Vascular complications of liver transplantation: evaluation with gadolinium-enhanced MR angiography

Diagnostic performance of contrast-enhanced ultrasound in diagnosing hepatic artery occlusion after liver transplantation: A systematic review and meta-analysis

INTRODUCTION

Hepatic artery occlusion (HAO) is a significant complication post-liver transplantation. Doppler ultrasound (DUS) has been widely used as an initial screening test for detecting HAO; however, its performance is often not sufficient. Although other diagnostic tests such as computed tomography angiography (CTA), magnetic resonance angiography (MRA), and angiogram are more accurate, they are invasive and have several limitations. Contrast-enhanced ultrasound (CEUS) is an emerging tool for detecting HAO; however, the results from previous studies were limited due to a small number of patients. Therefore, we aimed to evaluate its performance by performing a meta-analysis.

METHOD

We performed a systemic review and meta-analysis of studies evaluating the performance of CEUS for the detection of HAO in an adult population. A literature search of EMBASE, Scopus, CINAHL, and Medline was conducted through March 2022. Pooled sensitivity, specificity, log diagnostic odd ratio (LDOR), and area under summary receiver operating curve (AUC) were calculated. Publication bias was assessed by Deeks' funnel plot.

RESULT

Eight studies were included, with 434 CEUS performed. Using a combination of CTA, MRA, angiography, clinical follow-up, and surgery as the gold standard, the sensitivity, specificity, and LDOR of CEUS for detection of HAO were .969 (.938, .996), .991 (.981, 1.001), and 5.732 (4.539, 6.926), respectively. AUC was .959. The heterogeneity between studies appeared universally low, and no significant publication bias was found (p = .44).

CONCLUSION

CEUS appeared to have an excellent performance for the detection of HAO and could be considered as an alternative when DUS is non-diagnostic or when CTA, MRA, and angiogram are not feasible.

Abdominal Applications of Pediatric Body MR Angiography: Tailored Optimization for Successful Outcome

OBJECTIVE. The purpose of this article is to summarize current common techniques and indications for pediatric abdominopelvic MR angiography and strategies for optimizing them to achieve successful outcomes. We also discuss newer MR angiography techniques, including whole-body imaging and blood pool contrast agents, as well as various approaches to reducing the need for anesthesia in pediatric MRI. CONCLUSION. Pediatric body vascular imaging presents a unique set of challenges that require a tailored approach. Emerging pediatric abdominopelvic MR angiography techniques hold promise for continued improvement in pediatric body MR angiography.

Patterns of portosystemic collaterals and diameters of portal venous system in cirrhotic patients with hepatitis B on magnetic resonance imaging: Association with Child-Pugh classifications

BACKGROUND AND OBJECTIVE

To determine associations of patterns of portosystemic collaterals and diameters of portal venous system in cirrhotic patients with hepatitis B on magnetic resonance (MR) imaging with Child-Pugh classification.

MATERIALS AND METHODS

Eighty-eight consecutive patients with cirrhosis resulting from chronic hepatitis B graded by Child-Pugh classifications were recruited and undergone MR portography. Patterns of the collaterals (presented as no collateral, isolated esophageal varices, and esophageal varices combined with other shunts), and diameters of portal venous system including portal vein (PV), left portal vein (LPV), right portal vein (RPV), splenic vein (SV) and superior mesenteric vein (SMV) were assessed statistically to determine associations of patterns of collaterals and diameters of the portal veins with Child-Pugh classification.

RESULTS

From no collateral, to isolated esophageal varices, and to the varices combined with other shunts, the Child-Pugh classifications tended to increase (r=0.516, P<0.001). Diameters of PV, LPV, RPV, SV and SMV tended to increase from Child-Pugh A to B but decrease from B to C. Differences in diameter of LPV and SV were significant between Child-Pugh A-B and C (all P<0.05) while no differences in diameters of other portal veins were found (all P>0.05). For discriminating Child-Pugh A-B from C, either a cut-off LPV diameter of 8.98mm or SV diameter of 9.10mm achieved a sensitivity of 67%-70%, specificity of 51%-53%.

CONCLUSION

Patterns of portosystemic collaterals and diameters of LPV and SV tend to be associated with Child-Pugh classifications of cirrhosis.

The ins and outs of liver imaging

Different imaging modalities including ultrasonography, computed tomography (CT), and MR imaging may be used in the liver depending on the clinical situation. The ability of dedicated contrast-enhanced liver MR imaging or CT to definitively characterize lesions as benign is crucial in avoiding unnecessary biopsy. Liver imaging surveillance in patients with cirrhosis may allow for detection of hepatocellular carcinoma at an earlier stage, and therefore may improve outcome. This article reviews the different imaging modalities used to evaluate the liver and focal benign and malignant hepatic lesions, and the basic surveillance strategy for patients at increased risk for hepatocellular carcinoma.

Diameters of left gastric vein and its originating vein on magnetic resonance imaging in liver cirrhosis patients with hepatitis B: Association with endoscopic grades of esophageal varices

AIM

To determine whether diameters of the left gastric vein (LGV) and its originating vein are associated with endoscopic grades of esophageal varices.

METHODS

Ninety-eight liver cirrhotic patients with hepatitis B undergoing magnetic resonance (MR) portography, and upper gastrointestinal endoscopy for grading esophageal varices were enrolled. Diameters of the LGV and its originating vein - the splenic vein (SV) or portal vein (PV) - were measured on MR imaging. Statistical analyses were performed to identify the association of the diameters with the endoscopic grades.

