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35i

Evaluation of Children for Liver Transplantation: Value of MR Imaging and Sonography

S. Bisset

George

Janet William

1111 L. Strife1

F. Balistreri2

Diagnostic imaging plays a major role in the diagnosis and treatment of chronic liver disease in children. Decisions regarding the need for sclerotherapy, palliative shunts, and anatomic suitability for hepatic transplantation are based on the upper abdominal anatomy. Thirty-six children with various forms of chronic liver disease were referred for diagnostic imaging, including MR and sonography. Each study was evaluated independently without knowledge of the other examination. The first six patients were evaluated retrospectively and the last 30 patients prospectively. The size of the portal vein and inferior vena cava varied in this population, with excellent agreement between sonography and MR. A 2-mm portal vein was shown only on MR imaging in two patients, but MR missed a 3-mm portal vein. Portosystemic collateral vessels also were evaluated and noted to be detected more readily with MR imaging (64%) than with sonography (22%). In particular, paraumbilical veins were detected more often with MR (28% vs 6% by sonography). Associated or coexisting anomalies were relatively common in children with chronic liver disease (14%). These included polysplenia (two cases), preduodenal portal vein (one), unilateral dysplastic kidneys (two), ureteropelvic junction obstruction (one), and splenic (one) and renal (one) cysts. MR imaging was more sensitive than sonography for detection of abnormal anatomy in this group of patients and should be considered the pretransplantation imaging technique of choice in children with end-stage liver disease. AJR

Received vision

March

February

2, 1990:

accepted

after re-

26, 1990.

‘ Department of Radiology. Children’s Hospital Medical Center and the University of Cincinnati College of Medicine, Elland & Bethesda Ayes., Cmcinnati, OH 45229-2899. Address reprint requests to G. S. Bisset Ill. 2 Division of Pediatric Gastroenterology and Nutrition, Children’s Hospital nati, OH 45229-2899. 0361 -803x/90/1

Medical

552-0351

0 American Roentgen Ray 5ociety

Center,

Cincin-

155:351-356,

August

1990

The advent and refinement of liver transplantation techniques has resulted in a substantial increase in the number of transplants performed. The paucity of donors has made careful selection of recipient candidates a crucial process. This process is undertaken by using a variety of imaging techniques. The major goal of pretransplantation imaging is to detect abnormalities that would preclude successful transplantation or necessitate modification of the standard surgical approach. In those patients with chronic end-stage liver disease who are treated medically, imaging may assist the hepatologist in answering basic questions: (i ) Are vances present and what is the extent? (2) Are unsuspected tumors present? (3) How diffuse is the liver parenchymal disease? (4) Is the patient anatomically suitable for hepatic transplantation? MR imaging has been used to evaluate portal venous anatomy [1 -5]. In prospective liver transplant recipients, however, sonography has been considered the primary screening procedure [i 6-8]. In our early experience with MR imaging in patients with end-stage liver disease, we demonstrated findings that were not previously documented by sonography. After several examinations were performed we elected to study the final group (n = 30) of patients prospectively, to evaluate whether MR imaging would add information to the sonognaphic examination. The purpose of this study was twofold: (i) to characterize, with MR imaging and sonognaphy, the abnormalities detected in children with end-stage liven disease and (2) to compare the two imaging techniques with regard to their ability to assess upper abdominal anatomy. ,

352

BISSET

Subjects

ET AL.

and Methods

AJR:155,

Sonographic

(Mountain Thirty-six ease

were

and

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consecutive referred

children

for

sonography,

i month

to

19 years

patients

retrospectively

irreversible,

an imaging

examination,

possible

transplantation.

before

studies were undertaken. performed between i987 Fifteen

with

chronic which

at the

initial

were

male

and

in the

first

six

examination

21 were patients

other

and

MR

age,

Data

5 years).

were

in the

last

30. All

patients

had

extrahepatic

(five

patients);

neonatal lism

atresia

chronic

hepatitis

(two

genic

biopsy-proved

biliary

patients);

cirrhosis,

active

(three

cirrhosis

diagnoses.

(i 3 patients);

hepatitis

patients);

congenital (two

tyrosinemia,

(three

inborn

hepatic

patients);

Diagnoses

fibrosis

and

(two

isolated

mitochondrial

in bile

metabolic

and obstructive

a choledochal

cyst.

