Imaging findings of cesarean delivery complications: cesarean scar disease and much more

Abstract

In the last years, there has been a significant increase in the number of cesarean deliveries and, with it, of the number of complications following the procedure. They can be divided into early and late ones. We will illustrate herein the most common complications following cesarean section to help radiologists to recognize them. To familiarize with these various pathologic conditions is crucial to alert referring clinicians for a prompt and appropriate maternal and fetal management. Special attention will be given to the cesarean scar defect (CSD), the most common but also the most unknown of such conditions. Although often asymptomatic, a severe CSD represents a predisposing factor for subsequent complications especially in future pregnancies.

Full text

E D U C A T I O N A L R E V I E W Open Access
Imaging findings of cesarean delivery
complications: cesarean scar disease and
much more
F. Rosa
1*
, G. Perugin
1
, D. Schettini
2
, N. Romano
1
, S. Romeo
1
, R. Podestà
2
, A. Guastavino
2
, A. Casaleggio
3
and
N. Gandolfo
2
Abstract
In the last years, there has been a significant increase in the number of cesarean deliveries and, with it, of the
number of complications following the procedure. They can be divided into early and late ones. We will illustrate
herein the most common complications following cesarean section to help radiologists to recognize them. To
familiarize with these various pathologic conditions is crucial to alert referring clinicians for a prompt and
appropriate maternal and fetal management. Special attention will be given to the cesarean scar defect (CSD), the
most common but also the most unknown of such conditions. Although often asymptomatic, a severe CSD
represents a predisposing factor for subsequent complications especially in future pregnancies.
Keywords: Cesarean delivery, Gynecology, Emergencies, Chronic cesarean delivery complications, Cesarean scar
defect
Key points
Early complications of caesarean-delivery.
Late complications of caesarean-delivery.
Detailed description of prevalence, clinical
presentations, and imaging features of CSD.
Background
The number of cesarean delivery is increasing and accounts
for about one-third of all births both in the USA and in
Italy [1]. The procedure is not free of peri- and postproce-
dural complications that can be divided into early and late
ones [1]. Given cesarean delivery’s increasing use, there is
also an increase of complications encountered.
Early complications include peri- and postprocedural
conditions within 30 days after a cesarean delivery; late
complication may occur also after some years and espe-
cially in a successive pregnancy (revision 2).
Overall early complication rate is about 14.5% and in-
fection (such as endometritis and wound infections) is
the most common complication. Fortunately, severe
complications (i.e., uterine rupture) remain uncommon.
Prolonged ruptured membranes, increased duration of
labor prior to surgery but also anemia and obesity are
considered risk factors for postoperative morbidity [2].
Familiarity with normal postprocedural findings of
cesarean delivery (Table 1) is necessary to differentiate
them from significant early complications such as hemato-
mas, abscesses, wound infections, uterine dehiscence or
rupture, and pelvic thrombophlebitis. In the immediate
postoperative period, typical symptoms as fever, dropping
hemoglobin level, unexpectedly heavy vaginal bleeding,
and pain often motivate imaging studies. In this clinical
scenario, ultrasonography (US) and computed tomog-
raphy (CT) are the modalities of choice while the role of
magnetic resonance (MR) is limited especially by its avail-
ability and acquisition time.
Among late cesarean delivery complications, cesarean
scar defect (CSD) is the most common but also the most
neglected. In pregnant patients with a history of prior
cesarean delivery, a severe CSD is a risk factor for both
early (i.e., uterine rupture) and for late complications (i.e.,
ectopic pregnancy at the scar level and other scar-related
abnormalities). For the evaluation of late complications
© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and
reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.
* Correspondence: francescarosa892@gmail.com
1
Department of Health Sciences (DISSAL), University of Genova, via A. Pastore
1, 16132 Genova, Italy
Full list of author information is available at the end of the article
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Rosa et al. Insights into Imaging (2019) 10:98
https://doi.org/10.1186/s13244-019-0780-0

