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1 Department of Radiology, Oita Medical University, 1-1, Idaigaoka,
Hasama-machi, Oita-gun, Oita, 879-5593, Japan.
2 Department of Radiology, Oita Prefectural Hospital, 476, Bunyo, Oita-shi,
Oita, 870-8511, Japan.
3 Department of Radiology, Nagatomi Neurosurgical Hospital, Omichi-Machi,
Oita-shi, Oita, 870-0822, Japan.
Received June 7, 2002;
accepted after revision December 6, 2002.
Address correspondence to H. Mori.
Abstract
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MATERIALS AND METHODS. Between 1989 and 2001, we treated 10 patients with symptomatic intrahepatic portosystemic venous shunt by performing transcatheter embolization with Gianturco coils, fibered platinum coils, detachable balloons, and detachable microcoils using one of three approaches to access the portal venous system: transileocolic obliteration (n = 2), percutaneous transhepatic obliteration (n = 4), or retrograde transcaval obliteration (n = 4).
RESULTS. In all patients, complete obliteration or nearly complete obliteration was confirmed angiographically, and symptoms related to portal–systemic encephalopathy improved after treatment. Complications were observed in three patients: adhesive ileus in a patient treated by transileocolic obliteration and thrombosis of intrahepatic portal branches in two patients treated by percutaneous transhepatic obliteration.
CONCLUSION. On angiography, two types of intrahepatic portosystemic venous shunt were seen: intrahepatic portal venous–hepatic venous communication and intrahepatic portal venous–perihepatic venous communication. Transcatheter embolization is effective for treatment of intrahepatic portosystemic venous shunt. Retrograde transcaval obliteration is the least invasive technique and is recommended as the first choice for treatment of portosystemic venous shunt except in patients with multiple shunts.
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Conservative therapy (restriction of protein, ingestion of lactulose, oral administration of nonabsorbable antibiotics) [4], surgery (portal vein ligation or hepatic lobectomy), and transcatheter embolization have been used for the treatment of intrahepatic portosystemic venous shunt. Transcatheter embolization is a well-established, useful, and less invasive treatment for several vascular diseases. In this report, we describe methods of embolization with three approaches in respective types of intrahepatic portosystemic venous shunt, and we refer to the pathogenesis of the condition based on angiographic findings.
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Laboratory test results and transcatheter portal venous pressure measurements were as follows: serum ammonium ratio, 1.50–5.00 (mean, 2.65); Fischer's ratio, 0.94–1.65 (mean, 1.31); and portal venous pressure, 5.0–18.0 cm H2O (mean, 11.0 cm H2O). Serum ammonium ratios are defined as ratios of serum ammonium levels relative to normal values because the units and normal values differed among the institutions where patients were treated.
Transcatheter Embolization
Transcatheter embolization was performed via one of the following three
access routes: transileocolic obliteration, percutaneous transhepatic
obliteration, and retrograde transcaval obliteration. These access techniques
are described and are illustrated in Figures
1A,
1B,
1C.
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Transileocolic obliteration.—After exposure of the distal ileum under a small abdominal incision, a catheter was advanced into the portal venous system via the ileocolic vein.
Percutaneous transhepatic obliteration.—After percutaneous puncture of the intrahepatic portal branch under sonographic guidance, a catheter was advanced into the portal venous system.
Retrograde transcaval obliteration.—Two catheters were advanced in a retrograde manner into the portal venous system via bilateral transfemoral venous access. One flexible and straight catheter (Tracker 38, BSJ, Tokyo, Japan) was advanced into the main portal vein through the shunt to obtain a portogram and measure portal venous pressure before and during embolization. Another catheter was used for placement of embolic materials.
Retrograde transcaval obliteration and percutaneous transhepatic obliteration were performed with the patient under local anesthesia, and transileocolic obliteration were performed with the patient under epidural anesthesia.
These approaches were selected as follows: If the patient had one large shunt or a few shunts, retrograde transcaval obliteration was selected as the access route for the initial treatment. If we failed with this approach, another approach was attempted. If the patient had multiple shunts in a unilateral lobe, percutaneous transhepatic obliteration was selected. Transileocolic obliteration was selected only if multiple shunts were present in the bilateral lobe or if treatments with other approaches had failed.
Embolization was performed by transileocolic obliteration in two patients, percutaneous transhepatic obliteration in four patients, and retrograde transcaval obliteration in four patients. Several embolic materials including Gianturco coils (William Cook Europe, Bjaeverskov, Denmark), detachable balloons (BSJ), and microcoils were used. Four patients were treated using Gianturco coils only, one was treated with Gianturco coils and detachable balloons, and five were treated with Gianturco coils and microcoils (fibered platinum coils, Detach Coil System [William Cook Europe], or both). Three to 30 coils that ranged from 5 to 15 mm in diameter were used in each patient. When a 5-French catheter could not be advanced into the shunt vessels because of their extreme tortuosity, we used microcatheters and microcoils. As a follow-up examination within 3–12 months after the procedure, CT, sonography, or both were performed. The clinical follow-up period ranged from 24 to 156 months.
