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1
Department of Radiology, Division of Magnetic Resonance Imaging, Basement,
Schwartz Bldg., NYU Medical Center, 530 First Ave., New York, NY 10016.
2
Department of Surgery, Division of Transplant Surgery, NYU Medical Center, 403
E. 34th St., New York, NY 10016.
3
Present address: Department of Radiology, Beth Israel Deaconess Medical
Center, 330 Brookline Ave., Boston, MA 02215.
4
Present address: Departement de Radiologie, Hopital Maisonneuve-Rosemont, 5415
Blvd. de l'Assomption, Montreal, Quebec H1T 2M4, Canada.
Received November 28, 2000;
accepted after revision May 22, 2001.
Address correspondence to V. S. Lee.
Abstract
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MATERIALS AND METHODS. Twenty-three consecutive adult patients underwent 30 MR imaging examinations between 2 days and 99 months (mean, 15 months) after transplantation using a breath-hold 3D gradient-echo sequence (TR range/TE range, 3.7-4.7/1.8-1.9; flip angle, 12-30°) with an intermittent fat-saturation pulse and interpolation in the section-select direction to enable pixel size 3 mm or less in all dimensions. Unenhanced and triphasic contrast-enhanced 3D imaging (average dose, 0.13 mmol/kg of gadopentetate dimeglumine) was performed. A subset of patients (n = 13) also underwent MR cholangiopancreatography using half-Fourier single-shot turbo spin-echo imaging. MR imaging examinations were correlated with digital subtraction angiography (n = 8), contrast-enhanced cholangiography (n = 9), sonography (n = 13), and histopathology (n = 14).
RESULTS. MR imaging revealed abnormal findings in 27 (90%) of 30 examinations, including vascular disease in nine, biliary complications in four, and evidence of intra- or extra-hepatic hepatocellular carcinoma recurrence in six. Digital subtraction angiography confirmed seven MR angiography examinations but suggested disease overestimation in one. Contrast-enhanced cholangiography confirmed findings of MR cholangiopancreatography in seven cases but suggested disease underestimation in two.
CONCLUSION. Dynamic interpolated 3D MR imaging combined with dedicated MR cholangiopancreatography can provide a comprehensive assessment of vascular, biliary, parenchymal, and extrahepatic complications in most recipients of liver transplants.
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Certain vascular, biliary, parenchymal, and extrahepatic complications in recipients of liver transplants can be shown well on imaging when the appropriate modality is used. However, because these patients frequently present with nonspecific clinical symptoms, a multimodality approach is often required. Sonography is commonly used to screen for vascular, biliary, and parenchymal abnormalities, although its sensitivity for the detection of hepatic arterial and biliary disease may be low [6,7,8]. Thus, conventional angiography and cholangiography are used to identify definitively vascular and biliary complications, respectively. Additionally, CT and MR imaging are often used to evaluate the liver parenchyma and extrahepatic structures. Although CT in conjunction with CT angiography can provide a noninvasive evaluation of parenchymal and vascular structures [9, 10], supplementary cholangiography is still required for a comprehensive evaluation. MR cholangiopancreatography has proven to be an accurate means of evaluating the biliary system in recipients of transplants [11, 12]. Moreover, hepatic MR angiography can be performed in the same setting as MR cholangiopancreatography and serves as a compelling alternative to invasive angiography [13,14,15]. Until recently, however, hepatic MR angiography has been performed to optimize vascular imaging at the expense of background structures, such as liver parenchyma [13,14,15].
An MR imaging approach using three-dimensional (3D) interpolated gradient-echo MR imaging has recently become available that enables high-resolution, near-isotropic imaging of the entire abdomen in a breath-hold. When performed dynamically after contrast administration, this technique allows simultaneous evaluation of the liver parenchyma and vascular structures [16, 17]. The addition of MR cholangiopancreatography sequences to dynamic 3D MR imaging allows all relevant anatomic systems to be depicted at a single MR imaging examination [11, 12, 18].
In this study, we compared the MR imaging results of a retrospectively identified cohort of recipients of orthotopic liver transplants who underwent 3D MR imaging with or without supplementary MR cholangiopancreatography with those of correlative imaging examinations, including conventional angiography, cholangiography, and sonography, and with relevant histopathology. Our purpose was to evaluate the accuracy and usefulness of a comprehensive MR imaging strategy for recipients of liver transplants.
