| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Department of Medicine and Department of Radiology, Abdominal Imaging Section,
University of California at San Francisco, Box 0628, 505 Parnassus Ave., San
Francisco, CA 94143-0628.
2 Department of Radiology, Mahidol University, 2 Prannok Rd., Bangkok, 10700
Thailand.
3 Department of Medicine, Division of Gastroenterology, University of California
at San Francisco, Box 0538, 505 Parnassus Ave., San Francisco, CA
94143-0538.
Received April 10, 2003;
accepted after revision June 26, 2003.
Address correspondence to F. V. Coakley
(fergus.coakley{at}radiology.ucsf.edu).
Abstract
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
MATERIALS AND METHODS. We retrospectively identified 36 patients with cirrhosis, 18 with hepatopetal and 18 with hepatofugal flow in the main portal vein, who underwent contemporaneous abdominal sonography and CT. Two independent observers evaluated the following features on the randomized CT studies: diameter of the portal, splenic, and superior mesenteric veins; spleen size; and the presence of ascites, varices, or arterial phase portal venous enhancement. These data were correlated with the flow direction seen on sonography.
RESULTS. A small main portal vein was the only sign significantly
(p 
0.05) predictive of hepatofugal flow by univariate and
multivariate analyses. Observers 1 and 2 recorded a portal vein diameter of
less than 1 cm in eight (44%) and seven (39%) of the 18 patients with
hepatofugal flow compared with one (6%) and none of the 18 patients with
hepatopetal flow, respectively (p < 0.02). Receiver operating
characteristic analysis using the size of the portal vein to predict flow
direction revealed an area under the curve of 0.83 for observer 1 and 0.74 for
observer 2.
CONCLUSION. A diameter of less than 1 cm for the main portal vein is highly specific, although not sensitive, for hepatofugal portal venous flow in patients with cirrhosis. This sign may be useful when sonography is limited, or this sign may prompt sonographic assessment in patients not known to have hepatofugal flow.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
The mean age of patients in the hepatopetal group was 59 years (range, 44–80 years) versus 51 years (range, 17–73 years) in the hepatofugal group. The hepatopetal group comprised 10 men and eight women, and the hepatofugal group comprised seven men and 11 women. In the hepatopetal group, the diagnosis of cirrhosis was established by histology in six patients and on clinical grounds in 12; in the hepatofugal group, cirrhosis was established by histology in five patients and on clinical grounds in 13. Of those patients without histologic confirmation, cirrhosis was diagnosed by a gastroenterologist in all but two, both of whom had hepatofugal portal venous flow. In these two patients, cirrhosis was diagnosed on the basis of clinical evidence including a history of severe alcohol abuse; gross findings of cirrhosis on imaging studies; and large varices, ascites, hypoalbuminemia, and coagulopathy. The causes for cirrhosis in the group with hepatopetal flow and in the group with hepatofugal flow, respectively, included the following: chronic viral hepatitis, 11 and four patients; viral hepatitis and ethanol abuse, two patients and one patient; ethanol abuse alone, 0 and six patients; autoimmune hepatitis, one and three patients; nonalcoholic steatotic hepatitis, one patient and 0 patients; primary sclerosing cholangitis, one and three patients; and cystic fibrosis, 0 and one patient. Cirrhosis was cryptogenic in two patients with hepatopetal flow.
The median time between sonography and CT was 23 days (range, 0–148 days) in the hepatopetal group and 3 days (range, 0–97 days) in the hepatofugal group. If sonography had been performed more than 48 hr before or after the CT examination (hepatopetal group, n = 14; hepatofugal group, n = 9), we identified a second Doppler sonographic study of flow direction in the main portal vein for each patient so that sonography occurred before and after the CT examination (hepatopetal group, n = 9; hepatofugal group, n = 5). Alternatively, if CT had not been performed between the sonographic examinations, we identified the two sonographic examinations closest in time to the CT examination (hepatopetal group, n = 2; hepatofugal group, n = 2). In these patients, the time lag between CT and sonography for the two patients with hepatopetal flow was 3 and 31 days, and for the two patients with hepatofugal flow, the lag was 37 and 62 days. Additional studies were not available for the remaining three hepatopetal and two hepatofugal patients. All additional sonographic studies evaluated confirmed the flow direction seen on the initial study.
