Infected aortoiliofemoral grafts: magnetic resonance imaging

Three patients with proved infected aortoiliofemoral grafts were examined by magnetic resonance (MR) imaging using a spin echo technique. MR clearly identified the perigraft abscess, the involvement of adjacent structures, and the longitudinal extent of the process in all patients. The MR findings were: Abscesses create a high signal intensity, somewhat less than fat. The perigraft abscess has a great contrast with the signal void of flowing blood in the graft. Inflammatory changes cause an inhomogeneous intermediate signal, slightly more intense than muscle. Both abscesses and edematous areas increase their signal intensity with long repetition rates and long echo delays. Areas of gas appear black. They cannot be distinguished from calcified plaques. Additional information is gained about the graft patency. Although the specificity has to be proved, MR imaging is sensitive in the detection of infected grafts and for defining the longitudinal extent of the perigraft abscess.     

Incorporation versus infection of retroperitoneal aortic grafts: MR imaging features

The magnetic resonance (MR) imaging characteristics of normal aortic graft healing were compared with those of perigraft infection in 57 patients after aortic graft implantation. Thirty-three patients without postoperative complications underwent MR imaging in a 0.35-T unit 1 week after graft implantation, and 13 of those patients were reexamined 2-3 months after graft implantation. Twenty-four patients with clinically suspected perigraft infection underwent MR imaging 6 weeks to 18 years after graft implantation. Early normal postoperative changes were characterized by a perigraft collar of low to medium signal intensity on T1-weighted images and of high intensity on T2-weighted images in all 33 cases, consistent with perigraft fluid collection. In 10 of 13 patients reexamined 2-3 months postoperatively, the MR images demonstrated a collar of tissue consistent with perigraft fibrosis. In cases of clinical suspicion of retroperitoneal graft infection, MR imaging showed eccentric fluid collections of low to medium signal intensity on T1-weighted images and high intensity on T2-weighted images at more than 3 months after surgery. The MR findings were diagnostic of retroperitoneal perigraft infection in 17 of 20 patients shown to be infected at surgery. Retroperitoneal infection was correctly excluded on the basis of MR findings in four patients. Thus, MR imaging is an accurate imaging method for the diagnosis of aortic graft infection. In the early postoperative phase, resolving perigraft fluid cannot be differentiated from perigraft infection.     

Detection of prosthetic vascular complications: comparison of CT and angiography

The value of CT and angiography to detect complications of prosthetic arterial grafting was compared in 24 patients. There was a total of 27 grafts including 18 aortic or aortofemoral, five femoral-popliteal, two femoral-femoral, and two axillary-femoral reconstructions. Nineteen grafts were uninfected; eight were infected. In the absence of infection, the complications and the percentages detected by the two procedures were as follows: five graft occlusions (CT 80%, angiography 100%), six pseudoaneurysms (CT 100%, angiography 83%), three with perigraft fluid (CT 100%, angiography 0%), and one with pseudointimal hyperplasia (CT 100%, angiography 0%). Seven grafts were normal and without abnormalities on both CT and angiography. In the presence of infection the results were as follows: eight with perigraft fluid (CT 100%, angiography 0%), four with perigraft or intragraft gas (CT 100%, angiography 0%), three pseudoaneurysms (CT 100%, angiography 100%), two open groin wounds (CT 100%, angiography 0%), and two graft occlusions (CT 100%, angiography 100%). In addition, three patients with infected grafts had graft enteric fistulae. All three had fluid around the proximal anastomosis and two had gas around the graft as well. The data show that angiography is sufficient for patients with graft occlusion if there is no suspicion of infection, postoperative hemorrhage, or anastomotic pseudoaneurysm. In these cases CT has an ancillary role in detecting hemorrhage and defining pseudoaneurysms. CT is superior to angiography in patients with graft infection.     

Composite graft replacement of the ascending aorta: leakage detection with gadolinium-enhanced MR imaging.

