In this study complete regression of symptoms of the AVM was reported at 80% while technical success of embolization was 60%. One of the 2 Yakes IIIB patients with incomplete embolization (25%) required additional surgery whereas the other with a 75% devascularization had a good evolution with conservative treatment.
Classification of AVMs is useful for planning optimal therapeutic approach, and predicting therapeutic outcomes (Yakes et al., 1996; Cho et al., 2006). Cho et al. (2006) demonstrated better outcome in type II Cho AVMs involving extremities or the thoraco-abdominal region.
Yakes classification was preferred to Cho classification in this study because it was more representative of the angioarchitecture observed on imaging. The Yakes classification is more comprehensive especially the distinction between type IIIa and III b which applied for 42% (3/7) of our patients.
Six of seven patients had no history of previous abdominal surgery, splenic or portal vein thrombosis or pancreatitis, these patients probably had in-born AVMs discovered at the adult age. The patient showed in Fig. 3 who had a previous abdominal surgery, portal thrombosis and chronic pancreatitis could have an acquired AVM.
Ideally, the embolization endpoint is to obtain a complete nidus occlusion of the PDAVM. Transarterial approach was used in first intention to embolize the PDAVM. Transvenous approach was selected in second intention following failure of transarterial approaches or when multiple arterial feeders were present with a dominant draining vein.
Transvenous approach was useful, however embolization should be performed carefully to minimize the risk of splenic or portal thrombosis. We observed one case of the latter, which was successfully managed by mechanical thrombectomy and local heparin infusion.
Different embolic agents have been used in previous reports: particles and ethanol were described with good technical success (Frenk et al., 2016), embolization with Onyx® showed complete regression of PDAVMs (Cassinotto & Lapuyade, 2015; Grasso et al., 2012), and Glue utilized as well (Tatsuta et al., 2014). Liquid embolic agents are the most useful. Onyx® provides the best control for liquid agent and should be preferred to minimize the risk of non-target embolization (Guimaraes & Wooster, 2011). The speed of polymerization of glue is more difficult to predict and the slow injection rate of Onyx® give more chance to the operator to prevent non target embolization (Li & Barthes-Biesel, 2017). Glue had a higher risk of bowel infarction and glue reflux into other vessels may result in non-target embolization. On the venous side, the combination of mechanical occlusion with coils or plugs with a liquid agent is recommended (Soulez et al., 2019; Lee et al., 2019). Insertion of a covered stent-graft combined with embolization of a venous aneurysm is an elegant approach to maintain the patency of splanchnic veins in case of an aneurysmal draining vein ( Yakes IIB, IIIA) (Beyer et al., 2015). Ethanol embolization has the potential to cure the AVM, however it carries a higher-risk of non-target embolization and potential gastroduodenal ulcer or pancreatitis.
Reported complications included gastric ulcer, pancreatitis, portal vein thrombosis, bowel ischemia (Lee, 2020). The occurrence of duodenal ulceration following the arterial approach being the most frequent (Cassinotto & Lapuyade, 2015; Grasso et al., 2012). Selective TAE with NBCA in the pancreas caused localized ischemic necrosis without clinically significant pancreatitis in a swine model (Okada et al., 2012).
The transvenous approach for PDAVM was not reported yet. This approach carries a risk of portal, mesenteric or splenic vein thrombosis. It is important to control reflux of liquid embolic agent into the portal system by occluding potential re-entry in the portal system. This could be achieved by occluding draining veins connected to the portal system with plugs or coils. Intra-nidal sclerotherapy by direct puncture was not performed because the AVM were deeply located and difficult to image under ultrasound or non-contrast or delayed contrast enhanced CT. Moreover, this requires to puncture through digestive structures in most cases.
In an emergent setting, microparticles were used because the operator was not used to liquid embolics. Using 300-500um particles, there was no significant complication as previously reported by Aina et al for gastroduodenal bleeding (Aina et al., 2001).
Additional surgery could be proposed in case of persistent of symptomatic AVM after embolization.
Radiotherapy has been reported (Kishi et al., 2011), in asymptomatic patients, showing shrinkage of the AVM. TIPS was described in case of failure of PDAVM embolization, with good efficacy (Hayashi et al., 1998).
Total or partial pancreatectomy is the only complete cure treatment, however there is a risk of massive intraoperative bleeding, hypoglycemia, and pancreatic juice leakage (Song et al., 2012).
The limitations of the study were the small number of patients and the retrospective design using different embolic agents. Particles were used only in emergency when the interventionalist in charge was not comfortable with the use of liquid embolics. Imaging follow-up were made by CT, thus, small residual AVMs with minimal AV shunting may have been overlooked. However, all patients did not have bleeding recurrence or evidence of portal hypertension during the follow-up. PDAVMs are rare, making a prospective study impossible in a reasonable time frame.
In conclusion, embolization of PDAVMs is a safe approach and can be effective. In case of persistent symptomatic PDAVM after embolization, surgery is a valid option. Yakes Grade IIIb PDAVM are more challenging and partial devascularization can be observed.