RESULTS

Univariate analysis showed that the SV was predominantly the originating vein of the LGV, and diameters of the LGV and SV were associated with grades of esophageal varices. Diameters of the LGV (P = 0.023, odds ratio [OR] = 1.583) and SV (P = 0.012, OR = 2.126) were independent risk factors of presence of the varices. Cut-off LGV diameters of 5.1 mm, 5.9 mm, 6.6 mm, 7.1 mm, 7.8 mm and 5.8 mm; or cut-off SV diameters of 7.3 mm, 7.9 mm, 8.4 mm, 9.5 mm, 10.7 mm and 8.3 mm, could discriminate grades 0 from 1, 0 from 2, 0 from 3, 1 from 3, 2 from 3, and 0-1 from 2-3, respectively.

CONCLUSION

Diameters of the LGV and SV are associated with endoscopic grades of esophageal varices.

The importance of portal venous blood flow in ischemic-type biliary lesions after liver transplantation

Ischemic-type biliary lesions (ITBL) are the most frequent cause of nonanastomotic biliary strictures after liver transplantation. This complication develops in up to 25% of patients, with a 50% retransplantation rate in affected patients. Traditionally, ischemia-reperfusion injury to the biliary system is considered to be the major risk factor for ITBL. Several other risk factors for ITBL have been identified, including the use of liver grafts donated after cardiac death, prolonged cold and warm ischemic times and use of University of Wisconsin preservation solution. In recent years however, impaired microcirculation of the peribiliary plexus (PBP) has been implicated as a possible risk factor. It is widely accepted that the PBP is exclusively provided by blood from the hepatic artery, and therefore, the role of the portal venous blood supply has not been considered as a possible cause for the development of ITBL. In this short report, we present three patients with segmental portal vein thrombosis and subsequent development of ITBL in the affected segments in the presence of normal arterial blood flow. This suggests that portal blood flow may have an important contribution to the biliary microcirculation and that a compromised portal venous blood supply can predispose to the development of ITBL.

Percutaneous transluminal venoplasty after venous pressure measurement in patients with hepatic venous outflow obstruction after living donor liver transplantation

PURPOSE

The aim of this study was to evaluate retrospectively the outcome of percutaneous transluminal venoplasty (PTV) after venous pressure measurement in patients with hepatic venous outflow obstruction following living donor liver transplantation (LDLT).

MATERIALS AND METHODS

We studied 24 consecutive patients suspected of having hepatic venous outflow obstruction after LDLT. Pressure gradients were measured proximal and distal to the lesion, and gradient values >3 mmHg were considered hemodynamically significant. We evaluated the technical success, complications, outcome of venoplasty and recurrence, and the patency rate.

RESULTS

In all, 11 female patients manifested a pressure gradient >3 mmHg across the anastomotic site; they underwent subsequent PVT. The initial balloon venoplasty procedure was technically successful in 10 of the 11 patients (91%), and the pressure gradient was reduced from 5.8 to 1.1 mmHg (P < 0.01). Clinical improvement was observed in 9 of these 10 patients; one patient failed to improve and underwent retransplantation. Recurrent obstruction occurred in four patients; they underwent PTV with (n = 2) or without (n = 2) stent placement. There were no major procedural complications.

CONCLUSION

PTV following venous pressure measurement is an effective and safe treatment for venous outflow obstruction in patients subjected to LDLT. In patients with recurrent obstruction, re-venoplasty is recommended.

Management of venous stenosis in living donor liver transplant recipients

AIM: To retrospectively evaluate the management and outcome of venous obstruction after living donor liver transplantation (LDLT).

METHODS: From February 1999 to May 2009, 1 intraoperative hepatic vein (HV) tension induced HV obstruction and 5 postoperative HV anastomotic stenosis occurred in 6 adult male LDLT recipients. Postoperative portal vein (PV) anastomotic stenosis occurred in 1 pediatric left lobe LDLT. Patients ranged in age from 9 to 56 years (median, 44 years). An air balloon was used to correct the intraoperative HV tension. Emergent surgical reoperation, transjugular HV balloon dilatation with stent placement and transfemoral venous HV balloon dilatation was performed for HV stenosis on days 3, 15, 50, 55, and 270 after LDLT, respectively. Balloon dilatation followed with stent placement via superior mesenteric vein was performed for the pediatric PV stenosis 168 d after LDLT.

RESULTS: The intraoperative HV tension was corrected with an air balloon. The recipient who underwent emergent reoperation for hepatic stenosis died of hemorrhagic shock and renal failure 2 d later. HV balloon dilatation via the transjugular and transfemoral venous approach was technically successful in all patients. The patient with early-onset HV stenosis receiving transjugular balloon dilatation and stent placement on the 15th postoperative day left hospital 1 wk later and disappeared, while the patient receiving the same interventional procedures on the 50th postoperative day died of graft failure and renal failure 2 wk later. Two patients with late-onset HV stenosis receiving balloon dilatation have survived for 8 and 4 mo without recurrent stenosis and ascites, respectively. Balloon dilatation and stent placement via the superior mesenteric venous approach was technically successful in the pediatric left lobe LDLT, and this patient has survived for 9 mo without recurrent PV stenosis and ascites.

CONCLUSION: Intraoperative balloon placement, emergent reoperation, proper interventional balloon dilatation and stent placement can be effective as a way to manage hepatic and PV stenosis during and after LDLT.