PURPOSE: To assess the value of magnetic resonance (MR) imaging in the detection of postoperative complications after composite valve graft replacement. MATERIALS AND METHODS: Spin-echo and gradient-echo MR imaging was performed in 52 patients 1/2 to 200 months after composite graft replacement of the ascending aorta (22 for dissection, 30 for aneurysm). The prosthetic aortic segment, distal and proximal anastomoses, general morphologic characteristics, and diameter of the reimplanted coronary arteries were evaluated. In patients with abnormal perigraft thickening, additional spin-echo imaging was performed after injection of gadopentetate dimeglumine. RESULTS: Normal postoperative perigraft thickening (< or = 10 mm) was observed in 42 patients. Ten patients had abnormal periprosthetic thickening of 15-52 mm. Gadolinium-enhanced MR imaging demonstrated leakage in five of those 10 patients. The lack of enhancement excluded the presence of bleeding in the remaining five patients (three with chronic hematomas, one with infection, and one with granulation tissue). These findings were confirmed at surgery or with subsequent follow-up MR examinations. CONCLUSION: MR imaging was an optimal imaging modality for evaluating the morphologic characteristics of composite grafts and reimplanted coronary arteries. Gadolinium-enhanced MR imaging is a simple, accurate, and noninvasive method for detecting a leak, which necessitates urgent repeat surgery.     

Magnetic resonance imaging evaluation of the ascending aorta after graft-inclusion surgery: Comparison between an ultrafast contrast-enhanced MR sequence and conventional cine-MRI

The aim of this study was to compare the value of two magnitude-based MR sequences, a contrast-enhanced ultrafast MR sequence and a cine MR sequence, for the detection of flow around the graft in the postoperative ascending thoracic aorta. Thirteen patients who underwent ascending aortic surgery for dissection (n = 11) and aneurysm (n = 2) were enrolled. They were referred to MRI for mediastinum enlargement on the chest x-ray or mediastinal symptoms. All patients had replacement of the diseased ascending aorta using a graft-inclusion technique (with wrapping of the native aorta over the graft). Delays between surgery and MRI ranged from 15 days to 8 years (mean: 10 months). All patients were examined using a T1-weighted spin-echo sequence, a magnitude-based cine gradient-echo sequence, and an ultrafast contrast-enhanced MR sequence. MR images of the cine and the contrast-enhanced sequences were retrospectively and independently analyzed by two qualified radiologists for evidence of flow or thrombus around the graft, including perigraft structure and aneurysmal formations. Evidence of flow was detected by both methods in all aneurysmal formations of the ascending aorta located at suture level (n = 6). Evidence of flow in the perigraft structure was found in seven cases by contrast-enhanced MR sequence and in only four cases by cine MR sequence. Contrast-enhanced ultrafast MR sequence could be proposed as a minimally invasive and fast modality for assessing the perigraft structure, in graft-in-clusion surgical procedures of the ascending aorta, when noncontrast enhanced MR sequences do not exclude the possibility of flowing blood in this structure.     

MR angiography of lower-extremity arterial disease: preliminary experience.

Nineteen patients underwent magnetic resonance (MR) angiography for evaluation of lower-extremity arterial disease. The underlying conditions included atherosclerotic occlusive disease in 12 patients, femoral or popliteal aneurysms in four, and bypass graft stenoses or occlusion in four. In the patients with occlusive disease, the iliac and femoropopliteal vessels were classified as patent, moderately stenotic, severely stenotic, or occluded. Fifteen of 16 occlusions (accuracy = 94%) were correctly classified. In the one missed case, there was a long delay between MR angiography and x-ray angiography and it is likely that the occlusion occurred during the interval. Three of five severe stenoses were correctly classified with MR angiography. In two cases of iliac artery stenosis, there was a signal void at the point of maximal stenosis, which on the basis of anatomic features could be recognized as severe stenosis rather than an occlusion. Three of four moderate stenoses were correctly classified. Correlation with x-ray angiography or surgery demonstrated the ability of MR angiography to accurately depict the status of runoff vessels.     

Aortic anastomotic pseudoaneurysms: US, CT, MR, and angiography.

Correlation of imaging and anatomic findings in seven men with abdominal aortic graft prostheses (four "end-to-end" anastomoses and three "end-to-side" anastomoses) was done to compare the value of different imaging modalities in detecting postoperative complications, especially aortic anastomotic pseudoaneurysms (AAPs). In all cases, angiographic and CT studies were carried out. In six patients ultrasound and MR examinations were also performed. Anatomic verification was obtained by surgery in six patients and autopsy in one case. Five patients had an AAP (four at surgery and one at autopsy), one had a true abdominal aortic aneurysm above the anastomosis, and one a nondetectable abnormality of the aortic suture line. Digital subtraction angiography diagnosed one of five AAPs, missed the true aneurysm in the sixth patient, and was normal in the patient without any aneurysm. Computed tomography correctly diagnosed the five AAPs and the true aneurysm and was normal in the last patient. Ultrasound correctly diagnosed the AAPs in three of four patients, incorrectly diagnosed an AAP in the patient who had the true aneurysm, and was normal in the patient without any aneurysm. Magnetic resonance diagnosed four of four AAPs and the true aneurysm and was normal in the last patient. Computed tomography seems to be the best imaging modality with which to diagnose and evaluate an aortic AAP in patients with aortoiliofemoral graft prosthesis.     

