A visual guide for emergency radiologists navigating the complexity of abdominal vasculitis: part 1 - true vasculitis.

Systemic vasculitides are rare, multi-organ inflammatory disorders involving blood vessels, classified by the size of the affected vessels. When abdominal arteries are involved, diagnosis becomes particularly challenging due to nonspecific symptoms such as fever, fatigue, and abdominal pain, which can mimic other acute conditions and hinder identification in emergency settings. Examples include Takayasu arteritis (large vessels), polyarteritis nodosa (medium vessels), and lupus-associated or drug-induced vasculitis (small vessels), each exhibiting distinct imaging features. Imaging techniques, particularly contrast-enhanced computed tomography (CECT) and computed tomography angiography (CTA), are vital for evaluating acute presentations and identifying characteristic abnormalities. Part 1 of this pictorial essay presents illustrative cases of abdominal vasculitis, incorporating advanced imaging modalities such as CECT, CTA, 3D volume rendering, and 3D cinematic rendering to emphasize key diagnostic features. Early recognition of these imaging findings by radiologists is crucial to ensure accurate diagnosis, guide appropriate treatment, and assess the need for surgical intervention. By enhancing awareness and understanding of these rare vascular pathologies, this review aims to facilitate timely diagnosis, improve clinical decision-making, and optimize patient outcomes.