2 months

of

ceptable

in patients

anatomic

change

ated

by

of acute

biliary

inferior

tract

Factors vena

and This

with

end-stage

cava

interval

liver

pediatric

examinations. disease

(i.e.,

evaluated

crypto-

of

Wilson

were was

since

two

studies

performed

were

evalu-

each

had clinical

(i)

cholecystitis) portal

(3) presence

blinded

and

vein

size

extent

to

the

evidence at the time

and

flow,

(2)

of portosystemic

collateral vessels, extent of hepatic

(4) gallbladder size, (5) presence of ascites, (6) parenchymal abnormalities, (7) systemic venous anomalies, (8) biliary obstructive pattern, and (9) presence of hepatic tumors. Pathologic correlation was available in i 6 patients who had undergone liver transplantation, three of whom have died. Any discordance noted, died

while

norenal tion

between after

review awaiting

shunting,

or have

had

operative of the

findings operative

and

transplantation. and

i 7 patients

transplantation

imaging

or autopsy One are

child

awaiting

evaluation

reports. has

undergone

possible

deferred.

A Fig. 1.-Transaxial spin-density-weighted MR image (SE 2000/20) through porta hepatis in a child with biliary atresia shows tiny portal vein (arrowhead) immediately posterior to gallbladder (arrow). This portal vein was not identified on sonography.

Two

porta

by

artery

Real-time

on patient

sector

size.

hepatis.

using

images

The

spectral

portal

where

vein

i 28

and

color

it crossed

LaboDoppler

with variable diameter

of portal

analysis

Acuson and

transducer

The direction

was scanned

an

Technology

was

venous flow

flow

analysis.

the portal

vein near

hepatis.

Twenty-one patients also had Doppler examinations of the portal vein in an attempt to characterize the direction of portal vein flow. patients

MR

were

randomly

examinations

Signa

selected,

at

the

discretion

of

the

were

unit. Initial coronal

performed

on

localizing

scans

a General

pulse sequence.

with two signal averages.

Electric

were obtained

i .5-T

with a spin-

A 256 x 128 matrix was

The second

pulse sequence

used

a TR of 2000 msec and TE of 20 and 80 msec. A 256 x 128 or 256 x 192 matrix

was

acquired,

plane. In the older children, gradient-recalled acquisition was

further

No patients cholangitis,

ac-

little

radiologists,

depending

determined

acquired dis-

considered

system.

with

with a 3.0- or 5.0-MHz

echo (SE) 600/20 (TR/TE)

posthepatitic

disease caused by

disease, The

included

patency,

patients);

sonography

be anticipated.

two

of the other

of study.

imaging another.

would

separately

results

MR one

metabo-

disorder,

ease, perinatal hemochromatosis, within

idiopathic acid

cases

WA)

in the porta

The hepatic

performed

VIII (Advanced

1990

sonographer.

deficiency

patients);

errors

was

These

included

alpha1-antitrypsin

Bothell, zones

was

CA) or ATL Mark

were obtained

measured

the

evaluated

prospectively

ratories,

images focal

imaging

examinations were ranged in age from (mean

female.

dis-

included

No

All MR and sonographic and i989. The patients

liver

examination

View,

August

obtained.

Gradient

moment

to diminish flow artifact. x 1 28 matrix with two

characterize filled

flow

with

two

Axial signal

nulling images

in the

axial

used

with

acquired

this

This sequence

patterns

and to distinguish

large

required

for MR examinations

sequence

a 256 was used to

by using

varices

from

air-

bowel.

Sedation

was

00 mg/kg)

(75-i 7 years

old

citrate)

peristaltic

administered

sedated as bowel

with described motion

subcutaneously

in patients

younger

than 2 years old, chloral hydrate

was used as an oral agent.

were

fentanyl

minimize was

averages,

was were

averages.

than 7 years old. In those younger

and

signal

when breath-holding was possible, a final 30/i2, with a flip angle of 25 degrees,

Children

IV medication

(sodium

[9].

previously artifact,

0.5-i

or IV in each

between

2 and

pentobarbital

In an attempt to .0 mg of glucagon

patient.

were children

Results

sple-

transplanta-

Portal vein size varied with patient age, body weight, and diagnosis. The sonographic and MR measurements of portal

B

Fig. 2.-A, Transaxial spin-density-weighted MR image (SE 2000/20) through porta hepatis in a child with biliary atresia shows tiny linear area of signal void (arrowhead). This represents a tiny portal vein. Other findings of chronic liver disease include small left hepatic lobe (LL) and dilated portosystemic collateral vessel (arrow). B, Tiny portal vein was not identified prospectively on transaxial sonogram through same area. In retrospect, this vein is identified (arrowhead) just anterior to inferior vena cava (IVC). Large portosystemic collateral vessel is noted (arrow).

