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Department of Radiology
Seth G.S. Medical College and K.E.M. Hospital, Mumbai , India
Interventional Case Record
Interventional Case Record
Endovascular management of an arterio-venous malformation in the liver
Endovascular management of an arterio-venous malformation in the liver
.Contributed by : Akash L. Shah
.Contributed by : Akash L. Shah
Introduction:
Introduction:
Hepatic arterioportal malformations are communications between the portal vein and the hepatic artery and can be divided into congenital and acquired. Acquired causes of hepatic arterioportal malformations include cirrhosis, neoplasms, trauma, and iatrogenic causes including liver biopsy, biliary surgery and gastrectomy. They are often asymptomatic but, in rare instances, can have debilitating symptoms that threaten survival. Some of the symptoms include those due to portal hypertension, with hepatofugal flow in the portal vein which becomes arterialized; splenomegaly, hypersplenism, variceal, bleeding, ascites, intestinal dysfunction including malabsorption, diarrhoea and steatorrhea. Congenital vascular malformations are a the rare type of vascular malformation with one study reporting prevalence of less than 1%. They may be associated with certain conditions including hereditary haemorrhagic telangiectasia, Ehlers-Danlos syndrome, and biliary atresia. These patients typically present with portal hypertension (GI bleeding), malabsorption, and failure to thrive in infancy They are often extremely unwell and not ideal candidates for open surgery. Therefore, minimally invasive treatment presents a suitable alternative. Most have been treated with hepatic arterial embolization and/or arterial ligation with limited success with recurrences sometimes requiring liver transplantation. The term acquired hepatic artery - portal vein (HA-PV) malformation is used to represent cases where the following criteria are met: (a) There is no direct single arterioportal communication (no direct arterioportal shunt); (b) there is a complex intervening network of HA-PV communications (nidus); and (c) preceding imaging having not shown a vascular abnormality.
Hepatic arterioportal malformations are communications between the portal vein and the hepatic artery and can be divided into congenital and acquired. Acquired causes of hepatic arterioportal malformations include cirrhosis, neoplasms, trauma, and iatrogenic causes including liver biopsy, biliary surgery and gastrectomy. They are often asymptomatic but, in rare instances, can have debilitating symptoms that threaten survival. Some of the symptoms include those due to portal hypertension, with hepatofugal flow in the portal vein which becomes arterialized; splenomegaly, hypersplenism, variceal, bleeding, ascites, intestinal dysfunction including malabsorption, diarrhoea and steatorrhea. Congenital vascular malformations are a the rare type of vascular malformation with one study reporting prevalence of less than 1%. They may be associated with certain conditions including hereditary haemorrhagic telangiectasia, Ehlers-Danlos syndrome, and biliary atresia. These patients typically present with portal hypertension (GI bleeding), malabsorption, and failure to thrive in infancy They are often extremely unwell and not ideal candidates for open surgery. Therefore, minimally invasive treatment presents a suitable alternative. Most have been treated with hepatic arterial embolization and/or arterial ligation with limited success with recurrences sometimes requiring liver transplantation. The term acquired hepatic artery - portal vein (HA-PV) malformation is used to represent cases where the following criteria are met: (a) There is no direct single arterioportal communication (no direct arterioportal shunt); (b) there is a complex intervening network of HA-PV communications (nidus); and (c) preceding imaging having not shown a vascular abnormality.
Case presentation:
Case presentation:
A 35 year old woman presented with complaints of abdominal pain which was of moderate intensity and poorly controlled by medications. She also had had multiple episodes of hematemesis over the course of her ailment. She has been having progressive abdominal distension. She gave history trivial upper abdominal trauma in childhood. The patient was screened for other stigmata of hereditary hemorrhagic telangiectasia [HHT] (including recurrent nosebleeds, skin or mucous membrane telangiectasia or AVM involving other organs like lungs, brain, or gastrointestinal tract). There was no known family history of hereditary hemorrhagic telangiectasia (HHT) in first or second degree relatives.
