You are in: eMedicine Specialties > Radiology > VASCULAR/INTERVENTIONAL Polyarteritis NodosaArticle Last Updated: May 26, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 9
  Author: Robert L Cirillo Jr, MD, MBA, Assistant Professor of Radiology, Florida State University College of Medicine; Medical Interventional Radiologist, Director/CEO, South Georgia Vascular Institute and South Georgia Laser Vein Center Robert L Cirillo, Jr, is a member of the following medical societies: American College of Physician Executives, Cardiovascular and Interventional Radiological Society of Europe, Society for Vascular Technology, and Society of Interventional Radiology Editors: Fredric A Hoffer, MD, FAAP, FSIR, Professor of Radiology, University of Washington; Section Chief of Interventional Radiology, Department of Radiology, Seattle Children's Hospital and Regional Medical Center; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; George Hartnell, MB, Professor of Radiology, Tufts University School of Medicine, Director of Cardiovascular and Interventional Radiology, Department of Radiology, Baystate Medical Center; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Kyung J Cho, MD, FACR, William Martel Professor of Radiology, Fellowship Program Director, Department of Radiology, Division of Interventional Radiology, University of Michigan Medical School Author and Editor Disclosure Synonyms and related keywords: PAN, autoimmune systemic inflammatory vasculitis, fibrinoid necrotizing vasculitis, transmural fibrinoid necrosis, classic polyarteritis nodosa, microscopic polyarteritis nodosa, microscopic polyangiitis INTRODUCTIONSection 2 of 9
  BackgroundPolyarteritis nodosa (PAN) is an autoimmune systemic inflammatory vasculitis that results in transmural fibrinoid necrosis with surrounding inflammation in small and medium-size vessels. PAN commonly affects the kidneys, heart, liver, and gastrointestinal (GI) tract, with the kidney being the organ most commonly involved (79% of cases at autopsy).1, 2 PathophysiologyPAN causes a fibrinoid necrotizing vasculitis of small and medium-size muscular arteries. Arterioles, capillaries, and venules are not involved. The organs most often involved include the kidneys (80-90%), heart (<70%), GI tract (50-70%), liver (50-60%), spleen (45%), and pancreas (25-35%). Less commonly involved are the brain, lungs, and diaphragm. The small intestines are the site affected most commonly in the GI tract, followed by the mesentery and colon. Fibrinoid necrosis of PAN most often involves the media, with subsequent involvement of the intima and adventitia, although involvement of all layers can occur concurrently. Secondary changes are common and include characteristic aneurysmal formation, hemorrhage, and thrombosis. There are 2 forms of PAN: macroscopic (classic), and microscopic (microscopic polyangiitis). In macroscopic PAN, the kidneys are involved in 85% of patients with necrotizing inflammation of small or medium-size arteries. The glomerulus and pulmonary capillaries usually are not involved. In microscopic polyangiitis, involved vessels often are smaller; the glomerulus and pulmonary capillaries often are involved in these patients. The cause of the arterial necrotizing inflammation appears to be the deposition of immune complexes. The complexes can be detected in the serum, but they are often absent in biopsy samples of skeletal muscle.3 FrequencyUnited StatesThe estimated annual frequency of PAN is 4-9 cases per million. Mortality/MorbidityIn cases in which PAN goes untreated, mortality is related to progressive renal failure or complications involving the GI tract. The 5-year survival rate for untreated patients is 15%. Treatment of PAN with corticosteroids and cyclophosphamide results in a cure in as many as 90% of patients; however, relapses occur in 40% of patients. SexThe male-to-female ratio is 2-3:1. AgeThe disease commonly occurs in the fourth to seventh decades of life. Clinical DetailsBecause PAN affects a spectrum of organs, recognition of the disease process is occasionally difficult, owing to the potential multitude of vague symptoms. Unfortunately, the range of symptoms often delays diagnosis and treatment. Clinical features of PAN most commonly include fever, abdominal pain, and weight loss. Hypertension is not a common initial feature, although it is present in most patients examined. Other clinical findings include arthralgia or arthritis, retinopathy, painful subcutaneous nodules, painless hematuria, elevated