Background To evaluate the imaging findings in patients with renal involvement of Polyarteritis nodosa (PN) to diagnose as early as possible. Materials and methods Four patients diagnosed as having PN participated in the present study. Two patients underwent abdominal dynamic CT, one underwent only pre- and post-contrast CT, and the remaining patient underwent only noncontrast CT and MR imaging, including dynamic contrast study. Results The common findings of CT and MR imaging were diffuse enlargement, multiple small wedge-shaped less-enhanced areas on dynamic contrast study, and indistinctness of the margin between the cortex and medulla on equilibrium-phase CT. Renal arteriogram showed multiple microaneurysms on arterial phase image in all four cases, and PN was diagnosed. The common CT and MR findings of renal involvement of PN mimicked those of pyelonephritis, when microaneurysms were not demonstrated. Conclusion The differentiation between PN and pyelonephritis on CT and MR imaging is difficult. Therefore, the radiologist should be familiar with the imaging findings of renal involvement of PN. When PN is suspected, angiography should be performed as early as possible to make a definite diagnosis.
Kumi Ozaki1 Shiro Miyayama2 Yasuyuki Ushiogi3 Osamu Matsui1
[1] Department of Radiology, Kanazawa University Graduate School of Medical Science, 13-1 Takara-machi, Kanazawa 920-8641, Japan;[2] Department of Diagnostic Radiology, Fukuiken Saiseikai Hospital, Fukui, Japan;[3] Department of Internal Medicine, Fukuiken Saiseikai Hospital, Fukui, Japan