A 35 year old woman presented with complaints of abdominal pain which was of moderate intensity and poorly controlled by medications. She also had had multiple episodes of hematemesis over the course of her ailment. She has been having progressive abdominal distension. She gave history trivial upper abdominal trauma in childhood. The patient was screened for other stigmata of hereditary hemorrhagic telangiectasia [HHT] (including recurrent nosebleeds, skin or mucous membrane telangiectasia or AVM involving other organs like lungs, brain, or gastrointestinal tract). There was no known family history of hereditary hemorrhagic telangiectasia (HHT) in first or second degree relatives.
Routine blood investigations revealed low hemoglobin which required blood transfusion. There was slightly raised SGOT and SGPT with bilirubin within normal range.
Routine blood investigations revealed low hemoglobin which required blood transfusion. There was slightly raised SGOT and SGPT with bilirubin within normal range.
Ultrasonography revealed hepatomegaly with a dilated left hepatic artery and a significantly dilated left branch of portal vein showing mixed arterio-venous spectral waveform. There were multiple tortuous vessels around this area which raised suspicion of an arteriovenous malformation. There was moderate to gross ascites.
Ultrasonography revealed hepatomegaly with a dilated left hepatic artery and a significantly dilated left branch of portal vein showing mixed arterio-venous spectral waveform. There were multiple tortuous vessels around this area which raised suspicion of an arteriovenous malformation. There was moderate to gross ascites.
CT of the abdomen showed abnormal communication between the dilated left branch of hepatic artery and the left branch of portal vein with early opacification of the portal vein and superior mesenteric vein on arterial phase imaging (Fig 1, 2). These findings were suggestive of a hepatic arterio-venous malformation (Fig 3). The patient was referred to us for endovascular management.
CT of the abdomen showed abnormal communication between the dilated left branch of hepatic artery and the left branch of portal vein with early opacification of the portal vein and superior mesenteric vein on arterial phase imaging (Fig 1, 2). These findings were suggestive of a hepatic arterio-venous malformation (Fig 3). The patient was referred to us for endovascular management.
Fig. 1,2: CECT showing opacification of the portal vein on the arterial phase raising suspicion of AVM. Gross ascites seen.
Fig 3. Reformatted CECT image showing anatomy of the arterio-venous malformation with arterial supply from theleft hepatic artery and venous drainage into the left branch of portal vein with opacification of the portal vein on arterial phase imaging.
Interventional technique
Interventional technique
Interventional Technique:
Interventional Technique:
After assessment of the clinical parameters and evaluation of the radiological findings, it was decided to embolise the arterio-venous malformation. After written informed consent, the patient was taken up for the procedure.
After assessment of the clinical parameters and evaluation of the radiological findings, it was decided to embolise the arterio-venous malformation. After written informed consent, the patient was taken up for the procedure.
A right common femoral artery access was secured with an introducer sheath and initial angiograms were obtained by selectively catheretising the celiac artery using a 4F C1 catheter. The angiogram revealed a dilated, tortuous common hepatic artery with dilated tortuous left hepatic artery. There was shunting of the blood with early draining venous communication into the left branch of portal vein which was opacified in the arterial phase with visualization of a complex intervening network of HA-PV communications (nidus) confirming the diagnosis of an arterio-venous malformation (Fig 4 & 5).
A right common femoral artery access was secured with an introducer sheath and initial angiograms were obtained by selectively catheretising the celiac artery using a 4F C1 catheter. The angiogram revealed a dilated, tortuous common hepatic artery with dilated tortuous left hepatic artery. There was shunting of the blood with early draining venous communication into the left branch of portal vein which was opacified in the arterial phase with visualization of a complex intervening network of HA-PV communications (nidus) confirming the diagnosis of an arterio-venous malformation (Fig 4 & 5).
Fig. 4,5 .Celiac angiogram showing dilated tortuous hepatic artery and its left branch with early venous draining channels seen in arterial phase via abnormal communications between the left hepatic artery and left branch of portal vein confirming the diagnosis of AVM.