Diagnosis and treatment of pediatric patients with late-onset portal vein stenosis after living donor liver transplantation

Portal vein stenosis (PVS) after living donor liver transplantation (LDLT) is a serious complication that can lead to graft failure. Few studies of the diagnosis and treatment of late-onset (> or = 3 months after liver transplantation) PVS have been reported. One hundred thirty-three pediatric (median age 7.6 years, range 1.3-26.8 years) LDLT recipients were studied. The patients were followed by Doppler ultrasound (every 3 months) and multidetector helical computed tomography (once a year). Twelve patients were diagnosed with late-onset PVS 0.5-6.9 years after LDLT. All cases were successfully treated with balloon dilatation. Five cases required multiple treatments. Early diagnosis of late-onset PVS and interventional radiology therapy treatment may prevent graft loss.

Detection and grading for esophageal varices in patients with chronic liver damage: comparison of gadolinium-enhanced and unenhanced steady-state coherent MR images

The purpose of this study was to compare observer interpreted steady-state coherent coronal images and gadolinium-enhanced axial images in terms of the detection and grading of esophageal varices. Magnetic resonance imaging (MRI) and gastrointestinal endoscopy were performed within 2 weeks in 90 patients with chronic liver damage, including 55 with untreated esophageal varices, for periodic screening purposes. Two blinded readers retrospectively reviewed T1- and T2-weighted images with gadolinium-enhanced (gadolinium image set) and steady-state coherent (coherent image set) images. Sensitivity for the detection of esophageal varices was higher (P<.001) in the gadolinium image set (76%) than in the coherent image set (35%); on the other hand, specificity was higher (P<.001) in the coherent image set (91%) than in the gadolinium image set (66%). Furthermore, area under the ROC curve was higher for the gadolinium image set (Az=0.823) than the coherent image set (Az=0.761) (P=.48). Moderate and weak positive correlations with endoscopic grades were found for the gadolinium image (r=0.48, P<.01) and coherent image sets (r=0.34, P=.018). The addition of steady-state coherent imaging to the current routine liver imaging protocol did not improve the detection or grading of esophageal varices, whereas gadolinium-enhanced imaging was found to be potentially valuable. Nevertheless, endoscopy was confirmed to be mandatory in patients with esophageal varices suspected by MRI of the liver.

The role of noninvasive vascular imaging in splanchnic and mesenteric pathology

Traditionally, catheter angiography (CA) has been the mainstay of diagnosis for mesenteric arterial diseases. However, CA is invasive and is associated with complications that result from the procedure itself, depending on the experience of the operators, site of vascular access, ionized radiation that could be significant when combined with interventional procedures, and administered contrast material. During the past 2 decades, technical improvements in computed tomography (CT) and magnetic resonance hardware and methods have contributed new, noninvasive tools, specifically CT angiography (CTA) and 3-dimensional gadolinium-enhanced magnetic resonance angiography (3D Gd-MRA). This article outlines the current applications, strengths, and weaknesses of CTA and 3D Gd-MRA in imaging of the mesenteric vessels.

Role of contrast-enhanced 3D magnetic resonance portography in evaluating portal venous system compared with color Doppler ultrasonography

AIM

The purpose of this study was to evaluate the capability of contrast-enhanced three-dimensional (3D) MR portography in detecting abnormal findings associated with the portal venous system compared with the results of color Doppler ultrasonography (CDUS).

MATERIALS AND METHODS

MR portography findings were retrospectively compared with the results of CDUS examinations in 161 patients, who were suspected of having portal venous system abnormalities. Portal venous vessels were divided into main 5 groups including the main portal vein, its left and right intrahepatic branches, splenic vein and superior mesenteric vein. Imaging findings were classified as normal, occluded, or partially thrombosed. Results of clinical and imaging follow-up examinations including CDUS, MR portography or angiography, if available, were used as a proof of final diagnosis. The potential sites of varicose veins and collateral vessels were also examined by both imaging methods.

RESULTS

Vascular abnormalities were identified in 79 of 161 patients. There was a statistically significant agreement between the results of MR portography and CDUS in evaluating portal venous system (kappa = 0.871, P < 0.05). The sensitivity of MR portography was slightly superior to CDUS in detecting partially thrombosis and occlusion in the main portal venous vessels. In addition, MR portograms were superior to CDUS in the management of patients with portal hypertension by identifying portosystemic collaterals more adequately, and clearly demonstrated portal venous vessels that cannot be visualized at CDUS.

CONCLUSION

Results of present study indicates that contrast-enhanced 3D MR portography is well suited and superior to CDUS in the management of patients with portal hypertension.

Multimodality postoperative imaging of liver transplantation

Liver transplantation is the only effective and definitive treatment for patients with end-stage liver disease. The shortage of cadaveric livers has lead to the increasing use of split-liver transplantation and living-donor liver transplantation, but the expansion of the donor pool has increased the risk for postoperative vascular and biliary complications. Early recognition of the imaging appearances of the various postoperative complications of liver transplantation is crucial for both graft and patient survival. This review describes the imaging findings of normal and abnormal transplanted liver parenchyma and of vascular and biliary post-transplantation complications.

Complications of liver transplantation: multimodality imaging approach

Liver transplantation is currently an accepted first-line treatment for patients with end-stage acute or chronic liver disease, but postoperative complications may limit the long-term success of transplantation. The most common and most clinically significant complications are arterial and venous thrombosis and stenosis, biliary disorders, fluid collections, neoplasms, and graft rejection. Early diagnosis is crucial to the successful management of all these complications, and imaging plays an important role in the diagnosis of all but graft rejection. A multimodality approach including ultrasonography and cross-sectional imaging studies often is most effective for diagnosis. Each imaging modality has specific strengths and weaknesses, and the diagnostic usefulness of a modality depends mainly on the patient's characteristics, the clinical purpose of the imaging evaluation, and the expertise of imaging professionals.

