Ultrasound Features of Uterine Arteriovenous Malformation with Concomitant Uterine Dehiscence Presenting as Secondary Postpartum Hemorrhage: A Case Report

Abstract

Background

Uterine arteriovenous malformation (UAVM) is a rare cause of vaginal bleeding but potentially life-threatening condition. Defined as an abnormal vascular communication characterized by a direct connection between the uterine arterial and venous system without any capillary network contribution. The main clinical presentation of UAVM is recurrent, severe bleeding refractory to medical treatment, particularly after surgical procedures on the uterus, such as cesarean section (CS) or curettage. Although definitive diagnosis is ideally established by pelvic angiography, ultrasonography (US), particularly color Doppler US, serves as a valuable noninvasive tool for the diagnosis of UAVMs. The management of UAVM becomes increasingly difficult due to the concomitant presence of uterine dehiscence. The diagnosis of uterine dehiscence can be established using transvaginal US.

Case Report

A 29-year-old woman, Para 1, Abortus 0 (P1A0), presented with recurrent, massive vaginal bleeding that began 12 days after a cesarean delivery. On admission, she was two months postpartum following her most recent CS. We performed an US examination and revealed a small hypoechoic area within the myometrium adjacent to the CS scar site with hypervascular appearance, turbulent multidirectional flow, high velocity and low resistance flow, raising the suspicion for UAVM. From transvaginal US we also found a triangular indentation at the CS scar site measuring 10.9 mm in length and 7.5 mm in depth with adjacent myometrial thickness (AMT) 9.9 mm and no residual myometrial thickness (RMT) indicating cesarean scar defect (uterine dehiscence). Given the presence of severe vaginal bleeding refractory to medical treatment, hysterorrhaphy was performed to achieve hemostasis, repair the uterine defect, and preserve fertility.

Conclusion

Color Doppler US can rapidly and accurately establish the diagnosis of UAVM and uterine dehiscence, allowing prompt management of patients who present with heavy vaginal bleeding, often accompanied by hemodynamic instability.

Introduction

Uterine arteriovenous malformation (UAVM) is a rare but potentially life-threatening vascular abnormality of the uterus, with fewer than 100 well-documented cases reported in the literature.¹ It was estimated that the incidence of UAVM was 0.63% after childbirth or abortion.² UAVM is an uncommon but potentially life-threatening cause of heavy and recurrent uterine bleeding, which results from abnormal direct communications between the uterine arterial and venous systems.³ This condition represents a significant clinical risk, as it may lead to urgent medical intervention.

UAVM may be classified as congenital, resulting from abnormal embryologic vascular development, or more commonly acquired, typically occurring after uterine trauma.³ Acquired AVMs have been associated with surgical interventions such as dilatation and curettage, cesarean section (CS), myomectomy, endometrial surgery, and trophoblastic disease.⁴ In recent years, the increasing rate of cesarean delivery worldwide has been suggested as a contributing factor to the rising number of reported cases of UAVM.⁵

Ultrasonography (US), specifically transvaginal color Doppler US is the first-line imaging modality, as it is rapid, noninvasive, and widely accessible. However, diagnosis can be challenging because the grayscale appearance of UAVM is often nonspecific and may overlap with other causes of abnormal uterine bleeding, including retained products of conception, gestational trophoblastic disease, and post-surgical vascular changes. Transvaginal ultrasonography (TVUS) may demonstrates heterogeneous myometrial echotexture, multiple cystic structures, or tubular anechoic spaces within the myometrium, findings that are not pathognomonic for UAVM. Therefore, color Doppler assessment is essential, as it can reveal marked hypervascularity, multiple tortuous vessels, and characteristic high-velocity turbulent blood flow within the lesion, substantially improving diagnostic accuracy.⁶

Pelvic angiography remains the gold standard for definitive diagnosis and allows simultaneous therapeutic intervention. Management depends on the patient’s hemodynamic status, severity of bleeding, and fertility desire. Uterine artery embolization is currently considered the preferred fertility-preserving treatment and has shown high success rates. Hysterectomy remains the definitive option for uncontrolled hemorrhage or in women who have completed childbearing.⁷

