cyst or an intra-ovarian lesion (Brown and Doubilet, 1994). The most highly specific finding is the identification of an extra-uterine GS that contains a yolk sac or an embryo (with or without cardiac activity). However, the most common adnexal finding is an echogenic homogeneous or heterogeneous, rounded, or elongated solid structure, located outside but in proximity to the ovary, indicating haematosalpinx (Atri et al., 1992
). In tubal pregnancy, the Fallopian tube is enlarged by products of conception, blood, and blood clots (Rottem et al., 1990
; Atri et al., 1992
). Sonography identifies this haematosalpinx based on echogenic and morphological characteristics. Unfortunately this diagnosis is not specific since sonography is not able to characterize blood. On the other hand, MR imaging is capable not only of identifying blood but also of determining the age of blood products as acute (intermediate signal intensity on T1WI and marked low signal intensity on T2WI), subacute (peripheral high signal intensity with a distinct central area of low signal intensity on T1WI and T2WI) or chronic (entirely high signal intense on T1WI and T2WI) (Gomori et al., 1985
; Rubin et al., 1987
).
Our MR imaging criteria for diagnosis of tubal pregnancy are based on two findings: one is haematosalpinx and the other is wall enhancement of dilated Fallopian tube. These criteria are supported by a report that no lumen was identifiable within normal Fallopian tubes on specimen studies (Outwater et al., 1996). In 1998, Outwater et al described the correct identification of dilated Fallopian tubes in 31 of 41 study patients and correct exclusion of dilated Fallopian tubes in a mean 34 of 38 control subjects (Outwater et al., 1998
). Increased vascularity of the tubal wall observed following implantation can explain wall enhancement (Togashi et al., 1994
; Momma et al., 1995
).
In our surgically confirmed cases, MR gave 12 true positive, three true negative, three false negative, and no false positive results for the diagnosis of tubal pregnancy, distinguishing them from other rare types of ectopic pregnancy, with the use of diagnostic criteria (definitive tubal pregnancy indicated by simultaneous presence of tubal enhancement and haematoma). Among six patients who underwent surgery and had been classified as suspicious or equivocal by MR imaging, tubal pregnancy was found in three and other types of ectopic pregnancy were confirmed in the other three. Other clinical conditions that might be included in the differential diagnosis are salpingitis or pyosalpinx for suspicious cases, and other haemorrhagic disease entities (such as corpus luteum, haematoma, or endometriosis) for the equivocal group. However, these conditions can be excluded by clinical history.
Appropriate high HCG concentrations justified MTX administration in two cases negative on MR imaging. These cases show that, although highly specific in the diagnosis of tubal pregnancy, MR imaging can produce false negative results.
The predominant signal intensity of the tubal haematomas was intermediate on T1WI, and distinct hypointensive on T2WI, which means an acute phased haematoma (Rubin et al., 1987). Identification of fresh blood seems to be highly important in the diagnosis of early tubal pregnancy, and MR imaging is unique as the only modality to enable identification of the stage of a haematoma.
It is not our purpose to replace sonography as the standard imaging study for the diagnosis of tubal pregnancy. MR study is proposed to provide additional information for a limited number of patients who need precise diagnosis. For example, in patients with pre-existing damage in the contralateral tube, and desiring future pregnancy, where the preservation of patency in the remaining tube is very important. In our study, 10 patients were undergoing treatment for infertility, and MR examination allowed a specific early diagnosis of tubal pregnancy, contributing to the decision for determining early non-surgical therapy.
In conclusion, MR imaging with contrast enhancement is a promising modality for diagnosis of tubal pregnancy, enabling the recognition of tubal wall enhancement and fresh tubal haematoma.
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Notes |
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References |
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Submitted on April 15, 1999; accepted on July 12, 1999.