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1 Department of Radiology, Hospital Clinic, C/Villarroel, 170, Barcelona 08036,
Spain.
2 Laboratori d'Hemodinàmica Hepàtica, Institute of Digestive
Diseases, Hospital Clinic of Barcelona, Barcelona 08036, Spain.
Received January 14, 2003;
accepted after revision June 10, 2003.
Address correspondence to X. Bargalló
(xbarga{at}clinic.ub.es).
Abstract
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MATERIALS AND METHODS. Our study included a group of 16 patients with Budd-Chiari syndrome. We compared this patient group with a control group of 40 patients with cirrhosis and 66 healthy subjects without liver disease. On sonography, we measured the diameter of the caudate lobe and the presence and diameter of the caudate vein. These measurements were then compared for both groups.
RESULTS. In half of the patients with Budd-Chiari syndrome, sonography showed a visible caudate vein (3–21 mm; mean, 7.3 mm; median, 4.6 mm). However, in the control group, spontaneous visualization was seen in only eight (7.5%) of 106 subjects, none of whom had cirrhosis. The caudate lobe was larger in patients with cirrhosis than in healthy subjects. Likewise, in patients with Budd-Chiari syndrome, the caudate lobe was larger than that in patients with cirrhosis.
CONCLUSION. When sonography reveals a caudate vein equal to or larger than 3 mm in diameter in the appropriate clinical setting, one should strongly suspect Budd-Chiari syndrome.
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The caudate lobe has a special relevance in patients with Budd-Chiari syndrome because in many cases, the liver venous drainage is preserved through the caudate vein. Thus, the caudate vein receives blood not only from the caudate lobe but also from the other parts of the liver through collateral vessels, leading to an enlargement of both the vein and the lobe. The existence of an evident caudate vein in Budd-Chiari syndrome has been reported [4], but its relevance as a diagnostic sign has not been evaluated. The aim of this study was to evaluate the diagnostic accuracy of the caudate vein and lobe measurements as a diagnostic sign of Budd-Chiari syndrome.
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Budd-Chiari Group
Budd-Chiari syndrome was diagnosed in 21 patients at our institution during
a 10-year period. The diagnosis was performed by means of X-ray venography
performed through retrograde cannulation of hepatic veins and biopsy. The
cause of Budd-Chiari syndrome was polycythemia vera (n = 9),
essential thrombocytosis (n = 3), myelofibrosis (n = 1),
paroxysmal nocturnal hemoglobinuria (n = 4), primary antiphospholipid
syndrome (n = 3), and idiopathic (n = 1). Two patients, one
with polycythemia vera and one with essential thrombocytosis, also had a
factor V Leiden mutation. Sixteen of 21 patients with Budd-Chiari syndrome
were included in the study because all sonographic images could be retrieved
from the PACS (picture archiving and communication system) and evaluated
offline. This group consisted of six men and 10 women (age range, 28–60
years; mean age [± SD], 42 ± 10 years).
We divided patients with Budd-Chiari syndrome into two subgroups according to the time of diagnosis to assess the relationship between the duration of the disease and the presence of the caudate vein. The patients diagnosed between 1991 and 1997 (n = 9) were the first subgroup, and those diagnosed between 1998 and 2001 (n = 7) were the second one. We chose these subgroups because we had no way of knowing when the caudate vein appeared; until 1998, we had not specifically searched for this vein.
Control Group
One hundred fourteen consecutive patients were prospectively studied with
color Doppler sonography. Eight patients were excluded because they had a
substernal left hepatic lobe that prevented the performance of the caudate
lobe measurements in normal breathing. Therefore, the control group consisted
of 106 patients and included 66 patients without clinical and laboratory
evidence of chronic liver disease (31 men and 35 women; age range, 23–93
years; mean age, 61 ± 16 years) and 40 patients with cirrhosis (30 men
and 10 women; age range, 36–89 years; mean age, 62 ± 13
years).