erythrocyte sedimentation rates, and peripheral and central nervous system dysfunction (including peripheral neuropathy). Involvement of the skin and skeletal muscles is not as common as renal involvement, but characteristic tender subcutaneous nodules are seen in 15% of patients. If the kidneys are involved, renal failure or hypertension can occur. If the heart is involved, myocardial infarction, congestive heart failure, and pericarditis can ensue. Overall, as many as two thirds of patients with PAN have abdominal pain, nausea, vomiting, and other symptoms involving the GI tract. Symptoms are related to bowel ischemia and infarction. GI hemorrhage occurs in approximately 6% of patients, bowel perforation occurs in 5%, and bowel infarction occurs in 1.4%.4, 5 Preferred ExaminationFor an accurate diagnosis of PAN, selective arteriography is the criterion standard. In the past, biopsy was used. Analysis of biopsy specimens from the subcutaneous nodules or skeletal muscle may be helpful in establishing the diagnosis, although biopsy has a success rate of only 20-35%. Antineutrophilic cytoplasmic autoantibodies (ANCA) are often present in the serum of patients with PAN; in such patients, ANCA levels often correlate with disease activity. However, ANCA can be present in patients with other vasculitides, including Churg-Strauss syndrome, Wegener granulomatosis, and microscopic polyangiitis. Patients with PAN may have hypergammaglobulinemia. As many as 30% of patients with PAN test positive for hepatitis B surface antigen. Limitations of TechniquesAlthough biopsy was used more extensively in the past, it has fallen into disfavor because of sampling errors and its low success rate. Angiography can be helpful in confirming or supporting the clinical diagnosis of PAN; however, it is an invasive test.6, 7, 8 DIFFERENTIALSSection 3 of 9
Other Problems to Be ConsideredDrug-induced vasculitis
RADIOGRAPHSection 4 of 9
FindingsExcretory urographic findings are often normal in patients with PAN. Subtle findings can include increased renal size, ureteral dilatation, perinephric hematoma, and renal infarction.9 CT SCANSection 5 of 9
FindingsCT findings are nonspecific, but they include bowel wall thickening; vascular engorgement; haziness in the mesentery; ascites; ureteral dilatation; renal, hepatic, and splenic infarctions; and perinephric hematoma.10 ANGIOGRAPHYSection 6 of 9
FindingsSelective arteriography is the best modality for evaluating and diagnosing PAN. The most striking pathognomonic finding is the appearance of aneurysms, usually microaneurysms, which are believed to be caused by rupture of a vessel wall (see Images 1-2). Microaneurysms are often multiple, usually numbering 10 or more in any single visceral circulation. In most patients, they are 2-5 mm in size. Saccular aneurysms (1-5 mm) of small and medium-sized vessels are typically found. Usually, microaneurysms can be identified in 60-80% of patients, and although they are considered to be pathognomonic for PAN, they can be encountered in other vasculitides. The aneurysms are caused by segmental occlusion of the arteries with weakening of the arterial wall, which occurs as a result of the necrotizing inflammatory process. The most common sites of involvement of PAN are the branching points and bifurcations of arteries. Common sequelae of PAN are intravascular thrombosis, aneurysm rupture, and arterial occlusion with resultant infarctions. In the kidneys, these sequelae can cause ischemic atrophy and hemorrhage. The hemorrhage is usually intrarenal, perinephric, subcapsular, or retroperitoneal. Other angiographic features of PAN include tortuous vessels with irregular lumina, segmental luminal narrowing or dilatation, infarctions, vascular irregularity, segmental occlusions, and hypervascularity in regions of PAN.6, 7, 8 Degree of ConfidenceAlthough angiographic findings of microaneurysm, ectasia, and/or occlusive disease suggest the diagnosis of PAN, these findings may be seen in other vasculitides, including rheumatoid vasculitis, Churg-Strauss syndrome, necrotizing angiitis associated with drug abuse, and systemic lupus erythematosus. Correlation with the clinical evaluation is important. INTERVENTIONSection 7 of 9
Transcatheter embolization should be considered only in cases involving larger aneurysms, because of the potential for rupture, and when bleeding occurs from rupture of the aneurysm. MULTIMEDIASection 8 of 9
REFERENCESSection 9 of 9
Article Last Updated: May 26, 2008 | |||||||||||||||||||