In addition to UAVM, uterine dehiscence following cesarean delivery is another uncommon but important cause of secondary postpartum hemorrhage. Because both conditions may present with recurrent vaginal bleeding and may be difficult to identify on routine imaging, concomitant occurrence can pose a significant diagnostic challenge. In this case report, we present a patient with recurrent vaginal bleeding following CS, further complicated by subsequent curettage, which was ultimately attributed to an acquired UAVM concomitant with uterine dehiscence.

Case Illustration

A 29-year-old woman, Para 1, Abortus 0 (P1A0), was referred to the emergency department due to recurrent massive vaginal bleeding which began on postoperative day 12 following a CS and recurred intermittently until postoperative day 69. There was no history of fever, malodorous vaginal discharge, or surgical site infection.

Between postoperative days 12 and 69, the patient experienced five episodes of massive vaginal bleeding requiring repeated hospitalizations. During these admissions, she received intravenous tranexamic acid (1000 mg three times daily) and a cumulative total of 18 units of packed red blood cells (PRCs).

During these hospitalization, the patient underwent multiple gynecological ultrasonographic examinations, which revealed no retained products of conception. During one of the previous hospitalizations, uterine curettage was performed because of recurrent massive vaginal bleeding refractory to medical treatment. Histopathological examination demonstrated endometrial tissue without chorionic villi. As her clinical condition improved, she was discharged on the second postoperative day following curettage.

On postoperative day 69, the patient was readmitted to the regional hospital because of sudden, spontaneous, and profuse vaginal bleeding. The hemoglobin level was 7.7 g/dL, and three units of PRC were transfused. On the third day of hospitalization, she experienced another episode of profuse bleeding and was subsequently referred to our tertiary care center.

On initial assessment, the patient exhibited signs of hemorrhagic shock, including blood pressure of 92/55 mmHg, heart rate of 122 beats per minute, and respiratory rate of 26 breaths per minute with moderate pallor and cold extremities. Fluid resuscitation was initiated with isotonic saline. Bleeding was present through the cervix based on speculum examination. The hemoglobin level was 7.5 g/dL, and a transfusion of 3 units of PRC was planned.

After hemodynamic stabilization, transabdominal and transvaginal ultrasonography with color Doppler evaluation was performed. This revealed a small hypoechoic area within the myometrium adjacent to the CS scar (Figure 1A), showing marked hypervascularity and turbulent multidirectional flow with a peak systolic velocity (PSV) of 136 cm/s and a resistive index (RI) of 0.32 (Figure 1B), suggestive of UAVM.

Figure 1.

Ultrasound imaging of the uterus. (A) Transabdominal ultrasound demonstrating a small hypoechoic area within the myometrium adjacent to the previous cesarean section (CS) scar (yellow arrow). (B) Transvaginal ultrasound (TVUS) with color Doppler applied to the hypoechoic area identified in panel A, showing red and blue signals consistent with a hypervascular appearance and turbulent multidirectional flow (yellow arrow). (C) A triangular indentation at the CS scar site measuring 10.9 mm in length and 7.5 mm in depth. (D) Adjacent myometrial thickness (AMT) measured at 9.9 mm, with absence of residual myometrial thickness (RMT), consistent with a cesarean scar defect (uterine dehiscence).

In addition, TVUS demonstrated a triangular niche-like defect at the cesarean scar site measuring 10.9 mm in length and 7.5 mm in depth (Figure 1C), with an adjacent myometrial thickness (AMT) of 9.9 mm and absence of residual myometrial thickness (RMT), consistent with a cesarean scar defect/uterine dehiscence (Figure 1D). Given the severe recurrent vaginal bleeding refractory to conservative treatment, hysterorrhaphy was performed to achieve hemostasis and restore uterine integrity while preserving future fertility.