Ultrasound of arterial graft surgery complications.

The value of gray scale ultrasound in evaluating primary diseases of the abdominal aorta and peripheral vessels has been well documented. However, only limited attention has been given to complications associated with arterial graft surgery. Twelve patients with a variety of complications are reported. These include 10 anastomotic pseudoaneurysms, one abscess, two "aneurysms" in degenerated graft material, and four serous fluid collections around intact Dacron grafts. The latter two complications are previously unreported.     

Perivalvular pseudoaneurysm complicating bacterial endocarditis: MR detection in five cases

Bacterial endocarditis usually affects the valve leaflets, but erosion into the valve anulus and adjacent myocardium may form a myocardial abscess. Perivalvular abscesses can drain into the ventricles or aorta, forming a life-threatening pseudoaneurysm. We reviewed our experience with cardiac MR imaging of this disorder. Fourteen patients with complicated bacterial endocarditis underwent ECG-gated spin-echo cardiac MR imaging in addition to conventional duplex two-dimensional echocardiography (2-D echo). Angiography was performed in seven patients, six of whom underwent surgery for valve replacement. MR imaging detected the pseudoaneurysms in all five of the surgically proved cases, while 2-D echo detected only three. Clinical follow-up suggested there were no false-negative examinations, but no autopsy data were available for confirmation. Postoperative MR imaging studies were conducted in three patients, revealing two recurrent pseudoaneurysms and one thrombosed aneurysm. Cardiac MR imaging provides useful pre- and postoperative information in patients with perivalvular pseudoaneurysms due to endocarditis.     

Stent-graft placement for pseudoaneurysm of the aorta

PURPOSE: To evaluate the use of endovascular stent-graft placement to repair pseudoaneurysm of the aorta. METHODS: Six patients were treated with stent-grafts for pseudoaneurysms located in the thoracic aorta (n=2), thoracoabdominal aorta (n=3), and abdominal aorta (n=1). Etiologies of the pseudoaneurysms included leakage from surgical graft, penetrating atherosclerotic ulcer, pneumonia, perforated esophageal ulcer, and mycotic aneurysm. All patients were clinically considered to be at high surgical risk. RESULTS: Stent-grafts were successfully placed in all patients. There was one death in the perioperative period due to massive hemoptysis before stent-grafting. Two patients died of persistent infection. One patient with persistent perigraft leak died of rupture. Two other patients needed no further therapy for pseudoaneurysm. CONCLUSION: Stent-graft placement for pseudoaneurysm of the aorta can play the role of a temporizing method prior to surgical repair in high-risk cases and be a therapeutic alternative in cases without infection or perigraft leakage.     

Fluid collections in the intraperitoneal and extraperitoneal spaces: comparison of MR and CT

Fourteen patients with abnormal subdiaphragmatic fluid collections (eight intraperitoneal, two extraperitoneal, and four intra- and extraperitoneal) were examined with computed tomography (CT) and magnetic resonance (MR) imaging. MR and CT provided equivalent information concerning the presence and extent of fluid collections in 13 of the 14 cases. Image acquisitions with two different repetition times (TRs) and two echo times (TEs) were necessary, in most cases, to detect and discriminate between different types of pathologic fluids. Transudative ascites demonstrated long T1 and T2 relaxation times, whereas abscesses, phlegmon, pancreatic pseudocyst, exudative pancreatitis, and chronic hematoma demonstrated an intermediate or short T1 and a long T2.     

Inflammatory myofibroblastic tumor of the hepatobiliary system: report of MR imaging appearance in four patients

The purpose of this report is to describe the magnetic resonance (MR) imaging features of hepatic inflammatory myofibroblastic tumor (IMT). Two observers retrospectively analyzed images from six MR imaging examinations in four consecutive patients. Tumor location, size, extent, morphology, and number; signal intensity on nonenhanced images; enhancement pattern on serial gadolinium-enhanced images; duct wall thickness; and presence of biliary dilatation, vascular invasion, and lymphadenopathy were assessed. MR imaging findings were compared with histologic findings. On MR images, hepatic IMT manifested as a mass-like lesion in two patients and an area of periportal soft-tissue infiltration in three; one patient had both patterns. Because periportal infiltration is a common feature in both IMT and other malignant tumors of the porta hepatis, histologic examination should be considered before diagnosis and treatment.     