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20 sec) of 3D MR imaging
in fire cases; these examinations were excluded from the study. The remaining
30 examinations were performed in 23 patients who constituted the study group
(18 men, five women; age range, 31-67 years; mean age, 50 years). A subset of
these patients was studied on two (n = 1) or three (n = 3)
separate occasions. Original causes of liver failure in the study group included cirrhosis caused by chronic hepatitis C (n = 13), hepatitis B (n = 2), or coinfection with hepatitis B and C (n = 2); fulminant hepatitis B (n = 1) or hepatitis E (n = 1); alcohol-related liver disease (n = 1); primary biliary cirrhosis (n = 1); cryptogenic cirrhosis (n = 1); and autoimmune liver disease (n = 1). Previous graft rejection necessitated retransplantation in two patients before MR imaging. Fourteen (61%) of twenty-three patients had histologic evidence of HCC in their native explanted livers.
Each MR imaging examination was requested by our institution's liver
transplantation team with the intention of answering a specific clinical
question directly related to patient care. Referral indications included the
following: HCC surveillance (n = 7), abnormal finding on sonography
suggesting vascular insufficiency (n = 6), elevated results on liver
function tests (n = 5), elevated 
-fetoprotein (n =
4), abdominal pain (n = 3), abnormal findings on contrast-enhanced
cholangiography suggesting biliary compromise (n = 2), intermittent
fever (n = 1), abnormal findings on sonography suggesting fluid
collection (n = 1), and follow-up imaging for hepatic artery
angioplasty (n = 1). MR imaging was performed from 2 days to 99
months after liver transplantation (mean interval, 15 months). Although most
examinations were performed to assess complications arising more than 1 month
after transplantation (n = 28), two were performed within 1 month of
surgery.
MR Imaging Protocol
After written informed consent for the administration of contrast material,
all patients underwent imaging with a 1.5-T MR system and a torso phased array
coil. Most examinations (n = 22) were performed on a unit with a 25
mT/m maximal gradient strength and 600-µsec rise time (Vision; Siemens,
Erlangen, Germany); the remainder (n = 8) were performed on a unit
with a 20 mT/m maximal gradient strength and 400-µsec rise time (Symphony;
Siemens). Before the study, a 22-gauge IV catheter was placed in an arm vein
and attached to an MR-compatible power injector (Spectris; Medrad, Pittsburgh,
PA). Before 3D MR imaging, all patients underwent imaging with fast short
inversion time inversion recovery turbo spin-echo and T1-weighted in-phase and
out-of-phase gradient-echo sequences, according to our routine protocol.
Three-Dimensional Volumetric Imaging
We used an interpolated 3D spoiled gradient-echo sequence similar to that
described in the literature
[16,
17]. Imaging parameters
included the following: TR range/TE range, 3.7-4.7/1.8-1.9; flip angle,
12° (n = 25) or 18-30° (n = 5); mean acquisition
time, 20 sec (range, 15-27 sec). Sequence details are summarized briefly as
follows: symmetric echo (160 points) in the read direction (ky,
left-to-right); symmetric echo in the phase-encoding direction (ky,
anteroposterior) in the original sequence design (n = 16), and 80%
partial Fourier sampling (128/160 points) in a revised sequence (n =
14) in which each 160 partition was interpolated to a 256 matrix; asymmetric
echo sampling in the section-select direction (kz,
superior-to-inferior) to obtain 32-64 data points that were then interpolated
using zero-filling (sinc interpolation) to produce 64-128 partitions.
Use of a rectangular field of view resulted in an inplane spatial resolution of 2.8 mm or less for the 160 matrix; pixel size of 1.8 mm or less was obtained using the full 256 matrix. Section thickness ranged from 160 to 232 mm to ensure full coverage of the liver and yielded a partition thickness of 1.6-3.0 mm. The 3D sequence incorporated a frequency-selective fat-saturation pulse before each partition (section) loop. Each partition loop was centric-reordered to maximize fat saturation.
In all cases, unenhanced interpolated 3D MR imaging was performed first, followed by a timing examination, and then repeated three times at 45-sec intervals after administration of 19 mL of gadopentetate dimeglumine (average, 0.13 mmol/kg; Magnevist; Berlex Imaging, Wayne, NJ). The timing examination was performed as described by Earls et al. [19], who used a 1-mL test dose of contrast material; delay time was calculated as described by Prince et al. [20]. All 3D examinations were performed during breath-holding at the end of expiration.
