Question

A 7-year-old boy presents with right lower quadrant abdominal pain and fever, mimicking acute appendicitis. Stool culture grows the likely organism. Which infection best explains this clinical scenario?

• A. Yersinia enterocolitica
• B. Campylobacter jejuni
• C. Salmonella typhi
• D. Entamoeba histolytica

Hint:

Key association for exams: Pseudoappendicitis Right lower quadrant pain + Mesenteric adenitis = Yersinia enterocolitica (grown best at cold enrichment CIN agar).

Answer 1

The Correct Option is A

Concept:
"Pseudoappendicitis" is a recognized clinical syndrome in children and adolescents presenting with acute right lower quadrant abdominal pain, fever, and leukocytosis that closely mimics acute appendicitis.
The classic bacterial pathogen responsible for mesenteric adenitis and terminal ileitis leading to this presentation is Yersinia enterocolitica.
Explanation:
• Yersinia enterocolitica is a gram-negative, non-lactose-fermenting, zoonotic coccobacillus that exhibits psychrotrophic properties (ability to grow at refrigeration temperatures, $4^\circ\text{C}$).

• Transmission occurs primarily via ingestion of contaminated, undercooked pork products, unpasteurized milk, or contaminated water.

• In older children and adolescents, the organism invades the intestinal mucosa through M cells overlying Peyer's patches, producing marked acute terminal ileitis and mesenteric lymphadenitis.

• This pronounced inflammation localized to the ileocecal region produces tenderness and guarding in the right iliac fossa, leading to surgical consultations for suspected appendicitis where normal appendices are found on laparoscopy/laparotomy.

• Stool culture on selective media, such as Cefsulodin-Irgasan-Novobiocin (CIN) agar, readily confirms the growth of Yersinia.
Final Answer:
The infectious etiology most commonly responsible for right lower quadrant abdominal pain mimicking acute appendicitis (pseudoappendicitis) is Yersinia enterocolitica.