Percutaneous transhepatic venous angioplasty in a two-yr-old patient with hepatic vein stenosis after partial liver transplantation

We report one case of severe hepatic vein stenosis, in a two-yr-old pediatric patient with a left lateral split liver transplantation (S2-S3) and severe ascites, in whom color Doppler ultrasound failed to make the diagnosis and transhepatic balloon angioplasty was successfully performed.

Pediatric liver transplantation: a pictorial essay of early and late complications

Orthotopic liver transplantation is currently the treatment of choice in patients with end-stage liver disease for which no other therapy is available. In children, segmental liver transplantation with living donor, reduced-size cadaveric, and split cadaveric allografts has become an important therapeutic option. However, the resulting expansion of the donor pool has increased the risk for postoperative vascular and biliary complications, which affect children more frequently than adults. Early recognition of these complications requires radiologic evaluation because their clinical manifestations are frequently nonspecific and vary widely. Doppler ultrasonography (US) plays the leading role in the postoperative evaluation of pediatric patients. Current magnetic resonance (MR) imaging techniques, including MR angiography and MR cholangiography, may provide a wealth of pertinent information and should be used when findings at US are inconclusive. Computed tomography is a valuable complement to US in the evaluation of complications involving the hepatic parenchyma as well as extrahepatic sites and is commonly used to guide percutaneous aspiration and fluid collection drainage. Familiarity with and early recognition of the imaging appearances of the various postoperative complications of pediatric liver transplantation are crucial for graft and patient survival.

Outcome of percutaneous transhepatic venoplasty for hepatic venous outflow obstruction after living donor liver transplantation

PURPOSE

To evaluate retrospectively the outcome of percutaneous transhepatic venoplasty of hepatic venous outflow obstruction after living donor liver transplantation (LDLT).

MATERIALS AND METHODS

The institutional Human Subjects Research Review Board approved the interventional protocol and the retrospective study, for which informed consent was not required. Before treatment, informed consent was obtained from the patient or the patient's parents in all cases. Of 26 consecutive patients (nine male, 17 female; median age, 9 years) suspected of having hepatic venous outflow obstruction after LDLT, 20 patients confirmed to have anastomotic outflow stenosis at percutaneous hepatic venography and manometry underwent venoplasty. Pressure gradients before and after venoplasty were evaluated by using a paired t test. Patients in whom obstruction recurred during follow-up were re-treated with venoplasty with or without expandable metallic stents. Patency was analyzed by using Kaplan-Meier analysis.

RESULTS

The initial balloon venoplasty was technically successful in all 20 patients, all of whom had improved clinical findings. The pressure gradient +/- standard deviation was reduced from 14.6 mg Hg +/- 8.6 to 2.2 mg Hg +/- 2.4 (P < .001). Eleven patients had recurrent obstruction and were treated with balloon venoplasty; one of them underwent stent placement, as well as venoplasty. The primary (event-free) patency and 95% confidence interval (CI) at 3, 12, and 60 months after venoplasty were 0.80 (95% CI: 0.62, 0.98), 0.60 (95% CI: 0.38, 0.81), and 0.60 (95% CI: 0.38, 0.81), respectively. The primary assisted patency, maintained with repeated venoplasty and expandable metallic stents, was 1.00 at 60 months.

CONCLUSION

Percutaneous venoplasty is an effective treatment for hepatic venous outflow obstruction after LDLT.

Interventional radiology in liver transplantation

Improvements in surgical technique, advances in the field of immunosuppresion and the early diagnosis and treatment of complications related to liver transplantation have all led to prolonged survival after liver transplantation. In particular, advances in diagnostic and interventional radiology have allowed the Interventional Radiologist, as part of the transplant team, to intervene early in patients presenting with complications related to organ transplant with resultant increase in graft and patient survival. Such interventions are often achieved using minimally invasive percutaneous endovascular techniques. Herein we present an overview of some of these diagnostic and therapeutic approaches in the treatment and management of patients before and after liver transplantation.

Magnetic resonance angiography of abdominal and lower extremity vasculature

Magnetic resonance angiography (MRA) has evolved over the past years from an experimental imaging modality to a technique that is now widely applied in clinical practice. This article reviews the fundamentals of the different magnetic resonance angiographic techniques and how they can be applied for abdominal and peripheral arterial imaging. Currently, contrast-enhanced magnetic resonance angiography (CE-MRA), whereby a luminogram is obtained during initial arterial passage of contrast material, is the most widely used technique. With current hardware and software, high-spatial resolution images of the abdominal aorta and proximal visceral branches can be obtained that are equivalent to intra-arterial digital subtraction angiography (IA-DSA). High-quality imaging of the renal arteries demands isotropic voxels and reformations orthogonal to the vessel axis for evaluation. Contrast-enhanced magnetic resonance angiography of the peripheral vascular tree is now a highly accurate technique and has replaced diagnostic intra-arterial digital subtraction angiography and duplex ultrasonography in many hospitals.

Angiographie par résonance magnétique dans les anévrismes et pseudoanévrismes des artères splanchniques

PURPOSE

To correlate Magnetic resonance angiography (MRA) with computed tomography for the diagnosis of splanchnic artery aneurysms.

MATERIALS-METHODS

We retrospectively reviewed the MRA findings of splanchnic arteries performed in 16 patients with known splanchnic aneurysms. Sixteen patients underwent computed tomography (CT), and MRA. Conventional angiogram was performed to confirm the diagnosis in six cases. This study was conducted on a 1.5T MR Symphony system (Siemens, Erlangen, Germany). CE-MRA was performed by using a 3D RF-spoiled FLASH sequence. Acquisition of source images was performed in the coronal plane and reconstructed by means of maximum-intensity projection (MIP) post-processing.