At laparotomy, the uterus and adnexal structures appeared unremarkable. After sharp and blunt dissection of the bladder flap, a 2×1.5 cm cesarean scar defect was identified at the midpoint of the previous uterine incision. Active bleeding originated from vessels located on the left margin of the defect (Figure 2A). Hysterorrhaphy was performed successfully (Figure 2B). Postoperatively, the hemoglobin level increased to 8.1 g/dL, and the patient was discharged on the third postoperative day. During 1 month of follow-up, she remained asymptomatic with no further episodes of vaginal bleeding.

Figure 2.

Intraoperative photographs. (A) A cesarean scar defect (uterine dehiscence) measuring 2×1.5 cm was visible in the middle of the previous cesarean incision. (B) Post hysterorrhaphy.

Discussion

UAVM is a rare condition, representing 0.22% of postpartum women, but potentially life-threatening cause of postpartum hemorrhage.^8–11 UAVM was first described by Dubreuil and Loubat in 1926.^12–14 To date, there are fewer than 200 cases reported in the literature.⁸ Defined as an abnormal vascular communication characterized by a direct connection between the arterial and venous system within the uterus, UAVMs are traditionally classified as congenital or acquired.^15–17 The congenital UAVM is believed to arise from a failure of differentiation during fetal angiogenesis.^18,19 The most common cause of acquired lesion is women with a history of surgical instrumentation of the uterus, such as CS, curettage, or pelvic surgery.^1–12 As this patient’s UAVM became apparent 12 days after a CS delivery and complicated by uterine dehiscence, we believe this case represented an acquired UAVM.

In the postpartum period, UAVM presents with recurrent, severe vaginal bleeding refractory to medical treatment.^8–11 Anemia and hemodynamic instability may occur with up to 30% of cases requiring blood transfusion.¹⁸ In our case, recurrent massive bleeding resulted in multiple hospitalizations, severe anemia, and substantial transfusion requirements. A curettage was performed during a previous hospitalization because retained products of conception remained a diagnostic consideration. However, the subsequent diagnosis of UAVM highlights the importance of excluding vascular abnormalities before undertaking intrauterine procedures, as curettage may precipitate or worsen bleeding in patients with UAVM.^12,18

Clinical findings alone are insufficient to establish the diagnosis of UAVM; therefore, imaging plays a central role in diagnosis and management. TVUS combined with color Doppler and spectral analysis is the recommended first-line imaging modality.^15–17 Color Doppler allows real-time assessment of arterial and venous flow dynamics and can be performed rapidly at the bedside, making it particularly useful in hemodynamically unstable patients.¹⁵ Grayscale US may demonstrate hypoechoic or anechoic tubular structures within the myometrium, but these findings are nonspecific. Therefore, color Doppler evaluation is essential to demonstrate the characteristic hypervascular lesion with turbulent multidirectional flow, high peak systolic velocity, and low-resistance flow.^15–17 In this case, the lesion demonstrated a PSV of 138 cm/s and an RI of 0.32, findings highly suggestive of UAVM (Figure 1A and B).

Pelvic angiography remains the gold standard for diagnosis, although it is more commonly performed with the intent of therapeutic intervention.^11,20 Other imaging modalities including CT scan and MRI, may provide additional anatomical information regarding lesion extent and surrounding pelvic structures.¹⁷ Nevertheless, Doppler US remains the preferred initial imaging modality because it is rapid, accessible, cost-effective, and noninvasive.¹⁵ Importantly, this case illustrates that imaging evaluation of recurrent postpartum hemorrhage should not focus solely on identifying vascular lesions. Careful assessment of the cesarean scar region is equally important because multiple pathologies may coexist. Failure to recognize a concurrent uterine scar defect may delay definitive diagnosis and management.