AJR:155,

August

1990

END-STAGE

vein size were within 2 mm of one another. The largest portal measured i .6 cm in diameter. The smallest identifiable portal vein was 2 mm in diameter. In two children, in whom no identifiable portal vein was shown by sonography, 2-mm portal veins were seen on MR imaging (Figs. 1 and 2). In both cases, a portal vein diameter of 2 mm was documented at the time of transplantation. In two children, no portal vein was detectable by sonognaphy or MR. At exploration, a small (3mm) portal vein was isolated in one child; the second child is awaiting surgery. Portal vein flow patterns were evaluated by Doppler examination in 2i patients. This examination showed hepatopedal flow in i 5 patients, bidirectional flow in two patients, and hepatofugal flow in one patient. In three children, this examination was unsuccessful, because no portal vein was identified. Instead of flow void, MR signal was identified in four (i 1 %) f 36 patients on asymmetric first- and/or secondecho images (Fig. 3). This was presumed to be due to slow blood flow. In 35 of 36 patients, patent inferior vena cavae were demonstrated by MR imaging and sonography. In each patient, measurements by both techniques were within 2 mm of one another. In one patient there was an absence of the intrahepatic portion of the inferior vena cava with azygos continuation. Although this finding was readily detected by MR, the sonographic examination was inconclusive as to the exact nature of the intrahepatic venous drainage (Fig. 4). Portosystemic collateral vessels were identified in 23 (64%) of 36 patients on MR imaging and in eight (22%) of36 patients on sonognaphy (Figs. 5-7). Locations ofvarices included distal esophageal, gastric, retnopentoneal, splenic hilar, epidural, and penoportal regions. Paraumbilical veins were seen in 10 patients on MR imaging and in two patients on sonognaphy (Fig. 8). The gallbladder was absent in 12 of 1 3 patients with biliany atnesia and was small in the remaining patient with this vein

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PEDIATRIC

Fig. 3.-Transaxial spin-density-weighted MR image (SE 2000/20) through junction of splenic and portal veins. Increased signal intensity (arrow. head) within structures indicates slow blood flow. Also noted Is a markedly enlarged spleen (Sp).

LIVER

DISEASE

353

disease. There was agreement between sonognaphy and MR imaging in each case. In the patients without biliany atresia, sonography showed normal to slightly dilated gallbladders. In one child with chronic active hepatitis, a gallbladder was not cleanly identified by MR imaging. Ascites was identified by one or both imaging techniques in i 4 (39%) of 36 patients. In three children, the sonographic examination showed a small amount of ascites that was not seen on MR images. Seven patients had MR evidence of ascites or hepatic pencapsulan fluid collections, with normal sonographic examinations. Both techniques showed ascites in four patients. Liver parenchyma was assessed on the basis of echogenicity on sonography. Increased echogenicity was judged by comparison with renal cortex and examination of peniportal echo patterns. MR evaluation of the liver panenchyma was based on multifocal on diffusely abnormal hepatic signal intensity, as compared with the spleen on Ti- and T2-weighted images, and/or the presence of low-signal-intensity fibrous septa. In 31 (86%) of 36 patients abnormal parenchyma was seen on sonograms, and in seven (1 9%) of 36 patients abnormal signal was seen on MR images. When configunational changes of the liven (macronodules, large caudate lobe, hepatomegaly, small left lobe) were considered to indicate panenchymal abnormalities, 30 (83%) of 36 children were deemed abnormal (Fig. 9). Spleen size could be characterized on both MR images and sonograms. In the children who were able to hold their breath (those older than 7 years), gradient-refocused imaging provided additional information in the spleen. Of i 1 children scanned with this technique, focal low-signal-intensity rounded lesions in the splenic parenchyma were seen in five (45%). None of these presumed siderotic nodules were visible on sonognaphy. In only one child (with congenital hepatic fibrosis with Caroli disease) was there dilatation of the biliary tract. Both sonog-

Fig. 4.-A, Coronal Ti-weighted MR image (SE 600/20) through upper abdomen in an infant with biliary atresia. Infrahepatic vena cava (arrowhead) is directiy connected to azygos vein (Az). Aorta (Ao) is positioned to left. B, Transaxial Ti-weighted MR image (SE 600/20) through upper abdomen. Note midline position of liver and portal vein (arrowhead). Stomach (St) is positioned on right side immediately anterior to right-sided spleen (Sp). Dilated azygos vein (AZ) is posterior to right crus.

