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.     

血管造影在肝移植后血管并发症中的应用

目的：探讨血管造影在肝移植后血管并发症中的应用。方法：报道4例肝移植后肝动脉血栓形成和狭窄病例，结合文献分析血管并发症的临床表现和血管造影结果。结果：肝动脉血栓3例，肝动脉血栓合并吻合口狭窄1例。肝门区有侧支循环2例，门静脉扩张3例。结论：肝动脉及间接门静脉造影对肝移植后血管并发症的诊断，了解向肝侧支动脉血管重建情况，为再次肝移植均具有重要临床价值。     

肝移植术后血管和胆系并发症的MRI诊断价值

目的探讨磁共振血管造影(MRA)和MR胰胆管成像(MRCP)对诊断肝移植术后血管及胆管并发症的价值。方法7例原位肝移植术后患者均用磁共振(MR)快速自旋回波(TSE)序列及快速小角度激发梯度回波(FLASH)序列常规扫描、MRCP、钆喷替酸葡甲胺(Gd-DTPA)动态增强3DMRA检查，分析各序列图像特点。结果术后正常2例，主要表现少量腹水，积血和轻度淋巴结增大。血管并发症4例：肝动脉过长迂曲1例，肝动脉供体端瘤样轻度扩张2例；门静脉轻度狭窄2例，位于吻合口；肝静脉末梢分支杵状扩张2例。胆系并发症3例：吻合口胆管狭窄3例；在吻合口以外的胆管狭窄2例，位于肝门及肝内；胆总管在吻合口扭曲2例；胆囊管残端黏液囊肿2例；胆漏1例。结论MRA和胆管造影作为1种非侵袭性影像检查方法，可准确、快速诊断肝移植术后出现的血管和胆管并发症，对指导临床诊断及治疗具有重要意义。     

Percutaneous vascular intervention based on gadolinium-enhanced MR angiography

PURPOSE: To determine if gadolinium-enhanced magnetic resonance angiography (Gd-MRA) could be used to reliably plan percutaneous vascular procedures. PATIENTS AND METHODS: Over the course of 13 months, 31 patients underwent attempted percutaneous intervention solely on the basis of a preceding Gd-MRA study. A total of 49 arterial segments were targeted (28 extremities, 21 visceral). Five segments in four patients were not treated (less impressive disease severity on conventional catheter angiography [CA] in four segments, diffuse intrarenal atherosclerosis in one segment). Interventions attempted were percutaneous transluminal angioplasty (n = 10), angioplasty with stent placement (n = 29), and thrombolysis (n = 3). Interventions were successful in all segments, except two because of the inability to cross an occlusion. RESULTS: Good to strong correlation was noted between Gd-MRA and CA regarding stenosis severity and length and the presence of poststenotic dilatation. MRA underestimated the complexity of stenosis. Subjective quality and preintervention confidence were excellent in the majority of MRA studies and satisfactory in the rest. The overall value in "procedural planning" was judged high in 40 segments, satisfactory in five segments, and poor in four segments. The procedural planning and positive predictive values of MRA were significantly lower for visceral arteries compared to iliac and peripheral arteries. CONCLUSION: In most cases, Gd-MRA reliably yielded the anatomic and diagnostic information necessary to plan percutaneous vascular interventions noninvasively and without iodinated contrast. In the authors' practice, Gd-MRA is becoming a key imaging modality in the workup of patients in whom percutaneous intervention is anticipated.     

Three-dimensional gadolinium-enhanced MR angiography: applications for abdominal imaging.