Embolization was initially performed using steel coils. The dilated left hepatic artery which was supplying the arteriovenous malformation was cannulated and embolization was performed using multiple coils. Post coiling angiogram showed complete occlusion of the main branch of left hepatic artery supplying the AVM. However, another arterial feeder to the AVM was now seen ( Fig 6 )
Embolization was initially performed using steel coils. The dilated left hepatic artery which was supplying the arteriovenous malformation was cannulated and embolization was performed using multiple coils. Post coiling angiogram showed complete occlusion of the main branch of left hepatic artery supplying the AVM. However, another arterial feeder to the AVM was now seen ( Fig 6 )
Fig. 6 : Coil embolization of the main arterial feeder from the left hepatic artery to the AVM. Note the appearance of another feeding artery to the AVM post embolization of main arterial feeder.
The arterial feeder was selectively cannulated and embolization was performed with cyanoacrylate glue (Fig 7). The check angiogram then showed complete absence of the arterio-venous shunting and no filling in of any abnormal arterial feeders or abnormal draining veins (Fig 8).
The arterial feeder was selectively cannulated and embolization was performed with cyanoacrylate glue (Fig 7). The check angiogram then showed complete absence of the arterio-venous shunting and no filling in of any abnormal arterial feeders or abnormal draining veins (Fig 8).
Fig 7 :Embolization of the other arterial feeder was done using liquid embolic agent (Glue).
Fig 8 : Post Glue embolization angiogram showing complete embolization of the abnormal arterio-venous communications and no venous filling on angiograms.
Post embolization celiac angiogram showed no residual component of the AVM with disappearance of abnormal feeding arteries and complete absence of any A-V shunting to the portal vein (Fig 9).
Post embolization celiac angiogram showed no residual component of the AVM with disappearance of abnormal feeding arteries and complete absence of any A-V shunting to the portal vein (Fig 9).
Fig 9: Fig 9: Post embolization celiac angiogram showing complete embolization of the arterio-venous malformation with no residual A-V Shunting
On two month follow up, the patient had complete resolution of symptoms of abdominal pain and discomfort. There was no abdominal distension. A follow up CECT was performed which showed no residual component of the Arterio-Venous Malformation with no abnormal feeding arteries or draining veins. There was no A-V shunting noted. There was also complete resolution of the gross ascites that patient had before intervention (Fig 10 & 11).
On two month follow up, the patient had complete resolution of symptoms of abdominal pain and discomfort. There was no abdominal distension. A follow up CECT was performed which showed no residual component of the Arterio-Venous Malformation with no abnormal feeding arteries or draining veins. There was no A-V shunting noted. There was also complete resolution of the gross ascites that patient had before intervention (Fig 10 & 11).
Fig. 10 11 Before and after AVM embolization CECT imaging showing successful embolization of the hepatic AVM with no residual arterio-portal shunting.
Discussion:
Discussion:
Hepatic arterio-venous malformations [previously coined under, “arteriovenous fistula (AVF)’’] are one of the less common congenital vascular anomalies involving the liver. Although both forms are “high-flow” vascular anomalies, an AVF is a single communication between an artery and vein and can typically be easily identified using cross-sectional imaging or angiography. On the other hand, an AVM is composed of multiple small communications involving a “nidus”, or nest, of vessels and can be more difficult to identify and treat. Treatment is often much more complicated, aimed at embolizing the nidus rather than the feeders, and inappropriate treatment can exacerbate the lesion by stimulating growth with other feeders and making future treatments more difficult.
Hepatic arterio-venous malformations [previously coined under, “arteriovenous fistula (AVF)’’] are one of the less common congenital vascular anomalies involving the liver. Although both forms are “high-flow” vascular anomalies, an AVF is a single communication between an artery and vein and can typically be easily identified using cross-sectional imaging or angiography. On the other hand, an AVM is composed of multiple small communications involving a “nidus”, or nest, of vessels and can be more difficult to identify and treat. Treatment is often much more complicated, aimed at embolizing the nidus rather than the feeders, and inappropriate treatment can exacerbate the lesion by stimulating growth with other feeders and making future treatments more difficult.
