Imaging Pearls ❯ Kidney ❯ Vasculitis
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- “Immunoglobulin G4 (IgG4)–related disease is an immune-mediated systemic disease that can affect nearly every organ. The pancreas is the most common organ to be affected, and up to 35% of patients who develop autoimmune pancreatitis have renal involvement, referred to as IgG4-related kidney disease (IgG4-RKD) . Isolated IgG4-RKD without other organ involvement is rare. The most common histologic features of IgG4-RKD are tubulointerstitial nephritis with lymphoplasmacytic infiltration, increased IgG4-positive plasma cells, and fibrosis. IgG4- RKD usually responds well to steroids, but if not treated, it can progress to irreversible renal failure.”
Infiltrative Renal Malignancies: Imaging Features, Prognostic Implications, and Mimics
Sweet DE et al.
RadioGraphics 2021; 41:0000–0000 - “There are several imaging patterns of IgG4- RKD parenchymal involvement, including a single nodule, multiple nodules, and diffuse patchy infiltrative lesions. The nodules are rounded or wedge shaped and can have ill defined margins. The most common appearance is that of multiple small nodules in both kidneys, predominantly in the renal cortex. Renal lesions in IgG4-RKD usually are not visible on noncontrast CT images. On contrast-enhanced CT images, the renal parenchymal lesions have low attenuation relative to the normal parenchyma. .”
Infiltrative Renal Malignancies: Imaging Features, Prognostic Implications, and Mimics
Sweet DE et al.
RadioGraphics 2021; 41:0000–0000 - “Infiltrative renal malignancies are a diverse subset of renal lesions characterized by an ill-defined margin between the mass and the normal renal parenchyma. Infiltrative renal malignancies are often more aggressive and confer a worse prognosis compared with more well defined neoplasms such as conventional RCC. However, other causes such as infectious, vascular, and autoimmune processes also can have an infiltrative appearance at imaging. As such, it is important to correlate imaging findings with the patient history and corresponding laboratory results. The radiologist should carefully consider these mimicking processes while evaluating the kidney, as they can easily be mistaken for infiltrative masses, resulting in the patient undergoing unnecessary surgery.”
Infiltrative Renal Malignancies: Imaging Features, Prognostic Implications, and Mimics
Sweet DE et al.
RadioGraphics 2021; 41:0000–0000 
Infiltrative Renal Malignancies: Imaging Features, Prognostic Implications, and Mimics
Sweet DE et al.
RadioGraphics 2021; 41:0000–0000
Infiltrative Renal Malignancies: Imaging Features, Prognostic Implications, and Mimics
Sweet DE et al.
RadioGraphics 2021; 41:0000–0000
- Angiographic Findings in Patients with PAN
Polyarteritis Nodosa: Spectrum of Angiographic Findings
Anthony W. Stanson et al.
RadioGraphics 2001; 21:151-159 - PAN Vascular Findings
- occlusive lesions (luminal irregularities resulting in reduction of caliber, stenosis, or occlusion)
- microaneurysms
Polyarteritis Nodosa: Spectrum of Angiographic Findings
Anthony W. Stanson et al.
RadioGraphics 2001; 21:151-159 - Differential Dx for Multiple Renal Artery Aneurysms on CT
- polyarteritis nodosa
- rheumatoid vasculitis,
- systemic lupus erythematosus,
- Churg- Strauss syndrome
- IVDA - “As seen in this review of the spectrum of angiographic findings in PAN, a variety of arterial beds may be affected and a variety of lesions may be seen. Skeletal muscle arterial disease was seen in nearly one-third of our patients. The lesions seen most frequently were occlusive. The presence of aneurysms increases the specificity of the diagnosis of PAN, but in their absence other arterial lesions such as luminal irregularities, stenoses, and occlusions can suggest the diagnosis. In a patient without fulminant disease but in whom clinical suspicion is firm, comprehensive angiography may lead to the diagnosis of PAN on the basis of the constellation of angiographic findings.”
Polyarteritis Nodosa: Spectrum of Angiographic Findings
Anthony W. Stanson et al.