US (if possible both transabdominal-US and transvaginal-
US, TV-US), hysterography and MR imaging are the mo-
dalities of choice.
In this article, we will review the most common early
and late complications of cesarean delivery and we will
describe in detail the CSD in consideration of its high
prevalence and its role as risk factor for the major part
of the other caesarean delivery complications.
Cesarean delivery complications
Complications of cesarean section (C-section) can be di-
vided into early and late ones [1] as shown in Table 2.
Early complications
The most frequent early complications are infections
(such as endometritis, surgical wound infections, and ab-
scesses) and hemorrhages (Fig. 1).
Hemorrhage can be due to lacerations of intra-abdominal
(uterine and ovarian) or extra-abdominal arterial or venous
vessels. They can be massive and life-threatening conditions.
Extra-abdominal vessels laceration frequently involves
the lower epigastric arteries (Fig. 2)andcanleadtothe
formation of a hematoma within the rectus abdominis
muscle (rectus sheath hematoma) or to an extraperitoneal
hemorrhage with blood collection in the pre-vesical space,
posterior to the rectus and transversalis muscles and an-
terior to the peritoneum (subfascial hematoma) [1].
These two clinical entities can coexist and are rarely
associated to hemoperitoneum (Figs. 3and 4).
The so called “bladder flap hematoma”is located in
the space between urinary bladder and lower uterine
segment and its spread is limited by the overlying peri-
toneum [3,4]. Small bladder flap hematoma can occur
in up to 50% of the patients undergoing cesarean deliv-
ery with a low transverse incision and is considered a
normal finding if < 4 cm [1]. Bladder flap hematoma lar-
ger than 5 cm is uncommon but it can be correlated to
uterine scar dehiscence. Moreover, it can be a source of
bacterial superinfection and, if large, it can spread
through the broad ligaments into the retroperitoneum
and into the peritoneal cavity with hemoperitoneum. For
these reasons, the presence of a large bladder flap
hematoma (> 4–6 cm) and sepsis unresponsive to ad-
equate antibiotherapy would justify re-laparotomy. On
US and CT, it is visualized as a hyperechogenic or
hyperdense heterogeneous collection between the blad-
der and the inferior uterine segment; gas bubbles, in-
ternal septa, and peripheral vascularization are present
in case of abscess formation. It is important to discrim-
inate significant bladder flap hematomas from subfascial
hematomas because only the first ones require incision
of the peritoneum.
Uterine rupture is the most severe early complication
and is defined as the complete laceration of the uterine
wall including its serous layer, creating a communication
between the endometrial and peritoneal cavities with gas
and blood leakage and consequent hemoperitoneum
(Fig. 5). The incidence of uterine rupture among women
with at least one prior CS was 0.5% and severe CSD is
an important risk factor [5].
Partial rupture of the uterine wall, in which the serous
layer remains intact, is called uterine dehiscence. The
differential diagnosis between these two entities may be
difficult [1].
“Red flags”for uterine dehiscence are the presence of
a bladder flap hematoma > 5 cm and large pelvic hema-
tomas. On the other hand, the presence of gas within
the uterine defect, extending from the endometrial cavity
to the extra uterine parametrium in association with
hemoperitoneum is highly suspicious for uterine rup-
ture. Demonstration of a continuous pathway between
the endometrial cavity and the extrauterine collection,
Table 1 Normal postprocedural findings [1]
Normal postprocedural findings of C-section
Uterus dimension Enlarge (average size is 9 × 12 × 14 cm)
Endometrial cavity < 2 cm
Fluid in the
uterine cavity
Normal (do not confuse it with infection or
retained products of conception!)
Intracavitary gas Possible findings in asymptomatic women up to 3
weeks postpartum (differential diagnosis with
endometritis!)
Bladder flap
hematoma
Normal if < 4 cm of diameters
Table 2 Acute and chronic caesarean delivery complications (adapted from [1])
Early complications Late complications
Infections (most common)
Endometritis, wound infection, abscess
Cesarean scar defect (most common)
Subfascial hematoma Abdominal wall endometriosis
Bladder flap hematoma (> 4 cm) Morbidly Adherent Placenta
(placenta accreta, increta, and percreta)
Uterine dehiscence Cesarean scar ectopic pregnancy
Uterine rupture Cesarean scar retained products of conception
Rosa et al. Insights into Imaging (2019) 10:98 Page 2 of 14

