AJR 2001; 177:1305-1306
© American Roentgen Ray Society
MR Imaging and MR Angiography of an Abdominal Pregnancy with Placental Infarction
Vartan Malian1 and
J. H. Edmund Lee
1
Both authors: Department of Diagnostic Radiology, University of California
Davis Medical Center, 4860 Y St., Ste. 3100, Sacramento, CA 95817
Received March 13, 2001;
accepted after revision May 15, 2001.
Address correspondence to J. H. E. Lee.
Introduction
Approximately 0.1% of pregnancies are abdominal, with a considerably higher
risk for morbidity and mortality due to delayed diagnosis, compared with both
intrauterine and other types of ectopic pregnancies. Sonography is considered
the front-line diagnostic imaging study, with MR imaging serving as an adjunct
in cases when sonography is equivocal and in cases when the delineation of
anatomic relationships may alter the surgical approach
[1]. Reports have described the
normal MR imaging appearance of the placenta and the use of MR imaging in
extrauterine pregnancy [1,
2], but there are no reports,
to our knowledge, of the appearance of placental infarction in human pregnancy
or of the use of MR angiography in ectopic pregnancy. We report a case of
abdominal pregnancy in which MR imaging showed placental infarction and in
which MR angiography helped direct surgical therapy.
Case Report
A 33-year-old woman (gravida 2, para 0) was transferred to our medical
center with suspected abdominal pregnancy of approximately 18 weeks'
gestation. Her medical history was notable for a prior therapeutic abortion
with subsequent difficulty conceiving. The abdominal pregnancy was strongly
suspected initially on sonographic evaluation
(Fig. 1A), which did not show
definite fetal movement or fetal cardiac activity. The obstetric service
subsequently requested MR imaging to confirm the diagnosis and to plan
surgical termination for the unviable pregnancy. The obstetric service also
asked for an evaluation of the extent of uterine invasion by the placenta to
see if the uterus could be spared. Lastly, the obstetric service requested
evaluation of the vascular supply to exclude the involvement of mesenteric
blood vessels that would necessitate bowel and mesenteric resection. MR
imaging confirmed a single abdominal pregnancy posterior to the uterus with
minimal invasion of the superior uterus
(Fig. 1B). A 2 x 4
x 6 cm T1 and T2 hypointensity at the superior placenta was noted along
with a smaller similar lesion at the inferior placenta (Figs.
1B and
1C). Gadolinium—bolus MR
angiography was performed and showed two small arteries arising from the right
iliac circulation. A prominent right ovarian vein drained from the placenta to
the inferior vena cava. The mesenteric vasculature was not involved
(Fig. 1D). The
gadolinium-enhanced images showed no enhancement of the placental
hypointensity (Fig. 1E).
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Fig. 1B. —33-year-old woman with abdominal pregnancy and placental
infarcts. Sagittal T2-weighted single-shot fast spin-echo image (TR/TE,
21,317/96) (B) and T1-weighted in-phase fast-spoiled gradient-echo
breath-hold image (180/4.2; flip angle, 80°) (C) show abdominal
pregnancy with areas of hypointensity (arrows) corresponding to
infarction in superior and inferior placenta. No uterine invasion by placenta
is present.
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Fig. 1C. —33-year-old woman with abdominal pregnancy and placental
infarcts. Sagittal T2-weighted single-shot fast spin-echo image (TR/TE,
21,317/96) (B) and T1-weighted in-phase fast-spoiled gradient-echo
breath-hold image (180/4.2; flip angle, 80°) (C) show abdominal
pregnancy with areas of hypointensity (arrows) corresponding to
infarction in superior and inferior placenta. No uterine invasion by placenta
is present.
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Fig. 1D. —33-year-old woman with abdominal pregnancy and placental
infarcts. Gadolinium bolus arterial phase MR angiogram (three-dimensional fast
spoiled gradient-echo, 6.1/1.3; flip angle, 40°) maximum intensity
projection 30° right posterior oblique view shows retroperitoneal right
ovarian vein (arrow) draining pregnancy. No vascular connection to
mesentery is present.
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Fig. 1E. —33-year-old woman with abdominal pregnancy and placental
infarcts. Sagittal T1-weighted fat-saturated gadolinium-enhanced fast-spoiled
gradient-echo image (190/1.8; flip angle, 80°) shows no appreciable
enhancement of hypointense placental lesions (arrows), consistent
with infarcts seen at pathology.
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The patient underwent exploratory laparotomy 1 day later with delivery of
the abdominal pregnancy, lysis of adhesions, and right salpingo-oophorectomy.
The fetus was dead at the time of delivery. Blood supply arose from the
infundibulopelvic vasculature with no mesenteric involvement. The extent of
uterine invasion was minimal and matched the region shown by MR imaging, and
the uterus was left mostly intact. Postoperative histologic examination of the
placenta revealed necrosis of the placenta matching the regions of signal
hypointensity and nonenhancement seen on MR imaging.
Discussion
In this patient, MR imaging confirmed the diagnosis of extrauterine
pregnancy, delineated the extent of peritoneal involvement for preoperative
planning, and revealed the degree of uterine invasion. The use of MR imaging
for these reasons has been reported previously
[1]. MR imaging of the normal
placenta and MR angiography evaluation of placental perfusion have been
reported previously as well [2,
3], but placental infarction
has not been reported to our knowledge. In our patient, the placental infarcts
showed T1 and T2 hypointensity with no enhancement. The T2-weighted and
gadolinium-enhanced images, in particular, showed the regions of infarction
clearly. Although MR imaging has not been previously used to examine placental
infarction, T2-hypointense lesions in the placenta that are found incidentally
on prenatal MR imaging may represent placental infarction, as in our
patient.
MR angiography showed the location and origins of the vasculature supplying
the pregnancy. Involvement of the mesenteric vasculature was successfully
excluded, providing valuable preoperative planning. To our knowledge, the use
of MR angiography for preoperative planning in ectopic pregnancy also has not
been previously reported. The effect of IV gadolinium on the human fetus is
unknown; therefore, its routine use in pregnancy is not recommended
[2,
4]. The use of gadolinium was
possible in this patient because the patient was already scheduled for
pregnancy termination. In such patients, the use of gadolinium bolus MR
angiography may add valuable preoperative information.
In summary, we present a case of abdominal pregnancy evaluated with MR
imaging and MR angiography. Placental infarction showed T1 and T2
hypointensity with no enhancement. MR imaging helped surgical planning by
evaluating the extent of mesenteric and uterine involvement.
Gadolinium—bolus MR angiography was successfully used for preoperative
evaluation of vascular anatomy.
References
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Wagner A, Burchardt A. MR imaging in advanced abdominal pregnancy.
Acta Radiol 1995;36
: 193-195[Medline]
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Marcos HB, Semelka RC, Worawattanakul S. Normal placenta:
gadolinium-enhanced, dynamic MR imaging. Radiology
1997;205:493
-496[Abstract/Free Full Text]
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Duncan K, Gowland P, Francis S, et al. The investigation of
placental relaxation and estimation of placental perfusion using echo-planar
magnetic resonance imaging. Placenta
1998;19:539
-543[Medline]
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Levine D, Barnes PD, Edelman RR. Obstetric MR imaging.
Radiology
1999;211:609
-617[Abstract/Free Full Text]
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Introduction
Case Report
