AJR 2003; 181:435-439
© American Roentgen Ray Society
MR Imaging of Retained Products of Conception
Jaime B. Noonan1,
Fergus V. Coakley2,
Aliya Qayyum2,
Benjamin M. Yeh2,
Louis Wu3 and
Lee-may Chen4
1 Emory University School of Medicine, 1440 Clifton Rd., N.E., Atlanta, GA
30322-4510.
2 Department of Radiology, Abdominal Imaging, University of California San
Francisco, 505 Parnassus Ave., Box 0628, San Francisco, CA 94143-0628.
3 Department of Radiology, University of Toronto, 30 Bond St., Toronto, ON M5B
1W8, Canada.
4 Department of Gynecologic Oncology, University of California San Francisco,
San Francisco, CA 94143-0628.
Received September 30, 2002;
accepted after revision February 4, 2003.
Address correspondence to F. V. Coakley.
Abstract
OBJECTIVE. The objective of this article is to describe the MR
imaging appearances of retained products of conception.
CONCLUSION. Retained products of conception appear on MR imaging as
an intracavitary uterine soft-tissue mass with variable amounts of enhancing
tissue and variable degrees of myometrial thinning and obliteration of the
junctional zone. These findings should not be misinterpreted as indicating
gestational trophoblastic disease, particularly in the setting of a postpartum
patient with a normal or minimally elevated ß-human chorionic
gonadotropin level. MR imaging may also be helpful in showing anatomic
variants that hinder successful instrumentation of the uterine cavity in
patients with suspected retained products of conception.
Introduction
Retained products of conception complicate nearly 1% of all pregnancies,
occurring with greater frequency after termination of pregnancy than after
vaginal or cesarean delivery
[1]. Common symptoms include
vaginal bleeding and abdominal or pelvic pain
[2]. Patients with gestational
trophoblastic disease may present with similar postpartum symptoms.
Differentiation of these entities is important because retained products of
conception may be treated conservatively or with curettage
[1], whereas gestational
trophoblastic disease may require chemotherapy. The serum level of
ß-human chorionic gonadotropin (ß-HCG) is a helpful distinguishing
factor in the postpartum period. The ß-HCG characteristically remains
elevated in patients with gestational trophoblastic disease, whereas the
hormone falls to an undetectable level over 2–3 weeks in patients with
retained products of conception
[3]. Sonography is the primary
modality used for the radiologic evaluation of retained products of
conception, but the reported diagnostic accuracy of sonography is variable
[2,
4]. Other imaging modalities
might therefore be helpful in the evaluation of suspected retained products of
conception, although the MR imaging findings have only been described in a
small number of case reports
[5–7].
We undertook this study to describe the MR imaging appearances of retained
products of conception on the basis of our recent experience with four
patients who had this condition.
Materials and Methods
This was a retrospective study and was approved by our institutional review
board. Informed consent was not required. Between January 1998 and December
2001, pelvic MR imaging was performed in four patients who had a
histologically confirmed diagnosis of retained products of conception.
Clinical and imaging findings were recorded by review of all available medical
and radiologic records. Three patients were imaged at our institution, and one
patient was imaged at another institution.
In all patients, pelvic MR imaging was performed on a 1.5-T whole-body MR
scanner (Signa, General Electric Medical Systems, Milwaukee, WI). Patients
were examined in the supine position with a pelvic surface coil (General
Electric Medical Systems). MR sequences included axial and sagittal
T2-weighted fast spin-echo (TR/effective TE, 4000/85; slice thickness, 5 mm;
gap, 1 mm; field of view, 24–28 cm; number of acquisitions, 2; matrix,
512 x 256) and sagittal (n = 3) or coronal (n = 1)
contrast-enhanced breath-hold T1-weighted in-phase spoiled gradient-echo
(TR/TE, 150/4.2; flip angle, 75°; slice thickness, 5–10 mm; gap,
1–2 mm; field of view, 24–28 cm; number of acquisitions, 1;
matrix, 256 x 128–192) before and after an IV bolus injection of
0.1 mmol/kg of gadolinium chelate (Magnevist, Berlex, Wayne, NJ).