either by CT or MRI, is a pathognomonic finding for
uterine rupture.
Due to the rarity of these conditions and the low correl-
ation between radiological and surgical findings, there are
not standardized diagnostic criteria. However, in an ad-
equate clinical setting, these “red flags”can help radiolo-
gists at least to suspect a uterine rupture and to promptly
guide patient management. Although uterine rupture is
usually clinically recognized and managed by laparotomy,
some cases with clinical indolent signs and symptoms may
be more likely to be diagnosed with imaging. CT with
multiplanar reformatted reconstruction can be considered
a good initial imaging modality, due to its availability,
rapid imaging acquisition time, and the possibility to use
reformatted images, perpendicular to the plane of incision
[1]. Nevertheless, MR could be superior to CT for the dif-
ferential diagnosis between uterine dehiscence and rup-
ture by delineating all uterine wall layers and identifying
an intact serosa covering the myometrial gap [6]. More-
over, large hematoma or abscess usually associated with
true dehiscence can be easily detected on MR. Differential
diagnosis is important because uterine dehiscence can be
managed conservatively instead uterine rupture require a
surgical treatment.
Late complications
As mentioned before, we will describe in detail the CSD
due to its high prevalence and because it can be consid-
ered as a predisposing factor for the major part of the
Fig. 1 C-section wound infection: in the correct clinical scenario, inflammatory changes associated with gas within the soft tissues adjacent to
the scar (white arrow) makes the diagnosis
Fig. 2 Extra-abdominals arteries or vein: inferior epigastric vessels lacerations can lead to rectus abdominis sheath hematoma or to
subfascial hematoma
Rosa et al. Insights into Imaging (2019) 10:98 Page 3 of 14

other cesarean delivery complications. Other common late
complications are abdominal wall endometriosis, morbidly
adherent placenta (MAP), cesarean scar ectopic preg-
nancy, and retained products of conception (RPOC) at the
C-section scar level.
Cesarean scar defect
The CSD is the most common complication after a
cesarean delivery; it is reported with different nouns in
literature (pouch, niche, or histhmocoele). It is defined
as a focal thinning of myometrium or a dehiscence of
the uterine scar, which appears with a triangular shape
in continuity with the endometrial cavity [7].
CSD is considered severe if the incision depth is at
least 50 or 80% of the anterior myometrium, or if the
remaining myometrial thickness is ≤2.2 mm when eval-
uated by transvaginal ultrasound (US) [8].
Risk factors
Fig. 3 Subfascial hematoma associated with massive hemoperitoneum. aUS examination showed a complex collection in this case in the rectus
muscles (white arrow). bAfter contrast CT imaging confirmed the subfascial hematoma (white arrow) and showed also hemoperitoneum
(dashed arrow)
Fig. 4 (Same patient of Fig. 3). Contrast-enhanced CT (a,b) showed contrast material extravasation (white arrow) suggestive for active bleeding
confirmed by arteriography (c)
Rosa et al. Insights into Imaging (2019) 10:98 Page 4 of 14

