Figure 4. A 9-year-old boy with mesenteric lymphadenitis (follow-up study). (a) A normal appendix without faecal impaction (initial examination). (b) Follow-up 18 days after the initial examination. Faecal impaction with a small echogenic faecolith (longest arrow) is seen. The normal echogenic mucosa–lumen interface (short arrows) and hypoechoic mucosal layer (long arrows) are preserved. The outer transverse diameter of the appendix is 6.7 mm. (c) Follow-up 19 days after the initial examination. Faecal impaction with a small echogenic faecolith is also noted. The outer transverse diameter of the appendix is 6.5 mm.