Gadolinium-enhanced images were obtained dynamically at scanning delays of 20
and 80 sec and 2, 3, and 5 min.
Results
Patient 1
A 38-year-old gravida 2 para 1 woman developed persistent vaginal bleeding
7 weeks after a forceps-assisted vaginal delivery at term with manual
extraction of the placenta. Sonography showed a uterine mass with apparent
myometrial invasion. Dilatation and curettage showed retained and partially
necrotic placental tissue. Three days after the procedure, the patient became
febrile. Her serum ß-HCG level was 6 mIU/mL (normal, < 5 mIU/mL).
MR imaging was performed (Fig.
1A,
1B). An anteverted retroflexed
uterus containing a 6.7-cm intracavitary soft-tissue mass with thinning of the
overlying myometrium was seen. The lesion was isointense to myometrium on
T1-weighted images and heterogeneous on T2-weighted images and showed small
briskly enhancing strands of tissue after IV administration of gadolinium. The
patient was treated expectantly and her symptoms resolved. Follow-up
sonography that was performed 9 months later showed complete resolution of the
uterine mass.
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Fig. 1A. —38-year-old woman with fever 3 days after dilatation and curettage
was performed for postpartum bleeding 7 weeks after vaginal delivery at term.
Serum ß-human chorionic gonadotropin level was 6 mIU/mL. Sagittal
T2-weighted MR image (TR/TE, 4000/85) of pelvis shows retroflexed uterus with
intracavitary mass (arrow) with heterogeneous signal intensity.
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Fig. 1B. —38-year-old woman with fever 3 days after dilatation and curettage
was performed for postpartum bleeding 7 weeks after vaginal delivery at term.
Serum ß-human chorionic gonadotropin level was 6 mIU/mL. Sagittal
T1-weighted MR image (150/4.2) obtained after IV administration of gadolinium
shows hypointense predominantly nonenhancing mass with focal areas of
enhancement (arrows).
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Patient 2
A 36-year-old gravida 10 para 8 woman presented with abdominal pain and
vaginal bleeding 12 weeks after elective termination of pregnancy. The patient
had negative findings on a urinary screening test for ß-HCG. Sonography
showed a vascular uterine mass, and the diagnosis of an arteriovenous
malformation was suggested.
MR imaging showed a 5.0-cm intracavitary soft-tissue mass in the uterus,
with thinning of the overlying myometrium and obliteration of the junctional
zone. The lesion was isointense to myometrium on T1-weighted images and
heterogeneous on T2-weighted images and showed focal brisk enhancement after
IV administration of gadolinium (Fig.
2A,
2B). Because preservation of
fertility was not desired, the patient underwent a total abdominal
hysterectomy that showed partially necrotic placental tissue in the
endometrial cavity.
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Fig. 2A. —36-year-old woman with vaginal bleeding, abdominal pain, and
negative findings on urine ß-human chorionic gonadotropin test 12 weeks
after elective termination of pregnancy. Sagittal T2-weighted MR image (TR/TE,
4000/85) shows heterogeneous mass (arrow) in uterine cavity. Note
obliteration of overlying junctional zone with thinning of myometrium at
uterine fundus.
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Fig. 2B. —36-year-old woman with vaginal bleeding, abdominal pain, and
negative findings on urine ß-human chorionic gonadotropin test 12 weeks
after elective termination of pregnancy. Sagittal T1-weighted MR image
(150/4.2) obtained after IV administration of gadolinium shows areas of brisk
enhancement (arrow) within intrauterine mass. Note presence of fluid
(asterisk) in upper vagina due to persistent postpartum
hemorrhage.
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Patient 3
A 32-year-old gravida 2 para 0 woman presented with vaginal bleeding and
passage of tissue 2 months after treatment of an incomplete spontaneous
abortion at 8 weeks' gestation. The serum ß-HCG level was 45 mIU/mL.
Sonography revealed an intrauterine mass suspected to be gestational
trophoblastic disease. Dilatation and curettage was terminated prematurely
because of persistent brisk bleeding from the cervical os despite application
of suction and bimanual uterine massage. Some tissue was obtained, and
histologic analysis showed degenerating chorionic villi.
Because of the incomplete dilatation and curettage, MR imaging was obtained
to further characterize the lesion (Fig.
