Mesenteric adenitis

Mesenteric adenitis is a self-limiting inflammatory process that affects the mesenteric lymph nodes in the right lower quadrant, and is clinically often mistaken for acute appendicitis.

Mesenteric adenitis is most common in children and adolescents although it is also occasionally encountered in adults. 

Presentation is similar to acute appendicitis. 

Pathogens are thought to gain access via intestinal lymphatics, and then multiply in mesenteric lymph nodes. On gross pathology, lymph nodes are enlarged and soft. On microscopy, there is non-specific hyperplasia and when suppurative, there is necrosis and pus.

Mesenteric adenitis has a number of causes:

  • variety of viruses
  • Yersinia enterocolitica
  • Helicobacter jejuni
  • Campylobacter jejuni
  • Salmonella spp
  • Shigella spp

Yersinia enterocolitia is considered the most common pathogen in temperate Europe, North America and Australia. It is more common in boys.

Occasionally in young children and infants, ileocolitis may be also present suggesting that the lymph node involvement may be secondary to a primary enteric pathogen.

As mesenteric adenitis usually presents in the young, ultrasound is often the investigation of choice. CT is usually reserved for older patients, if needed at all. 

Features on either modality include: 

  • enlarged lymph nodes
  • ileal or ileocecal wall thickening may be present
    • wall is thicker than 3 mm over at least 5 cm of the bowel despite bowel lumen opacification (CT) and distention

In most cases, mesenteric adenitis is self-limiting, and typically abates over the course of a few weeks. 

Interestingly, when mesenteric adenitis (or appendicitis) occurs in childhood or adolescence, therer is a significantly reduced risk of ulcerative colitis later in life.3

The clinical differential includes:

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