RadioGraphics 2001; 21:151-159 - “Many of the clinical symptoms are related to organ ischemia secondary to arterial branch occlusions. Aneurysm rupture is a less common cause of pain. Arthralgias are noted in 50% of patients as are peripheral neuropathies (mononeuritis multiplex), which are often symptomatic early. Renal involvement including proteinuria and hypertension are found in 75%. Branch vessel occlusions can lead to multiple renal infarcts. Abdominal pain from ischemia or infarction secondary to occlusive lesions is the most common gastrointestinal complaint. Abdominal pain may also be caused by rupture of an aneurysm in one of the viscera: liver, kidney, or mesentery. Cutaneous lesions include palpable purpura, infections, and ischemic ulcers. Muscle pain and limb claudication may occur.”
Polyarteritis Nodosa: Spectrum of Angiographic Findings
Anthony W. Stanson et al.
RadioGraphics 2001; 21:151-159 - “Polyarteritis nodosa (PN) is a systemic necrotizing vasculitis of medium and small arteries, and is typically found in middle-aged men. The most common clinical symptoms are persistent fever, weight loss, and polyarthragia. As these symptoms are nonspecific, diagnosing PN is sometimes difficult and delayed. The kidney is the most commonly involved, and multiple small wedge-shaped less-enhanced areas are typically seen on enhanced CT. These are considered to be multiple bilateral renal cortical infarctions due to vasculitis of the interlobar arteries and arcuate arteries.”
Renal involvement of polyarteritis nodosa: CT and MR findings
Ozaki, K., Miyayama, S., Ushiogi, Y. et al.
Abdom Imaging (2009) 34: 265. https://doi.org/10.1007/s00261-008-9377-7 - Some studies reported that multiple small wedge-shaped less-enhanced areas were observed on enhanced CT, which were multiple bilateral renal cortical infarctions from vasculitis of the interlobar arteries and the arcuate arteries. In addition, perirenal hematoma by aneurysmal rupture, and small microaneurysms are sometimes observed.
Renal involvement of polyarteritis nodosa: CT and MR findings
Ozaki, K., Miyayama, S., Ushiogi, Y. et al.
Abdom Imaging (2009) 34: 265. https://doi.org/10.1007/s00261-008-9377-7 - “Most aneurysms are 2–10 mm in diameter. In the present study, multiple microaneurysms, 2–3 mm in diameter, were observed in all patients. However, it is important to note that renal microaneurysms are not specific to PN. They may be demonstrated in other systemic necrotizing vasculitis, drug abuse, and bacterial endocarditis. The specificity of angiographic findings of microaneurysm becomes much higher when the clinical symptoms are supportive.”
Renal involvement of polyarteritis nodosa: CT and MR findings
Ozaki, K., Miyayama, S., Ushiogi, Y. et al.
Abdom Imaging (2009) 34: 265. https://doi.org/10.1007/s00261-008-9377-7 
Hur JH, Chun EJ, Kwag HJ, Yoo JY, Kim HY, Kim JJ, Lee KW. CT Features of Vasculitides Based on the 2012 International Chapel Hill Consensus Conference Revised Classification. Korean J Radiol. 2017 Sep-Oct;18(5):786-798.
Hur JH, Chun EJ, Kwag HJ, Yoo JY, Kim HY, Kim JJ, Lee KW. CT Features of Vasculitides Based on the 2012 International Chapel Hill Consensus Conference Revised Classification. Korean J Radiol. 2017 Sep-Oct;18(5):786-798.
Hur JH, Chun EJ, Kwag HJ, Yoo JY, Kim HY, Kim JJ, Lee KW. CT Features of Vasculitides Based on the 2012 International Chapel Hill Consensus Conference Revised Classification. Korean J Radiol. 2017 Sep-Oct;18(5):786-798.- Polyarteritis Nodosa: Facts
- Polyarteritis nodosa (PAN) is a necrotizing vasculitis of medium and small arteries without glomerulonephritis, and is unassociated with the anti-neutrophil cytoplasmic antibody (ANCA). Absence of ANCA is a distinguishing point from microscopic polyangiitis (MPA), which is an ANCA-associated small vessel vasculitis that shares similar pathologic and radiologic findings with PAN.
