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Objectives: The aim of this study was to evaluate the value of fully integrated [18F]-FDG PET/MRI in the assessment of retroperitoneal fibrosis with regard to disease activity, extent and vascular involvement compared to clinical and laboratory parameters., Methods: Seventeen [18F]-FDG PET/MRI examinations were performed in fourteen patients. Qualitative (visual 4-point scale) and quantitative PET parameters (maximum standardised uptake value, SUVmax; target-background ratio, TBR) as well as RF thickness and volume were correlated to clinical and inflammatory parameters and compared between therapy-naïve patients and patients under immunosuppression. Evidence for associated large-vessel vasculitis was examined. Magnetic resonance angiography (MRA) was performed to detect aneurysms or stenoses., Results: Clinical parameters, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) only incompletely displayed inflammatory activity and did not correlate with PET/MRI parameters. In 29% (4/17) resp. 50% (8/16) of PET/MRI examinations active disease was detected although CRP resp. ESR were in the normal range. SUVmax, TBR and volume of the retroperitoneal mass differed significantly between therapy-naïve patients and patients under therapy (SUVmax p=0.004, TBR p=0.015, volume p=0.015), whereas thickness of the retroperitoneal mass did not (p=0.406). Large-vessel vasculitis was detected in 21% (3/14) and aortic aneurysms in 14% (2/14) of patients. Vasculitis occurred apart from the site of RF in two patients., Conclusions: Whole body hybrid [18F]-FDG-PET/MRI is superior to clinical and inflammatory parameters in disease activity assessment of RF. There may be substantial disease activity despite inflammatory parameters in the normal range. Associated large-vessel vasculitis and aneurysms may occur apart from the site of RF.

Retroperitoneal fibrosis, inflammatory aortic aneurysm, and pericardial and mediastinal fibrosis are characterized by infiltration of immuno-inflammatory cells and deposition of thickened fibrous tissues. Several recent studies suggested that an immunoglobulin-G4 (IgG4)-related immunological mechanism may play a role in these diseases. By searching the clinical database of patients admitted to our department between 2000 and 2010, we summarized the clinical data of 11 patients who were diagnosed to have these disorders. The diagnoses were idiopathic retroperitoneal fibrosis (8 cases), mediastinal and/or pericardial fibrosis (4 cases), inflammatory abdominal aneurysm (2 cases), and inflammatory coronary periarteritis (1 case). Hypertension, diabetes, and dyslipidemia were found in 45%, 36%, and 55%, respectively, in these patients, and they were all either current or former smokers. Two patients with pericardial involvement showed a rushed clinical course, resulting in in-hospital death. Serum levels of IgG were elevated in 67%, and soluble interleukin-2 receptor was elevated in 75%, when measured. Immunohistochemical analysis showed marked infiltration of IgG4-positive plasma cells in the pericardium in patients who died of constrictive pericarditis. Our data support the notion that immune-inflammatory mechanism, which might be IgG4-related sometimes, may play a role in idiopathic retroperitoneal fibrosis, inflammatory aortic aneurysm, and mediastinal/pericardial fibrosis, although clinical course may differ substantially., (Copyright © 2011 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)

This paper presents three case reports as a basis for discussing the differential diagnosis of retroperitoneal processes and for describing the possibilities and limitations of diagnostic imaging procedures. A definitive differentiation is not possible by CT and MRI alone, but always requires histologic confirmation. Nevertheless, imaging procedures are indispensable for assessing the extent of a lesion and for follow-up. On the basis of the cases presented here and reports in the literature, it can be hypothesized that benign retroperitoneal fibrosis is caused by a chronic inflammatory or autoimmune response of the vessels since the vast majority of cases are associated with pronounced wall abnormalities of the abdominal aorta.

This report reviews the authors' experience in diagnosing and managing 17 consecutive patients with inflammatory abdominal aortic aneurysm (AAA). Among 491 patients undergoing repair for AAA during a 10-year period, 17 (3%) had evidence of associated periaortic fibrosis, which was confirmed histologically. No patient had acute rupture, and two patients (12%) had chronic contained rupture. Ureteral obstruction was evident in seven patients. In 41% of the patients, available surgical correlation demonstrated that computed tomographic (CT) scan accurately delineated the extent of the disease. Sixteen patients underwent aneurysm resection. Ureteral obstruction was relieved by ureterolysis in three patients treated early in this series. In the last period of the study, well-documented hydronephrosis spontaneously subsided in two patients without special treatment. Of these 17 patients, 15 (88%) were early (30-day) survivors. There were two late deaths at 2 months and 5 years; 12 (71%) patients are still alive and free of symptoms up to 10 years after operation. On the basis of our study, we conclude the following: (1) precise preoperative diagnosis and detailed anatomic information are widely available with CT; (2) aneurysm resection is the treatment of choice because the risk of rupture still exists, and this procedure seems to reverse the inflammatory process; (3) good early and late results can be expected with proper surgical technique; and (4) routine follow-up with CT is recommended to document resolution or progression of the fibrotic process after aneurysm resection.