The pathophysiology of acquired hepatic artery -hepatic vein (HA-PV) malformations is unknown. There are two possible processes: (a) neo-angiogenesis initiated by an ischemic episode (given two patients had documented hepatic arterial anastomotic stenosis), (b) a post-thrombotic phlebitis process similar to that proposed in the formation of dural AVFs (i.e. venous thrombosis leading to inflammation with subsequent hypertrophy of the vasa vasorum) (1). The peribiliary plexus (PBP) has been described by Kobayashi et al. and represents the small vessels supplying the biliary tree. Cirrhosis causes hypertrophy of the PBP. In addition to the PBP, there is also a periportal plexus (PPP) which represents the vasa vasorum of the portal veins. Ischemia due to decreased arterial flow may lead to hypertrophy of the PPP (to increase portal flow to the liver) eventually leading to the formation of acquired HA-PV malformations.
The pathophysiology of acquired hepatic artery -hepatic vein (HA-PV) malformations is unknown. There are two possible processes: (a) neo-angiogenesis initiated by an ischemic episode (given two patients had documented hepatic arterial anastomotic stenosis), (b) a post-thrombotic phlebitis process similar to that proposed in the formation of dural AVFs (i.e. venous thrombosis leading to inflammation with subsequent hypertrophy of the vasa vasorum) (1). The peribiliary plexus (PBP) has been described by Kobayashi et al. and represents the small vessels supplying the biliary tree. Cirrhosis causes hypertrophy of the PBP. In addition to the PBP, there is also a periportal plexus (PPP) which represents the vasa vasorum of the portal veins. Ischemia due to decreased arterial flow may lead to hypertrophy of the PPP (to increase portal flow to the liver) eventually leading to the formation of acquired HA-PV malformations.
Acquired HA-PV malformations are far more complex than simple HA-PV fistulae. The diagnosis of HA-PV malformations on imaging requires awareness of the following findings: (a) arterialization of PV waveform on Doppler imaging; (b) early filling of portal vein on arterial phase of CT or MR imaging; (c) complex hypertrophied arteries around the portal vein (even in the periphery of the liver) and; (d) dilated portal vein branch/branches. The complex hypertrophied vessel (artery) network seen around the portal vein is the cross-sectional imaging finding in these lesions which most easily differentiates them from simple AVFs. On angiography, any portal vein filling during selective hepatic arterial angiography is pathognomonic. (2) However, acquired HA-PV malformations can be diagnosed if multiple hypertrophied hepatic arterial branches supplying outflow portal vein(s) can be identified. Embolization of one arterial branch can lead to recruitment of other arterial branches.
Acquired HA-PV malformations are far more complex than simple HA-PV fistulae. The diagnosis of HA-PV malformations on imaging requires awareness of the following findings: (a) arterialization of PV waveform on Doppler imaging; (b) early filling of portal vein on arterial phase of CT or MR imaging; (c) complex hypertrophied arteries around the portal vein (even in the periphery of the liver) and; (d) dilated portal vein branch/branches. The complex hypertrophied vessel (artery) network seen around the portal vein is the cross-sectional imaging finding in these lesions which most easily differentiates them from simple AVFs. On angiography, any portal vein filling during selective hepatic arterial angiography is pathognomonic. (2) However, acquired HA-PV malformations can be diagnosed if multiple hypertrophied hepatic arterial branches supplying outflow portal vein(s) can be identified. Embolization of one arterial branch can lead to recruitment of other arterial branches.