Risk factors to develop a CSD can be divided in non-
modifiable and modifiable ones.
Non-modifiable risk factors can be mother-related (age,
retroverted uterus) or labor-related ones (duration of labor
> 5 h and cervical dilation at the time of delivery > 5 cm).
Modifiable risk factors are mostly related to the surgi-
cal technique (incision close to internal os, exclusion of
endometrium during repair, single-layer closure) [8–11].
Clinical symptoms
The exact prevalence of symptomatic CSD is difficult to
quantify due to several factors such as heterogeneity of
population studied, lack of knowledge about this problem,
and the absence of accepted guideline criteria. However, it
has been reported to range from 19.4 to 88% [12–14].
Severe complication, i.e., uterine rupture during a suc-
cessive pregnancy, has an incidence of only 2% but this
percentage increase up to 5% if the CSD is considered
severe.
Clinical presentation is strongly heterogeneous, from
absence of symptoms (most frequently) to presence of
uterine bleeding, infertility, dyspareunia, and pelvic pain.
Abnormal vaginal bleeding is the most frequent symp-
tom: a retrospective study showed that it is present in
76% of women with CSD. It is defined as a persistent va-
ginal bleeding from 2 to 12 days after the end of men-
strual phase [15]. This bleeding is thought to be due to
retention of blood within the defect cavity (niche) and
its delayed emptying. Some authors consider the bleed-
ing as due to in situ angiogenesis [16].
The mechanism of CSD-related infertility is not so
clear: the main hypotheses are that retained blood or
chronic inflammatory state can have negative influence
on sperm transport and implantation [17,18].
Etiology of chronic pelvic pain is related to the chronic
inflammatory state associated with mucus-blood stagna-
tion in the niche.
Lastly, a severe CSD, in women who desire another
pregnancy, is considered as a risk factor for severe com-
plications since it can be the site of ectopic pregnancy,
placenta adhesive disorders, and uterine rupture.
Notwithstanding their high prevalence, CSDs are often
undiagnosed. Since frequently asymptomatic, or with
non-specific symptoms, they are no considered and not
looked for. They are often diagnosed when abnormal
findings are demonstrated during examinations done for
other purposes.
Radiologists can help gynecologists, especially through
MR examinations, to understand if symptoms are really
CSD-related or due to other pathologic conditions and
to individuate women with a severe CSD with a higher
risk of severe complications.
Radiological features
There are several imaging techniques to detect the
CSD but there is no universal consensus about which is
the gold standard. Moreover, there are no standardized
diagnostic criteria.
TV-US is a first level and widely used imaging technique.
CSD is described as an anechoic, triangular shape defect
with apex pointing anteriorly, located at the anterior isth-
mus. It can also look like a cystic lesion between bladder
and lower uterine segment (Fig. 6). Differential diagnosis in-
cludes Nabothian cysts, prominent uterine vessels, and
small leiomyomas.
The role of saline infusion sonohysterography is contro-
versial: Osser at al. made a study of agreement between
transvaginal sonographic findings with and without saline
Fig. 5 Uterine rupture:CT examination (a,b) showed the presence of gas within the uterine defect, extending from the endometrial cavity to
the extra uterine parametrium (white arrow), in association with hemoperitoneum (asterisks). In the appropriate clinical setting, these features are
highly suspicious for uterine rupture
Rosa et al. Insights into Imaging (2019) 10:98 Page 5 of 14

contrast enhancement [18,19]. The agreement was good
(percentage agreement varying from 88 to 100% and with
Cohen’s kappa varying from 0.679 to 1.000). The authors
concluded that CSD were better evaluated through saline
contrast enhancement TV-US than with unenhanced ultra-
sound examination, because the demarcations of scar de-
fects were more clearly delineated, more defects were
detected, and more defects were classified as large at saline
contrast-enhanced TV-US. These findings can be explained
by possible washing away of mucus from the niche during
saline infusion. So, some authors recommend this tech-
nique especially in the surgical planning [15–20]. However,
it is more invasive, carries a small risk of complications
(such as infections), and can overestimate the defect (about
1–2 mm) because of over-distention of the niche [20].
Hysterosalpingography is an imaging technique used
to evaluate uterine cavity and tubal patency.
Major indications are infertility, recurrent miscarriage,
and evaluation of tubal ligation efficacy [21]. Hysterosal-
pingography can identify the CSD that can be the cause
of secondary infertility after CS (Figs. 7and 8). CSD is
visualized as a leakage of contrast from the endometrial
cavity into a defect of the myometrium at the location of
a previous hysterotomy. Oblique views, with the patient
leaning on her side, may better demonstrate the con-
tinuity between uterine cavity and the niche.
MR is a second level imaging technique. Due to its
panoramic capabilities, it evaluates not only the lumen
but also the uterine wall and allows an accurate differen-
tial diagnosis. Its role is fundamental to rule out other
causes of symptoms like adenomyosis and leiomyomas.
So, MR is especially useful in surgical planning, espe-
cially if other pathological conditions are present.
T2-WI (weighted imaging) clearly demonstrates the
CSD with morphologic features analogue to the other
modalities (Fig. 9).
Classification
Most studies to evaluate CSD dimension and severity
have been performed with transvaginal ultrasound and
the same criteria can be also applied to MR [22]. The
possibility to use the same classification systems makes
easier the communication with gynaecologists.
The CSD severity is established through measurement
of the ratio between myometrial thickness at the scar
level and the thickness of adjacent myometrium: it is
considered severe if the ratio is equal or inferior to 50%
(Fig. 10)[8]. Another possible method is to use a cut-off
of 2.2 mm for the remaining myometrium thickness at
transvaginal US and a value ≤2.5 mm when the patient
is evaluated by sonohysterography [8,21].
It has been demonstrated that a ratio ≤50% correlates
with symptomatic CSD [13,18,20,23,24] that are the
only ones on which there is consensus about the need
for treatment [19]. Imaging is crucial to rule out other
causes at the basis of symptoms and to decide the most
adequate treatment: from hormonal therapies to surgery
with different approaches (laparoscopy, hysteroscopy,
and vaginal procedure depending on the expertise of the
surgeon). Furthermore, incidental and asymptomatic
CSD must be always documented and reported, espe-
cially before gynecological procedures (evacuation, endo-
metrial ablation, intrauterine device implantation)
because of increased risk of complications (also fistula
and abscess).
Fig. 6 Cesarean scar defect: CSD appearance at TV-US examination (white arrow). It can look like a cystic lesion (a) or it can be an anechoic,
triangular shape defect with apex pointing anteriorly, located at the anterior isthmus (b). Anterior uterine wall (yellow dashed arrows),
endometrium (asterisks)
Rosa et al. Insights into Imaging (2019) 10:98 Page 6 of 14

