What is mesenteric adenitis?

What is Mesenteric Adenitis

Mesenteric adenitis is a self-limiting inflammatory condition affecting the mesenteric lymph nodes that typically presents with right lower quadrant abdominal pain mimicking acute appendicitis, most commonly occurring in children, adolescents, and young adults. 1

Clinical Definition and Pathophysiology

Mesenteric adenitis, also called acute nonspecific or primary mesenteric lymphadenitis, represents inflammation of the lymph nodes within the mesentery of the intestine. 1 The condition is characterized by enlargement of mesenteric lymph nodes without an identifiable underlying inflammatory process such as inflammatory bowel disease or malignancy. 1

The term "mesenteric lymphadenitis" should be reserved for specific inflammation of lymph nodes rather than simply describing their presence on imaging, as enlarged abdominal lymph nodes are frequently encountered in asymptomatic children and should not always be considered abnormal. 2

Clinical Presentation

Cardinal Features

• Right lower quadrant abdominal pain that clinically mimics acute appendicitis or intussusception 1
• Fever (often up to 40°C) 3
• Self-limited course with complete recovery within 2-4 weeks without residuals 1

Distinguishing from Acute Appendicitis

Patients with mesenteric adenitis differ from those with acute appendicitis in several key ways:

• Longer duration of symptoms prior to emergency department presentation (2.4 days vs 1.4 days for appendicitis) 4
• Multiple emergency department visits (1.3 vs 1.05 presentations) 4
• Lower white blood cell count (10.16 × 10³/dl vs 15.8 × 10³/dl) with lymphocyte predominance (24.6% vs 13%) 4
• Lower C-reactive protein levels (0.48 vs 1.6 mg/dl) 4
• Less frequent migration of pain (7% vs 28% in appendicitis) 4
• Less frequent vomiting (34% vs 62% in appendicitis) 4
• Absence of classic peritoneal signs (20% vs 72% in appendicitis) 4

Diagnostic Criteria

Imaging Findings

Ultrasonography is the mainstay of diagnosis, revealing specific criteria: 1

• Three or more mesenteric lymph nodes with a short-axis diameter of 8 mm or more 1
• Nodes typically clustered in the right lower quadrant 5
• Normal appendix must be identified 5
• May have associated ileal or ileocecal wall thickening in some cases 5

Important Diagnostic Threshold

Enlarged abdominal lymph nodes exceeding 10 mm in their shortest axis in children with abdominal pain may represent mesenteric lymphadenitis of various causes, as this size threshold shows statistically significant difference between symptomatic and asymptomatic children (P = 0.0117). 2 However, lymph nodes between 5-10 mm are frequently seen in asymptomatic children (64% of controls) and may not be pathological. 2

Laboratory Findings

White blood count and C-reactive protein are of limited usefulness in distinguishing between patients with and without mesenteric lymphadenitis. 1 However, when present, lymphocyte predominance and lower inflammatory markers favor mesenteric adenitis over appendicitis. 4

Epidemiology and Clinical Significance

Mesenteric adenitis is an important clinical mimic of appendicitis, accounting for 19.8% of discharge diagnoses other than appendicitis in patients admitted with suspected appendicitis. 5 Approximately 7.7% of patients admitted with a diagnosis of appendicitis are ultimately diagnosed with mesenteric adenitis. 5

The condition shows a tendency of increased occurrence with age, peaking at 10 years, with a decrease thereafter. 2

Etiology

While often nonspecific, mesenteric adenitis can be caused by specific infectious agents:

• Salmonella enterica (particularly serovar Enteritidis in certain geographic regions like Taiwan) 3
• Yersinia species (more common in Western countries) 3
• Various viral and bacterial pathogens causing reactive lymphadenopathy 1

Unlike Yersinia-associated cases that are typically self-limited, Salmonella enterica carries potential risk for serious systemic complications such as meningitis or septic arthritis, making microbiological identification important for both therapeutic and epidemiological purposes. 3

Management Approach

Once the diagnosis is established, supportive care including hydration and pain medication is advised. 1 No surgical intervention is required. 1

Critical Management Steps

• Reassure patients and families by explaining the benign, self-limiting nature of the condition 1
• Provide symptomatic treatment with analgesics and hydration 3
• Expect complete resolution within 2-4 weeks 1
• Consider stool cultures if diarrhea is present to identify specific pathogens that may require treatment or have public health implications 3

Relationship to Other Conditions

In the context of inflammatory bowel disease, reactive lymphadenopathy measuring 1-1.5 cm in short axis diameter is considered normal in Crohn's disease, with adenopathy defined as lymph nodes ≥1.5 cm in short axis. 6 Appendicitis and mesenteric lymphadenitis during childhood or adolescence are linked to a reduced risk of developing ulcerative colitis in adulthood. 6