Renal aneurysms and pseudoaneurysms

Pseudoaneurysms and aneurysms are abnormal dilatations of the vessel lumen. Pseudoaneurysm is a perfused hematoma contained by the adventitia and perivascular tissues that is in communication with the lumen of an adjacent artery or vein. Aneurysm is a dilatation of the vessel lumen involving all three layers of the blood vessel wall. Renal artery aneurysms (RAA) are uncommon but the widespread use of cross-sectional imaging and incidental detection of RAA may result in an increasing number of cases diagnosed. Renal artery pseudoaneurysms are suspected in bleeding patients after penetrating renal trauma. Imaging plays a major role in the detection of renal pseudoaneurysms and aneurysms and diagnoses aneurysm rupture and active bleeding. Computed tomography (CT), magnetic resonance imaging, and digital subtraction angiography can characterize lesion size, shape, and location and identify other aneurysms and pseudoaneurysms, helping to narrow the differential diagnosis and to understand the vascular anatomy for guiding proper treatment. Endovascular treatments have contributed considerably in the management of renal pseudoaneurysms and aneurysms. The use of coil embolization or covered stent placement prevents the mortality and mobility of surgery. The article describes imaging features and the endovascular therapies to treat these vascular processes and their possible complications.     

CT of aortoenteric fistulas

We compared CT findings with endoscopic, angiographic and surgical results in ten patients suspected of having an aortoenteric fistula (AEF) because of gastrointestinal bleeding (seven) or recurrent sepsis (three). CT correctly diagnosed AEF in six patients and excluded it in the other four. CT findings of AEF consisted of perigraft fluid (PGF) (5/6) and/or gas within the bed of the graft (4/6) later than three months after graft surgery. All six patients with AEF had perigraft infections; PGF with gas was found in 50%, PGF alone in 33%, and in one patient perigraft gas alone was found. Angiography and endoscopy failed to identify AEF. Our findings indicate that CT should be the initial imaging procedure in patients with suspected AEF who do not require immediate surgical intervention.     

Multimodality imaging of pancreas-kidney transplants

Simultaneous pancreas-kidney transplant remains a treatment option for patients with insulin-dependent diabetes mellitus type 1, aimed at restoring normoglycemia, alleviating insulin dependency, avoiding diabetic nephropathy, and thereby improving the quality of life. Imaging remains critical in the assessment of these transplant grafts. Ultrasound with Doppler remains the primary imaging modality for establishing baseline assessment of the graft as well as for evaluating vascular, parenchymal, and perigraft complications. Noncontrast MR imaging is preferred over non-contrast CT for evaluation of parenchymal or perigraft complications in patients with decreased renal function, although contrast-enhanced CT/MR imaging may be obtained following multidisciplinary consultation in cases with high clinical and laboratory suspicion for graft dysfunction. Catheter angiography is reserved primarily for therapeutic intervention in suspected or confirmed vascular complications. An understanding of the surgical techniques and imaging appearance of a normal graft is crucial to identify potential complications and direct timely management. This article provides an overview of surgical techniques, normal imaging appearance, as well as the spectrum of imaging findings and potential complications in pancreas-kidney transplants.     

Endovascular repair of the abdominal aortic aneurysm with the ancure endograft: CT follow-up of perigraft flow and aneurysm size at 6 months

PURPOSE: Perigraft flow--flow outside the graft lumen but contained within the abdominal aortic aneurysm (AAA)--is a potential complication after endovascular repair of AAA. Such flow may permit AAA growth and rupture. The purpose of this study is to evaluate with computed tomography (CT) the rate of spontaneous closure of perigraft flow and the effect of persistent flow on AAA diameter. MATERIALS AND METHODS: During a 30-month period, the authors evaluated all CT scans in 50 patients who underwent AAA repair using the Ancure endograft system. CT was performed at discharge, 6, 12, and 24 months, and at 3 months if there was perigraft flow at discharge. Scans were reviewed for the presence, size, and location of perigraft flow, and measurement of AAA diameter. Transcatheter embolization was performed on those patients with persistent leak at 6 months. RESULTS: Sixteen (32%) of 50 patients demonstrated perigraft flow on CT performed within 72 hours of placement. Resolution of perigraft flow by 6 months was found in nine (56%) of the 16 patients, in whom AAA size had decreased in five, had increased in none, and was unchanged in four. Seven patients had persistent leaks at 6-month CT; AAA size had decreased in one, had increased in one, and was unchanged in five. In 34 patients without leaks, AAA size had decreased in nine, had increased in one, and was unchanged on 24. There was no statistically significant difference for the relationship between resolution or persistence of perigraft flow and subsequent course of AAA diameter (P = .16). CONCLUSIONS: Although perigraft flow is frequently seen (32%) early after repair of AAA with the Ancure system, spontaneous resolution by 6 months occurs in 56% of cases. AAA size decreased in a larger percentage of patients in whom perigraft leak was absent or resolved by 6 months compared with those in whom perigraft leak persisted at 6 months.     