RESULTS

Patient population included 7 men and 9 women aged from 31 to 85 years old (mean age 59.5 years old). Splanchnic aneurysms were located as follows: splenic (n=5), hepatic (n=6), celiac trunk (n=4) and gastroduodenal (n=1). In 9 cases, MRA provided results similar to CT. In 3 cases, MRA provided more accurate information on the location of the aneurysm or detected additional aneurysms. In 4 patients, a diagnosis of aneurysm was made first or only made on MRA.

CONCLUSION

This small series showed a good correlation between CT and MRA for detection and characterization of splanchnic aneurysms.

Feasibility of morphologic assessment of vascular and biliary anatomy in pediatric liver transplantation: all-in-one protocol with breath-hold magnetic resonance

BACKGROUND/PURPOSE

Noninvasive imaging for children with liver transplantation for possible sites of vascular and biliary complication remains a challenge. The aim of this study was to investigate the feasibility of magnetic resonance (MR) imaging as a comprehensive noninvasive test for the above purpose.

METHODS

Thirteen children (age, 8-16 years) with biliary atresia and who received liver transplantation underwent a comprehensive MR study including MR cholangiography and gadolinium-enhanced MR angiography. Images were interpreted by 3 radiologists for liver parenchymal abnormalities; definition of hepatic arterial and venous, portal venous, and biliary anatomy; and detection of any complications. Findings were correlated with surgical records. Conventional angiography and percutaneous cholangiography were obtained for correlation in 2 patients. Confidence level scores (1-5) for depiction of anatomy were given for source, multiplanar, and 3-dimensional images.

RESULTS

Hepatic artery anastomosis was visualized in 12 patients (92%) and the intrahepatic arteries were demonstrated in 10 (77%). The portal, hepatic venous, and biliary anastomoses were clearly demonstrated in all patients. Stenosis of hepatic artery anastomosis and multiple biliary strictures were detected in 1 patient each and confirmed by conventional imaging. High confidence scores (higher than 4) were obtained for all kinds of MR images.

CONCLUSIONS

Comprehensive MR imaging can be used in long-term follow-up of pediatric liver transplant recipients for depiction of hepatic structures and possible complications.

Multi-detector computed tomography angiography of the hepatic artery in liver transplant recipients

PURPOSE

To evaluate the ability of multi-detector row computed tomography angiography (CTA) in detecting hepatic artery complications in the follow-up of liver transplant patients, performing volume-rendering as reconstruction technique.

MATERIAL AND METHODS

The anatomy of hepatic artery was studied in 27 liver transplant recipients with a four-row CT scanner using the following parameters: collimation, 1 mm; slice width, 1 mm; table feed, 6-8 mm/s; spiral reconstruction time, 0.5 s; reconstruction interval, 0.5 mm; mAs, 160; kVp, 120. Before the study, the patients received 1000 ml of water as oral contrast agent to produce negative contrast in the stomach and the small bowel. A non-ionic contrast medium was infused intravenously at a rate of 5 ml/s with a bolus tracking system. Volume-rendering of hepatic artery was performed with the 3D Virtuoso software.

RESULTS

The celiac trunk, the hepatic artery, and the right and left hepatic arteries were successfully displayed in high detail in all patients. Side branches, including small collaterals, and hepatic artery anastomosis could also be readily visualized. Volume-rendered CTA detected six hepatic artery stenoses, two hepatic artery thromboses, and two intrahepatic pseudoaneurysms. In two cases, CT detected hepatic artery stenosis with a diameter reduction of less than 50%, while digital subtraction angiography showed a normal artery.

CONCLUSION

Volume-rendered multi-detector CTA is a promising non-invasive technique, since it allows images of high quality to be generated with excellent anatomical visualization of the hepatic artery and its complications in liver transplant recipients.

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Diagnostic Value of Gadolinium-Enhanced 3D Magnetic Resonance Angiography in Patients With Suspected Hepatic Arterial Complications After Liver Transplantation

PURPOSE

To evaluate the accuracy and clinical role of gadolinium-enhanced 3D magnetic resonance angiography (MRA) in patients with suspected hepatic arterial complications after liver transplantation.

MATERIALS AND METHODS

Thirty-six consecutive MRA studies were performed in 33 liver transplant recipients after transplantation. MRA image quality was assessed subjectively. Thirty-two MRA studies were retrospectively reviewed and correlated with surgery (n = 2), conventional angiography (n = 18), or clinical follow-up (n = 12). MRA findings were also correlated with those of Doppler sonography in 30 of the cases. In 20 cases, concordance between MRA and surgery or conventional angiography was evaluated for each grade of hepatic artery stenosis (normal, mild [<50%], moderate [50-75%], severe [>75%], or occluded).

RESULTS

MRA image quality was degraded 13 of 36 cases (36.1%) studies. The sensitivity, specificity, and accuracy of MRA by consensus reading for more than 50% of hepatic artery stenosis or occlusion were 67%, 90%, and 81.3%, respectively. Of the 19 cases in which Doppler sonography was abnormal, MRA correctly characterized hepatic artery stenosis in 16 (84.2%). MRA also correctly identified all 5 occurrences of celiac artery stenosis. However, MRA overestimated the severity of hepatic arterial stenosis in 3 (15%) of 20 cases and underestimated 5 (25%) of 20 cases.