The so-called "inflammatory" aneurysm of the aorta of the abdominal wall is a special form of the arteriosclerotic aneurysm of the aorta observed in 5-15% of the abdominal aorta aneurysms. It is characterized by more or less marked periaortal fibrotization. The pathological correlate is represented by lymphocytous and plasmacellular infiltrates that are mainly seen and identified in the region of the adventitia. The etiology has not yet been clarified. Since surgery of the inflammatory aneurysm of the abdominal wall aorta is rendered difficult due to neighbouring organs (e.g. ureters) becoming callous and adhesive, safe preoperative diagnosis is desirable. Suspicion of an aneurysm of the abdominal wall can be fairly safely confirmed by sonography. In case of a partially thrombotic aneurysm a characteristic fourfold stratification can be seen: free lumen/thrombus/calcified wall of aorta/law-echo outer layer. This last-named layer--the "inflammatory" portion--is tapelike, semicircular and more or less strongly developed. The inflammatory aneurysm of the abdominal wall is often symptomatic. Hence, the most important differential diagnosis concerns the covered perforation and the dissecting aortic aneurysm, as well as Ormond's disease, periaortal lymphomas and other retroperitoneal tumours.

The histological findings of retroperitoneal fibrosis in 17 operated patients are described. Of these patients 6 showed a simultaneous aneurysm of the abdominal aorta verified either by computerized tomography, ultrasound, arteriography or during an operation. Of the patients 14 were operated on primarily because of ureteral obstruction, 2 because of aortic aneurysm and 1 because of rupture of the abdominal aorta. Advanced fibrosis with varying amounts of inflammation was detected in all 17 patients. The same histological pattern was present in patients with aneurysm of the abdominal aorta and in those without aneurysm. Accompanying vasculitis with destruction of the vascular wall was noted in 8 patients, including 6 with an abdominal aortic aneurysm. In 3 patients who underwent aneurysm resection as well as in 1 patient with aortic rupture the process extended into the aortic wall. The only patient with vasculitis and no aortic process suffers from severe rheumatoid arthritis. On the basis of the different histological findings we suggest that retroperitoneal fibrosis with vasculitis and aneurysm may represent a distinct pathological entity.

Three cases of ureteral obstruction associated with aortoiliac aneurysms were studied with computed tomography. CT was able to document the presence of aneurysm and display the perianeurysmal, fibrotic, contrast-enhancing mass accounting for ureteral obstruction. The value of computed tomography in the diagnosis and evaluation of these cases is described.

The computer tomographic appearances of four patients with the rare inflammatory aneurysm of the abdominal aorta are described. The condition, whose aetiology is not known, affects mostly men in the fifth, sixth and seventh decade. Computed tomography shows, in addition to the typical changes due to an aortic aneurysm, horse-shoe shaped, circular, homogeneous peri-aneurysmal masses, which enhance after intravenous contrast. Bolus injection of contrast is necessary in order to differentiate these from a dissection or retroperitoneal lymphoma. Distinction between these conditions is possible as a result of the various types of enhancement which occur in the aortic lumen, in fibrosis and in lymphoma.

Aorto-iliac aneurysms may entrap the ureters in perianeurysmal fibrosis, causing medical ureteral deviation and/or obstruction. The latter has been described only in male patients; a further 5 cases due to iliac and 3 to aortic aneurysm are reported. The radiologic picture resembles retroperitoneal fibrosis; the correct diagnosis may be suggested when ureteral tethering or narrowing lies near arterial calcification. Sonography is usually the most appropriate investigation to confirm the diagnosis. When sonography shows an aortic aneurysm, the kidneys should be scanned to rule out hydronephrosis. Similarly, films of the kidneys should be obtained when an abdominal aneurysm is demonstrated by aortography.

Atherosclerotic abdominal aortic aneurysms typically present either asymptomatically or with abdominal or back pain. Inflammatory, mycotic, and traumatic aortic aneurysms and aneurysms complicated by venous fistula are less common. The different clinical presentations of these latter aneurysms should raise a suspicion to their diagnosis and appropriate preoperative evaluation. The radiographic and clinical features of inflammatory, mycotic, traumatic, and complicated atherosclerotic aneurysms are presented and discussed.

Inflammatory aortic aneurysms are aneurysms that are surrounded by a variable amount of periaortic fibrosis. This periaortic fibrosis may involve abdominal viscera, such as the duodenum, inferior vena cava, renal veins, or ureters, to a variable degree. On ultrasonographic images, the periaortic fibrosis appears as a hypoechoic mass surrounding the anterior and anterolateral aspects of a dilated aorta. Computed tomography scans reveal a periaortic mass of inflammatory tissue surrounding a dilated atherosclerotic and thickened aorta. The inflammatory mass may enhance to the same extent or slightly less than the aortic lumen following intravenous administration of a contrast agent. Magnetic resonance imaging scans may show the periaortic mass of inflammatory tissue to have a pseudocapsule of compressed fat at its periphery. Recognition of this entity and the extent of the inflammatory process is important to the definitive management of this condition, as illustrated by the case presented.