MR Cholangiopancreatography
MR cholangiopancreatography was performed in 14 examinations in 13 patients
with coronal or axial half-Fourier acquisition single-shot turbo spin-echo
imaging, or both. Half-Fourier acquisition single-shot turbo spin-echo
sequence parameters for both coronal and axial imaging varied as follows:
TR/effective TE, infinite/43 or 62 msec; refocusing pulse, 120-180°; field
of view, 300-400 mm; matrix, 128-208 x 256; section thickness, 4.0-8.0
mm; mean acquisition time, 29 sec. MR cholangiopancreatography was performed
before gadolinium contrast administration in all patients.
Image Processing and Interpretation
Before 3D MR imaging, all patients underwent imaging with short tau
inversion recovery and T1-weighted in-phase and out-of-phase gradient-echo
sequences, according to our routine protocol. Volumetric 3D imaging source
data were routinely evaluated interactively on a commercially available MR
workstation (Numaris, Siemens), and pertinent multiplanar reconstructions were
performed. For each study, the time required to create multiplanar
reconstructions was approximately 8-10 min.
Abnormal findings on vascular evaluations were prospectively reported to show thrombotic disease, focal stenotic disease, or "vessel attenuation," a term used to describe diffuse narrowing without dominant focal stenoses. The hepatic parenchyma was evaluated for focal disease, including tumor and fluid collection, and the presence of diffuse hepatic processes, such as periportal edema and perihepatic fluid. The biliary system was primarily evaluated for stricture and bile leak. All abnormal extrahepatic findings, including findings suggestive of recurrent metastatic HCC in particular, were also reported prospectively. MR imaging reports dictated at the time of imaging served as the primary source of data in this study. In cases of discrepancy between MR imaging findings and correlative imaging results, MR imaging studies were retrospectively reviewed to evaluate possible sources of error.
Data Analysis
Each patient's imaging records were reviewed to identify digital
subtraction angiography, contrast-enhanced cholangiography (T-tube
cholangiography, percutaneous transhepatic cholangiography, and endoscopic
retrograde cholangiopancreatography), and sonographic evaluations that were
performed close to the time of MR imaging. Our search yielded correlative
imaging studies for 20 (67%) of 30 3D MR imaging examinations and 17 (74%) of
the 23 patients included in this study. Correlative vascular imaging studies
(digital subtraction angiography, sonography, or both) were available for 17
(57%) of 30 3D MR imaging examinations and 14 (61%) of the 23 patients
included in the study. Correlative imaging studies included eight digital
subtraction angiography examinations performed within 45 days (mean interval,
12 days) after eight MR imaging studies from seven patients; 13 sonographic
examinations performed within 7 days (mean interval, 3 days) before 13 MR
imaging studies from 11 patients; and nine contrast-enhanced cholangiograms
obtained within 5 days (mean interval, 2 days) of nine MR imaging studies from
seven patients. Dedicated MR cholangiopancreatograms were used in six of the
nine MR imaging examinations from six of the seven patients with correlative
contrast-enhanced cholangiography.
Correlative histopathology was available for 14 (47%) of 30 MR imaging examinations from 10 (43%) of 23 patients, five of whom underwent liver biopsy to evaluate for diffuse parenchymal disease, such as graft rejection, and five of whom underwent biopsy of an extrahepatic mass to determine HCC recurrence. Of the 20 MR imaging examinations for which correlative imaging was available, nine also had correlative histopathology. Thus, correlative digital subtraction angiography, sonography, contrast-enhanced cholangiography, histopathology, or a combination of these was available for 25 (83%) of 30 MR imaging examinations and 18 (78%) of 23 patients in the study.
Patient medical records were reviewed in all cases to determine the clinical context of each imaging study and to ensure that patients' clinical courses did not change between MR imaging and correlative imaging evaluation. In addition, the liver transplantation team clarified the clinical course and follow-up of patients with complicated histories.
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Vascular Complications
Vascular complications at MR imaging were detected in nine examinations
from eight patients and included the following findings: celiac artery
stenosis (n = 2) (Fig.
1A,1B),
hepatic artery thrombosis (n = 2) (Fig.
2A,2B),
hepatic artery attenuation (n = 2), mild to moderate hepatic artery
stenosis (n = 2), attenuation of intrahepatic arterial branches
(n = 4), and portal vein stenosis (n = 1).