CONCLUSION

MRA complements Doppler ultrasound to exclude significant hepatic artery stenosis. However, a substantial number of MRA studies were technically inadequate, and MRA demonstrated limited efficacy for correctly grading the severity of hepatic artery stenosis.

Magnetic resonance imaging features of focal liver lesions after intervention

The aim of this article is to provide an overview of MRI features of primary and secondary liver lesions after intervention. Emphasis is given to T2- and T1-weighted pre and post intravenous gadolinium chelates appearance of successfully treated lesions and, from residual/recurrent tumors after therapy. In addition, complications after procedures are briefly cited. Liver resection, radiation therapy, systemic chemotherapy, transcatheter arterial chemoembolization, ablative therapies and liver transplantation are the methods discussed in this review. Among these methods, special attention is given to MRI findings after ablative therapies since radiofrequency ablation is commonly performed in our institution.

3D contrast-enhanced MR angiography of the abdominal aorta and its distal branches: Interobserver agreement of radiologists in a routine examination

RATIONALE AND OBJECTIVES

To evaluate the quality of images of the aorta and visceral arteries made at a high level of spatial resolution with thin slices and an optimized acquisition time by three-dimensional contrast-enhanced magnetic resonance angiography (3D CE-MRA).

MATERIALS AND METHODS

3D CE-MRA with a 1.4-mm slice thickness and 512-pixel base matrix was done on 62 consecutive patients with a 1.5-T magnetic resonance imaging MRI unit. A bolus test with a power injector was used to calculate the optimal scan delay time. For quantitative evaluation, the signal-to-noise ratio (SNR) was measured in 3 regions of interest. Qualitative image analysis was evaluated independently by two radiologists and graded on a scale of 0-3. Separate analyses were done for the aorta and distal visceral arterial branches.

RESULTS

The means SNR values were respectively 56.2 +/- 15.2 (mean +/- SD) for the aorta, 59.2 +/- 15.1 for the celiac trunk, and 57 +/- 15.2 for the superior mesenteric artery, with a homogeneous distribution (P = .99). Consistent enhancement was confirmed by the lack of statistically significant differences between the SNR values. The average score for vessel visualization on source images ranged from good to excellent for different segments. After post-processing of images, the average score for distal arterial segments was significantly improved. The overall agreement between the 2 reviewers in the visualization of definite artery segments was excellent (k = .91).

CONCLUSION

3D CE-MRA with a 512-pixel base matrix and thin slices can be applied in a reproducible way with excellent depiction and delineation of small vessels. Such a protocol could be used routinely.

Complications of orthotopic liver transplantation: imaging findings

Orthotopic liver transplantation has become the major treatment for end-stage chronic liver disease and for severe acute liver failure. Despite the improvement in survival due to advances in organ preservation, improved immunosuppressive therapy agents, and refinement of surgical techniques, there are significant complications after liver transplantation. These complications mainly include biliary strictures, stones, and leakage; arterial and venous stenoses and thromboses; lymphoproliferative disorders; recurrent tumors; hepatitis virus C infection; liver abscesses; right adrenal gland hemorrhage; fluid collections; and hematomas. The diagnosis of acute rejection, one of the most serious complications after liver transplantation, is established with graft biopsy and histologic study. The role of imaging methods consists of excluding the other complications, which can have clinical signs and symptoms similar to those of acute rejection. This pictorial essay describes imaging findings of the various complications after liver transplantation and focuses on their radiologic diagnosis. Knowledge and early recognition of these complications with the most suitable imaging modality are crucial for graft and patient survival.

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Scintigraphic patterns of veno-occlusive disease in liver transplantation

Venous vascular complications in liver transplant recipients are rare. Diagnosis is usually based on clinical criteria and typical findings on liver biopsy. The scintigraphic patterns of posttransplant liver veno-occlusive disease are described, and the value of follow-up studies is suggested. The authors present 2 patients who developed posttransplantation hepatic veno-occlusive disease. The first patient had a severe form of the disease and a fatal outcome. The second patient had a mild to moderate form of this disorder with complete resolution following treatment.

Angiografia por ressonância magnética: aspectos técnicos de um método de estudo vascular não-invasivo

As primeiras técnicas de angiografia por ressonância magnética (angio-RM) utilizavam seqüências sensíveis ao fluxo sanguíneo para estabelecimento do contraste vascular. Há três técnicas fundamentadas neste princípio: contraste de fase ("phase-contrast"), TOF ("time-of-flight") e as técnicas de sangue escuro ("black blood"). Estas seqüências, de aquisição demorada, são mais suscetíveis a artefatos de movimento, perda de sinal em áreas de estenoses ou turbilhonamento de fluxo, e apresentam ainda baixa sensibilidade à detecção do fluxo lento. O uso do contraste paramagnético para estudos angiográficos pela ressonância magnética ofereceu um método simples, rápido e de excelente detalhamento vascular, baseando o contraste da imagem no realce do sinal vascular em oposição à supressão dos demais tecidos. Metodologias modernas que priorizam a obtenção do espaço k central, responsável pelo contraste da imagem, e o aperfeiçoamento das técnicas de planejamento do intervalo temporal para aquisição dos dados foram fatores fundamentais para o aprimoramento técnico da angio-RM. O papel atual da angio-RM como ferramenta diagnóstica merece destaque na avaliação de anomalias anatômicas, estenoses, oclusões e complicações vasculares pós-cirúrgicas, principalmente nos casos de transplantes de órgãos. Suas principais vantagens estão na não utilização do contraste iodado ou radiação ionizante, rapidez e fácil execução, mínima invasividade e possibilidade de avaliar complementarmente o parênquima de órgãos adjacentes de interesse diagnóstico.