3A,
3B). A 6.1-cm intracavitary
mass was seen in the uterus, with thinning of the overlying myometrium and
obliteration of the junctional zone. The lesion was isointense to myometrium
on T1-weighted images and heterogeneous on T2-weighted images and showed focal
brisk enhancement after IV administration of gadolinium.
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Fig. 3A. —32-year-old woman with vaginal bleeding and serum ß-human
chorionic gonadotropin of 45 mIU/mL 2 weeks after spontaneous abortion. Axial
T2-weighted MR image (TR/TE, 4000/85) shows irregular uterine mass (black
arrow) of heterogeneous intensity obliterating most of junctional zone
with marked thinning of myometrium (white arrow).
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Fig. 3B. —32-year-old woman with vaginal bleeding and serum ß-human
chorionic gonadotropin of 45 mIU/mL 2 weeks after spontaneous abortion.
Sagittal T1-weighted MR image (150/4.2) obtained after IV administration of
gadolinium shows areas of brisk enhancement (arrow) in intrauterine
mass.
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Repeated dilatation and curettage with hysteroscopic and laparoscopic
guidance showed degenerating chorionic villi without atypical trophoblastic
cells. The patient's symptoms resolved, and follow-up pelvic MR imaging
performed 2 months later showed no evidence of a uterine mass.
Patient 4
A 33-year-old gravida 1 para 0 woman with a known bicornuate unicollis
uterus had an incomplete spontaneous abortion requiring dilatation and
evacuation at 16 weeks' gestation. She subsequently developed persistent
vaginal bleeding and pelvic pain requiring repeated uterine aspiration, during
which minimal tissue was obtained. Eight weeks after the initial incomplete
abortion, the patient's serum ß-HCG level remained slightly elevated at
15 mIU/mL. MR imaging showed a bicornuate unicollis uterus with a 5.2-cm
intracavitary soft-tissue mass in an enlarged right horn with thinning of the
overlying myometrium (Fig. 4A,
4B,
4C). The lesion was focally
hyperintense on T1-weighted images and heterogenously hyperintense on
T2-weighted images and showed foci of brisk and marked enhancement after IV
administration of gadolinium.
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Fig. 4A. —33-year-old woman with bicornuate unicollis uterus and persistent
vaginal bleeding 8 weeks after spontaneous abortion at 16 weeks' gestation.
Two attempts at aspiration of uterine contents had been unsuccessful. Serum
ß-human chorionic gonadotropin level was 15 mIU/mL. Coronal T1-weighted
unenhanced MR image (TR/TE, 150/4.2) shows partially hyperintense mass
(arrow) in right cornu.
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Fig. 4B. —33-year-old woman with bicornuate unicollis uterus and persistent
vaginal bleeding 8 weeks after spontaneous abortion at 16 weeks' gestation.
Two attempts at aspiration of uterine contents had been unsuccessful. Serum
ß-human chorionic gonadotropin level was 15 mIU/mL. Axial T2-weighted MR
image (4000/85) shows irregular mass (arrow) in right cornu
associated with thinning of myometrium.
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Fig. 4C. —33-year-old woman with bicornuate unicollis uterus and persistent
vaginal bleeding 8 weeks after spontaneous abortion at 16 weeks' gestation.
Two attempts at aspiration of uterine contents had been unsuccessful. Serum
ß-human chorionic gonadotropin level was 15 mIU/mL. Coronal T1-weighted
MR image (150/4.2) obtained after IV administration of gadolinium shows
enhancing areas of lesion (arrows) in enlarged right cornu.
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Repeated hysteroscopy with dilatation and curettage was performed that
showed degenerating chorionic villi and chronic endometritis. The patient was
treated with methotrexate, misoprostol, and antibiotics, and her symptoms
completely resolved. Pelvic MR imaging performed 5 months later showed no
evidence of a uterine mass.
