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Angiographic features and transarterial embolization of retained placenta with abnormal vaginal bleeding

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Objectives To clarify characteristic angiographic features and clinical efficacy of selective transarterial embolization (TAE) of retained placenta with abnormal vaginal bleeding. Methods The study cohort comprised 22 patients (mean age, 33.5 years; range, 22–24 years) who underwent selective TAE for retained placenta with abnormal bleeding between January 2018 and December 2020 at our institution. Angiographic images were reviewed by two certified radiologists with consensus. Medical records were reviewed to evaluate the efficacy of TAE. Angiographic features of retained placenta, technical success (disappearance of abnormal findings on angiography), complications, clinical outcomes (hemostatic effects and recurrent bleeding) were evaluated. Results Pelvic angiography showed a dilated vascular channel mimicking arteriovenous fistulas or an aneurysm contiguous with dilated uterine arteries in the mid-arterial–capillary phase in 20 patients; it showed contrast brush in the remaining two patients. TAE technical success was achieved in all patients. No major complications were observed in any patients. Fifteen patients were followed up with expectant management after TAE; all but one patient showed no re-bleeding during the follow-up period (mean follow-up interval, 3.4 months; range, 1–17 months). One patient showed minor rebleeding, which resolved spontaneously. Seven patients underwent scheduled hysteroscopic resection within 1 week after TAE, and no excessive bleeding was observed during or after the surgical procedure in all seven patients. Conclusions The characteristic angiographic feature of retained placenta is “dilated vascular channel that mimic low flow AVM.” TAE is a safe and effective treatment to manage retained placenta with abnormal bleeding.
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O R I G I N A L A R T I C L E Open Access
Angiographic features and transarterial
embolization of retained placenta with
abnormal vaginal bleeding
Ryo Takaji
1*
, Hiro Kiyosue
1
, Miyuki Maruno
1
, Norio Hongo
1
, Ryuichi Shimada
1
, Satomi Ide
1
, Kohei Tokuyama
1
,
Mamiko Okamoto
2
, Yasushi Kawano
2
and Yoshiki Asayama
1
Abstract
Objectives: To clarify characteristic angiographic features and clinical efficacy of selective transarterial embolization
(TAE) of retained placenta with abnormal vaginal bleeding.
Methods: The study cohort comprised 22 patients (mean age, 33.5 years; range, 2224 years) who underwent
selective TAE for retained placenta with abnormal bleeding between January 2018 and December 2020 at our
institution. Angiographic images were reviewed by two certified radiologists with consensus. Medical records were
reviewed to evaluate the efficacy of TAE. Angiographic features of retained placenta, technical success
(disappearance of abnormal findings on angiography), complications, clinical outcomes (hemostatic effects and
recurrent bleeding) were evaluated.
Results: Pelvic angiography showed a dilated vascular channel mimicking arteriovenous fistulas or an aneurysm
contiguous with dilated uterine arteries in the mid-arterialcapillary phase in 20 patients; it showed contrast brush
in the remaining two patients. TAE technical success was achieved in all patients. No major complications were
observed in any patients. Fifteen patients were followed up with expectant management after TAE; all but one
patient showed no re-bleeding during the follow-up period (mean follow-up interval, 3.4 months; range, 117
months). One patient showed minor rebleeding, which resolved spontaneously. Seven patients underwent
scheduled hysteroscopic resection within 1 week after TAE, and no excessive bleeding was observed during or after
the surgical procedure in all seven patients.
Conclusions: The characteristic angiographic feature of retained placenta is dilated vascular channel that mimic
low flow AVM.TAE is a safe and effective treatment to manage retained placenta with abnormal bleeding.
Keywords: Retained placenta, Angiography, Transarterial embolization
Introduction
Retained placenta is a major cause of postpartum
hemorrhage. Notably, retained placenta in the presence
of severe postpartum hemorrhage has a reported fre-
quency of 11.4%33.3% among the patients with severe
postpartum hemorrhage (Nyfløt et al. 2017; Hulse et al.
2020; Kodan et al. 2020; Shams et al. 2020; Sosa et al.
2009; Widmer et al. 2020). Retained placenta can cause
life-threatening severe vaginal bleeding. Hence, diagnosis
and appropriate management of retained placenta are
important.