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354

Fig. 5.-Transaxial Ti-weighted MR image (SE 600/15) through upper abdomen in a 9-year-old child with biliary atresia. Extensive esophageal varices (arrowheads) appear as rounded areas of signal void.

BISSET

Fig. 6.-A,

a 16-year-old

ET AL.

AJR:155,

August

1990

spin-density-weighted MR image (SE 2000/20) through upper abdomen in giri with chronic active hepatitis. Large portosystemic collateral vessel is identified

Transaxial

immediately posterior to left lobe of liver (arrowhead). This most likely represents a markedly dilated coronary vein. Note coarse fibrous strands extending through hepatic parenchyma (arrows). B, Gradient-echo image (30/12/25#{176} flip angle) through same location shows vascular nature of large portosystemic collateral vessel (high signal intensity). Siderotic nodules are identified as rounded, low-signal-intensity foci within spleen (arrow).

Fig. 7.-A, Transverse sonogram through upper abdomen in a patient with biliary obstructive disease due to previous choledochal cyst. Several retroperitoneal collateral vessels are identified (arrowheads) and verified by Doppler studies. B, Corresponding transaxial spin-density-weighted MR image (SE 2000/20) shows extent of retroperitoneal portosystemic collateral vessels (arrowheads).

naphy and MR imaging showed biliary tract dilatation in this case. Associated anomalies in this group of patients included polysplenia (two patients), preduodenal portal vein (one patient), unilateral dysplastic kidneys (two patients), right ureteropelvic junction obstruction (one patient), right renal cyst (one patient), and splenic cyst (one patient). Each of the anomalies was identified by MR imaging. Sonography failed to detect the preduodenal portal vein (Fig. 1 0). In one patient with polysplenia and biliary atresia, a multilobed spleen was detected posterior to the stomach on MR (Fig. 1 i ). The spleen

was not recognized raphy.

Fig. 8.-Transaxial spin-density-weighted MR image (SE 2000/20) through upper abdomen in a i-year-old child with biliary atresla shows area of signal void corresponding to patent paraumbilical vein (arrowhead). Liver appears small and shows diffuse high signal intensity, consistent with fatty infiltration. Note marked ascites (arrows).

behind

the distended

stomach

on sonog-

Discussion Imaging children with chronic liver disease plays a major role in diagnosis and treatment. From information obtained, more reliable decisions can be made concerning long-term medical therapy and possible liven transplantation. Several reports have addressed the appropriate nadiologic investiga-

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AJR:155,

August

Fig. 9.-Transaxial image (SE 2000/20)

a 12-year-old

PEDIATRIC

1990

spin-density weighted MR through upper abdomen in

child with biliary atresia

shows

macronodular changes in liver associated with a small left lobe (LL). Spleen (Sp) is moderately enlarged.

END-STAGE

LIVER

Fig. 10.-Transaxial spin-density weighted MR image (SE 2000/20) through midportion of liver In a child with a preduodenal portal vein (arrowhead). Note extensive gastric fundal varices (arrow).

