Mesenteric lymphadenitis refers to inflammation of the mesenteric lymph nodes and is considered present if a cluster of three or more lymph nodes, each measuring 5 mm or greater, is detected in the right lower quadrant mesentery.  This process may be acute or chronic, depending on the causative agent, and it causes a clinical presentation that is often difficult to differentiate from acute appendicitis, [1, 2, 3] particularly in children. [4, 5]
Microbial agents are thought to gain access to the lymph nodes via the intestinal lymphatics. Organisms subsequently multiply and, depending on the virulence of the invading pathogen, elicit varying degrees of inflammation and, occasionally, suppuration. 
Grossly, the lymph nodes are enlarged and often soft. The adjourning mesentery may be edematous, with or without exudates. If a contiguous primary source of infection (eg, the appendix) is present, evidence of inflammation is often apparent.
Microscopically, the lymph nodes show nonspecific hyperplasia and, in suppurative infection, necrosis with numerous pus cells.
Numerous organisms have been cultured from mesenteric lymph nodes and blood, such as beta-hemolytic streptococcus, Staphylococcus species, Escherichia coli, Streptococcus viridans, Yersinia species (responsible for most cases currently), Mycobacterium tuberculosis, Giardia lamblia, and non– Salmonella typhoid. Viruses, such as coxsackieviruses (A and B), rubeola virus, and adenovirus serotypes 1, 2, 3, 5, and 7, have also been implicated.
Mesenteric node involvement can also be part of infectious Epstein-Barr virus (EBV), acute human immunodeficiency virus (HIV) infection, and catscratch disease (CSD).
The frequent association of this condition, especially in children with upper respiratory tract infection, has popularized a theory that swallowed pathogen-laden sputum may be the primary source of infection.
Fecal-oral transmission occurs in Y enterocolitica infection and may present as a common source outbreak. This infection has also been associated with meat, milk, and water contamination. Rarely, person-to-person or zoonotic contacts with fecal carriers can lead to infection.
United States data
The true incidence of this disease is not known, because it can be easily missed or mistaken for other diagnoses. The condition is generally thought to be common. Up to 20% of patients undergoing appendectomy have been found to have nonspecific mesenteric adenitis.
Frequency is similar to that of the United States. Yersinia enterocolitica infection has a geographic variation. This infection is most common in the temperate countries of Europe, North America, and Australia; it has been particularly noted in Eastern Europe.
Sex- and age-related demographics
The condition affects males and females equally. Yersinia infection is more common in boys than in girls.
Mesenteric lymphadenitis can occur in adults but is more common in children and adolescents younger than 15 years, and this condition during childhood or adolescence is linked to a significantly reduced risk of ulcerative colitis in adulthood. 
Frisch et al reviewed Swedish and Danish cohort studies involving 709,353 patients who had undergone appendicectomy and were followed up for subsequent ulcerative colitis to determine the role of appendicitis and mesenteric lymphadenitis in the risk of ulcerative colitis following appendicectomy.  The investigators also studied the impact of appendicectomy in 224,483 patients with a family history (parents or siblings) of inflammatory bowel disease and found that regardless of familial predisposition to inflammatory bowel disease, appendicitis and mesenteric lymphadenitis during childhood or adolescence is linked to a significantly reduced risk of ulcerative colitis in adulthood. 
The prognosis is good. Typically, complete recovery can be expected without specific treatment. Death is rare.
Mesenteric lymphadenitis generally is a benign disease, but patients with sepsis may have a fatal outcome.
Complications of mesenteric lymphadenitis include the following:
Volume depletion and electrolyte imbalance in patients with severe diarrhea, nausea, and vomiting
In cases where the underlying pathogen is Y enterocolitica, some patients may develop arthralgias. These symptoms typically develop 1 month after the initial episode of diarrhea and usually resolve after 1-6 months. A rash on the legs and/or trunk, erythema nodosum, may also appear and is also self-limited.
Explain the benign nature of the disease to patients; however, because there is a risk of recurrence, also explain that they must seek prompt medical attention in each instance to exclude other more emergent etiologies.
In cases of Yersinia infection as the underlying infectious agent, instruct patients to avoid unpasteurized milk, raw pork (particularly chitterlings), and contaminated water. 
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