F18-FDG PET/CT Diagnoses Vasculitis after a Negative Indium-111 Leukocyte Scan

We present a case of a 38-year-old man with a prior episode of fever of unknown origin (FUO) four years ago who presented with acute severe dull nonradiating abdominal pain centered in the epigastric region associated with nausea and vomiting. Bloodwork showed a normal leukocyte count but elevated erythrocyte sedimentation rate of 26 and elevated C-reactive protein of 40; syphilis titers and anti-neutrophil cytoplasmic antibodies (pANCA and cANCA) were negative. CT angiogram (CTA) of the abdomen and pelvis showed diffuse medium vessel vascular inflammation. Indium-111 labeled leukocyte scan did not show evidence of infection and, specifically, no evidence of infectious vasculitis. Subsequent F18-FDG PET/CT scan showed diffuse uptake in the mesenteric vasculature in the area of abnormality seen on prior contrast-enhanced CT and confirmed the diagnosis of vasculitis, subsequently deemed by rheumatology to be most consistent with segmental arterial mediolysis.