In this case, UAVM appeared to coexist with and likely arise in association with uterine dehiscence. The diagnosis of uterine dehiscence was established by TVUS, which demonstrated a cesarean scar defect characterized by a triangular indentation at the site of the previous uterine incision. The recommended assessment of a cesarean scar defect includes measurement of its length, width, and depth in the plane where the defect is best visualized.^20–22

This case highlights an important learning point: in women presenting with recurrent secondary postpartum hemorrhage following cesarean delivery, clinical attention should not be limited to retained products of conception, infection, or vascular abnormalities alone. Careful evaluation of the cesarean scar should be performed routinely, as uterine dehiscence may be an underlying or coexisting cause of persistent bleeding. Unlike UAVM, which often requires Doppler interrogation for characterization, uterine dehiscence may be suspected on routine TVUS through identification of scar niche formation, myometrial discontinuity, or marked thinning of the residual myometrium.

The diagnosis of UAVM and uterine dehiscence through US may be challenging. On grayscale TVUS, UAVM may appear as multiple hypoechoic or anechoic myometrial spaces, findings that are often nonspecific and may mimic retained products of conception. Similarly, subtle uterine dehiscence may be overlooked unless the cesarean scar is specifically evaluated. These diagnostic challenges may explain why no definitive pathology was identified during the patient’s earlier assessments despite recurrent hemorrhagic episodes. Earlier recognition of these findings might have facilitated earlier referral and definitive management, potentially reducing repeated hospitalizations, transfusion requirements, and associated morbidity.

Additionally, RMT and AMT were measured. The RMT should be assessed at its thinnest point, whereas the AMT should be measured at the thickest adjacent myometrial area.²¹ In this case, the cesarean scar defect appeared as a triangular indentation measuring 10.9 mm in length and 7.5 mm in depth, with AMT 9.9 mm and no RMT (Figure 1C and D). The absence of RMT in this case indicates the presence of complete uterine dehiscence, which is the underlying cause of UAVM. In general, if there is an indication to repair a cesarean scar defect, hysteroscopic repair is the preferred approach. However, if the RMT is <2–3 mm, then laparoscopic, laparotomic, or transvaginal repair appears to be the most appropriate option.^21,22

Currently, there is no consensus on a clinical guideline to treat UAVM, most likely due to its low incidence, unknown etiology, and distinct fertility demands by different patients.¹⁴ In clinical practice, management of UAVM depends on the patient’s symptoms, hemodynamic stability, degree of hemorrhage, and their desire to preserve fertility.¹² Initial management includes stabilizing the patient’s hemodynamic condition and controlling ongoing bleeding.^15–17

Uterine artery embolization performed during pelvic angiography is generally considered the preferred fertility-preserving treatment for UAVM.^8,18 However, in the present case, the coexistence of complete uterine dehiscence necessitated surgical intervention. While embolization may have controlled the vascular component, it would not have corrected the underlying structural defect. Therefore, hysterorrhaphy was performed to achieve definitive hemorrhage control, restore uterine integrity, and preserve future fertility.

The findings of this report should be interpreted within the limitations of a single observational case. Although the clinical, ultrasonographic, and intraoperative findings strongly supported the diagnosis, histopathological confirmation was unavailable. Nevertheless, this case emphasizes the importance of comprehensive ultrasonographic assessment, including evaluation of both vascular abnormalities and cesarean scar integrity, in women presenting with recurrent secondary postpartum hemorrhage after cesarean delivery.

Conclusion

This case highlights the importance of comprehensive ultrasonographic assessment in women presenting with recurrent secondary postpartum hemorrhage following cesarean delivery. While color Doppler examination is essential for identifying UAVM, careful evaluation of the cesarean scar region is equally important to detect uterine dehiscence. Early recognition of these conditions may facilitate timely referral and definitive management, potentially reducing repeated hospitalizations, transfusion requirements, and associated morbidity.

Informed Consent Patient Statement

The authors confirm that written informed consent has been obtained from the involved patient. The patient has been informed about the details of the case and has provided approval for the information to be published in this case report.

Disclosure

The authors declare that they have no competing interests in this work.