What is mesenteric adenitis?

Mesenteric Adenitis

Mesenteric adenitis is a self-limiting inflammatory condition affecting the mesenteric lymph nodes, characterized by abdominal pain that mimics appendicitis, typically occurring in children, adolescents, and young adults. 1

Definition and Pathophysiology

Mesenteric adenitis is defined as inflammation of the mesenteric lymph nodes without any identifiable underlying inflammatory process. It is characterized by:

• Enlargement of at least 3 mesenteric lymph nodes with a short-axis diameter of 8 mm or more 1
• Primarily affects the right lower quadrant mesenteric lymph nodes
• Can be primary (nonspecific) or secondary to an identifiable cause

Clinical Presentation

The clinical presentation of mesenteric adenitis often mimics appendicitis, making differential diagnosis challenging:

• Right lower quadrant abdominal pain (present in all cases) 2
• Fever (present in approximately 73% of cases) 2
• Diarrhea (present in approximately 80% of cases) 2
• Nausea and vomiting (present in approximately 27% of cases) 2
• Rebound tenderness (present in only about 27% of cases) 2

The classic presentation is abdominal pain that may be out of proportion to physical examination findings, similar to what is seen in acute mesenteric ischemia, though less severe 3.

Etiology

Mesenteric adenitis can be classified as:

1. Primary (nonspecific): No identifiable cause
2. Secondary: Due to identifiable infectious or inflammatory processes

Common causes of secondary mesenteric adenitis include:

• Yersinia enterocolitica infection 2
• Salmonella infection (including S. Enteritidis and non-typhoidal Salmonella) 4, 2
• Tuberculosis 2
• Typhoid fever 2
• Viral infections (including Epstein-Barr virus)

The etiology appears to vary by geographic region. In Korean adults, studies have identified causative agents in about 47% of cases, with bacterial infections being predominant 2.

Diagnosis

Imaging

• Ultrasonography: The mainstay of diagnosis

  • Findings: 3 or more mesenteric lymph nodes with short-axis diameter ≥8 mm
  • Normal appendix
  • No other identifiable inflammatory process 1

• CT scan: May show:

  • Enlarged mesenteric lymph nodes
  • Normal appendix
  • No signs of other intra-abdominal pathology 5

Laboratory Tests

• White blood cell count and C-reactive protein have limited usefulness in distinguishing mesenteric adenitis from other causes of abdominal pain 1
• Stool cultures may identify causative pathogens in secondary cases 4, 2
• Serologic tests for specific pathogens may be helpful in certain cases

Differential Diagnosis

The main differential diagnoses include:

• Acute appendicitis
• Intussusception
• Inflammatory bowel disease
• Mesenteric ischemia
• Infectious enterocolitis
• Lymphoma or other malignancies affecting mesenteric lymph nodes 5

Management

For primary (nonspecific) mesenteric adenitis:

• Supportive care including hydration and pain medication 1
• Reassurance to patients and families about the self-limiting nature of the condition
• Complete recovery typically occurs within 2-4 weeks without residual effects 1

For secondary mesenteric adenitis:

• Treatment of the underlying cause
• Specific antimicrobial therapy for identified bacterial pathogens
• Patients with tuberculosis or typhoid fever require specific antibiotic therapy 2

Prognosis

• Primary mesenteric adenitis is self-limiting with complete recovery within 2-4 weeks 1
• Secondary mesenteric adenitis prognosis depends on the underlying cause
• Most patients improve spontaneously without antibiotics, except those with specific infections requiring targeted therapy 2

Clinical Pearls and Pitfalls

• Pearl: Mesenteric adenitis should be considered in the differential diagnosis of right lower quadrant pain, especially in younger patients with normal appendix on imaging.
• Pitfall: Misdiagnosis as appendicitis can lead to unnecessary surgical intervention.
• Pearl: The presence of diarrhea and fever with right lower quadrant pain is more suggestive of mesenteric adenitis than appendicitis.
• Pitfall: While often benign, mesenteric adenitis can sometimes be a manifestation of more serious underlying conditions like tuberculosis or malignancy, requiring thorough investigation in persistent cases.