Other late complications
Abdominal wall endometriosis is a rare event (incidence
rate reported at 0.4% to 0.1%.); it is due to iatrogenic seed-
ing of endometrial cells during hysterotomy that create a
functioning endometrial tissue mass outside the uterine
cavity [25]. It is a possible cause of painful abdominal
mass in young women, classically with cyclic presentation.
However, pain can be also constant.
US is the first level examination and demonstrates a
round or oval, heterogeneously hypoechoic solid lesion in
the subcutaneous fat, muscle, or fascial layers. However,
MR imaging is the modality of choice to evaluate the ex-
tension of disease because of its superior soft-tissue con-
trast and its capability to detect deep endometriosis. On
MR, the typical lesion contains areas of T1 hyperintensity
from subacute blood products. Depending on major con-
tent of fibrous tissue, as well as compact smooth muscle,
some lesions may have an intermediate-to-low signal in-
tensity on T1-WI and on T2-WI (Fig. 11)[26]. T1-WI
after contrast administration typically shows late and pro-
gressive contrast enhancement (Fig. 12).
A rare differential diagnosis and cause of mass at the
level of the abdominal wall in young women after
cesarean delivery is the abdominal wall desmoid tumor
(about 3.7 new cases occurring per one million individ-
uals each year) [27]. These are rare, slow-growing benign
muscular-aponeurotic fibrous tumors with the tendency
to be locally aggressive.
Fig. 7 A 35-year-old woman underwent hysterosalpingography for infertility after a previous cesarean delivery CSD is detected as a leakage of
contrast from endometrial cavity into a defect of the myometrium at the location of the previous C-section
Fig. 8 A hysterosalpingography (a,b) was performed for infertility after a previous cesarean delivery and right tubectomy due to a previous
ectopic tubal pregnancy. a,bshowed right antero-lateral istmocele (white arrow) in continuity with endometrial cavity (pink arrow), b
demonstrated left normal intraperitoneal spill of contrast (yellow arrow). cTransvaginal US confirmed all findings and well demonstrated the
continuity between the istmocele (white arrow) and the endometrial cavity (pink arrow)
Rosa et al. Insights into Imaging (2019) 10:98 Page 7 of 14

Fig. 9 A 40-year-old woman underwent to MR for abnormal uterine bleeding. CSD is detected on T2WI as a myometrium defect with apex
pointing anteriorly, located at the anterior isthmus (white arrow)
Fig. 10 CSD classification and calculation of remaining myometrium. A = thickness of remaining myometrium; B = full-thickness adjacent to
defect. Percentage of myometrium remaining: xð%Þ¼A
B100
Rosa et al. Insights into Imaging (2019) 10:98 Page 8 of 14