Evaluation
All data including clinical data, radiologic findings, and clinical
outcomes were collected retrospectively. The angiographic findings evaluated
by three radiologists were the type of drainage vein, multiplicity, and
associated intrahepatic venous abnormalities. The intrahepatic portosystemic
venous shunt was classified by the type of drainage vein and multiplicity.
Possible approaches for several types of shunt, their technical success rates,
and complications were investigated. We evaluated the effects of these
procedures on clinical symptoms, laboratory test results, and portal venous
pressures. Clinical symptoms, except for consciousness level, were evaluated
without any scale by degree of patient's complaint. Consciousness level was
evaluated using the Glasgow Coma Scale. Laboratory tests included serum
ammonium ratios and Fischer's ratios. The changes in these data were analyzed
using Wilcoxon's signed rank test.
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Intrahepatic portosystemic venous shunts were divided into two types according to the drainage vein. One was a communication between the intrahepatic portal vein and the hepatic vein, whereas the other was a communication between the intrahepatic portal vein and the inferior vena cava via the perihepatic veins (adrenal vein or inferior phrenic veins). The former type of shunt was identified in eight patients including two patients with multiple shunts. None of the cases of intrahepatic portal venous–hepatic venous shunt were associated with liver cirrhosis. Portograms or hepatic venograms showed the eight cases were associated with intrahepatic vein anomalies including five portal vein aneurysms (Fig. 2), one portal vein anastomosis (Fig. 3), and two hepatic vein anastomoses (Fig. 4). The latter type of shunt, the portal venous–perihepatic venous shunt, was observed in two patients with liver cirrhosis.
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Three of the five patients with multiple intrahepatic portosystemic venous shunts underwent percutaneous transhepatic obliteration. In the remaining two patients, retrograde transcaval obliteration was tried but failed initially because of technical difficulty in approaching the shunts. These two patients were subsequently treated by transileocolic obliteration (Figs. 5A, 5B). One of the five patients with a single shunt underwent percutaneous transhepatic obliteration. Because the shunt was not completely obliterated after the initial procedure, reembolization was subsequently performed and the shunt was completely occluded. The remaining four patients were treated by retrograde transcaval obliteration (Figs. 6A, 6B). Reembolization was required in one of these patients because of residual shunt flow. In nine of the 10 patients, intrahepatic portosystemic venous shunts were shown to be completely obliterated on angiograms obtained after the obliteration procedures. Nearly complete obliteration was achieved in the remaining patient who had multiple shunts.
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Procedure-related complications were observed in three patients: adhesive ileus was seen in a patient treated by transileocolic obliteration a few days after the procedure, occlusion of the left portal vein due to coil migration was found in a patient treated by percutaneous transhepatic obliteration, and thrombosis of the left portal venous branch related to the puncture procedure was observed in a patient treated by percutaneous transhepatic obliteration. The latter two complications were seen on follow-up CT after the procedure and did not cause any clinical symptoms. No other complications, including peritoneal complications, were encountered after the treatments.
Symptoms related to portal–systemic encephalopathy completely disappeared in eight patients and improved in two patients after treatment. Serum ammonium ratios significantly decreased and Fischer's ratios increased after embolization (Figs. 7A and 7B). The portal venous pressure tended to increase to levels above those recorded before treatment (Fig. 7C). In the two patients with liver cirrhosis, the pressures after treatment were above the reference value.
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Although surgical occlusion had been used for treatment of patients with this condition in the past [20, 23], transcatheter embolization and its usefulness have been reported in recent years [24–28]. In our patients, clinical symptoms and laboratory data improved immediately after occlusion treatment. Although the portal venous pressures recorded after treatment tended to be higher than the levels before treatment, this relative increase in pressure was not associated with overt clinical problems.
Transcatheter embolization was performed using one of three routes to access the intrahepatic portosystemic venous shunts: transileocolic obliteration, percutaneous transhepatic obliteration, or retrograde transcaval obliteration. Of the patients in our study group, two with multiple shunts underwent transileocolic obliteration. This procedure offers the easiest control of catheters through its anterograde access route. On the other hand, transileocolic obliteration is the most invasive among the three techniques used by our team because it requires an abdominal incision with the patient under general anesthesia or epidural tubing. Furthermore, this procedure carries the risk of adhesion because it requires an abdominal incision. One of our patients experienced adhesive ileus after the procedure. Therefore, transileocolic obliteration should be limited to patients with multiple shunts located in both lobes of the liver.
Percutaneous transhepatic obliteration is useful for patients with contralateral distribution of shunts because it offers good catheter control of the portal vein contralateral to the punctured side. In our patients, three with multiple shunts in identical segments and one with a single shunt underwent percutaneous transhepatic obliteration. The procedure resulted in successful and complete obliteration as confirmed angiographically. Although percutaneous transhepatic obliteration is a relatively invasive technique, Ohta et al. [29] reported that 16.5% of their patients treated using percutaneous transhepatic catheterization developed procedure-related complications.
