Polyarteritis nodosa presenting atypically as appendicitis and pyelonephritis in a single patient

A 17-year-old man presented to the emergency department 10 days postlaparoscopic appendicectomy with ongoing lower abdominal pain. The pain was associated with fevers, chills, sweating and constipation. There were no other associated symptoms. On examination, there was suprapubic and right lower quadrant tenderness and an elevated blood pressure (140/90 mm Hg). The patient later developed severe bilateral flank pain. Investigations revealed elevated C reactive protein, leukocyturia and microscopic haematuria. Blood and urine cultures were negative. CT angiogram demonstrated bilateral wedge-shaped peripheral renal hypodensities suggestive of several peripheral infarcts with intrarenal microaneurysms. Treatment with steroids and cyclophosphamide was initiated, leading to significant clinical improvement. Review of the histological appendix specimen revealed features consistent with small-medium vessel vasculitis.