Three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) angiography is a versatile technique that combines speed, superb contrast, and relative simplicity. It has a wide range of applications, particularly in the abdomen and pelvis, where superb images of the abdominal aorta and renal arteries are routinely obtained. Aneurysms, atherosclerotic lesions, and occlusions of the major mesenteric arteries are also well depicted. In addition, 3D gadolinium-enhanced MR angiography is ideal for noninvasive evaluation of the systemic and mesenteric veins and can be used to demonstrate parenchymal lesions in the liver, pancreas, kidneys, and other organs. It is also useful in staging genitourinary neoplasms: Parenchymal lesions, venous extension, and adenopathy are all clearly depicted. Three-dimensional gadolinium-enhanced MR angiography can be useful in the preoperative evaluation of potential transplant donors and recipients and in the evaluation of vascular complications following transplantation. Delayed 3D acquisitions of the kidneys, ureters, and bladder can be performed routinely to generate gadolinium-enhanced urograms and demonstrate obstruction, delayed function, filling defects, and masses. A variety of methods for increasing the speed and improving the resolution of 3D acquisition are currently under investigation. These include novel imaging and reformatting techniques and the use of intravascular contrast agents with much longer vascular half-lives.     

Catheter-directed gadolinium-enhanced MR angiography

In the setting of MRI-guided endovascular interventions, catheter-directed Gd-enhanced MRA offers many of the same capabilities as conventional x-ray DSA. Local injections permit rapid depiction of blood vessels and help guide interventions. The primary benefit of IA injections is significant reduction of administered contrast-agent dose compared with conventional IV injections. Another major benefit is facilitated background suppression, including that of adjacent vascular beds. As MRI guidance methods improve, catheter-based Gd injections should gain expanded use in clinical practice.     

Using gadolinium-enhanced three-dimensional MR angiography to assess arterial inflow stenosis after kidney transplantation

OBJECTIVE: Our objective was to evaluate use of gadolinium-enhanced three-dimensional (3D) MR angiography in the assessment of suspected arterial inflow stenosis after kidney transplantation. SUBJECTS AND METHODS: Twenty-eight consecutive patients receiving kidney transplants (26 single-kidney transplants and two en block transplants) with suspected arterial inflow stenosis were examined with two MR angiography sequences: gadolinium-enhanced 3D fast spoiled gradient-recalled (SPGR) imaging and 3D phase-contrast imaging. Twenty-four of these patients then were examined using the gold standards: either digital subtraction angiography (DSA) (n = 23) or surgery (n = 1). MR angiography and DSA studies were independently and prospectively analyzed for the presence of arterial stenoses (mild [<50%], severe [50-90%], or critical [>90%]) in the iliac, anastomotic, and renal artery segments. Two independent observers retrospectively evaluated the MR angiography sequences for ability to detect or exclude significant (> or = 50%) arterial stenoses. RESULTS: In 22 single-kidney transplants, DSA showed eight significant stenoses in 66 arterial segments. MR angiograms adequately showed 66 of 66 segments (prospective observers) and 64 of 66 segments (each retrospective observer), which were subsequently evaluated. The sensitivity and specificity of MR angiography in revealing significant stenoses were 100% and 98% (prospective analysis), 88% and 98% (retrospective observer 1), and 86% and 100% (retrospective observer 2). Concordance between observers showed kappa values exceeding .85 for all comparisons except the analysis of phase-contrast series (kappa = .62). In one en block transplant, DSA showed that stenosis was greater than 90%, although it had been graded at less than 50% with MR angiography. CONCLUSION: Gadolinium-enhanced 3D MR angiography accurately evaluated arterial inflow in single-kidney transplants.     

Evaluation of vascular complications of pancreas transplantation with high-spatial-resolution contrast-enhanced MR angiography