Patients in the cirrhosis group had been referred for the sonography study to screen for focal hepatic lesion or to undergo a preoperative study before hepatic transplantation. The cause of their cirrhosis was hepatitis C (19/40), hepatitis B (2/40), alcohol abuse (8/40), hepatitis C and alcohol abuse (1/40), primary biliary cirrhosis (2/40), cardiac (1/40), or cryptogenic origin (7/40). Cirrhosis was confirmed by sonographic evaluation in combination with clinical evidence of portal hypertension (earlier or actual decompensation or esophageal varices or both).
Procedure
In the Budd-Chiari syndrome group, the PACS sonography database was
searched for images of the caudate lobe. Data analyzed included the caudate
lobe longitudinal and anteroposterior diameters. The presence or absence of
the caudate vein and its diameter (in gray scale) were assessed.
In the control group, the variables analyzed were age, sex, the longitudinal and anteroposterior caudate lobe diameters, and the visualization of the caudate vein on both gray-scale sonography and color Doppler sonography. When the vein was visible, the diameter and branching were documented.
Sonography was performed with the same equipment (Powervision, Toshiba, Nasu, Japan) with a multifrequency convex transducer (3–6 MHz). We performed the examination with all patients in the supine position and measured the two maximal diameters of the caudate lobe in the sagittal epigastric line (Fig. 1A).
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We scanned the caudate lobe in transverse and longitudinal planes searching for the caudate vein. When present, the diameter of the vein was measured following the longitudinal axis of the vein at 1 cm of its opening to the inferior vena cava.
All data were statistically analyzed with SPSS software (Statistical Package for the Social Sciences, Chicago, IL). Continuous variables were expressed as mean ± SD. The Student's t test was used for comparing groups. Given the small size of the population with Budd-Chiari syndrome, a nonparametric test (Mann-Whitney U test) was used to determine statistical differences. A difference was considered significant when the p value was less than 0.05.
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When comparing the two subgroups of Budd-Chiari syndrome patients (before and after 1998), we found some differences, although without statistical power, which was probably because of the small number of patients (Table 2).
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Caudate Vein Visualization
Eight (50%) of 16 patients in the Budd-Chiari syndrome group had a caudate
vein that was easily seen (Figs.
2,3A,
3B,4),
the diameter of which ranged from 3 to 21 mm (mean, 7.3 mm; median, 4.6 mm).
In contrast, the caudate vein was visualized spontaneously (in gray scale) in
eight (7.5%) of 106 patients in the control group, but in all cases, it
measured less than 3 mm (Figs.
1B and
5). No caudate vein in the
group of patients with cirrhosis was visualized spontaneously. No branching
was seen.
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We found the sensitivity and specificity of visualizing the caudate vein on
sonography as a diagnostic sign of Budd-Chiari syndrome to be 50% and 94%,
respectively. The positive predictive value was 57%, and the negative
predictive value was 93%. If we consider the diameter of the vein (
3 mm),
the specificity and positive predictive value reached 100%.
In the Budd-Chiari syndrome group, those patients in whom the caudate vein was visualized had larger caudate diameters than those in the remainder of the patients with Budd-Chiari syndrome. The diameters were 83.9 ± 21 mm and 43.5 ± 9 mm when the vein was seen, and 62.1 ± 16 mm and 33.9 ± 10 mm in the subgroup without caudate vein visualization, showing statistically significant differences between them. When analyzing the two subgroups of patients with Budd-Chiari syndrome, we found that only two patients of the recent group (patients diagnosed after 1998) had visible caudate veins.
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The subacute or chronic form is more difficult to diagnose because the clinical picture is variable, depending on the number of hepatic veins affected and the ability of the liver to develop collateral circulation. Color Doppler sonography findings in these forms include a fibrous tract replacing the obstructed hepatic vein, a fragmented vein with flow inversion, or new venous vessels that drain subcapsular circulation to another hepatic vein or directly to the inferior vena cava. This collateral circulation is the most sensitive feature for the diagnosis, being present in more than 80% of patients [6]. It is not unusual for patients with chronic forms of Budd-Chiari syndrome to be diagnosed with liver cirrhosis. In fact, we consider Budd-Chiari syndrome when chronic liver disease remains unexplained after other common or uncommon causes have been excluded [6]. Such patients may be referred to the sonography unit for hepatocellular carcinoma screening or for study of mildly abnormal findings on liver tests. In this setting, a shrunken fibrotic liver can be observed on sonography, and the assessment of hepatic vein patency may be difficult to perform or may even be overlooked. In this scenario, the visualization of an evident caudate vein on gray-scale sonography may help to address the attention of the sonographer to this entity. The presence of the caudate vein in Budd-Chiari syndrome has been previously mentioned [4], although its frequency and characteristics have not been studied. To our knowledge, ours is the first study in the literature focused on this matter. According to our results, the great specificity and negative predictive value of this sign would allow us to diagnose Budd-Chiari syndrome if a caudate vein larger than 2 mm is seen on gray-scale sonography. The low sensitivity (50%) may be in part due to the retrospective nature of the study and the fact that in some cases, the caudate vein can be obstructed.
