Spontaneous perirenal haematoma due to polyarteritis nodosa.

Polyarteritis nodosa (PAN) is a systemic disease which involves the kidneys in 70% of cases. We report a case in which the pre-operative diagnosis was perirenal abscess or perirenal tumour, but at operation a perirenal haematoma was found. After pathological examination, it was recognised as renal involvement with PAN. The diagnosis of PAN is often difficult. Renal arterial changes, including aneurysm formation, are frequent. Since Kussmaul and Maier first described PAN in 1866, diagnosis has remained difficult because it is based upon tissue examination obtained at biopsy or post-mortem. In this report we present a case of renal involvement of PAN resulting in a perirenal haematoma due to spontaneous rupture of intrarenal arterial aneurysms.