Uterine arteriovenous malformation secondary to cesarean scar ectopic pregnancy: a rare case report from Nepal

Abstract

Introduction:

Uterine arteriovenous malformations are abnormal vascular connections between uterine veins and arteries, bypassing the capillary network. Cesarean scar ectopic is a rare cause of acquired uterine arteriovenous malformation, with only a few cases described in the literature.

Case Presentation:

A 30-year Gravida 3 Para 2 Living 1 female presented with amenorrhea for 2.5 months and intermittent vaginal bleeding with passage of clots for 3 weeks. She was hemodynamically stable at the time of examination, with per speculum examination revealing active bleeding. Transvaginal sonography revealed a scar ectopic at the previous caesarean scar, and she was given methotrexate for medical management. The bleeding did not control, warranting further investigations with Doppler ultrasonography (USG) and a computed tomography angiography scan, revealing a uterine arteriovenous malformation. Then, uterine artery embolization was done, following which surgery was done due to persistent vascularity.

Discussion:

Per vaginal bleeding in young women may be caused by scar ectopic and uterine arteriovenous malformations. Doppler USG is the first-line investigation, and computed tomography scan and magnetic resonance imaging help in confirming the diagnosis. Methotrexate, along with uterine artery embolization, is used in the treatment. Surgery is required if persistent bleeding occurs.

Conclusion:

Cesarean scar ectopic can be a cause of acquired uterine arteriovenous malformation, and early diagnosis and treatment should be done to prevent complications.

Introduction

The entire or partial implantation of the gestational sac in the scar from a prior caesarean section is known as caesarean scar ectopic pregnancy (CSEP)^[1]. According to research, the incidence of CSEP ranges from 1/1800 to 1/2500 of all previous hysterectomies^[2]. Active bleeding, miscarriage, rupture, abnormally invasive placental adhesion, and hysterectomy are among the hazards associated with CSEP^[2,3].

Rare vascular abnormalities known as uterine arteriovenous malformations (UAVMs) are defined by an abnormal and direct connection between the uterine veins and arteries, bypassing the capillary network^[4]. This causes the myometrium to have high-flow, low-resistance vascular channels, which can cause abrupt, heavy, and potentially fatal uterine hemorrhage^[5]. There are two types of uterine arteriovenous malformations (UAVMs): acquired and congenital^[6]. Women of reproductive age are more likely to experience acquired UAVMs, which usually originate from damage to the uterine vasculature during operations like dilatation and curettage (D&C), cesarean sections, or other uterus surgeries^[7]. During the healing process, these vascular injuries may result in aberrant arteriovenous connections.

HIGHLIGHTS

• Cesarean scar ectopic may be a rare cause of secondary uterine arteriovenous malformations.

• Doppler ultrasonography is the first line of diagnosis, and computed tomography angio and magnetic resonance imaging help in the confirmation of the diagnosis.

• Surgery may be required if bleeding is not controlled via uterine artery embolization, which, alongside methotrexate, is regarded as first line.

It is possible for UAVMs to be unintentionally found when imaging for unrelated disorders. Color Doppler transvaginal ultrasonography (USG) is the first diagnostic method and usually reveals high-velocity mixed arterial and venous flow^[8]. Since computed tomography (CT) angiography provides accurate visualization of aberrant vascular connections, it is regarded as the gold standard for confirmation^[9].

In this case, we highlight the clinical challenges associated with a rare acquired uterine arteriovenous malformation secondary to cesarean scar ectopic pregnancy, requiring surgery even after methotrexate therapy and uterine artery embolization. This work has been reported in line with the SCARE criteria^[10].

Case presentation

A 30-year-old married female from a rural area presented to the gynecology outpatient department with complaints of amenorrhea for 2.5 months and intermittent per vaginal (PV) bleeding with passage of clots for 3 weeks. At approximately 6 weeks of gestation, she experienced PV bleeding for 1 week, and a urine pregnancy test (UPT) was positive. A transvaginal ultrasound done around 9 weeks of gestation revealed a scar ectopic pregnancy at the site of a previous lower-segment cesarean section (LSCS) scar. She was managed with weekly intramuscular methotrexate, receiving a total of four doses.

Despite medical management, the patient developed on-and-off PV bleeding for about 3 weeks. Due to ongoing bleeding and symptomatic anemia, she required two episodes of intravenous blood transfusion, spaced 1 week apart. She had no significant past medical or personal history. Obstetric history revealed gravida 3, para 2, living 1. The first child was a term male delivered via normal vaginal delivery 8 years ago. The second was a female child delivered by cesarean section 3 years ago due to preterm premature rupture of membranes (PPROM); the neonate did not survive.

On clinical examination, she was pale but hemodynamically stable, with a blood pressure of 100/60 mmHg, a heart rate of 136 bpm, a respiratory rate of 20/min, a temperature of 99.8°F, and an SpO₂ of 99% on room air. There was no dehydration or peripheral edema. Abdominal examination was soft and nontender. Per speculum examination revealed minimal brownish discharge with active bleeding, and per vaginal examination showed a nontender uterus with cervical motion tenderness (CMT).