Imaging Technique
All CT examinations were performed on multidetector scanners (LightSpeed or
HiSpeed, General Electric Medical Systems, Milwaukee, WI). Thirty-four of the
36 patients received 150 mL of IV iohexol (Omnipaque 350, Nycomed Amersham,
Princeton, NJ), and images were acquired in the portal venous phase of
enhancement (70-sec scan delay with 5-mm slice collimation). Images were also
acquired in the arterial phase of enhancement (45-sec scan delay with 2.5-mm
slice collimation) in 20 of these patients. Two patients (one with hepatopetal
and one with hepatofugal flow) did not receive IV contrast material. All
patients received oral diatrizoate meglumine (Hypaque, Nycomed Amersham). All
images were contiguous. Color Doppler sonography of the direction of flow in
the main portal vein was performed using a scanner (Sequoia 512, Acuson
Solutions, Mountain View, CA) with a 1.75- to 4-MHz sector transducer (4V1,
Acuson Solutions) or a 2.5- to 4-MHz sector transducer (4V2, Acuson
Solutions).
CT Interpretation
Two radiologists independently reviewed the randomized CT images of all 36
patients on a PACS (picture archiving and communication system) workstation
(Impax DS 3000 [release 4.1], Agfa, Mortsel, Belgium). Observers were unaware
of clinical and sonographic findings. Both observers recorded the following CT
signs: short-axis diameter of the main portal vein, which was measured midway
between the splenoportal confluence and the portal vein bifurcation in the
porta hepatis; maximum short-axis diameter of the superior mesenteric vein,
measured on the first image that was clearly inferior to the splenoportal
confluence; diameter of the splenic vein, measured adjacent to the midportion
of the pancreatic tail; presence or absence of ascites; presence or absence of
varices; and spleen size, recorded as the maximum axial diameter. In addition,
for multiphase CT examinations (n = 20), the presence or absence of
early (i.e., arterial phase) enhancement of the main portal vein was
recorded.
Data Analysis
Statistical analysis was performed using statistical analysis software (SAS
version 8.1, SAS, Cary, NC). Continuous data (vessel diameters and spleen
size) were examined by univariate analysis using the two-tailed Cochran
t test. Noncontinuous data (all other categories) were examined using
Fisher's exact test. The univariate analyses were performed separately for the
data for each observer. All p values of 0.05 or less were considered
significant. Interobserver agreement for categorical data was measured with
kappa statistics [16].
Interobserver agreement for continuous data was assessed using Bland-Altman
regression [17] with
Bradley-Blackwood p values
[18]. Multivariate analysis
was performed using logistic regression with a generalized linear model to
account for the presence of two observers. Parameters were selected in a
stepwise fashion with a type 3 significance level of 0.05 or less required for
factors to remain in the model. Receiver operating characteristic (ROC)
analysis and area under the ROC curve (Az) calculations
were performed to evaluate predictive models.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
|
Observer 1 found that the main portal vein measured less than 1 cm in eight (44%) of 18 patients with hepatofugal flow, but in only one (6%) of 18 patients with hepatopetal flow (p < 0.02). Thus, the sensitivity of this sign for predicting hepatofugal flow was 44% and the specificity was 94%. Observer 2 found that the main portal vein measured less than 1 cm in seven (39%) of 18 patients with hepatofugal flow and 0 of 18 patients with hepatopetal flow (p < 0.01), for a sensitivity of 39% and a specificity of 100%.