Recently, transarterial embolization (TAE) has been
established as a treatment option for uncontrollable
postpartum hemorrhage (Tourne et al. 2003; Soyer et al.
2011). Based on a case series study and corresponding
literature review, Chauleur et al. found that uterine ar-
tery embolization was safe and effective for postpartum
hemorrhage caused by placenta accreta (Chauleur et al.
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* Correspondence: takajiry@oita-u.ac.jp
1
Departments of Radiology, Oita University Faculty of Medicine, Yufu City,
Oita 879-5593, Japan
Full list of author information is available at the end of the article
CVIR Endovascula
r
Takaji et al. CVIR Endovascular (2021) 4:77
https://doi.org/10.1186/s42155-021-00265-z
2008). To our knowledge, few studies (Bazeries et al.
2017; Kimura et al. 2020; Jiang et al. 2020; Takeda and
Koike 2017) specifically report the use of TAE for treat-
ment of retained placenta, although the use of TAE in
postpartum hemorrhage is well described as a safe and
effective treatment option. Furthermore, characteristic
angiographic features of retained placenta have not yet
been elucidated although successful embolization re-
quires recognition of the target lesion on angiography.
The objectives of this study were to clarify characteris-
tic angiographic features of retained placenta with vagi-
nal bleeding and to evaluate the efficacy and safety of
selective TAE for management of abnormal vaginal
bleeding specifically caused by retained placenta.
Materials and methods
Patient selection
This retrospective study was approved by the ethics
committee of our institution, and the requirement for
informed consent was waived because of the retrospect-
ive nature of the study. The radiology databases and
electronic medical records of our institution were
reviewed to identify patients with retained placenta who
had abnormal vaginal bleeding. Between January 2018
and December 2020, 22 consecutive patients were retro-
spectively extracted based on the following criteria: (a)
had undergone selective TAE; (b) had a symptomatic va-
ginal bleeding; (c) clinically diagnosed retained placenta
based on the patients medical history, clinical examina-
tions, and transvaginal ultrasonographic (TVUS) find-
ings. (d) had no other endometrial diseases. Retained
placenta tissue with marked vascularity was confirmed
by TVUS in all patients. In addition, biphasic contrast-
enhanced (CE) CT (21 patients) or dynamic CE MRI
(one patient) was performed to evaluate the location of
the retained placenta and its potential feeding arteries.
The characteristics of the 22 patients in this study are
summarized in Table 1. The mean patient age was 33.5
years (range, 2244 years). Of these 22 patients, 17 had a
history of dilation and curettage (three patients had
spontaneous miscarriage and 14 patients underwent ter-
mination of pregnancy). Of the remaining five patients,
three underwent vaginal delivery and two underwent
cesarean resection. The mean gestational ages in the
abortion and delivery groups were 9.3 weeks (range, 6
19 weeks) and 29.4 weeks (range, 1641 weeks), respect-
ively. Three of the 22 patients had severe vaginal bleed-
ing, and 19 patients had continuous minor vaginal
bleeding. The mean size of retained placenta on CE-CT
or MRI was 20.9 mm (range, 555 mm). The mean inter-
val from abortion or delivery to TAE was 44.3 days
(range, 11100 days). The mean hemoglobin level of the
22 patients was 12.4 g/dL (range, 614.7). Two patients
(9%) received blood transfusion before TAE procedure
(4, 6 unit). Majority of the patients (20/22, 91%) had
undergone elective TAE and emergency TAE was per-
formed in 9% (2/22).