Previously, hepatic artery ligation was considered the sole intervention, but now interventional radiology has the advantage of offering minimally invasive technique which further translates to reduced mortality and morbidity with shorter inpatient stay and fewer complications. The access can be transfemoral and in cases where this fails, a transhepatic approach can be attempted. The choice of embolization agent depends on the type of arterioportal malformation, size and number of the feeding arteries, location of the fistula which further determines the accessibility. Embolization agents include metallic coils, Amplatzer plugs, N-butyl cyanoacrylate, polyvinyl alcohol (PVA) or microspheres. One study has reported successful embolization of larger arterioportal malformations with detachable balloons which may be used either alone or in combination with other embolization agents. (3)
Previously, hepatic artery ligation was considered the sole intervention, but now interventional radiology has the advantage of offering minimally invasive technique which further translates to reduced mortality and morbidity with shorter inpatient stay and fewer complications. The access can be transfemoral and in cases where this fails, a transhepatic approach can be attempted. The choice of embolization agent depends on the type of arterioportal malformation, size and number of the feeding arteries, location of the fistula which further determines the accessibility. Embolization agents include metallic coils, Amplatzer plugs, N-butyl cyanoacrylate, polyvinyl alcohol (PVA) or microspheres. One study has reported successful embolization of larger arterioportal malformations with detachable balloons which may be used either alone or in combination with other embolization agents. (3)
Definitive therapy (with complete HA-PV shunting resolution) requires nidal occlusion which in this entity means outflow PV catheterization and occlusion. In case of need of portal vein access, it can be obtained in the lobe ipsilateral or contralateral to the HA-PV malformation. Embolization of the venous outflow (using coils, plugs, or liquid embolic agents such as Onyx and NBCA) is the preferred treatment as recommended by Yakes et al. Liquid embolic agents may be needed if there is persistent HA-PV shunting despite coil and plug embolization of the outflow PV. Care should be taken to prevent non-target embolization of liquid embolic materials (HA-PV malformation leads to hepatofugal flow in the PV). A combination of plug/coil embolization in the more central aspect of the PV outflow followed by liquid embolic embolization in the peripheral aspect of the lesion prevents non-target embolization. Portal vein embolization is well tolerated due to the dual nature of hepatic blood supply (arterial and portal). Embolization in a segmental or lobar fashion resulted in preserved portal venous flow to the remaining non-embolized segments. Arterial flow to the region of the liver undergoing portal vein embolization improves preserving viability of these segment(s). (4). Once portal vein embolization has been performed, tract embolization in the hepatic parenchymal tract is needed to decrease risk of post-procedural bleeding. The downside of the interventional-guided embolization can be that it may be limited by variant anatomy, tortuosity of vessels and elongation of the vessels die to a high dynamic flow. One of the complications to consider include migration of the embolization agent past the site of the arterioportal malformation and into a distal tributary of the portal vein which may cause portal venous thrombosis and subsequent infarction. The risk for migration of embolization increases with increasing size of the arterioportal malformation and high flow rates. (5)
Definitive therapy (with complete HA-PV shunting resolution) requires nidal occlusion which in this entity means outflow PV catheterization and occlusion. In case of need of portal vein access, it can be obtained in the lobe ipsilateral or contralateral to the HA-PV malformation. Embolization of the venous outflow (using coils, plugs, or liquid embolic agents such as Onyx and NBCA) is the preferred treatment as recommended by Yakes et al. Liquid embolic agents may be needed if there is persistent HA-PV shunting despite coil and plug embolization of the outflow PV. Care should be taken to prevent non-target embolization of liquid embolic materials (HA-PV malformation leads to hepatofugal flow in the PV). A combination of plug/coil embolization in the more central aspect of the PV outflow followed by liquid embolic embolization in the peripheral aspect of the lesion prevents non-target embolization. Portal vein embolization is well tolerated due to the dual nature of hepatic blood supply (arterial and portal). Embolization in a segmental or lobar fashion resulted in preserved portal venous flow to the remaining non-embolized segments. Arterial flow to the region of the liver undergoing portal vein embolization improves preserving viability of these segment(s). (4). Once portal vein embolization has been performed, tract embolization in the hepatic parenchymal tract is needed to decrease risk of post-procedural bleeding. The downside of the interventional-guided embolization can be that it may be limited by variant anatomy, tortuosity of vessels and elongation of the vessels die to a high dynamic flow. One of the complications to consider include migration of the embolization agent past the site of the arterioportal malformation and into a distal tributary of the portal vein which may cause portal venous thrombosis and subsequent infarction. The risk for migration of embolization increases with increasing size of the arterioportal malformation and high flow rates. (5)
For those patients in whom symptoms are not controlled, liver transplantation can be considered if available in the healthcare setting. The prognosis if left untreated results in arterialization of the portal vein with early onset of portal hypertension, hepatoportal sclerosis and fibrosis of the portal radicles further contributing to portal hypertension and fatal hepatic necrosis (6).