Coarctation of the aorta: MR imaging

Thirteen patients, aged 3-31 years, with coarctation of the thoracic aorta were examined by magnetic resonance (MR) imaging (total of 14 studies). Eight studies were performed preoperatively and six postoperatively. Catheterization data were available on 12 patients for verification of MR imaging findings. Electrocardiographically gated sagittal and left anterior oblique images best depicted the coarctations; however, involvement of arch vessels was best evaluated on transaxial images. MR imaging readily identified all coarctations but one, their site and extent, and involvement of the arch vessels. In addition, MR images depicted poststenotic dilatation and dilated collateral vessels. In patients studied postoperatively, restenosis could be evaluated, and complications such as postoperative aneurysm and perianastomotic hematoma were identified. MR imaging provides excellent anatomic detail of coarctation of the aorta, potentially obviating the need for angiography.     

Bone marrow edema and associated pain in early stage osteonecrosis of the femoral head: prospective study with serial MR images

PURPOSE: To determine the accuracy of magnetic resonance (MR) cholangiography for demonstration of the biliary tract and detection of biliary complications in patients who have undergone orthotopic liver transplantation. MATERIALS AND METHODS: Breath-hold half-Fourier rapid acquisition with relaxation enhancement MR cholangiography was performed in 25 patients who had undergone orthotopic liver transplantation. MR cholangiograms were prospectively and independently interpreted by two radiologists for depiction of the biliary tract and ductal anastomosis and for complications (eg, biliary dilatation, stricture, stones). MR cholangiographic findings were correlated with findings from direct cholangiography (n = 24) and surgery (n = 1). RESULTS: MR cholangiography completely demonstrated first-order intrahepatic bile ducts in 23 (92%) patients, the donor extrahepatic bile duct in 25 (100%), the recipient extrahepatic bile duct in 17 of 18 (94%), and the anastomosis in 24 (96%). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of MR cholangiography for detection of biliary dilatation and stricture were each 100%. Complete interobserver agreement occurred in the detection of biliary dilatation and stricture. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of MR cholangiography for detection of stones were 100% for one radiologist and 86%, 100%, 96%, 100%, and 95%, respectively, for the other. Both radiologists agreed on the diagnosis of bile duct stones in six of seven cases (kappa = 0.90). CONCLUSION: MR cholangiography enables accurate depiction of the biliary tract and detection of biliary complications in patients with an orthotopic liver transplant.     

Coronary artery bypass graft patency: noninvasive evaluation with MR imaging

A noninvasive means of determining coronary artery bypass graft (CABG) patency in symptomatic patients would be an important clinical asset. The accuracy of magnetic resonance (MR) imaging was evaluated for this purpose. Multiphasic electrocardiographically gated MR imaging examinations were performed in 25 patients with a total of 72 grafts. Transverse images of the heart at ten anatomic levels were obtained at five or six phases of the cardiac cycle. The MR images were read blindly to determine CABG patency versus occlusion, and these results were compared with those of coronary angiography performed within 2 months before the MR imaging. MR imaging correctly disclosed 43 patent grafts and 13 occluded grafts (predictive accuracy, 78%). Patency and occlusion were incorrectly diagnosed from MR imaging findings in five and four CABGs, respectively. CABG status could not be determined in seven (10%) grafts because the grafts were visualized at only one anatomic level. Thus, the accuracy of a definitive MR imaging evaluation was 91% (43 of 47 grafts) for patency determination and 72% (13 of 18 grafts) for occlusion determination. MR imaging appears to be a useful method for the noninvasive evaluation of CABGs.     

Splanchnic artery aneurysms and pseudoaneurysms: transcatheter embolization

Over the past 7 years, eight patients with splanchnic artery aneurysms and pseudoaneurysms were studied and treated. Transcatheter embolization resulted in occlusion of the lesions in all eight patients. Potentially risky and difficult surgery was avoided completely in four patients. Three patients had elective surgery at a later date when their condition was more stable. The remaining patient had definitive surgery after embolization. Transcatheter embolization should be the initial treatment of choice in splanchnic artery aneurysms and pseudoaneurysms.