Angiography and selective transarterial embolization
The decision indication for the procedure was taken by
multidisciplinary agreement referring to TVUS and CE-
CT or MRI findings. All TAE procedures were per-
formed by experienced interventional radiologists with
more than 10 years of experience using digital subtrac-
tion angiography equipment (Infinix Celeve-I
INFX8000C, Canon Medical Systems). Bilateral internal
iliac angiographies with anterior and anterior oblique
projections were performed using a 4-Fr or 5-Fr diag-
nostic catheter with injection of a nonionic iodinated
contrast media (iopamidol, Iopamiron 350; Bayer Health
Care) at a flow rate of 35 mL/sec (total volume, 915
mL) through an automatic injector. Then, a 2.7-Fr
microcatheter was introduced through the diagnostic
catheter into the ipsilateral uterine artery, and selective
angiography of the uterine artery was subsequently per-
formed with manual injection of 24 mL of contrast
media. A 1.6-Fr or 1.9-Fr microcatheter was then ad-
vanced distally through the 2.7-Fr microcatheter to the
target feeder when uterine angiography showed
Table 1 Characteristics of 22 women with vaginal hemorrhage
due to retained placenta
Characteristics n=22
Age [years; mean (range)] 33.5 (2244)
Gravidity [n; mean (range)] 2.7 (16)
Parity [n; mean (range)] 0.9 (02)
Abortion [n]
Spontaneous miscarriage and dilation and curettage 3
Termination of pregnancy by dilation and curettage 14
Delivery mode [n]
Vaginal delivery 3
Cesarean delivery 2
Gestational weeks
Abortion [weeks; mean (range)] 9.3 (619)
Delivery [weeks; mean (range)] 29.4 (1641)
Hemorrhagic event [n]
Significant bleeding 3
Continuous small amount of bleeding 19
Hemoglobin* [g/dL; mean (range)] 14.7 (6
14.7)
Size of retained placenta on CE-CT or MRI [mm; mean
(range)]
20.9 (555)
Interval from abortion or delivery to TAE [days; mean
(range)]
44.3 (11
100)
CE-CT contrast-enhanced CT, TAE transarterial embolization
*Red blood cell transfusion was performed in two patients (4, 6 unit)
Takaji et al. CVIR Endovascular (2021) 4:77 Page 2 of 9
abnormal findings indicative of retained placenta and/or
possible source of bleeding. We adopted triaxial system
(1.6-Fr or 1.9-Fr non-taper microcatheter, 2.7-Fr micro-
catheter, 4-Fr or 5-Fr diagnostic catheter) to advance the
microcatheter into the tortuous uterine artery. In this
system it was easier to advance the 1.6-Fr or 1.9-Fr
microcatheter because the 2.7-Fr microcatheter stabi-
lized the position and prevented sagging or jumping. If
uterine angiography did not show definitive findings of
retained placenta, selective catheterization and angiog-
raphy of the contralateral uterine artery were performed.
Furthermore, target embolization was performed using
gelatin sponge pieces or a mixture of n-butyl-
cyanoacrylate (NBCA) and lipiodol (ratio of 1:35) when
the 1.6-Fr or 1.9-Fr microcatheter was able to reach the
appropriate feeders to the target lesion. If selective
catheterization failed or numerous feeders originated
from the proximal portion of the uterine artery, empir-
ical embolization was performed with gelatin sponge
pieces at the proximal site of the uterine artery. Embolic
materials were selected by each operator in accordance
with microcatheter reachability and angiographic fea-
tures including the size and numbers of feeding arteries,
as well as the size of the target lesion. After
embolization, disappearance of the target lesion was
confirmed by selective angiography of the bilateral uter-
ine arteries and the bilateral internal iliac arteries. When
residual supply to the target lesion was observed on
contralateral angiography, embolization from the feeders
of the contralateral uterine artery was performed by the
same techniques. TAE technical success was defined as
disappearance of the target lesion during the final angi-
ography examination.
Imaging interpretation
Two experienced radiologists reviewed all images ob-
tained before TAE treatment in all 22 patients. They
evaluated whether the angiographic findings corre-
sponded to retained placenta in each patient. Coronal
maximum intensity projection (MIP) images of CE-CT
or MRI in the arterial phase were used as a reference to
identify retained placenta.
Therapeutic decision after TAE procedure
The need for each patient to undergo additional hys-
teroscopic resection after TAE was assessed by the at-
tending gynecologist. Although patients were
scheduled for hysteroscopic resection after TAE dur-
ing the early portion of the study period, conservative
management was preferred during the late portion of
the study period. Expectant management after TAE
was performed in 15 patients (expectant management
group); hysteroscopic resection was performed within
1 week after the TAE procedure in the remaining
seven patients (surgical management group). Clinical
success was defined as the absence of re-bleeding re-
quiring additional treatment in the expectant manage-
ment group; it was defined as surgical completion
without excessive intraoperative bleeding (2000 mL)
in the surgical management group. Clinical success
was investigated by reviewing medical and operative
records. In the expectant management group, vascu-
larity of retained placenta on TVUS or CE-CT within
1 week and more than 1 month after the TAE proced-
ure were also evaluated.