For those patients in whom symptoms are not controlled, liver transplantation can be considered if available in the healthcare setting. The prognosis if left untreated results in arterialization of the portal vein with early onset of portal hypertension, hepatoportal sclerosis and fibrosis of the portal radicles further contributing to portal hypertension and fatal hepatic necrosis (6).
References:
References:
1. Cho SK, Do YS, Shin SW, Kim DI, Kim YW, Park KB, et al. Arteriovenous malformations of the body and extremities: analysis of therapeutic outcomes and approaches according to a modified angiographic classification. J Endovasc Ther. 2006;13:527–38. https://doi.org/10.1583/05-1769.1.
1. Cho SK, Do YS, Shin SW, Kim DI, Kim YW, Park KB, et al. Arteriovenous malformations of the body and extremities: analysis of therapeutic outcomes and approaches according to a modified angiographic classification. J Endovasc Ther. 2006;13:527–38. https://doi.org/10.1583/05-1769.1.
2. Dunham GM, Ingraham CR, Maki JH, Vaidya SS. Finding the Nidus: detection and workup of non-central nervous system arteriovenous malformations. Radiographics. 2016;36:891–903. https://doi.org/10.1148/rg.2016150177.
2. Dunham GM, Ingraham CR, Maki JH, Vaidya SS. Finding the Nidus: detection and workup of non-central nervous system arteriovenous malformations. Radiographics. 2016;36:891–903. https://doi.org/10.1148/rg.2016150177.
3. Sutcliffe R, Mieli-Vergani G, Dhawan A, Corbally M, Karani J, Heaton N. A novel treatment of congenital hepatoportal arteriovenous fistulas and arteriovenous malformations. J Pediatr Surg. 2008;43:571–3. https://doi.org/10. 1016/j.jpedsurg.2005.07.005.
3. Sutcliffe R, Mieli-Vergani G, Dhawan A, Corbally M, Karani J, Heaton N. A novel treatment of congenital hepatoportal arteriovenous fistulas and arteriovenous malformations. J Pediatr Surg. 2008;43:571–3. https://doi.org/10. 1016/j.jpedsurg.2005.07.005.
4. Yakes WF, Yakes AM. Classification of arteriovenous malformation and therapeutic implication. In: Mattassi R, Loose D, Vaghi M, editors. Hemangiomas and vascular malformations. Milano: Springer; 2015, pp. 263–276. https://doi.org/10.1007/ 978-88-470-5673-2_33.
4. Yakes WF, Yakes AM. Classification of arteriovenous malformation and therapeutic implication. In: Mattassi R, Loose D, Vaghi M, editors. Hemangiomas and vascular malformations. Milano: Springer; 2015, pp. 263–276. https://doi.org/10.1007/ 978-88-470-5673-2_33.
5. Choi BI, Lee KH, Han JK, Lee JM. Hepatic arterioportal shunts: dynamic CT and MR features. Korean J Radiol. 2002;3:1–15. https://doi.org/10.3348/kjr.2002.3.1.1.
5. Choi BI, Lee KH, Han JK, Lee JM. Hepatic arterioportal shunts: dynamic CT and MR features. Korean J Radiol. 2002;3:1–15. https://doi.org/10.3348/kjr.2002.3.1.1.
6. Picel AC, Koo SJ, Roberts AC. Transcatheter arterial embolization with n-butyl cyanoacrylate for the treatment of acquired hepatic vascular malformations. Cardiovasc Intervent Radiol. 2016;39:1170–6. https://doi.org/10.1007/s00270-016-1328-z.
6. Picel AC, Koo SJ, Roberts AC. Transcatheter arterial embolization with n-butyl cyanoacrylate for the treatment of acquired hepatic vascular malformations. Cardiovasc Intervent Radiol. 2016;39:1170–6. https://doi.org/10.1007/s00270-016-1328-z.
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