tion of adult patients with chronic liver disease [i 2]; however, little information is available in children [3]. Additionally, few studies have compared the efficacy of the various imaging techniques. Few data are available regarding MR imaging in this group of patients [i 0]. Although the imaging information in children may not differ greatly from that in adults, surgical therapy in adults, in the form of transplantation, is less often considered a therapeutic alternative. Sonognaphy has generally been considered the primary screening technique in this patient population. In this study, sonognaphy and MR imaging were concordant in most portal vein assessments. MR imaging, however, showed small pontal veins in two patients in whom sonography was false negative. Additionally, both MR imaging and sonography failed to show one surgically demonstrable small portal vein. These preliminary findings indicate that MR imaging should be performed in patients when the portal vein is not identified sonographically, before the patient is excluded as a transplantation candidate. If no portal vein is identified on MR imaging, angiognaphy should be considered. Additional studies are needed to evaluate this problem further. A lower limit of portal vein size has not been a contraindication to transplantation as long as potential reconstruction could be planned (Ryckman FC, personal communication). The usefulness of duplex scanning of the portal vein in patients with portal hypertension and portal venous thrombosis has been well documented [6]. In a previous report by Tomes et al. [5], MR imaging was believed to be accurate for assessing portal vein thrombosis; however, when compared with angiography, MR imaging was not useful for characterizing portal venous flow rates. The low prevalence of portal vein flow anomalies in this group of patients is not surprising. Portal flow is usually well maintained until portal hypertension becomes severe. The ,

355

DISEASE

Fig. ii.-Transaxial

(SE 600/15)

Ti-weighted

through upper abdomen

MR image in a child

with biliary atresla. A muftilobed spleen (arrowheads) is positioned immediately behind a right-sided stomach (St). At the time of sonography, multilobed spleen was not Identified; child was crying and stomach was distended with air. Note interruption of lnfrahepatic inforior vena cava (arrow).

decreased flow velocity is compensated by portal vein dilatation, resulting in a net overall maintenance of flow volume [ii]. The size and patency of the inferior vena cava was determined by sonography in nearly every case; the exception was a child with intrahepatic interruption and azygos continuation. This compares with a sonographic accuracy rate of only 80% reported by Candella and Amplatz [1 2]. In the patient with intrahepatic interruption of the inferior vena cava, MR imaging cleanly showed the retropenitoneal location of the dilated azygos vein, posterior to a gas-filled stomach. MR imaging in this situation obviates the difficulties encountered during sonognaphy with bowel gas in the upper abdomen. Portosystemic collateral vessels were present in the majority of children with end-stage liver disease. Identification of significant collaterals is important in long-term treatment of these patients. Prophylactic sclenotherapy may “buy time” before transplantation and may prevent life-threatening hemorrhage in children with large gastric or esophageal varices. Fewer collateral vessels were detected with sonography than with MR imaging (22% vs 64%, respectively). Limiting factors, such as obesity, intestinal gas, and massive ascites occasionally contributed to difficulties encountered with sonography. Previous reports also have indicated that MR imaging appears to be superior to sonography in the detection of the extent of vanices [13]. The frequency of detection of coronary veins with sonognaphy in comparison with portography was 85% in a study by Dokmeci et al. [i 4]. In our study, the majority of undetected collaterals (with sonography) were in the splenic hilum (retrogastric) on in the gastric fundus or distal esophagus. Patent umbilical (or paraumbilical) veins are a highly specific finding for portal hypertension [1 5, 1 6]. These veins were noted in 28% of these children with chronic liver disease. MR

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356

BISSET

was more sensitive than sonography in demonstrating these vessels. In the eight patients in whom umbilical veins were shown by MR imaging and not by sonography, limiting factors included four previous Kasai procedures (with anteriorly positioned bowel loops), ascites (one patient), and small (2 mm) vein size (four patients). It should be noted that the inferiority of sonography in this respect may have been operator dependent. If the patent umbilical vein was not specifically sought, it may have gone undetected. MR imaging affords some advantage over sonography in the evaluation of liver and spleen size. Although qualitative judgments concerning liver and spleen size were made with sonography, the exact measurement was difficult to assess. The limited acoustic window accessed by sector-type scanning is relatively inaccurate in providing direct measurement of large organs, and currently B-mode scanning is performed infrequently. In contradistinction, MR imaging permitted direct measurement of craniocaudal, anteropostenior, and right-toleft diameters of liver and spleen. Although these measurements are of uncertain value, they may be beneficial in following progress of disease and may be important in planning segmental liver transplantations in smaller patients who are receiving partial adult livers. In evaluating the spleen, MR imaging provided additional information concerning portal hypertension that was not available by sonographic examination. The presence of siderotic Gamna-Gandy nodules within the splenic parenchyma is another indicator of portal hypertension [1 7, 18]. Although these dense hemosidenn deposits were recognized readily on the fast-scan MR series, they were not seen prospectively or retrospectively on the sonographic examinations. Duplex sonography did define the direction of portal venous flow infonmation not available from MR imaging. Associated anomalies were relatively common (i 4%) in these children. It is noteworthy that each of the anomalies detected was in the subgroup of patients with biliary atresia. This is a recognized phenomenon, with previous reports stating a prevalence of congenital anomalies of 1 0% in extrahepatic biliary atresia [1 9, 20]. MR imaging and sonography detected most of the anomalies, although in one of the patients with polysplenia sonography failed to detect the small, multilobed spleen situated posterior to the dextropositioned stomach. MR imaging proved superior to sonography in the identification of portal veins, portosystemic collaterals, intrahepatic venous drainage, paraumbilical portal veins, and siderotic nodules of the spleen. We believe that MR imaging should be