Results
The angiographic findings and results of selective TAE
are summarized in Table 2.
Angiographic findings
Pelvic angiography (including internal iliac angiog-
raphy and uterine angiography) showed a dilated
vascular channel contiguous with multiple feeders
from dilated uterine arteries in the mid-arterial to
capillary phase, followed by drainage into the uter-
ine veins in the capillary to venous phase in 20 pa-
tients (Figs. 1and 2). Those angiographic features
Table 2 Angiographic findings and TAE procedures
n=22
Angiographic findings [n (%)]
Contrast blush 2 (9%)
Dilated vascular channel that mimic low flow AVM* 20 (91%)
Pseudoaneurysm 0 (0%)
Extravasation 0 (0%)
Embolization site [n (%)]
Target embolization 15 (68%)
Empirical embolization** 7 (32%)
Embolic material [n (%)]
GS 18 (82%)
NBCA 3 (14%)
GS and NBCA 1 (4%)
Technical success*** 22 (100%)
Complication [n (%)]****
Transient hypotension 2 (9%)
Gluing microcatheter into blood vessel 1 (4%)
* Dilated vascular channel contiguous with multiple feeders from dilated
uterine arteries in the mid-arterial to capillary phase, which drained into the
uterine veins in the capillary to venous phase
** Reasons for Emprical embolization were failed super selective
catheterization into target feeders (n= 6) and large retained placenta with
numerous feeders (n=1)
***Technical success was defined as disappearance of the target lesion during
the final angiography examination
****Serious complications were not observed (complications were classified as
CIRSE grade 1)
NBCA N-butyl-cyano-acrylate, GS gelatin sponge
Takaji et al. CVIR Endovascular (2021) 4:77 Page 3 of 9
Fig. 1 A 33-year-old woman with vaginal bleeding caused by retained placenta. a. Color doppler TVUS showed vascularity (arrowhead) in the
uteroplacental tissue. b. Coronal MIP image of arterial phase CE-CT showed intrauterine vascular mass (arrowhead) fed by left uterine artery. c.
Left uterine arteriogram showed dilated vascular channel (arrowhead) in arterial phase uterine arteriography. d. Venous drainage (arrow) from
dilated vascular channel (arrowhead) depicted in the capillary phase. Drainage vein connected to right uterine vein in the venous phase.
Microcatheter was inserted into the blood sinus feeding artery. Target embolization was performed using GS. e. Post-embolization left uterine
arteriography confirmed disappearance of the dilated vascular channel. f. At 2 days after the TAE procedure, the intrauterine hyper vascular lesion
disappeared on TVUS. In this case, expectant management after TAE was chosen and no re-bleeding was observed
Takaji et al. CVIR Endovascular (2021) 4:77 Page 4 of 9
mimicked low-flow arteriovenous malformation/fis-
tulas, but there were no early venous filling. In the
remaining two patients, pelvic angiography showed
contrast blush corresponded to a retained placenta
in the mid-arterial to capillary phase.
Results of selective TAE procedure
Regarding embolic materials, gelatin sponge (GS) pieces (12
mm) were used in 18 patients (Figs. 1), NBCA-lipiodol mix-
ture in three patients (Fig. 2), and both of these materials in
one patient. Target embolizationwasperformedin15patients
and empirical embolization was performed in the remaining
seven patients. Reasons for empirical embolization were failed
super selective catheterization into target feeders (n=6) and
large retained placenta with numerous feeders (n=1).
Angiography after selective TAE showed disappear-
ance of abnormal findings related to retained placenta in
all 22 patients; therefore, the rate of TAE technical suc-
cess was 100%, regardless of embolic materials or target/
non-target embolization.
