It is the second most frequent vasculitis in children (25%). It occurs typically before the age of 5 years with a slight male predominance. Medium and small arteries are involved [9]. Typical US imaging findings include coronary artery aneurisms. During the acute phase of disease, fever, unilateral cervical lymph nodes, skin lesions, and non-specific abdominal symptoms may be present. The latter include abdominal pain, hydrops of the gallbladder (Fig. 29.7), ascites, intestinal pseudo-obstruction, focal colitis, bowel infarction, and bowel stricture secondary to ischemia [16]. Abdominal imaging may help earlier recognition of the disease before the development of coronary aneurisms (see also Chap. 21).

Takayasu arteritis is the third most frequent childhood arteritis and involves typically the large arteries. The mean age at diagnosis is 13 years with a female predominance; the youngest case reported was a 6-month-old [17]. Initial clinical presentation includes headache, prolonged fever, and weight loss. Later, the evolution of the disease results in various symptoms including claudication, abdominal angina, diminished vascular pulsations, and hypertension [9]. Renal artery involvement with renal hypertension is the most common manifestation at presentation. It occurs in 66–93% of children [18]. Direct and indirect signs (parvus-tardus) of stenosis can be depicted in US-Doppler. However, due to their ability to evaluate accurately all thoracic and abdominal arterial vessels, preferably MR imaging or CE-CT is recommended. Edema, thickening as well as enhancement of the arterial wall are major findings. Early treatment will prevent irreversible damages. Stenosis and thrombosis with the development of collaterals and aneurysms represent the potential evolution of the early features.

This vasculitis causes necrotizing inflammation in small and medium-sized arteries and its presentation may overlap with Kawasaki disease. Association with Mediterranean fever has been reported as well as hepatitis viral B triggering. Children are rarely affected, in average around 9 years [19]. Clinical manifestations before 1 year of age are exceptional [20]. There is no sex predilection. Clinical manifestations are multisystemic; the skin and peripheral nerves are most frequently involved. Depending of the subtype of polyarteritis nodosa (PAN), the gastrointestinal manifestations are variable and reported in about 17% of patients [19]. They are related to infarctions (abdominal cramping), rupture of aneurisms (hemorrhage) or obstruction and may reveal the disease [20, 21]. These aneurisms typically affect the renal, mesenteric, or hepatic arteries. Renal involvement (severe hypertension, renal failure) is frequent and is indicator of poor prognosis. Due to the size of the involved arteries, angiography is recommended in case of clinical suspicion.