Retrograde transcaval obliteration is the least invasive technique, but it has some applicable limitations with regard to the type, number, and location of intrahepatic portal systemic venous shunts. The presence of a large shunt close to the inferior vena cava allows easy catheterization of the main portal vein and retrograde portography to confirm the shunt and embolization. Because the inferior vena cava and the proximal portion of the hepatic vein have relatively large diameters, supporting catheters during placement of embolic material is difficult. Therefore, the catheter type and shape and the embolic material should be selected carefully. We recommend the use of a preshaped catheter adjusted to the hepatic vein, and detachable coils or a combination of microcatheters and microcoils. In our group, four patients with a single shunt and one patient with two shunts in the adjacent hepatic vein were successfully treated by retrograde transcaval obliteration. We believe that this technique should be applied to patients with a small number of shunts.
The cause of intrahepatic portosystemic venous shunt is not completely understood; however, two major theories have been proposed. The first is the congenital origin theory, which suggests the persistence of the communication between the portal and hepatic venous systems that occurs during embryonal development. The second is the acquired theory, which suggests the shunt results from portal hypertension, trauma, or rupture of a portal vein aneurysm. Intrahepatic portosystemic venous shunt in patients who do not have liver cirrhosis or a history of trauma are thought to be congenital in origin. Embryologically, the intra- and extrahepatic portal venous systems develop by the selective persistence of vitelline and umbilical systems between the fourth week and third month of fetal life (Figs. 8A, 8B, 8C, 8D). In the congenital origin theory, intrahepatic portosystemic venous shunt is thought to represent persistent communication between cranial and caudal hepatic sinusoids formed by vitelline veins and umbilical vein.
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Macroscopically evident intrahepatic portosystemic venous shunts have been classified according to their morphology [1, 4–6]. In the our study, we divided the intrahepatic portosystemic venous shunts into two types on the basis of pathogenic mechanisms. One is a shunt that consists of an intrahepatic portal venous–hepatic venous pathway, whereas the other is a shunt that consists of an intrahepatic portal venous–perihepatic venous pathway that includes the inferior phrenic veins, adrenal vein, and paraumbilical veins.
Intrahepatic Portal Venous–Hepatic Venous Pathway
This type of intrahepatic portosystemic venous shunt is depicted as tubular
or aneurysmal communication (single or multiple) between intrahepatic portal
veins and hepatic veins. To our knowledge, 42 cases have been reported in the
English-language literature [1,
2,
4–21,
24,
30–39].
These cases include 31 simple types and 11 multiple types. Portal vein
aneurysms were reported in 29 (69%) of these 42 cases. Most of these cases
(76%) were not associated with liver cirrhosis. Eight of our patients had this
type of shunt. Six (75%) of these patients had neither cirrhosis nor any other
hepatic disease. Associated anomalies of the hepatic vessels, which included
portal vein aneurysm, hepatic venous anastomosis, and portal vein anastomosis,
were observed (Figs. 2,
3,
4). Chagnon et al.
[2] indicated that portal vein
aneurysms including intrahepatic portosystemic venous shunts are congenital.
The latter two anomalies have not, to our knowledge, been reported previously.
These anomalies are thought to be formed in the hepatic sinusoid during fetal
development. Because of the low rate of coexisting liver cirrhosis and high
rate of coexisting anomalies, intrahepatic portal venous–hepatic venous
shunts are likely to be of the congenital origin type.
Intrahepatic Portal Venous–Perihepatic Venous Pathway
Radiologically, this type of intrahepatic portosystemic venous shunt shows
some communications between the intrahepatic portal vein and perihepatic
veins, and it drains into the inferior vena cava. Intrahepatic portosystemic
venous shunts through persistent paraumbilical veins are occasionally
encountered in patients with cirrhosis. Paraumbilical veins (also called veins
of Sappey) are known as potential communications between the intrahepatic
portal vein and veins of the abdominal wall
[40]. Other perihepatic veins,
such as the inferior phrenic veins and capsular vein, might constitute the
communicating venous system and form portosystemic venous shunt in this
type.
Intrahepatic portosystemic venous shunt between the right portal vein and inferior vena cava via venous structures around the right lobe are less common. To our knowledge, 22 cases of this type have been reported in the English-language literature [1, 3, 21, 22, 31, 32, 41–48], and these shunts were described as being located in the bare area and posteroinferior aspect of the right lobe. A high incidence of liver cirrhosis (71.4%) is reported in patients with this type of shunt. Our two patients with this type of shunt had liver cirrhosis. Because of the high rate of coexisting liver cirrhosis, the acquired theory could explain this type of shunt, and the perihepatic veins are thought to develop in association with portal hypertension as intra- and extrahepatic collateral pathways from existing venous structures including paraumbilical veins, inferior phrenic veins, and adrenal vein.
Intrahepatic portosystemic venous shunts are divided into two main types: intrahepatic portal venous–hepatic venous communication and intrahepatic portal venous–perihepatic venous communication. On the basis of the angiographic findings and clinical manifestations, the former type is considered to be of congenital origin, whereas the latter is thought to be an acquired condition associated with portal hypertension. Selection of the most suitable access route based on the morphology of shunt is an important aspect of treatment of intrahepatic portosystemic venous shunt by transcatheter embolization. In selected cases, retrograde transcaval obliteration is a useful, safe, and less invasive technique than the other options.
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