The frequency of caudate lobe hypertrophy in Budd-Chiari syndrome has not been accurately established, although some authors reported that the caudate lobe is markedly enlarged in about 50% of patients with this condition [10]. Thus, it has been reported that scintigraphy may help in making the diagnosis because of the typical appearance of increased uptake by the enlarged caudate lobe, but this sign is identified in only 17% of patients with this condition [7].
Given that the anteroposterior diameter of the caudate lobe may be up to 35 mm in healthy people, our patients with Budd-Chiari syndrome had a mean diameter greater than this limit (38.7 ± 10 mm). All except two patients fulfilled this criterion, and the two had a diameter of 33 mm, closer to the limit.
However, although caudate lobe size was larger in the patients with Budd-Chiari syndrome than in patients in the cirrhotic group, an overlap was observed. Thus, this parameter was not sensitive enough to discriminate both diseases.
Although no satisfactory hypothesis has been provided explaining why some cirrhotic livers develop caudate lobe hypertrophy, some studies have suggested that the degree of hypertrophy of the caudate lobe may be important in the maintenance of hepatic function [11, 12]. Similarly, the mechanism of caudate lobe hypertrophy in Budd-Chiari syndrome remains unclear, although it could be related to the fact that the caudate lobe would allow blood to be drained through a hypertrophied caudate vein. In our study, the differences in the size of the caudate lobe in the two subgroups of patients with Budd-Chiari syndrome do not have statistical power very likely because of the small number of patients. The duration of disease could influence the size of the caudate lobe. We hypothesize that the changes in the caudate lobe are related to the patency of the caudate vein and to the ability of the liver to form new vessels, because there are patients with long-term disease without collateral circulation. Obviously, those patients without newly formed collateral vessels will have a worse prognosis, and transjugular intrahepatic portosystemic shunt placement or orthotopic liver transplantation is warranted.
Only two of the patients recently diagnosed with Budd-Chiari syndrome had a
visible ( 3 mm) caudate vein. This finding is in agreement with the
shorter clinical evolution of these patients and the fact that the size of the
caudate lobe is also smaller in this subgroup.
In the past, the caudate vein was considered too small to be seen on sonography [13]. Only one report in the literature focused on sonography of the caudate vein [14]. Four patients with an enlarged (3–5 mm) caudate vein were reported. All these patients had an elevated central venous pressure greater than 18 mm Hg (normal pressure, 6 mm Hg), accounting for the visualization. Patients with chronic liver congestion could have dilated caudate veins, in a manner similar to that in which the remainder of hepatic veins are involved in this disorder. Only one of our control patients had cardiac cirrhosis; therefore, we cannot draw conclusions about this issue. Further studies are needed to establish the influence of chronic liver stasis on the size of the caudate vein. Moreover, patients with dilated caudate veins and Budd-Chiari syndrome will have a lack of visualization of the rest of the hepatic veins. Conversely, patients with heart failure will have dilatation of all hepatic veins, making it difficult to confuse these diseases.
In summary, our study shows that the visualization of the caudate vein
( 3 mm in diameter) on gray-scale sonography strongly suggests the
diagnosis of Budd-Chiari syndrome in the appropriate clinical setting, except
for those patients with cardiac failure. Preliminary data from our unit have
shown that the use of color Doppler sonography may increase the visualization
of the caudate vein. However, the color Doppler data would not provide
additional diagnostic support because this increase in the caudate vein
detection is also observed in healthy control subjects and in patients with
cirrhosis.
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