Keywords
uterine artery pseudoaneurysm - Yin-yang sign - secondary post-partum hemorrhage -
cesarean section
Introduction
Postpartum hemorrhage remains one of the major causes of maternal mortality. It occurs
in fewer than 5% of all deliveries and accounts for approximately 15% of all maternal
deaths.[1]Primary postpartum hemorrhage (PPH) is defined as hemorrhage that occurs within the
first 24hours of delivery. Uterine atony (approximately 70% of cases), retained placental
fragments, genital laceration, uterine inversion or rupture, and coagulation disorders
are the main causes of primary hemorrhage.[2] Vaginal bleeding starting after 24hours delivery up to 6 weeks is defined as secondary
postpartum hemorrhage.[3] Important causes include retained products of conception, vascular injuries, sub-involution
of the placental bed and endometritis.[4] Pseudoaneurysm is rare but fatal cause of hemorrhage following cesarean section.
Causes for pseudoaneurysm formation could be trauma to the uterine artery or its branches
during cesarean section, and myomectomy.[5] Pseudoaneurysm does not contain all three layers of vessels, differentiating it
from true aneurysm. It may be asymptomatic but often presents with secondary postpartum
hemorrhage.[6]
Ultrasound with Doppler imaging is the first imaging modality for secondary postpartum
hemorrhage. On grayscale images, pseudoaneurysm will be seen as anechoic or hypoechoic
lesion within the myometrium. On color Doppler images typical Yin-yang sign is seen
within the lesion which reveals characteristic to-and-fro spectral waveform and it
has been reported to have a diagnostic sensitivity of 95%.[7]
[8] Minimally invasive intervention procedure like uterine artery embolization is safe
and reliable technique with preservation of fertility.[9]
Case Report
We would like to report a case of a 41-year-old female patient, G3P2, who presented
to emergency department of our hospital with profuse per vaginal bleeding, 32 days
after cesarean section was done at outside hospital.
On per-abdominal examination cesarean section scar looked normal. On per vaginal examination
blood clots were noted in cervix and vagina.
Management and Outcome
Patient was in hypovolemic shock with hemoglobin level of 7.8g/dL and was managed
with rigorous fluid resuscitation and blood transfusion. Ultrasound was done on emergency
basis to rule out retained products of conception. On trans-abdominal and trans-vaginal
ultrasound scan, isoechoic to hyperechoic clots were noted in the endometrial cavity
with no significant vascularity.
A well-defined cystic lesion measuring 2.6×1.9cm was seen in the left lateral myometrium
of the lower uterine segment at the lateral margin of echogenic cesarean section scar
([Fig. 1]).
Fig. 1 Gray scale ultrasound image showing cystic lesion on left lateral wall of uterus
(arrow) adjacent to echogenic scar.
On color Doppler study the cystic lesion showed yin-yang sign with to and fro spectral
waveforms ([Fig. 2]), suggesting pseudoaneurysm probably arising from left uterine artery causing secondary
postpartum hemorrhage. CT angiography was performed immediately which confirmed the
findings. A well-defined arterial phase contrast enhancing lesion was seen in relation
to left uterine artery ([Fig. 3]).
Fig. 2 (A) Color Doppler showing Yin-yang flow in the cystic lesion (arrow) therefore confirming the presence of pseudoaneurysm. (B) Doppler image showing to and fro pattern of waveform in the pseudoaneurysm.
Fig. 3 Maximum intensity projection (MIP) images showing well-defined out-pouching (arrow) arising from tortuous left uterine artery suggestive of pseudoaneurysm.
Patient was then taken for Digital subtraction angiography. Left internal iliac angiogram
was performed by transfemoral route, followed by selective catheterization of left
uterine artery ([Fig. 4]).
Fig. 4 Selective catheterization of left internal iliac artery showing contrast blush and
pseudoaneurysm arising from the left uterine artery.
After confirming and identifying neck of pseudoaneurysm, superselective embolization
of neck of pseudoaneurysm was performed with platinum coils ([Fig. 5]). Clinically patient improved after the interventional procedure.
Fig. 5 Catheter angiography image showing platinum coil (arrow) in the region of neck of pseudoaneurysm.
Post-embolization ultrasound images obtained on post procedure day 2 showed no color
flow in the region of pseudoaneurysm suggesting complete occlusion ([Fig. 6]).
Fig. 6 Day 2 of post embolization, ultrasound, and color Doppler image showing no color
flow in the region of pseudoaneurysm suggesting complete occlusion of pseudoaneurysm
from the circulation.
Discussion
Postpartum period begins immediately after the delivery of the neonate and placenta
and is considered to extend up to 6 to 8 weeks. During this period physiologic changes
of pregnancy gradually revert to baseline.[10]
Imaging appearance of postpartum uterus is variable. Heterogeneously hyperechoic material
is seen in the endometrial cavity even in 21% asymptomatic women for 2 weeks with
physiological postpartum vaginal bleeding.[11]
The most common cause of PPH is an atonic uterus, which fails to contract. Another
important cause is retained products of conception (RPOC) which is defined as residual
fetal or placental tissue remaining after delivery, miscarriage, or termination.[10] In primary hemorrhage if RPOC is suspected, it is treated without imaging. Ultrasound
findings suggestive of the presence of an echogenic mass with increased color Doppler
flow in the endometrium appear to be the most accurate sign of RPOC, with reported
sensitivity and specificity of 79 and 89%, respectively.[12]
Uterine artery pseudoaneurysm is one of the important, potentially fatal but treatable
cause of secondary postpartum hemorrhage. Timely diagnosis with high index of suspicion
is important to avoid dreaded complications of hemorrhage. Ultrasound with color Doppler
imaging is first line of imaging in secondary postpartum hemorrhage to look for the
etiology. Hypoechoic or anechoic lesion in myometrium with Yin-yang flow on color
images which reveals to and fro spectral waveform pattern on Doppler study points
toward uterine artery pseudoaneurysm with sensitivity of 95%.[7]
[8] Higher imaging modalities like CT angiography is done for confirmation of findings.
Digital subtraction angiography followed by superselective embolization of neck of
pseudoaneurysm is treatment of choice in stable patients with preservation of fertility.[9] Minimal invasive procedure can prevent more invasive and radical ways to treat secondary
postpartum hemorrhage, like uterine artery ligation or hysterectomy.
In our case, on ultrasound imaging, along with endometrial clots, we saw well-defined
cystic lesion in the myometrium, which pointed toward one of the rare vascular causes
of postpartum hemorrhage but color Doppler pattern and angiography confirmed the diagnosis
of pseudoaneurysm.
Conclusion
In cases of secondary postpartum hemorrhage, ultrasound is the first imaging investigation
to look for the common etiologies. High index of suspicion is needed to search for
rare vascular causes like AVM and pseudoaneurysm. Further imaging with crosssectional
studies may be required in certain cases. Minimally invasive treatment modalities
available now a days help to avoid more radical surgeries like hysterectomy thus preserving
fertility.