PURPOSE: To retrospectively evaluate high-spatial-resolution contrast material-enhanced three-dimensional (3D) magnetic resonance (MR) angiography for assessment of vascular complications of pancreas allografts. MATERIALS AND METHODS: The institutional review board approved the study and waived the requirement for informed patient consent owing to the retrospective nature of the study with use of an anonymous-subject database. The study was HIPAA compliant. The clinical and MR angiography findings in 11 patients (eight men, three women; mean age, 43 years; age range, 30-54 years) who had a history of pancreatic transplant dysfunction and underwent a total of 13 contrast-enhanced 3D MR angiography examinations were retrospectively reviewed. Comparison with conventional angiography findings was possible for four MR angiography examinations, comparison with surgical findings was possible for two examinations, and clinical follow-up was possible for all examinations. Two observers in consensus and blinded to the clinical results performed image analysis of the arterial and venous segments. Classification agreement was assessed with quadratic weighted kappa statistics. RESULTS: Ten MR angiography examinations revealed vascular complications or signs suggestive of rejection. Only three examinations were considered to have completely normal results. All major complications were detected and included complete or partial arterial graft occlusion, stenosis of the arterial Y-graft caused by a kink, complete venous thrombosis, and arteriovenous fistula with pseudoaneurysm formation. For 46 arterial segments and 15 venous segments with angiographic and/or surgical comparison, overall agreement with MR angiography findings was nearly perfect (mean kappa, 0.983; standard error of the mean, 0.128). CONCLUSION: High-spatial-resolution MR angiography of pancreas allografts enables assessment of the arterial and venous vascular anatomy and can be used to reliably identify clinically relevant vascular complications.     

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.     

MR cholangiography of late biliary complications after liver transplantation.

OBJECTIVE: The aim of our study was to assess the role of MR cholangiography in the diagnosis of late biliary complications after liver transplantation. SUBJECTS AND METHODS: Twenty-three liver transplantation patients (18 men and five women; mean age, 46 years) underwent MR cholangiography using a nonbreath-hold, fat-suppressed three-dimensional turbo spin-echo sequence (TR/TE, 3000/700; echo train length, 128) optimized on a 0.5-T magnet. Inclusion criteria were liver function tests with abnormal results and hyperbilirubinemia with a clinical pattern not specific for biliary obstruction. All patients were referred by clinicians for contrast-enhanced cholangiography. Diagnostic confirmation was obtained with percutaneous transhepatic cholangiography (n = 4), endoscopic retrograde cholangiography (n = 8), T-tube cholangiography (n = 1), or clinical follow-up (n = 10). RESULTS: In 11 patients, no abnormalities of the biliary tract were revealed by MR cholangiography. In 11 patients, twelve strictures were diagnosed (nine anastomotic, two nonanastomotic-intrahepatic, and one nonanastomotic-extrahepatic, with association between anastomotic and nonanastomotic strictures in two cases). In one other patient, kinking of the common bile duct at the level of the anastomosis was observed. In all cases, MR cholangiography correctly showed the site of the stricture and the dilatation of bile ducts above, with excellent correlation with contrast-enhanced cholangiographic findings. Strictures were correctly graded in eight of 10 patients and were overestimated in two. Other findings included a 1-cm stone detected proximal to the obstructed common bile duct in one patient and multiple intrahepatic stones in another patient. CONCLUSION: MR cholangiography can show biliary obstruction and provide important information for planning therapeutic procedures.     

Biliary complications after liver transplantation: diagnosis with MR cholangiopancreatography

OBJECTIVE: We sought to evaluate MR cholangiopancreatography (MRCP) as the only imaging procedure used in the diagnosis and management of biliary complications after orthotopic liver transplantation (OLT). CONCLUSION: MRCP is a useful imaging procedure in the assessment of biliary complications after OLT.     

MR cholangiography in biliary complications after liver transplantation in children

PURPOSE: To evaluate the role of MR Cholangiography in a pediatric population with biliary complications after liver transplantation and particularly with anastomotic stenosis. PATIENTS AND METHODS: Ten MR cholangiography studies were performed in 10 children with liver transplant who were suspected of having biliary complications between December 1996 and April 1998. The findings on MR were correlated with the results from liver biopsy, liver ultrasound, liver function tests and with clinical information when available. RESULTS: MR cholangiography identified 9 children with biliary tree dilatation, 4 with anastomotic stenosis, 5 with multiple bile ducts stenosis, 2 with stones in the intra-hepatic biliary tree and 2 with abnormalities suspicious for acute cholangitis. Three of 4 anastomotic stenoses were confirmed and treated by percutaneous cholangiography. There was no correlation between the different exams in 6 children but MR cholangiography confirmed the final diagnosis. CONCLUSION: In children with liver transplantation, MR cholangiography may be useful to evaluate and to confirm a diagnosis of bile duct complications and it is helpful in the absence of correlation between liver biopsy, ultrasound and liver function test.     