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Of the eight MR angiographic studies with correlative digital subtraction angiography, MR angiography that showed no abnormal findings was confirmed in four cases, and abnormal findings on MR angiography were confirmed in three. Disease was overestimated in one patient who underwent MR angiography and digital subtraction angiography within 3 days after transplantation and in whom severe attenuation of the hepatic artery and of the hepatic artery branches seen on MR angiography was not depicted on digital subtraction angiography; digital subtraction angiography instead revealed only mild stenosis at the origin of the left hepatic artery (Fig. 3A,3B). However, slow flow suggestive of high hepatic arterial resistance was noted at digital subtraction angiography. A retrospective review of MR images from all phases of dynamic imaging with knowledge of digital subtraction angiography findings did not change the initial MR imaging interpretation in this case.
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An equivocal finding was present in the MR angiography examination of one patient; a region of signal loss in the hepatic artery was thought to be a result of either surgical clips or stenotic disease. A direct comparison of findings on MR angiography and digital subtraction angiography confirmed the presence of surgical clips in the region of question. This patient also had disease at the origin of the celiac axis detected on both MR angiography and digital subtraction angiography.
Thirteen MR imaging examinations from 11 patients were compared with 13 sonographic studies performed within 7 days before MR imaging. In four cases, both sonography and MR angiography revealed normal celiac and hepatic arterial systems; in five cases, both modalities depicted abnormal findings. In two of the five cases, arterial abnormalities were confirmed at digital subtraction angiography: in one, the absence of a hepatic arterial tracing at sonography led to subsequent evaluation with MR angiography and digital subtraction angiography, both of which revealed celiac artery stenosis consistent with median arcuate ligament compression; in the other, hepatic arterial stenosis found at sonography also led to subsequent evaluation with MR angiography and digital subtraction angiography, both of which revealed diffuse attenuation of the hepatic artery and intrahepatic arterial branches. In one of the five cases, discussed previously in the context of the patient in whom hepatic arterial disease was overestimated at MR angiography, sonographic findings also overestimated arterial disease when compared with those of digital subtraction angiography.
MR angiography and sonography yielded discrepant results in four examinations from three patients. In one patient, sonography showed likely hepatic arterial stenosis; however, findings on follow-up MR angiography were normal. Sonography revealed no hepatic artery disease in two patients in whom MR angiography revealed disease. In one patient, mild to moderate hepatic artery stenosis shown on MR angiography was not observed on sonography; in the other patient, sonography failed to reveal hepatic artery thrombosis noted on both MR angiography and digital subtraction angiography during the patient's first imaging workup. Sonography was equivocal at a later imaging workup of this patient, during which MR angiography showed recurrent thrombosis. Collateral arterial vessels were revealed on MR angiography on both occasions.
Sonography of the portal vein that showed no abnormal findings was consistent with MR angiographic findings in 12 cases. However, findings on MR angiography and sonography were discrepant in one patient in whom portal vein stenosis shown on MR angiography was not observed on sonography. The portal venous system was not further evaluated in this patient and was not a suspected cause of further complications in this patient at clinical follow-up.
Biliary Complications
Biliary abnormalities were shown on MR imaging in four examinations from
three patients and included presumed bile leak (n = 3) and a
choledochocholedochostomy anastomotic stricture (n = 1) (Fig.
4A,4B)
visualized on the basis of supplementary MR cholangiopancreatography sequences
in three of the four examinations. In the case of the anastomotic stricture,
MR imaging was performed before correlative contrast-enhanced cholangiography.
Periportal fluid collections visualized at MR imaging were assumed to
represent bile leaks on the basis of the knowledge of the results of prior
contrast-enhanced cholangiography.
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Of the nine MR imaging studies with correlative contrast-enhanced cholangiography, normal MR imaging findings were confirmed in three cases, and abnormal MR imaging findings were confirmed in four cases. False-negative interpretations of biliary disease occurred in two MR examinations from two patients, both of whom underwent dedicated MR cholangiopancreatography. A choledochocho-ledochostomy anastomotic stricture detected on contrast-enhanced cholangiography was missed on MR imaging in one patient. The stricture was detected in a retrospective review of this MR imaging study but was a subtle finding because of the absence of common bile duct dilatation proximal to the stricture. A plastic common bile duct stent in another patient resulted in regional signal loss, prohibiting an adequate analysis of the stent lumen at MR cholangiopancreatography. When the stent was subsequently removed at endoscopic retrograde cholangiopancreatography, it was found to be partially occluded.