She was admitted with a high-risk label for further evaluation. A pelvic ultrasound with color Doppler performed at that time showed a tubular anechoic structure in the anterior myometrium at the site of the previous LSCS scar, extending into the endometrial cavity. Color Doppler imaging demonstrated predominantly venous flow with a peak velocity of 38 cm/second, along with areas of low-resistance arterial flow, raising suspicion for a uterine arteriovenous malformation (AVM). A CT angiography further confirmed the diagnosis, as it showed multiple tortuous vessels in the uterine myometrium and endometrium along with a postcesarean scar. (Fig. 1)

Figure 1.

CT pelvis (plain: sagittal; contrast-enhanced: axial and sagittal views). (A, B, C) Contrast images show multiple tortuous vessels in the uterine myometrium and endometrium. Postcesarean section scar is also noted.

She subsequently underwent uterine artery embolization (UAE) via the right femoral artery approach. A 5 F arterial sheath and diagnostic catheter were used, followed by selective catheterization of bilateral uterine arteries using a 2.8 F nano-microcatheter and microwire system. Embolization was performed with polyvinyl alcohol (PVA) particles, followed by injection of glue mixed with lipiodol. Hemostasis was achieved successfully, and the patient was monitored postprocedure. No immediate complications occurred, and vital signs remained stable.

However, due to persistent vascularity and the presence of a necrotic area in the uterine scar region revealed by follow-up Doppler USG, the patient was planned for surgical management. Within 1 week of embolization, she underwent an emergency total abdominal hysterectomy with bilateral salpingectomy. Intraoperatively, the uterus was found to be approximately 6 weeks gestational size, with the lower uterine segment covered by vascular and necrotic tissue over the previous scar site. The bladder was adhered and displaced superiorly. Only the ampulla of the left fallopian tube was visualized; the right tube and both ovaries appeared normal (Fig. 2). On the cut section, the uterus was soft in consistency, with a necrosed area in the lower segment, uterocervical length of 9 cm, and myometrial thickness of 2.5 cm (Fig. 3). The procedure was carried out under standard aseptic precautions, with stepwise clamping and ligation of the round ligaments and broad ligament dissection. Given the presence of necrotic uterine tissue, the continued vascularity despite embolisation, and the significant danger of catastrophic hemorrhage if treatment is not received, an emergency hysterectomy was recommended.

Figure 2.

(A and B) Intraoperative images during total abdominal hysterectomy.

Figure 3.

(A and B): Gross and resected specimen showing necrosed vascular area in the lower uterine segment.

Postoperatively, the patient was managed with intravenous and oral antibiotics (cefixime, amoxicillin-clavulanate, clindamycin), iron supplementation, pantoprazole, paracetamol for pain, urinary alkalinizer, and Betadine vaginal pessaries. As perioperative prophylactics against surgical site infections and to lower the risk of subsequent infections in necrotic tissue, broad-spectrum antibiotics were used. Her hemoglobin had decreased from 10 g/dL to 8.4 g/dL, prompting a second transfusion. After stabilization, it improved to 9.4 g/dL. She was monitored for signs of infection and recurrent bleeding.

At discharge, she was counseled regarding warning signs such as fever with chills or rigors, abdominal pain, foul-smelling discharge, or heavy PV bleeding. She was advised to follow-up in the gynecology outpatient clinic after 2 weeks, and she had no issues during follow-up. A summary of β-hCG levels and timeline of our case is explained in Table 1 and Figure 4, respectively.

Table 1.

Serial β-hCG trend of our patient

Time Point	β-hCG Level (mIU/mL)
At presentation	7325
After 1 week	2525
After 2 weeks	318
After 3 weeks	160
After 4 weeks	99.78
After 5 weeks	42.86

Figure 4.

Summary of case presentation and management.

Discussion

The creation of an aberrant vascular link by invasive trophoblastic tissue inside the structurally compromised and fibrotic tissue at the site of the prior cesarean incision is probably the cause of UAVM consequent to caesarean scar pregnancy^[11]. The majority of multiparous women of reproductive age who have acquired AVMs exhibit symptoms, particularly those who have had gynaecological surgeries in the past. The presenting symptom that occurs most frequently is abnormal uterine bleeding^[12].

A heterogeneous, ill-defined mass with tubular anechoic or hypoechoic spaces of different diameters is usually visible on ultrasound. Low-resistance, high-velocity flow that suggests an arteriovenous shunt is shown by color Doppler, and spectral analysis helps to better characterize the lesion^[12,13]. Although Doppler USG can clearly suggest UAVM, it is not always able to fully identify the extent of the lesion. Although its results are nonspecific and usually indicate an enlarged uterus, an ill-defined mass, tubular hypoechoic vascular channels, a disturbed junctional zone, and prominent parametrial arteries, magnetic resonance imaging (MRI) provides an excellent non-invasive alternative for determining the degree of the disease and aiding in diagnosis^[12–14]. A precise imaging technique for defining the lesion’s extent, ruling out extrauterine extension, and locating arterial feeders is CT angiography. Additionally, it offers crucial anatomical information that is necessary for preoperative planning^[15].