ET AL.

AJR:i55,

considered

the

pretransplantation

imaging

August

technique

1990

of

choice. ACKNOWLEDGMENT We thank Brenda Moore for manuscript

preparation.

REFERENCES 1.

zajko

KM. Schade RR, Koneru B, Van Thiel DH. radiology in liver transplantation. Gastroentero! C/in North Am i988;17:i05-i43 Lund G, Letourneau JG, Day DL, Crass JR. MRI in organ transplantation. Radio! C/in North Am 1987; 25:281 -288 Day DL. Letoumeau JG, Allan BT, Ascher NL, Lund G. MR evaluation of the portal vein in pediatric liver transplant candidates. AJR i986;i 47:10271030 Williams DM, Cho KJ, Aisen AM, Eckhauser FE. Portal hypertension evaluated by MR imaging. Radiology 1985; 157:703-706 Torres WE, Gaylord GM, Whitmire L, Chuang VP, Bemardino ME. The correlation between MR and angiography in portal hypertension. AJR i987;148:1109-11i2 Koslin DB, Berland LL. Duplex Doppler examination of the liver and portal venous system. JCU 1987:15:675-686 Taylor KJW, Morse SS, Weltin GG, Riely CA, Flye MW. Liver transplant recipients: portable duplex US with correlative angiography. Radio!ogy i986;i 59:357-363 Claus D, Clapuyt P. Liver transplantation in children: role of the radiologist in the preoperative assessment and the postoperative follow-up. TransAB, Campbell

WL, Bron

Diagnostic and interventional

2. 3.

4. 5.

6. 7.

8.

p/ant Proc i987;19:3344-3357 9. Auringer ST, Bisset GS Ill, Kirks DR. Pediatric MRI decreases need for invasive exams. Diagn Imaging i989;1 1 :102-1 06 1 0. Stark DD, Goldberg HI, Moss AA, Bass NM. Chronic liver disease: evaluation by magnetic resonance. Radiology i984;i 50:149-151 11 . Moriyasu F, Nishida 0, Ban N, et al. “Congestion index’ of the portal vein. AJR i986;146:735-739 12. Cardella JF, Amplatz K. Preoperative an9iographic evaluation of prospective liver recipients. Radio! C/in North Am i987;25:299-308 13. Ohtorno K, Itai Y, Makita K, et al. Portosystemic collaterals on MR imaging. J Comput Assist Tomogr 1986:10:751-755 14. Dokmeci AK, Kimura K, Matsutani 5, et al. Collateral veins in portal hypertension: demonstrated by sonography. AJR 1981;137:1i73-i177 15. Glazer GM, Laing FC, Brown TW, Gooding GAW. Sonographk demonstration of portal hypertension: the patent umbilical vein. Radiology i980;136:16i-163 1 6. Saddekni 5, Hutchinson DE, Ccoperberg PL. The sonographically patent umbilical vein in portal hypertension. Radiology 1982;145:441-443 17. Minami M, Itai Y, Ohtomo K, et al. Siderotic nodules in the spleen: MR imaging of portal hypertension. Radiology 1989;172:681-684 1 8. Sagoh T, Itoh K, Togashi K, et al. Gamna-Gandy bodies of the spleen: evaluation with MR imaging. Radiology i989;172:685-687 19. Abramson SJ, Berdon WE, Altman RF, Amodio JB, Levy J. Biliary atresia and noncardiac polysplenic syndrome: ultrasound and surgical considerations. Radiology i987;163:377-.379 20. Hall RJ, Vasquey-Esterey JM, Greenholy SK, Lilly JR. Biliary atresia and the polysplenia syndrome. Hepatology i986;6: 1218-1222