Intrahepatic and Extrahepatic Tumor
Evidence of recurrent HCC was detected on MR imaging in six patients (Figs.
5 and
6), all of whom had histologic
evidence of multifocal HCC in their native explanted liver specimens. In these
six patients, evidence of recurrent extrahepatic HCC was detected on MR
imaging in the following distribution: lung bases (n = 4), adrenal
glands (n = 3), subcutaneous fat (n = 2), lymph nodes
(n = 2, paraaortic and portacaval), vertebral body (n = 1),
and peritoneum (n = 1). Of these patients, three also had
simultaneous evidence of intrahepatic HCC. Five of the six patients underwent
biopsy of an extrahepatic mass; histopathologic results confirmed HCC
recurrence in all cases. The remaining patient underwent digital subtraction
angiography before MR angiography, revealing multiple hypervascular hepatic
masses consistent with recurrent HCC; subsequent chemoembolization was
performed. One patient had a single 1-cm intrahepatic lesion that had signal
characteristics consistent with a fast-filling hemangioma, unchanged from a
prior CT. This patient was doing well 1 year after MR imaging with no clinical
data to suggest recurrent HCC.
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Diffuse Parenchymal Disease
Five patients underwent liver biopsy within 23 days of MR imaging. Biopsy
results included rejection (chronic [n = 2], acute [n = 1],
acute vs drug toxicity [n = 1]), and infectious hepatitis [n
= 1]). Two patients showed potentially associated, but nonspecific, findings
on MR imaging. Perihepatic fluid was noted in the patient with hepatitis, and
periportal edema was noted in the patient with acute rejection versus drug
toxicity by biopsy. Of the remaining three patients, one had a high resistance
pattern of the hepatic artery on sonography, and subsequent MR angiography
showed diffuse attenuation of the intrahepatic arterial branches. One had a
known biliary anastomotic stricture, and one had no evidence of vascular or
biliary compromise during her workup.
Miscellaneous Extrahepatic Findings
Extrahepatic findings on MR imaging included postoperative seroma
(n = 3), DeBakey type III aortic dissection (n = 1),
subcapsular fluid collection causing compression of the liver (n =
1), splenic infarct (n = 1), and incisional hernia (n = 1).
Although the aortic dissection and incisional hernia were previously known,
other findings were first depicted on MR imaging.
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Our combined vascular and parenchymal 3D MR imaging approach yielded results comparable with those reported using dedicated MR angiography sequences [13,14,15]. Two other groups of researchers have investigated the accuracy of dynamic 3D MR angiography in evaluating recipients of liver transplants using digital subtraction angiography, surgical findings, or both for comparison [14, 15]. Both studies used dedicated 3D MR angiography with a higher flip angle (35° [15] and 45° [14] vs 12° typically used in our study) to achieve greater background suppression and higher doses of gadolinium contrast material (40-60 mL vs 20 mL in our study). For their 19 patients with correlative digital subtraction angiography, surgical findings, or both, Glockner et al. [15] reported one false-negative and three false-positive MR angiographic interpretations of hepatic arterial stenosis and one false-positive interpretation of portal venous stenosis. Stafford-Johnson et al. [14] reported minor discrepancies of hepatic artery and inferior vena cava disease on MR imaging in four patients of the 13 they studied. In our study, MR angiographic findings were confirmed at digital subtraction angiography in seven of eight examinations; hepatic arterial disease was markedly overestimated on MR imaging in only one patient.
Although factors such as spatial resolution and signal loss in regions of disturbed flow are known causes of error in disease estimation on MR angiography, two other factors may arise in the context of recipients of liver transplants. First, surgical clips and stents create regional signal loss on MR imaging, although investigative efforts to identify MR imaging strategies that minimize such artifacts are underway [25, 26]. Second, low-flow states, commonly present in newly transplanted edematous, ischemic, or necrotic livers and during systemic hypotension and graft rejection, have been shown to contribute to false-positive interpretations of vascular disease [6, 27]. In the patient in our study in whom arterial disease was overestimated at MR angiography, slow hepatic arterial flow (as shown at digital subtraction angiography) likely resulted from edematous hepatic parenchyma associated with recent transplantation. Similarly, Glockner et al. [15] reported arterial disease overestimation on MR angiography in two patients with graft rejection. Thus, MR angiographic interpretation should be conducted with an understanding of clinical factors that may contribute to low-flow states.