Detection of vascular complications after liver transplantation: early experience in multislice CT angiography with volume rendering

OBJECTIVE: Our objective was to investigate the usefulness of three-dimensional multislice CT angiography for the evaluation of liver transplant recipients presenting with clinical or sonographic findings suggestive of hepatic vascular complications. CONCLUSION: Our early results indicate that three-dimensional multislice CT angiography with volume rendering can reveal common and potentially lethal vascular complications in patients who have undergone liver transplantation.     

Contrast-enhanced MR angiography (CE-MRA) in the evaluation of vascular complications of renal transplantation

Vascular complications associated with renal transplantation merit urgent investigation since they are often correctable, and timely intervention can help salvage the graft kidney. Contrast-enhanced MR angiography (CE-MRA) is a promising non-invasive technique, uses relatively non-nephrotoxic contrast agents and can rapidly demonstrate the underlying lesion in most instances. In this pictorial review we present the spectrum of abnormalities, as well as the pitfalls of interpretation of CE-MRA, that we encountered in 41 cases where there was clinical suspicion of vascular complications of renal transplantation. We believe that CE-MRA is a valuable, non-invasive screening technique in these cases, and further investigation and management of these patients can be confidently tailored to the results of the CE-MRA study.     

Three-dimensional low dose gadolinium-enhanced peripheral MR venography

Our initial experience with low dose contrast-enhanced (LCE) peripheral MR venography (MRV) is presented. Five subjects were studied using three-dimensional (3D) fast imaging with a steady-state precession (FISP) sequence. A dose of 60 ml of gadopentetate dimeglumine diluted 1:20 was used. A tourniquet was applied during lower extremity MR venography. The venous anatomy was well depicted with the 3D LCE technique in all subjects. Compared to the two-dimensional (2D) time-of-flight (TOF) technique, acquisition time of 3D LCE MRV was much shorter, images looked sharper, and more veins could be seen. It is not affected by in-plane saturation and can be performed repeatedly because of the low dose of contrast. This technique holds promise for the detection of venous thrombosis and other disorders.     

肝移植术后血管与胆管并发症介入治疗初探

目的：评价血管造影和胆管造影诊治肝移植术后血管及胆管并发症的价值。方法：46例原位肝移植术后B超提示血流速度不畅或频谱异常，下肢水肿或黄疸的患者16例，进行腹腔动脉造影10例次，下腔静脉造影并球囊扩张或支架置入6例次，经皮肝穿刺门静脉造影并支架置入2例次，经皮肝穿刺胆管造影并引流4例次。结果：肝动脉血栓形成2例，1例经溶栓治疗后部分开通；肝动脉狭窄4例，1例球囊扩张后狭窄减轻；所有下腔静脉和门静脉阻塞或狭窄行球囊扩张及置放支撑架后临床症状好转，4例胆管狭窄和吻合口瘘者行经皮肝穿刺胆管造影引流（PTCD）治疗后黄疸减轻。结论；对肝移植术后出现的血管和胆管并发症，血管造影和胆管造影不仅可明确诊断，而且能同时工取得较好的近期疗效。     

Three-dimensional gadolinium-enhanced magnetic resonance angiography of pulmonary arteriovenous malformation

Pulmonary arteriovenous malformations (AVMs) are rare vascular malformations of the lung. Although most patients are asymptomatic, AVMs can bleed and result in haemoptysis and haemothorax. We describes a case of pulmonary AVMs in a patient with Osler-Weber-Rendu syndrome with 3-D contrast-enhanced MR angiography. Magnetic resonance angiography provided accurately and non-invasively the number and size of the feeding arteries and draining veins.