Fig. 2 A 42-year-old woman with vaginal bleeding caused by retained placenta. a. Arterial phase CE-CT showed intrauterine enhancing lesion
(arrowhead). b, c. Bilateral uterine arteriogram showed dilated vascular channel (arrowhead) in the arterial phase. Venous drainage (arrow) was
depicted in the capillary phase through the vascular channel. d. Bilateral uterine arteries were embolized using 25% NBCA diluted with iodized
oil. After the TAE procedure, expectant management was chosen and no re-bleeding was observed. e. At 1 month after the TAE procedure, the
intrauterine enhancing lesion disappeared on CE-CT
Takaji et al. CVIR Endovascular (2021) 4:77 Page 5 of 9
No major complications were observed. Three minor
procedure-related complications (CIRSE grade 1) were
observed: transient hypotension (n= 2) and gluing
microcatheter in a feeder (n= 1). Transient hypotension
resolved with conservative management. In the patient
with an NBCA-adhered microcatheter, the amputated
catheter tip remained in the left uterine artery.
Clinical outcome
The clinical success rates in the expectant management
and surgical management groups were 100% (15/15 pa-
tients) and 100% (7/7 patients), respectively. Tables 3
shows the TAE clinical outcomes in the expectant man-
agement group. A few days after TAE, vascularity of the
retained placenta on TVUS or CE-CT was markedly re-
duced (n= 8) or disappeared (n= 7). Follow-up TVUS
and/or CE-CT at 1 month after TAE showed no abnor-
mal blood flow in the uterus in all 15 patients. Complete
hemostasis without recurrent bleeding was achieved in
14 of these 15 patients. In one patient, minimal vaginal
bleeding occurred after TAE, but spontaneously disap-
peared within 1 month.
Prevention effect of intraoperative bleeding after TAE
are summarized in Table 4. In the surgical management
group, scheduled hysteroscopic resection of retained pla-
centa was performed within 1 week; no patients showed
excessive bleeding during surgical procedures. All seven
patients showed no recurrent vaginal bleeding after
surgery.
Discussion
Thus far, few reports have specifically mentioned angio-
graphic features of retained placenta in patients with
postpartum hemorrhage (Bazeries et al. 2017; Kimura
et al. 2020; Kitahara et al. 2011]. In those reports, angio-
graphic features of retained placenta have included tor-
tuous dilated uterine artery flowing into a sac-like
structure, intrauterine vascular lesion with or without ar-
teriovenous (AV) shunt, focal contrast blush, and pseu-
doaneurysm. In the present study, most patients (91%)
showed a characteristic finding of dilated vascular chan-
nel in the mid-arterial to capillary phase which mimics
low-flow arteriovenous malformation/fistula. However,
the vascular lesion drained into the uterine veins in the
capillary to venous phase without early venous filling.
The placenta consists of the chorionic and basal plates,
and the intervillous space lies between these two plates.
The main stem villi, consisting of chorionic veins and ar-
teries, project into the intervillous space. Maternal endo-
metrial arteries and veins penetrate the basal plate;
exchange between fetal and maternal circulatory systems
occurs between the main stem villi and the maternal
endometrial vessels in the intervillous space (Jansen
et al. 2020; Cunningham et al. 2013; Bernischke 1967;
Kaufmann 1985) (Fig. 3). In addition, uterine arteries
and veins are presumed to exhibit arteriovenous anasto-
mosis separate from this intervillous short-circuit (James
et al. 2017). The retained placenta consists of intervillous
space and decidua basalis. In cases of retained placenta,
various extents of remnant intervillous space and ar-
teriovenous anastomosis of endometrial arteries/veins
could remain in the uterine cavity (Fig. 4). The angio-
graphic finding of dilated vascular channel may corres-
pond to remnant intervillous space. Furthermore,
endometrial arteries and veins connecting to the intervil-
lous space may represent one or more low-flow AV
shunts mimicking arteriovenous malformation (AVM)-
like findings. Uterine AVM is rare, and it involves abnor-
mal vascular channels in the endometrium or myome-
trium with early venous filling during the early arterial
phase (Vijayakumar et al. 2013; Ghai et al. 2003; Tim-
merman et al. 2003). Retained placenta can be incor-
rectly diagnosed as AVM. However, angiography in our
study showed venous drainage from the dilated vascular
channel of retained placenta was evident in the capillary
to venous phase. This angiographic finding of apparently
Table 3 Clinical outcomes of TAE without hysteroscopic
resection
Expectant management group (n= 15)
Follow-up period [months; mean (range)] 3.4 (117)
Clinical success* 15 (100%)
Vascularity of retained placenta on TVUS or CE-CT [n (%)]
Few days after TAE
Marked reduction 8 (53%)
Disappearance 7 (47%)
More than 1 month after TAE
Disappearance 15 (100%)
Vaginal bleeding after TAE [n (%)]
No bleeding 14 (93%)
Minimal bleeding** 1 (7%)
*Clinical success was defined as the absence of re-bleeding requiring
additional treatment in the conservative treatment group
** Minimal bleeding spontaneously disappeared within 1 month
TVUS transvaginal ultrasound, CE-CT contrast-enhanced CT, TAE
transarterial embolization
Table 4 Prevention effect of intraoperative bleeding after TAE
Surgical management group (n=7)
Clinical success* 7 (100%)
Intraoperative bleeding [n (%)]
Almost no bleeding 7 (100%)
Excessive bleeding 0 (0%)
*Clinical success was defined as surgical completion without excessive
intraoperative bleeding (2000 mL) in the surgical management group
TAE, Transarterial embolization
Takaji et al. CVIR Endovascular (2021) 4:77 Page 6 of 9
delayed venous drainage may differentiate retained pla-
centa from uterine AVM.
