When the appendix is normal or not seen, name what IS there: enlarged mesenteric nodes with ileal wall thickening (mesenteric adenitis), an ileocolic intussusception, an ovarian cause, or a Meckel diverticulum — and say whether the appendix was fully seen.
Orient first
- Mesenteric adenitis is a diagnosis made only after appendicitis is excluded — a normal appendix must be seen, not assumed.
- Clusters of three or more mesenteric nodes with a short axis above about 8 mm in the right iliac fossa support mesenteric adenitis — verify the threshold used locally.
- In girls, ovarian torsion and haemorrhagic cysts; in younger children, intussusception; in all ages, a Meckel diverticulum (a blind-ending loop with gut signature) and terminal ileitis.
Acquire the study
- Graded-compression ultrasound with a high-frequency linear probe in the right iliac fossa, plus a curvilinear survey of the pelvis and the right upper quadrant.
The manoeuvre
- Linear probe, graded compression: the appendix from base to tip — record whether it was seen completely and its diameter in mm.
- Mesentery in the right iliac fossa: count the nodes and measure the largest short axis.
- Terminal ileum: wall thickness in mm and Doppler hyperaemia (terminal ileitis, Yersinia).
- Transverse sweep from right iliac fossa to the right upper quadrant: an ileocolic intussusception (target sign).
- Pelvis with a full bladder: ovaries with colour Doppler, free fluid.
What confirms it
- A normal appendix seen in full, with a stated alternative such as enlarged mesenteric nodes and ileal thickening.
What licenses you to exclude it
- Appendicitis is excluded only when the whole appendix is seen and normal; "not visualised" does not exclude it.
The classic misread
- Writing "mesenteric adenitis" when the appendix was not seen — lymph nodes accompany appendicitis too.
- Missing an ovarian torsion because the scan stopped at the right iliac fossa.