The 1-cm measurement was the largest (most sensitive) threshold that could be used to predict hepatofugal flow without significantly reducing specificity, given that both observers measured the main portal vein at or slightly above 1 cm in several patients with hepatopetal flow (Fig. 1). A lower threshold would reduce sensitivity without significantly increasing specificity, and a higher threshold would greatly reduce specificity with only mildly increasing sensitivity (Fig. 2). A representative case illustrates the finding of a small portal vein in a patient with hepatofugal flow (Fig. 3A, 3B). Arterial phase enhancement of the portal vein was seen in only one patient; in that patient, flow in the portal vein was hepatopetal on sonography 1 day before CT (Fig. 4A, 4B).
|
|
|
|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Arterial phase enhancement of the portal vein has been reported as a sign of hepatofugal flow [1, 22]. In our study, this sign was present in only one of 20 patients undergoing CT with arterial phase contrast enhancement, and Doppler sonography of this patient 1 day before CT showed hepatopetal flow. The finding of arterial phase enhancement of the portal vein on CT in a patient with hepatopetal portal venous flow on sonography is puzzling but might be explained by transient changes in flow direction in the portal venous system. Such flow changes can occur spontaneously in cirrhotic patients [23], in the postprandial state [24, 25], and during hepatic arteriography [26]. Disturbance of baseline physiology during abdominal CT, such as due to breath-hold technique or bolus administration of IV contrast material, may alter portal venous hemodynamics. For example, contrast administration might elevate right heart and hepatic vein pressures, and the subsequent increased shunting of hepatic arterial blood into the portal venous system may result in temporary hepatofugal flow.
Our study has several limitations. The sample size was small and may have restricted the power of the study to detect differences between the hepatopetal and hepatofugal groups. For example, the prevalence of ascites and varices was higher in patients with hepatofugal flow, but these differences did not achieve statistical significance. These factors might exhibit an association with hepatofugal flow in a larger study. CT and sonography were not immediately contemporaneous. The lag between the examinations may have lowered the sensitivity of the study for additional predictors of hepatofugal flow, although the possible effects of the time difference would be expected to apply to both hepatopetal and hepatofugal groups of patients. The lag between studies would not be expected to generate spurious associations and should not detract from the finding that a small portal vein size is associated with hepatofugal portal venous flow. Analysis of additional sonography examinations of the study population provided evidence that the direction of portal venous flow in our subjects was stable. Therefore, it is reasonable to expect that the direction of flow at the time of CT would be accurately predicted by the contemporaneous sonographic examination that was evaluated.
High interobserver consistency was not seen for the measurement of spleen size and assessment for the presence or absence of varices. The discrepancy in identification of varices between observers could be explained by a greater sensitivity of observer 2 for varices in borderline cases, given that all cases identified as positive by observer 1 were also called positive by observer 2, but not vice versa. The interobserver variation regarding spleen size may have resulted from the complex and partly subjective methodology used, which involved identifying the maximal single dimension of the spleen on any axial image.
This study did not seek to measure the prevalence of hepatofugal flow in the entire population of cirrhotic patients, although this information would be required to determine predictive values. This is important given that our sign, although highly specific, is of limited sensitivity. The prevalence of hepatofugal flow in unselected cirrhotic patients has been previously estimated at 3.1–3.4% [2, 27], rising to 9% or more in patients with advanced cirrhosis [2, 28]. Finally, the diagnosis of cirrhosis was confirmed histologically in only about one third of the study subjects. However, most patients with a diagnosis of cirrhosis do not undergo histologic confirmation. Restricting the analysis to only those patients with a histologic diagnosis would have selected for substantially more diseased or symptomatic patients, possibly harming the generalizability of our results. Given that all patients in this study had significant risk factors for cirrhosis, had imaging features consistent with cirrhosis, and had either histologic confirmation of cirrhosis or had been assigned the diagnosis of cirrhosis at a tertiary care center (by a gastroenterologist in all but two cases), we believe that the probability of noncirrhotic patients existing within the study population is low.
In conclusion, our data suggest that a main portal vein diameter of less than 1 cm is highly specific for hepatofugal portal venous flow in cirrhotic patients, although the sensitivity of this sign is limited. If validated in prospective studies, this sign may be useful when sonography is limited or may prompt sonographic assessment in patients not known to have hepatofugal flow.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  P. T. Johnson and E. K. Fishman IV Contrast Selection for MDCT: Current Thoughts and Practice Am. J. Roentgenol., February 1, 2006; 186(2): 406 - 415. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
). Note that at
appropriate operating points, this sign is highly specific for hepatofugal
flow. Area under ROC curve (Az) was 0.83 for observer 1
and 0.74 for observer 2.