Regarding TAE specifically for the treatment of
retained placenta with bleeding, few case series focused
on retained placenta have been reported. Bazeries et al.
(2017) reported that TAE technical and primary clinical
successes, using mainly microspheres (size: 700
1200 μm), were achieved in 90.3% (27/31) and 74.2%
(23/31) of their patients. Kimura et al. (2020) reported
higher rates of TAE technical and clinical success using
Fig. 3 Schematic drawing of the placenta (cross-sectional image). The chorionic plate (fetal side) is a mass of connective tissue that contains the
amnion, main stem villi, and chorionic arteries and veins. The basal plate (maternal side) consists of trophoblastic and decidual cells; it contains
the placental septa, decidua basalis, and endometrial arteries and veins. The chorionic and basal plates are separated by the intervillous space;
exchange between fetal and maternal circulatory systems occurs between the main stem villi and the maternal endometrial vessels in this space
Fig. 4 Schematic drawing of the retained placenta (cross-sectional image). The retained placenta may consist of intervillous space and decidua
basalis. Endometrial arteries and veins, which are branches of uterine arteries and veins, are connected to each other through the intervillous
space. Angiographic findings including dilated vascular channel and contrast blush may correspond to remnant intervillous space. Endometrial
arteries and veins connecting to the intervillous space may represent low-flow AVM-like findings
Takaji et al. CVIR Endovascular (2021) 4:77 Page 7 of 9
GS (93%, 13/14; 100%, 14/14). NBCA embolization of
retained placenta increta was described in a case report;
complete occlusion and cure was achieved with single
embolization (Hamaguchi et al. 2003). Jiang et al. (2020)
reported favorable prevention effect of intraoperating
bleeding of TAE using GS followed by hysteroscopic re-
section (intraoperating blood loss; 100 ml, 90.3%, 28/
31, 100-400 ml, 6.5%, 2/31, 400 ml, 1%, 1/31). Takeda
and Koike (2017) reported that TAE/TACE (using GS
with or without dactinomycin) were key intervention for
uterus preserving treatment of retained placenta accrete
with marked vascularity (devascularization of retained
placenta and uterine preservation were achieved in all of
38 patients). In addition, there are some papers men-
tioned about the usefulness and safety of TAE using GS
and/or PVA for postpartum hemorrhage from various
causes including retained placenta (Ko et al. 2017; Pelage
et al. 1999; Horng et al. 2011). In our study, TAE for
retained placenta was performed using GS and/or
NBCA, according to the operators preference, and fa-
vorable outcomes were achieved.
Retained placenta can spontaneously resolve with con-
servative management. Hence, asymptomatic patients with
small and non-hypervascularized retained placenta may be
candidates for conservative management (Takahashi et al.
2019; Jain and Fogata 2007; Lee et al. 2014). In this study,
15 patients underwent expectant management after TAE.
Among these 15 patients, eight showed markedly reduced
residual vascularity of retained placenta. Images collected
at the 1-month follow-up showed vascular lesion dis-
appearance in the uterus, and there were no cases of re-
current bleeding that required any treatment. The safety
of uterine artery embolization has been indicated for reso-
lution of post-partum hemorrhage (Chauleur et al. 2008).
