Gastroenteritis is the most frequent cause of abdominal pain in children. Several organism may cause this usually self-limited disease in developed coun tries. Diarrhea, vomiting, and abdominal pain are common symptoms. There is overlap of symptoms with some cases of appendicitis; for this reason imaging is required in cases of atypical course. Plain film may show diffuse small and large bowel distension, with air-fluid levels on positional views (the pattern of an ileus) (Fig. 1.71a). US may detect generalized dilated bowel loops without wall thickening or significant ascites in non-invasive gastroenteritis cases (Fig. 1.71b). In cases of viral gastroenteritis, there are multiple loops of fluid-filled as well as air-filled intestine, with some patients demonstrating hyper-peristalsis, whereas others demonstrate variable b a d c
degrees of hypoperistalsis. Transient small bowel intussusceptions can be observed in those patients with hyperperistalsis (HaYden 1996). The normal appendix is not usually seen. Differential diagnosis with appendicitis may be difficult because appendicitis may produce similar US findings linked to ady-namic or mechanical ileus, mostly in evolutionated cases. However, the absence of echogenic peritoneal fluid or enlarged omental fat makes the probability of perforated appendicitis remote.
Acute terminal ileitis or ileocecitis (bacterial enteritis limited to the ileocecal region).
The term ileocecitis, proposed by PuYlaert et al. (1989), defines those bacterial enteritises that affect primarily the ileocecal region, mimicking clinically appendicitis. Yersinia, Campylobacter, and Salmonella are the most frequent infective organisms. In these cases, diarrhea is often absent or moderate. Sonographic diagnosis of these entities may avoid a significant number of unnecessary laparotomies. Sonographic findings consist of mural thickening of the terminal ileon, ileocecal valve, and the cecum, and the presence of multiple enlarged mesenteric lymph nodes. The thickened ileon appears mostly hypoechoic related to mucosal follicular hyperplasia. This finding may help differentiate it from Crohn's disease, which exhibits a transmural affectation. Abnormalities often extended along the proximal colon, giving rise to a prominent haustral pattern on the longitudinal view. The exaggeration of the haustrations leads to the "accordion" sign (Fig. 1.72). In many cases the appendix cannot be visualized. Nevertheless, the exclusion of appendicitis is justified when sonography reveals other pathology rather than lymph nodes that could explain the patient's symptoms (Püylaert et al. 1989). Crohn's disease may also be confused with bacterial infection of the ileocecal region. In this case no surgical dilemma will ensue since appendicectomy is not indicated (Püylaert et al. 1989).
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