# Eosinophilic Gastroenteritis with Appendix Involvement: Role of Intestinal Ultrasound
## 3 Discussion
An initial dose of prednisone 20-40 mg/day for 6-8 weeks achieves symptom regression in 90% of patients [34]. For patients with a relapsing disorder, treatment with budesonide has shown good tolerability and efficacy in controlling symptoms, together with an important reduction of systemic side effects [35]. For patients with steroid-dependent disease, the use of immunomododulators (azathioprine 6-mercaptopurine), leukotriene-receptor antagonists (i.e., montelukast), antihistamine medication (ketotifen), and biological agents (omalizumab; mepolizumab) has shown good efficacy in order to achieve long-term remission in small-size case series [15; 33]. The use of ultrasound for the diagnosis and follow-up of eosinophil gastroenteritis is documented [36; 37; 38; 39] but still limited. The most frequently reported signs in IUS [36; 37; 38; 39] are related to the different intestinal layers involved. Several pictures are described. One can find a moderate dilation of bowel loops showing mild-to-moderate bowel wall thickening starting from the stomach to the terminal ileum. Bowel wall stratification can be lost and the wall can be hyper-echoic with hypertrophy of valvular conniventes. The luminal content can be either brilliant (in the case of corpuscular content) or completely anechoic (in the case of liquid content). Mild free fluid within the bowel loops is frequently present and, if abundant, it should be sampled to demonstrate the presence of eosinophilic ascites, characterized by a high eosinophilic count. Intestinal intussusception, an extremely rare complication of eosinophilic gastroenteritis, can also be documented by IUS [40]. Previous reports have shown the utility of IUS for pediatric patients [38] who present with abdominal symptoms, since the technique is rapid, cheap, and non-invasive and provides useful diagnostic information. Being easily repeatable, IUS is particularly useful in a patient's follow-up, as it has been reported to be particularly useful in the detection and post-treatment follow-up of several intestinal diseases. Regarding our patient, in addition to ileac involvement, which is a quite common finding in EG, IUS also documented appendicular involvement. The utility of IUS is well known as first-line imaging for the diagnosis of acute abdomen as in the case of inflammatory involvement of the appendix. In acute appendicular inflammation, the most frequent US signs reported [41] are increased bi-parietal diameter (>6 mm) or single wall thickness (\(\geq\)3 mm) with hyper-vascularity and incompressibility. The \"target sign\" is a pathognomic sign, consisting in the involvement and thickening of whole layers of the appendicular wall. Free abdominal fluid, increased echogenicity of the local mesenteric fat, and local lymphadenopathy are often present. Appendicular carcinoid, which is a well-differentiated neuroendocrine tumor, was also a possible differential diagnosis, as it sometimes presents with an acute onset, mimicking acute appendicitis. However, in our case, its presence was excluded on the basis of both imaging (absence of mass within the appendicular wall) and laboratory findings (presence of intestinal and peripheral eosinophil) and, most importantly, the remission after immunosuppressive therapy. Acute abdomen is a possible manifestation of EG [36] and appendicular involvement has sporadically been described as leading to unnecessary surgery in most cases [5; 34; 36]. Furthermore, surgical case series reported a 16.7% rate of recurrent symptomatic intestinal eosinophil after appendectomy [42; 43]. There is no clear data about the timing and modalities of follow-up for EG, particularly in the case of appendicular involvement, given the rarity of this condition. Regarding our patient, the use of gastrointestinal ultrasound proved useful to corroborate the diagnostic suspicion of the disease and also to assess the response to steroidal therapy and subsequent resolution of appendicular inflammation, with no need for more expensive or invasive techniques.