Common adverse effects related to the TAE procedure in-
clude high fever, acute pelvic inflammation, and hip pain
(Chen et al. 2015; Liu et al. 2018). However, excessive
embolization may cause serious complications, such as
uterine necrosis and endometrial atrophy (Godfrey and
Zbella 2001; Cottier et al. 2002). Furthermore, Ohmaru-
Nakanishi et al. (2019) reported that patients who were
treated for retained placenta with TAE were at risk of
postpartum hemorrhage and difficulty in removing pla-
centa in future pregnancies, although, there were no effect
reproductive outcomes. As described previously, retained
placenta has a regressive nature. Progressive occlusion of
the blood sinus of retained placenta can occur after TAE.
Therefore, excessive embolization should be avoided when
the characteristic finding of retained placenta, dilated vas-
cular channel that mimic low flow AVM, is identified dur-
ing angiography examination. This information is
important for interventional radiologists to determine the
procedural endpoint of TAE for retained placenta with ab-
normal bleeding.
This study had several limitations including its retro-
spective nature, limited case number, and short follow-
up period (mean, 3.4 months; range, 117 months). Lar-
ger prospective studies are needed to confirm the safety
and efficacy of the TAE procedure as a monotherapeutic
approach for retained placenta with abnormal bleeding.
In summary, the characteristic angiographic feature of
retained placenta with vaginal bleeding is a dilated vas-
cular chaneel fed by multiple uterine arterial branches in
the arterial to capillary phase, which drains into the uter-
ine vein in the capillary to venous phase. TAE using GS
and/or NBCA can be a safe and effective treatment for
management of abnormal bleeding caused by retained
placenta.
Acknowledgments
Not applicable.
Authorscontributions
Guarantors of integrity of entire study, R.T., H.K., Y.A.,; study concepts/study
design or data acquisition or data analysis/interpretation, all authors;
manuscript drafting or manuscript revision for important intellectual content,
all authors; approval of final version of submitted manuscript, all authors;
literature research, R.T., H.K.; clinical studies, R.T., H.K., M.M., N.H., R.S., S.I.; and
manuscript editing, R.T., H.K., Y.A.
Funding
No funding was received for conducting this study.
Declarations
Ethics approval and consent to participate
All procedures performed in this study involving human participants were in
accordance with the ethical standards of the institutional research
committee and with the 1964 Helsinki declaration and its later amendments
or comparable ethical standards. IRB approval was obtained, and the need
for informed consent was waived for this retrospective study.
Competing interests
The authors declare that they have no conflict of interest.
Author details
1
Departments of Radiology, Oita University Faculty of Medicine, Yufu City,
Oita 879-5593, Japan.
2
Department of Obstetrics and Gynecology, Oita
University Faculty of Medicine, Yufu, Oita 879-5593, Japan.
Received: 21 July 2021 Accepted: 25 October 2021
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Objectives: To clarify the outcome of retained products of conception (RPOC) without placenta previa. Study design: This was a retrospective cohort study consisting of 59 patients who abdominally or vaginally gave birth to infants after 14 weeks without placenta previa and had RPOC between April 2006 and December 2018. Patients' background, characteristics, and outcomes were compared between those requiring and not-requiring intervention for RPOC. Results: Of the 59 patients, pregnancies after assisted reproductive technology accounted for 18 (31%). The ultrasound-measured RPOC length was 4 cm (median) and 39 (66%) showed hypervascularity within RPOC. Interventions were required in 36 patients (61%), with all due to bleeding-related events. Multivariate regression analyses revealed that the interventions were significantly more likely in the following situations: younger than 35 years (aOR: 4.2, 95%CI: 1.1-18.5), RPOC length ≥4 cm (aOR: 8.6, 95%CI: 2.4-39.2), and RPOC hypervascularity (aOR: 4.6, 95%CI: 1.3-18.8). Methotrexate was administered to 8 patients, of whom 4 (50%) required further hemostatic interventions. Conclusion: In patients with RPOC without previa, 61 and 39% did and did not require hemostatic interventions, respectively. In the latter, a wait-and-see strategy resulted in the resolution of RPOC. Patients with larger RPOC (≥4-cm fragment length) and hypervascularity were significantly more likely to require hemostatic intervention.