Fig. 11 Abdominal wall endometriosis: this is a case of a women with abdominal wall palpable mass within incisions after cesarean delivery. MR
imaging showed a solid nodule (white arrow) with low signal both on T1-TSE-WI (a) and T2-TSE-WI (axial, cand sagittal sections, d) with an iso-
hyperintense signal on T1-SPIR WI (b)
Fig. 12 (Same patient of Fig. 11). Abdominal wall endometriosis (white arrows) showed progressive and late contrast enhancement on T1-THRIVE
WI (b, arterial, c, portal and d, venous phases). a, T1-THRIVE WI before contrast administration
Rosa et al. Insights into Imaging (2019) 10:98 Page 9 of 14

Surgical trauma is an important trigger for tumor
growth as well as hormonal estrogenic influence [27,28].
The sub-umbilical sheath of the rectus abdominis is the
most common site (Fig. 13).
De Cian et al. also described a desmoid tumor arising
in a cesarean scar during pregnancy [29].
Maybe due to its rarity, desmoid tumor has not been
considered yet a chronic cesarean delivery complication.
But radiologist must keep in mind this possible differen-
tial diagnosis for abdominal wall mass that develops dur-
ing the postpartum period within 3 years after delivery.
Cesarean scar ectopic pregnancy is the implantation
of the embryo in the cesarean delivery scar and it is the
rarest form of ectopic pregnancy [1]. Estimated inci-
dence in overall cesarean delivery is 1/1800–1/2500 [30].
Any process that disrupts or scars the endometrium and
myometrium can predispose to abnormal pregnancy
implantation.
Complications are severe, like uterine rupture and
hemorrhage; these usually occur early in the pregnancy
necessitating hysterectomy and occasionally resulting in
death [31].
Early diagnosis is crucial to preserve fertility and re-
duce mortality. US is always the first level technique,
whereas MR plays a crucial role in difficult cases (Fig.
14).
Imaging shows an empty uterine-cervical cavity and
the gestational sac located predominantly in the lower
uterine segment myometrium between the bladder and
the anterior uterine wall.
Retained products of conception are estimated ap-
proximately 1% of term pregnancies [32].
Fig. 13 Desmoid tumor (white arrow) appears as homogeneously hypoechoic masses at US examination. On MR, typical signal characteristics
include T1-WI and T2-WI low signal intensity and variable contrast enhancement (homogeneous in this case)
Fig. 14 Cesarean scar ectopic pregnancy MR: T2-WI (a) show the gestational sac embedded in the myometrium of the anterior cervix–lower
uterine segment (in this case antero-lateral, dashed arrow). T1-WI (b) demonstrates endometrial cavity distension by blood with endoluminal clots
(white arrows) and the continuity between endometrial cavity and gestational sac itself
Rosa et al. Insights into Imaging (2019) 10:98 Page 10 of 14

