Appendicitis vs Mesenteric adenitis
How to tell Appendicitis and Mesenteric adenitis apart when a board question makes them look alike.
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Inflamed appendix over 6 mm on imaging is the decisive branch point for appendicitis.
Side by side
Periumbilical pain migrating to the right lower quadrant with focal McBurney tenderness and progressive anorexia strongly supports appendicitis.
Right lower quadrant pain after recent viral illness with diffuse mesenteric lymph node enlargement and normal appendix suggests mesenteric adenitis.
Appendiceal luminal obstruction causes bacterial overgrowth and transmural inflammation that can perforate.
Reactive inflammation of mesenteric lymph nodes follows enteric or upper respiratory infection without appendiceal obstruction.
Typical findings include leukocytosis often above 10000/uL with neutrophil predominance, and CT shows dilated appendix over 6 mm with wall thickening, periappendiceal fat stranding, or appendicolith.
Mesenteric adenitis imaging shows clustered enlarged mesenteric nodes, commonly at least 5 mm short-axis, with a normal-caliber appendix and no periappendiceal fat stranding.
The trap
The common trap is assuming post-viral RLQ pain is benign without imaging when focal peritoneal signs are present. The resolving clue is direct appendix visualization showing true appendiceal inflammation.
The repair move
Next best step: start preoperative IV fluids, analgesia, and broad coverage such as ceftriaxone plus metronidazole, then proceed to appendectomy for uncomplicated appendicitis. If imaging instead shows mesenteric adenitis with normal appendix, use supportive care and close return precautions.
Try a free question
CoreA 16-year-old boy has migrating abdominal pain to the right lower quadrant, fever, and focal rebound tenderness. Ultrasound shows noncompressible appendix measuring 7.5 mm. What is the most likely diagnosis?
Show answer and explanation
Answer: A. Appendicitis. Classic symptoms plus inflamed enlarged appendix on imaging indicate appendicitis.
Why the other choices are tempting
- B. Mesenteric adenitis would show normal appendix and nodal predominance.
- C. Gastroenteritis usually has diffuse symptoms without focal appendiceal imaging findings.
- D. Torsion causes acute scrotal findings rather than inflamed appendix imaging.
- E. Crohn disease can cause RLQ pain but does not typically produce isolated acute appendiceal dilation pattern.
Flashcards
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What imaging finding best confirms appendicitis in a right lower quadrant pain workup?
A noncompressible inflamed appendix greater than 6 mm with periappendiceal inflammatory change.
Which historical pain pattern most supports appendicitis over mesenteric adenitis?
Pain that migrates from periumbilical area to the right lower quadrant.
Quick answers
What is the fastest way to tell Appendicitis from Mesenteric adenitis?
Inflamed appendix over 6 mm on imaging is the decisive branch point for appendicitis.
What is the key clue for Appendicitis?
Periumbilical pain migrating to the right lower quadrant with focal McBurney tenderness and progressive anorexia strongly supports appendicitis.
What is the key clue for Mesenteric adenitis?
Right lower quadrant pain after recent viral illness with diffuse mesenteric lymph node enlargement and normal appendix suggests mesenteric adenitis.
What is the common trap with Appendicitis vs Mesenteric adenitis?
The common trap is assuming post-viral RLQ pain is benign without imaging when focal peritoneal signs are present. The resolving clue is direct appendix visualization showing true appendiceal inflammation.