Polyarteritis nodosa presenting as a bladder outlet obstruction.

Polyarteritis nodosa (PAN) of the urinary tract is rare. An unusual case of systemic PAN involving the bladder neck is described. A 27-year-old man, with known diastolic hypertension diagnosed 2 years earlier, was admitted with chronic urinary obstruction complicated by hydronephrosis. He had symptoms of myalgia and weight loss, was afebrile but had an elevated erythrocyte sedimentation rate and acute-on-chronic renal impairment. All virological and serological tests including hepatitis B and anti-neutrophil cytoplasmic antibody were negative. A computed tomography scan of the brain revealed small-vessel disease. A bladder neck mass was visualised on cystoscopy. Histological examination of this demonstrated a medium-sized necrotising vasculitis with small-vessel fibrinoid necrosis suggestive of PAN. At least six of the American College of Rheumatology criteria for PAN were met. The patient was treated with pulses of intravenous cyclophosphamide and oral corticosteroids with a good clinical response.