Mesenteric adenitis

Dr Mark Thurston and Radswiki et al.

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 may occasionally affect adults. 

Presentation is similar (or can be identical) to acute appendicitis, hence is a differential diagnosis for right iliac fossa (RIF) pain. 

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 enterocolitica 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
    • 3 or more nodes with a short-axis diameter of at least 5 mm clustered in the right lower quadrant (see normal mesenteric lymph nodes) 1,2
      • ​​enlarged lymph nodes are located anterior to the right psoas in the majority of cases, or in the small bowel mesentery 6.
  • ileal or ileocaecal wall thickening may be present
    • thicker than 3 mm over at least 5 cm of the bowel despite bowel lumen opacification (CT) and distention
  • a normal appendix (if seen)

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, there is a significantly reduced risk of ulcerative colitis later in life 3.

The clinical differential includes:

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rID: 13067
Tag: cases, refs
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