Discussion
Our results suggest that retained products of conception appear on MR
imaging as an intracavitary uterine soft-tissue mass with variable T1 and T2
signal intensities, variable amounts of enhancing tissue, and variable degrees
of myometrial thinning and obliteration of the junctional zone. Despite the
presumed presence of blood products, the intracavitary mass showed foci of
increased T1 signal intensity on unenhanced images in only one of our four
patients. All four patients had lesions that were heterogeneous on T2-weighted
imaging. These findings indicate that the MR imaging features of retained
products of conception can overlap with those of gestational trophoblastic
disease. Accordingly, radiologists interpreting an intrauterine mass in a
postpartum patient should be cautious in attempting to make a definitive
distinction between retained products of conception and gestational
trophoblastic disease.
Enhancement has been proposed as an imaging sign that can be used to
distinguish retained products of conception from gestational trophoblastic
disease. Prior case reports of MR imaging of retained products of conception,
which have been confined to cases of retained placenta accreta, describe a
uterine mass protruding into the endometrial cavity without enhancement after
IV administration of gadolinium
[5,
6]. The authors suggested that
lack of enhancement might be used to distinguish retained products of
conception from gestational trophoblastic disease. Our findings indicate that
this sign would be unreliable because all four of our patients showed at least
some areas of enhancement after IV administration of gadolinium, suggesting
the presence of vascularized and at least partially viable tissue. However,
the histopathologic basis of enhancement in these patients is speculative,
given the retrospective nature of our study and the use of curettage rather
than hysterectomy specimens as the tissue standard of reference in three of
the four patients.
Given that the T1, T2, and postgadolinium appearances of retained products
of conception overlap with those of gestational trophoblastic disease, it is
instructive to consider other factors that might help in the distinction
between the two conditions. The described MR findings in gestational
trophoblastic disease include myometrial thinning and obliteration of the
junctional zone [8,
9], but we observed these
findings in all four patients in this series with retained products of
conception. Abnormal uterine vasculature and ovarian theca lutein cysts
[8,
9] are recognized features of
gestational trophoblastic disease that have not been described in retained
products of conception and were not present in our four patients.
The serum ß-HCG level is a nonradiologic factor that is also helpful.
Typically, the ß-HCG level remains elevated after delivery to levels of
1000 mIU/mL or more in patients with gestational trophoblastic disease, but
decreases to normal or near normal levels in patients with retained products
of conception [8]. The failure
of the serum ß-HCG level to become undetectable in retained products of
conception is presumably due to a small amount of viable trophoblastic tissue
and may correlate with the presence of enhancing elements on MR imaging.
However, there are histologic subtypes of gestational trophoblastic disease in
which ß-HCG levels are normal or slightly elevated, including placental
site trophoblastic tumor [10].
Such variants could potentially be mistaken for retained products of
conception if undue emphasis was placed on the ß-HCG level as a
distinguishing feature. Descriptions of MR imaging in placental site
trophoblastic tumor are limited but suggest the tumor is characteristically
intramyometrial in location, rather than intracavitary
[11]. This description might
assist in the distinction of placental site trophoblastic tumor from retained
products of conception.
In two of our four patients, symptoms of retained products of conception
persisted after uterine curettage or evacuation, with an intracavitary mass
seen on subsequent MR imaging. Both patients had anatomic factors that may
have hindered successful instrumentation of the uterine cavity—namely,
bicornuate unicollis uterus and uterine retroflexion. These findings were
shown on MR imaging, which suggests that this type of modality may be
particularly appropriate when postpartum hemorrhage persists after dilatation
and curettage.
The major limitation of our study is the inevitable selection bias in
retrospective patient recruitment. Undoubtedly, the patients we studied
represented unusually complex cases of retained products of conception.
However, these patients are likely representative of the occasional case of
retained products of conception that requires MR imaging. Most cases are
probably adequately managed by clinical assessment and sonography; only rare,
problematic cases require more detailed imaging.
In conclusion, retained products of conception typically appear on MR
imaging as an intracavitary uterine soft-tissue mass with variable amounts of
enhancing tissue and variable degrees of myometrial thinning and obliteration
of the junctional zone. These findings should not be misinterpreted as
indicating gestational trophoblastic disease, particularly in the setting of a
postpartum patient with a normal or minimally elevated ß-HCG level. MR
imaging may also be helpful in showing anatomic variants that hinder
successful instrumentation of the uterine cavity.
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Abstract
Introduction