- Polyarteritis nodosa affects men twice as often as women in the 5–7th decades. Etiology is unclear, but the hepatitis B virus may play an important role in the development of the disease. Renal involvement is common with an incidence of 70–80%, resulting in proteinuria, hematuria, and hypertension, but not glomerulonephritis. Other involvements are the gastrointestinal tract and skin at an incidence rate of 50%; skeletal muscles and mesentery at an incidence rate of 30%; and the central nervous system at an incidence rate of 10%.
- Characteristic imaging findings of PAN are microaneurysms of medium or small arteries, often involving the renal arteries. - Polyarteritis Nodosa: Facts
- Small vessel vasculitides mainly affect small intraparenchymal arteries, arterioles, capillaries, and venules. They are divided into two categories; ANCA-associated small vessel vasculitis and immune complex-associated small vessel vasculitis.
- Anti-neutrophil cytoplasmic antibody is an antibody against intracellular antigens in neutrophils and monocytes. According to immunofluorescent staining pattern, there are cytoplasmic ANCA (c-ANCA) and perinuclear ANCA (p-ANCA). Granulomatosis with polyangiitis (GPA) is a c-ANCA (+) vasculitis, whereas eosinophilic GPA (EGPA) or MPA are characteristic of p-ANCA (+) vasculitis. Although ANCA is an important characteristic of ANCA-associated vasculitis, its positive predictive value is only around 45%. This means that ANCA negativity does not exclude the possibility of ANCA-associated vasculitis. - Behçet’s Disease: Facts
- Behçet's disease is a chronic, relapsing autoinflammatory condition involving multiple organs. Clinically, Behçet's disease manifests as recurrent oral or genital aphthous ulcers, and inflammatory lesions of the cutaneous, ocular, articular, gastrointestinal, and central nervous system. It is most prevalent in the 3rd and 4th decades of life, and is more common in males.
- Vascular involvement occurs in 5–30% of Behçet's disease cases, and it can be divided into three types: venous thrombosis, arterial aneurysm and aortic occlusion. Venous thrombosis is associated with a prevalence range of 10–30%. Deep vein thrombosis of the lower extremities is the most common finding, followed by superficial thrombophlebitis after venipuncture. Aneurysms, which are frequently seen in the aorta, pulmonary, subclavian, and popliteal arteries, can be the most serious complication of Behçet's disease. Saccular types are more frequent than fusiform aneurysms. In case of pulmonary involvement, pulmonary artery aneurysm is the most common finding with a prevalence of 1–10%, and tends to be multiple and bilateral. - Differential Diagnosis of Vasculitis: Facts
The presence of known etiology or associated systemic disease can be helpful for the differential diagnosis of vasculitis. Systemic lupus erythematosus or rheumatoid arthritis are systemic inflammatory disorders, which may lead to inflammation of the cardiovascular system. IgG4-related sclerosing disease is characterized by idiopathic inflammatory lesions infiltrated with numerous IgG4-positive plasma cells. IgG4-related periarteritis predominantly involves the abdominal aorta, iliac vessels and thoracic aorta. CT findings include arterial wall thickening, homogeneous enhancement at the delayed phase of contrast enhanced CT, luminal change (mostly dilation and rarely stenosis), and exaggerated atherosclerotic change. An elevated serum IgG4 level and associated organ damage are essential in discerning this disease from other vasculitides. A few cases of IgG4-related periarteritis affecting the coronary arteries have been reported, which appeared as soft tissue encasing the coronary artery with or without luminal narrowing, wall calcification, and aneurysm. - Differential Diagnosis of Vasculitis: Facts
Multidetector CT is a useful noninvasive imaging modality for the evaluation of vasculitis and vasculitis mimics because CT can provide the information of the vessel wall change and other accompanied findings. Although CT features of various vasculitis are often overlapping, CT features via consideration of the involved vessel type, location, morphology, and associated systemic disease, can be useful in narrowing down the differential diagnosis .Getting familiar with CT features will help radiologists to establish appropriate diagnosis for vasculitis. 