Magnetic resonance portography using contrast-enhanced fat-saturated three-dimensional steady-state free precession imaging

PURPOSE

To assess the feasibility of contrast-enhanced fat-saturated three-dimensional steady-state free precession (FIESTA) imaging for contrast-enhanced magnetic resonance (MR) portography.

MATERIALS AND METHODS

Contrast-enhanced fat-saturated three-dimensional fast spoiled gradient-echo (SPGR) and FIESTA were performed as MR portography. In 10 cases, fat-saturated three-dimensional FIESTA was first performed and followed by fast SPGR, and the order of post-contrast imaging was reversed in the other 10 cases. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were estimated for portal and visceral veins on the source images. The visualization of portal vein was scored on three-dimensional MR portography. Portal venous system disorders were assessed using three-dimensional MR portography.

RESULTS

The SNRs, CNRs, and visual assessment of portal and visceral veins were significantly higher in contrast-enhanced fat-saturated three-dimensional FIESTA than contrast-enhanced fat-saturated three-dimensional fast SPGR (P < 0.05). The contrast-enhanced fat-saturated three-dimensional FIESTA provided high venous signals even at 8 minutes after gadolinium injection. The abnormalities of portal venous system were well visualized with MR portography using contrast-enhanced fat-saturated three-dimensional FIESTA.

CONCLUSION

Contrast-enhanced fat-saturated three-dimensional FIESTA was valuable for MR portography, with flexible time window and high vascular signals. This imaging may allow for other post-contrast imaging options before portography and release patients from consecutive breath-holds.

Microbubble ultrasound contrast in the assessment of hepatic artery patency following liver transplantation: role in reducing frequency of hepatic artery arteriography

We prospectively evaluated the role of microbubble ultrasound contrast for detection of hepatic artery thrombosis following liver transplantation. The hepatic artery of adult liver transplant recipients with suspected thrombosis on surveillance Doppler ultrasound (US) were re-examined by a second observer. In patients with no hepatic spectral Doppler signal the microbubble contrast agent Levovist was used. The presence or absence of flow following microbubble contrast was evaluated against arteriography or repeated Doppler US findings. A total of 794 surveillance Doppler US examinations were performed in 231 patients. Hepatic artery flow was demonstrated in 759 of 794 (95.6%) examinations. Microbubble ultrasound contrast was administered in 31 patients (35 studies) with suspected hepatic artery thrombosis. Following microbubble US contrast the hepatic artery could not be demonstrated in 13 of 35 (37.1%) studies (12 patients). Eight patients had arteriography: there was hepatic artery thrombosis in 7 patients and 1 patient had a patent, highly attenuated artery. Detection of a patent hepatic artery increased from 759 of 794 (95.6%) to 781 of 794 (98.4%) with the addition of microbubble contrast. Upon independent reading of the data, the degree of operator confidence in the assessment of the hepatic artery patency prior to microbubble contrast was 4.7 (CI 1.92-7.5) but rose to 8.45 (CI 7.06-9.84) following microbubble contrast ( p<0.0001). In 22 of 35 (62.9%) of studies arteriography could potentially have been avoided. Ultrasound microbubble contrast media may reduce the need for invasive arteriography in the assessment of suspected hepatic artery thrombosis.

Vascular complications after living related liver transplantation: evaluation with gadolinium-enhanced three-dimensional MR angiography

OBJECTIVE

The purpose of this study was to evaluate the efficacy of gadolinium-enhanced three-dimensional (3D) MR angiography for detection of vascular complications in patients who have undergone living related liver transplantation.

MATERIALS AND METHODS

Seventy-six patients who underwent living related liver transplantation were evaluated with gadolinium-enhanced 3D MR angiography. All MR angiograms were assessed for patency of the hepatic artery and the portal vein using a four-point scale (grades I-IV). The results were correlated with conventional angiography (n = 23) and clinical follow-up with Doppler sonography (n = 53) for more than 6 months.

RESULTS

Seventy-three of 76 MR angiography procedures were technically adequate. When grades III (focal narrowing [> 50%] at the anastomotic site) and IV (abrupt cutoff at the anastomotic site with nonvisualization of the right [or left] hepatic artery distal to the anastomosis) were regarded as the diagnostic criteria for hepatic artery stenosis, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MR angiography were 100%, 74%, 29%, 100%, and 77%, respectively. In the portal vein, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MR angiography were 100%, 84%, 35%, 100%, and 85%, respectively, when grades III (narrowing [> 50%] without poststenotic dilatation) and IV (narrowing [> 50%] with poststenotic dilatation) were defined as criteria for portal vein stenosis.

CONCLUSION

MR angiography was sensitive but not specific in the detection of significant vascular stenosis after living related liver transplantation. However, normal MR angiography findings reliably exclude the possibility of significant stenosis.

Preoperative evaluation of the entire hepatic vasculature in living liver donors with use of contrast-enhanced MR angiography and true fast imaging with steady-state precession

PURPOSE

To preoperatively assess the entire hepatic vasculature in living related liver donors with use of a combination of contrast material-enhanced magnetic resonance (MR) angiography and true fast imaging with steady-state precession (FISP).