In our series, hepatic arterial thrombosis detected on MR angiography and on digital subtraction angiography was missed on sonography in one patient. In this patient, the presence of collateral arterial vessels shown on MR angiography likely accounted for disease underestimation on sonography, a reported limitation of sonography in the context of recipients of liver transplants [6, 7]. The use of high-resolution contrast-enhanced imaging as opposed to flow-dependent imaging likely reduces false-negative interpretations of hepatic arterial disease in the presence of collateral vessels.
HCC recurrence has been reported in 7-40% of recipients of liver transplants with a pretransplantation history of HCC [2,3,4,5]. Our MR imaging approach enabled detection of intra- and extrahepatic masses suspicious for recurrent HCC in six (26%) of 23 patients, all of whom had biopsy or other imaging data consistent with HCC recurrence. Three features of the 3D MR imaging technique described in this study serve to optimize tumor surveillance. First, interpolation methods allow imaging with thinner sections than those typically obtained in routine abdominal MR imaging, thereby improving the likelihood of small-lesion detection and characterization. Second, a timing examination ensures reliable arterial phase imaging for improved HCC detection. As many as 9-11% of patients with HCC have been reported to have tumors visible only during arterial phase imaging [28,29,30]. Third, our technique enables complete evaluation of the upper abdomen, including the lung bases and adrenal glands, common sites for HCC metastases [5]. Our technique is not sufficient for evaluation of suspected recurrent HCC in the chest, for which CT should be performed. A liberal extrahepatic examination does, however, provide valuable insight into nonspecific clinical symptoms, such as abdominal pain, by allowing detection of unsuspected abnormalities such as splenic disease or postoperative fluid collections, as observed in our series.
A limitation of the parenchymal evaluation provided by MR imaging is its inability to depict findings specific for rejection of a liver transplant [31]. Because other imaging modalities are also limited in identifying graft rejection [32, 33], patients with suspected rejection continue to require biopsy for a definitive diagnosis. The interpolated 3D MR imaging approach is also limited at present to patients who can breath-hold for 20 sec. Recipients of a transplant who are severely debilitated or intubated, therefore, cannot benefit from 3D MR imaging. However, continued improvements in MR technology already have shortened minimum TRs and TEs and will continue to do so, thereby reducing breath-hold requirements. Other limitations of the proposed approach are the inability to visualize accurately small hepatic vessels and the overestimation of vascular disease in low-flow states. Using higher doses of IV contrast material may improve both small artery visualization and vascular disease characterization in low-flow states and deserves further investigation.
Although no false-positive interpretations were made on MR cholangiopancreatography in our study, two complications detected at contrast-enhanced cholangiography were prospectively missed and illustrate important limitations of MR cholangiopancreatography in recipients of transplants. First, one anastomotic stricture was missed, in part because of the lack of biliary dilatation proximal to the stenosis. The absence of such dilatation has been reported to have poor negative predictive value for biliary duct obstruction on contrast-enhanced cholangiography in recipients of liver transplants [34]. Second, partial occlusion of a common bile duct stent was missed on MR cholangiopancreatography because of signal loss associated with the stent. In this setting, functional MR cholangiopancreatography has the potential to improve evaluation of the biliary system and deserves further investigation (Kim J-H et al., presented at the International Society for Magnetic Resonance in Medicine meeting, April 2000).
In our study, periportal fluid collections depicted on MR cholangiopancreatography were presumed to represent biliary leaks on the basis of known contrast-enhanced cholangiographic results. Currently, it is difficult to distinguish a periportal biliary leak from a postoperative seroma on MR cholangiopancreatography alone, without contrast-enhanced cholangiography. A new approach using MR imaging that may enable this distinction has been reported by Vitellas et al. [35], who have recently shown that mangafodipir trisodium, an approved MR imaging biliary contrast agent excreted by the biliary system, can be useful for detecting biliary leaks on MR cholangiopancreatography. In the future, this approach may obviate contrast-enhanced cholangiography for the diagnosis of biliary leaks in patients with periportal fluid collections.
In conclusion, the results of our study suggest that dynamic interpolated 3D MR imaging combined with dedicated MR cholangiopancreatography can provide a comprehensive assessment of vascular, biliary, parenchymal, and extrahepatic complications in most recipients of liver transplants. This study reflects our preliminary experience and is limited by its retrospective nature and number of patients; however, our results support further prospective investigation in this growing field of MR imaging.
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