Congenital pelvic AVMs arise from the presence of multiple connections between the arterial and low-resistance venous systems. These malformations are considered undifferentiated vascular structures that occur due to developmental arrest at different stages, and they are clinically uncommon. Common symptoms or signs of pelvic AVM may include the detection of palpable pulsatile masses during abdominal, pelvic, or rectal examinations. Progressive sequelae of high-output congestive heart failure, such as orthopnea, edema, and fatigue, are also common manifestations of pelvic AVMs but are less frequent. Additionally, AVMs in different locations exhibit unique clinical presentations[3]. Typical symptoms of iliac AVM include back pain (70%)[4] and ipsilateral lower limb swelling due to increased flow through the venous pathway.
This can cause venous dilation in the bladder wall, vagina, and rectal wall, leading to hematuria, excessive vaginal bleeding, and gastrointestinal bleeding, which is rare in pelvic AVMs. Additionally, AVMs can erode adjacent structures. Bleeding can either be chronic or sudden and can be life-threatening. Patients with pelvic vascular malformations may also have a history of infertility or miscarriages. However, if the location of the lesion is favorable, these symptoms may not be present [5]. In the past, this disease was often misdiagnosed due to limited understanding. However, with recent advancements in diagnostic techniques, the rate of accurate diagnosis has increased, and researchers are continuously exploring suitable treatment methods [1].
When patients are admitted with acute or chronic abdominal pain, surgical and gynecological emergencies are usually the main considerations, and vascular diseases are not initially targeted for investigation, which may result in a greater likelihood of missed diagnoses. However, improved diagnostic techniques have led to increased accuracy of ultrasonography and other diagnostic methods. Ultrasonography can now be used to screen for typical vascular diseases, providing an initial overall assessment of the nature and extent of the disease. Subsequently, contrast-enhanced CT or CTA can be employed for targeted evaluation and detection of AVMs. Moreover, considering the limited pelvic space and close proximity of visceral organs, AVMs commonly affect neighboring organs. Hence, specialized examinations should be conducted to assess the extent of organ involvement based on the patient's symptoms. DSA remains the gold standard for diagnosing AVMs due to its ability to provide a definitive diagnosis and guide treatment. It allows for dynamic assessment of blood flow perfusion, enabling precise treatment planning for the disease. Transcatheter embolization has emerged as the preferred treatment modality for AVMs [6].
Commonly used embolization agents include polyvinyl alcohol (PVA) particles, gelatin sponges, coils, cyanoacrylate, covered stents, and vascular plugs. However, the use of PVA particles, gelatin sponges, stainless steel coils, and cyanoacrylate in large-caliber vessels, such as the internal iliac artery, may be associated with significant residual shunting and an increased risk of embolization agent displacement [7]. In this case, the patient presented with abdominal pain and was diagnosed with an iliac arteriovenous fistula following ultrasound, CT angiography, and angiographic examinations. After undergoing embolization treatment, the patient experienced significant improvement in pain and had a good prognosis.
Trisomy 21, also known as Down syndrome (DS), is characterized by various clinical features that arise due to the presence of an additional copy of chromosome 21. Down syndrome is a phenotype that affects multiple body systems, especially the musculoskeletal, nervous, and cardiovascular systems. Common symptoms associated with Down syndrome include congenital heart defects, duodenal atresia, cataracts, Hirschsprung disease, megacolon, choanal atresia, and anorectal malformations [8].
Genetic testing revealed several mutations associated with AVMs, including phosphatase and tensin (PTEN) in Bannayan-Riley-Ruvalcaba or Cowden syndrome and RASA-1 mutations in Parkes Weber and capillary malformation-arteriovenous malformation (CM-AVM) [5]. Mutations in ALK-1 and endoglin have been linked to hereditary hemorrhagic telangiectasia (HHT). However, the impact of chromosome 21 on these genes remains unclear. Current evidence suggests that congenital anomalies of the umbilico-portal system may be associated with abnormalities of chromosome 21, such as polysplenia, biliary atresia, or cardiac malformations. Some genetic associations have also been described. The most common chromosomal alteration associated with these anomalies is trisomy 21 [9].
Several reports have documented abnormal anatomy of the portal venous system in individuals with Down syndrome [2]. In another case report, a boy with Down syndrome was diagnosed with a combination of multiple vascular abnormalities, including extrahepatic portal hypertension, ileocecal AVMs, caval/iliac venous malformation, and rectal bleeding [10]. Only one published case of an adult with Down syndrome and pelvic AVM complicated by hematuria has been reported, resulting in death after embolization and cystectomy [2]. To our knowledge, our patient represents the only reported surviving adult with Down syndrome and pelvic AVM treated interventionally. Although the underlying mechanisms remain incompletely understood, this case further supports a potential association between vascular malformations and trisomy 21.
In this case, the venous aneurysm did not cause compression, but the patient experienced significant pain, especially worsening pain after midnight (2 am-3 am). We considered the following reasons:
1) Pain due to pelvic congestion
2) Pain caused by vascular invasion of organs
3) Pain due to shunting of blood flow through the arteriovenous fistula leading to organ ischemia.
We believe that the main reason for the worsening abdominal pain symptoms after the patient lies flat for a long time at midnight is a decrease in iliac vein pressure and an increase in arteriovenous shunting. Additionally, the patient's poor pain tolerance, as evidenced by reporting greater pain during local anesthesia for subcutaneous injection, contributes to discomfort. Importantly, the uterus is more sensitive to ischemia, as the patient experienced significant pain when a small amount of gelatin sponge was used for embolization of the left uterine artery during the procedure. This sensitivity further exacerbates abdominal pain symptoms when the patient remains in a supine position for an extended period at night.
When the patient assumes a sitting position, venous pressure increases, shunting decreases, and blood perfusion to distant organs increases, resulting in pain relief. Correcting the blood supply to the target organs and reducing cardiac pressure requires occluding abnormal vessels in the patient. Dense embolization was considered the most reliable technique for treating this patient, and as such, dense embolization was performed. The postembolization effect was significant. However, for most patients with a large venous aneurysm cavity, the economic burden of dense embolization is significant. It remains to be investigated whether dense embolization of the inflow and outflow tracts and incomplete embolization of the aneurysm are feasible.
Conclusion
We present a case study of a female patient with Down syndrome who complained of abdominal pain and was diagnosed with symptomatic AVM. We successfully treated her using minimally invasive endovascular embolization. The significance of interventional embolization therapy has been growing in the field of minimally invasive treatments, which offer more precise outcomes. Consequently, it has gradually become the preferred treatment option for symptomatic AVMs. Furthermore, it is essential to emphasize vascular ultrasound examination as part of the physical examination for patients with Down syndrome. In cases where necessary, contrast-enhanced CT scans can be performed to screen for the presence of an AVM.