The goals of managing UAVM brought on by an ectopic pregnancy are to manage any residual ectopic tissue, control bleeding, and maintain fertility. The first-line therapy is UAE. It preserves the uterus and future fertility while successfully controlling bleeding. Several research studies and case reports have highlighted the usefulness of UAE in these situations^[16]. UAE and methotrexate are often used together in patients, particularly when beta-hCG levels are still high or retained products of conception are suspected^[12]. Although they have a higher risk of bleeding, surgical treatments such as excision, hysteroscopy, and dilatation and curettage may be utilized in stable individuals. To reduce this risk, preprocedural UAE could be required. When conservative measures fail or when bleeding becomes life-threatening, a hysterectomy is the only option, especially for women who do not want to get pregnant in the future^[17]. Due to scar formation, fertility is frequently impaired in UAVM, particularly when surgery is necessary. Since the patient did not want to become pregnant in the future, a hysterectomy was acceptable in our case. According to earlier authors like Visvalingam et al (2016) and Shah and Kaushal (2024), surgery is not always necessary for UAVMs^[12,16].

In line with documented short-term success rates of 88.4% and low complication rates (1.8%) in haemodynamically stable patients, initial therapy with UAE produced temporary hemostasis and stabilization without immediate consequences^[18]. Nevertheless, after a week, our patient had necrosis and prolonged vascularity at the scar site, requiring a hysterectomy. This demonstrates that although UAE is frequently used as a first-line treatment, it might not be sufficient to treat instances involving tissue necrosis or significant scar involvement. The patient was asymptomatic and free of recurrent bleeding during the favorable long-term follow-up.

One important factor to take into account for women with uterine AVMs is fertility preservation. Successful pregnancies have been documented with conservative methods such methotrexate or UAE, which can preserve fertility^[19]. However, a history of AVM or scar pregnancies raises the chance of aberrant placentation, such as recurrent cesarean scar pregnancy or placenta accreta spectrum. Given the significant danger of catastrophic hemorrhage, our patient’s hysterectomy saved her life even though it limited her fertility.

If untreated or inadequately controlled, uterine AVM carries a high risk of massive hemorrhage, hypovolemic shock, disseminated intravascular coagulation, and maternal mortality. Surgical management, though definitive, carries its own risks, including injury to adjacent structures, infection, and significant blood loss^[20]. In our case, early recognition and stepwise management allowed avoidance of such complications, and the recovery was uneventful.

It is important to thoroughly rule out differential diagnoses such as retained products of conception, uterine artery pseudoaneurysm, gestational trophoblastic illness, and subinvolution of the placental site, since they might exhibit similar radiological and clinical symptoms^[21–23]. Because of our case’s distinctive imaging characteristics and lack of response to medicinal treatment, the diagnosis of acquired AVM was established.

In this particular case, the patient’s cesarean scar pregnancy was treated with weekly injectable methotrexate as part of medical therapy. However, further testing was done because of the symptomatic anaemia caused by sporadic and continuous vaginal bleeding. An acquired UAVM was found near the location of the prior cesarean scar, according to imaging tests such as color Doppler USG and CT angiography. Selective UAE was used to stop the bleeding and aberrant vascularity. The uterine scar area required definitive surgical care due to persisting vascularity and necrotic tissue, even after successful embolization. To remove the diseased tissue and prevent additional problems, the patient had a total abdominal hysterectomy with bilateral salpingectomy within a week of embolization.

Conclusion

An uncommon but potentially fatal syndrome known as UAVM following cesarean scar ectopic pregnancy is characterized by aberrant vascular connections inside scar tissue. For proper treatment, an early diagnosis using MRI, CT angiography, color Doppler, and ultrasound is essential. To control bleeding and preserve the uterus, UAE is still the first-line fertility-preserving procedure. However, to avoid major problems, permanent surgical surgery, such as a hysterectomy, may be required in patients with chronic vascularity, necrosis, or failure of conservative therapy. For the best results, individualized, multidisciplinary care that takes into account the patient’s reproductive preferences and clinical state is crucial. This case highlights the importance of timely diagnosis and a stepwise therapeutic approach in managing this complex condition.

Ethical approval

Ethical approval is not required for case reports in our institution.

Consent

Written informed consent was obtained from the patient to publish this case report as well as for any accompanying images.

Source of funding

No funding for this research.

Author contributions

M.P.: Conceptualization, Writing - original draft, Writing - review & editing; S.D.: Conceptualization, Writing – original draft, Writing – review & editing; S.R.: Writing – original draft, Writing – review & editing; D.O.: Writing – original draft; K.K.Y.: Writing – original draft, Writing – review & editing; R.G.: Resources, Writing – review & editing.

Conflicts of interest disclosure

No conflicts of interest.

Guarantor

Milan Pokhrel.

Registration of research studies

Not applicable