The integration of clinical and ultrasonographic
data is essential for diagnosis. RPOC can occur at the
cesarean delivery scar and can be visualized at US as
an irregular saclike remnant, an echogenic mass, or a
mixed, solid, and cystic mass. However, the most ac-
curate sign is trophoblastic low-resistance high-vel-
ocity arterial flow on color and pulsed Doppler US
images [33]; in this study, the authors used both
transabdominal and TV-US.
Morbidly adherent placenta (MAP) (placenta
accreta, increta, and percreta) is abnormal placental
invasion into the uterine wall, leading to failure of
placental separation at delivery [34–41]. The inci-
dence of morbidly adherent placenta has increased,
with recent estimates approximating 1/333–1/533 de-
liveries [42,43].
MAP is classified according to the depth of placental
invasion into the uterine wall (Fig. 15):
•Accreta, the placenta is in direct contact with the
myometrium
•Increta, the placenta invades into the myometrium
•Percreta, the placental invasion extends beyond the
uterine serosa and into surrounding structures
US is always the first level technique while MR is use-
ful in difficult cases.
Several main sonographic features of invasive placen-
tation have been identified [44]:
–Direct visualization of placental tissue beyond the
uterine cavity, such as a bulging mass in the urinary
bladder (rare finding with low sensitivity but high
specificity)
Fig. 15 Morbidity adherent placenta classification
Fig. 16 Morbidity adherent placenta: placenta previa (asterisk in a), cervical hematoma (white arrow in b) and placenta invasion into the
myometrium (placenta increta, white box)
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–Abnormalities of the placental–uterine interface,
using grayscale ultrasound, such as loss of the
normal hypoechoic retroplacental space
–Reduced lower-segment myometrial thickness
–Abnormal color Doppler findings identified as
hypervascularity/abnormal vascularity of serosa–
bladder interface, hypervascularity of uterine serosa–
bladder interface, irregular intraplacental
vascularization with tortuous confluent vessels
across placental width
–Abnormal placental echostructure due to placental
lacunae
–Parametrial invasion through a previous uterine scar
MR features of MAP are dark intraplacental bands on
T2-WI; abnormal uterine bulge, thinning, or loss of the
retroplacental dark zone on T2-WI; myometrial thinning
or focal disruption of the myometrium; heterogeneous
placenta; and the possible invasion of adjacent organs
(bladder) (Figs. 16 and 17).
Another important feature is identification of abnor-
mal vasculature with multiple confluent, predomin-
ately small, serpiginous flow-void structures extending
[45]:
–Along the maternal surface of the placenta and the
uterine serosa, so-called serosal vessel
–From the uterine surface to the vesical-uterine fatty
interface or even into the bladder wall (“bladder
vessel”sign)
–From the surface of the uterus to the parametrial
fat, “parametrial vessel”
The two most important risk factors of MAP are prior
cesarean delivery and placenta previa.
MAP may lead to uncontrolled postpartum hemorrhage
necessitating an emergent postpartum hysterectomy. For
this reason, its prompt recognition can avoid important
consequences.
Conclusions
Due to the increasing frequency of cesarean delivery, ra-
diologists will encounter more often its acute and
chronic complications. Among these complications, CSD
is the most common but also the most often undiag-
nosed one.
Awareness of normal postprocedural findings (myome-
trial defect and small bladder flap hematoma) helps radi-
ologist to detect significant complications, including
major hematomas, uterine dehiscence, and rupture. Re-
peated cesarean sections and severe CSD represent a pre-
disposing factor for severe complications (such as
abnormal placental implantation), especially in subsequent
pregnancies: to familiarize with these various pathologic
conditions is crucial to alert referring clinicians for a
prompt and appropriate maternal and foetal management.
Abbreviations
CSD: Cesarean scar defect; C-section: Cesarean-section; CT: Computed
tomography; MAP: Morbidly adherent placenta; MR: Magnetic resonance;
RPOC: Retained products of conception; TV-US: Transvaginal-ultrasound;
US: Ultrasound; WI: Weighted imaging
Acknowledgements
Not applicable.
Authors’contributions
RF and PG made substantial contributions to the conception and design of
the study. GN has been involved in drafting the manuscript. GN, PR, GA, and
SD revised the manuscript critically for important intellectual content. RF and
RM prepared figures and drawn illustrations. CA and SR participated in the
design of the study. All authors read and approved the final manuscript.
Fig. 17 Morbidity adherent placenta MR findings on T2-WI (a, sagittal,Scientific Rep b, coronal): dark intraplacental bands (white arrows in a),
thinning or loss of the retroplacental dark zone (round dashed box in a), and abnormal uterine bulge (dashed arrows in b)
Rosa et al. Insights into Imaging (2019) 10:98 Page 12 of 14

Funding
The authors state that this work has not received any funding.
Ethics approval and consent to participate
This article does not contain any studies with human participants or animals
performed by any of the authors.
Consent for publication
Written informed consent was not required since the manuscript does not
contain any patient data.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Department of Health Sciences (DISSAL), University of Genova, via A. Pastore
1, 16132 Genova, Italy.
2
Diagnostic Imaging Department, Villa Scassi
Hospital-ASL 3, corso Scassi 1, Genova, Italy.
3
Diagnostic Imaging and
Senology Unit, Policlinico San Martino, Largo R. Benzi 10, 16132 Genoa, Italy.
Received: 27 May 2019 Accepted: 13 August 2019
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