MATERIALS AND METHODS

Twenty-five living potential liver donors were examined preoperatively on a 1.5T Siemens Sonata system. Twenty-four underwent surgery and two had catheter angiography performed to delineate complex anatomy. Contiguous 5-mm-thick, sub-second true FISP images of the liver were initially obtained during breath-holding in axial and coronal planes (repetition time [TR]/echo time [TE], 3.2/1.6; flip angle, 70 degrees ). MR angiography was performed with use of a three-dimensional (3D) gradient-echo fast low-angle shot (FLASH) pulse sequence (TR/TE, 3.0/1.2; flip angle, 25 degrees ), with 40 mL of Gadolinium DTPA injected at a rate of 2 mL/sec. One precontrast and two postcontrast coronal 3D volumes were acquired, each in a 20-second breath-hold, and two subtracted 3D sets were calculated. Arterial anatomy was assessed with use of maximum-intensity projection, volume rendering, and multiplanar reformatting algorithms. Hepatic and portal venous anatomy was evaluated with use of the true FISP images and the venous phase of the MR angiogram. Visualization of hepatic arterial branches was noted. Visualization of portal vein branches was scored on a scale of 0-5. The presence of anatomic variants was noted. Vascular anatomy was confirmed at the time of surgery and at catheter angiography.

RESULTS

Segmental branch vessels were visualized on MR angiography in the majority of cases. The segment four branch was identified in 96% patients. Variant arterial anatomy was seen in 50% of patients. MR angiography detected 10 of 11 arterial variants found at surgery and angiography. Visualization of portal vein branches was generally higher with true FISP compared to MR angiography. Twenty-four percent of patients had variant portal venous anatomy. Caudal hepatic veins were identified in 60% of patients, of which eight were significant (>5 mm). Hepatic and portal venous anatomy was accurately predicted by true FISP and MR angiography in all patients who went on to undergo surgery.

CONCLUSION

Preoperative imaging with use of a combination of contrast-enhanced MR angiography and true FISP provides a comprehensive assessment of the entire hepatic vasculature in living liver donors.

Esophageal varices: diagnosis with gadolinium-enhanced MR imaging of the liver for patients with chronic liver damage

OBJECTIVE

The purpose of our study was to evaluate the value of gadolinium-enhanced MR imaging of the liver in the detection and grading of esophageal varices in patients with chronic liver damage.

MATERIALS AND METHODS

Three independent off-site radiologists retrospectively reviewed MR images of the liver obtained in 72 patients with chronic liver damage, including 49 patients with untreated esophageal varices. All patients had undergone gastrointestinal endoscopy within 2 weeks of MR imaging. Both MR and endoscopic images were reviewed to determine whether esophageal varices were present and, if so, to determine the grade of the varices. Observer performances were tested with receiver operating characteristic curve analysis using the jackknife dispersion test. Correlations between the grades of the varices determined using MR images and those determined using endoscopic images were tested.

RESULTS

Sensitivity for detection of esophageal varices was significantly (p < 0.01) higher for the combination of unenhanced and gadolinium-enhanced MR images (81%) than for the unenhanced MR images alone (51%). The receiver operating characteristic curve analysis (area under the curve, [A(z)]) showed that performance using the combination of the unenhanced and gadolinium-enhanced MR images (A(z) = 0.641) was superior to that using unenhanced MR images alone (A(z) = 0.586). A statistically significant positive correlation (p < 0.05) was found between the grades determined using MR imaging and the grades determined using endoscopy.

CONCLUSION

Our results suggest the potential value of diagnosing the presence and grade of esophageal varices on MR imaging of the liver for patients with chronic liver damage. Gadolinium-enhanced MR imaging may increase the potential value.

MR angiography of the mesenteric vasculature

MRA has evolved from a research tool to a robust clinical diagnostic modality. In many centers worldwide, it is the technique of choice for evaluating patients with suspected CMI, assessing operability of patients with pancreatic cancer, and investigating the portal system. Evolving indications include the assessment of liver transplant patients before and after transplant and of living related liver transplant donors. The search for the bleeding source in patients with gastrointestinal hemorrhage may be an indication in the future, once intravascular contrast agents become available.

Magnetic resonance imaging for disorders of liver vasculature

Magnetic resonance imaging (MRI) provides a noninvasive technique to evaluate the hepatic vasculature. Angiographic and flow-based techniques include intrinsic properties of MRI as well as those that use contrast media. Clinical and technical perspectives of a wide range of vascular disorders affecting the liver, particularly cirrhosis and portal hypertension, portal vein obstruction, as well as imaging of the vasculature prior to and postliver transplantation are presented in this article.

Noninvasive assessment of portomesenteric venous thrombosis: current concepts and imaging strategies

Rapid, noninvasive imaging strategies, especially multidetector spiral CT and CT angiography (CTA) as well as gadolinium-enhanced MR angiography (MRA), have facilitated early diagnosis of splanchnic venous thrombosis, a potentially lethal cause of intestinal ischemia. Single breath-hold volumetric acquisitions permit superior temporal and contrast resolution while eliminating motion artifact and suppressing respiratory misregistration. Increased spatial resolution is aided by thinner slice collimation. These cross-sectional imaging techniques are becoming a preferred noninvasive alternative to conventional selective mesenteric angiography with delayed imaging for venous evaluation and should be considered the primary diagnostic modalities for evaluating patients with high clinical suspicion of nonsurgical mesenteric ischemia.

Magnetic resonance angiography of the pediatric abdomen and pelvis

Although abdominal and pelvic vascular disease is much less common in children than in adults, MR angiographic techniques widely used in adults can also be readily applied in the pediatric population with suspected vascular disease. MR techniques, equipment, and image analysis software are in a continual state of development and refinement. Given the advantages of MR angiography (i.e., its absence of ionizing radiation, capability to obtain images without iodinated contrast material, and limited invasiveness), the applications of MR angiography in the pediatric abdomen and pelvis are likely to continue to increase.