Figure 2. A 10-year-old-boy with primary mesenteric lymphadenitis. (a,b) A normal hypoechoic mucosal layer (long arrows in a) and echogenic lumen–mucosa interface (short arrows in a) are well delineated without disruption. (b) The outer transverse diameter of the appendix is approximately 8.2 mm. No evidence of peri-appendiceal infiltration is seen. Pathology confirmed lymphoid hyperplasia with faecal impaction.