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The entire gastrointestinal tract is derived from a common dorsal mesentery. During development, as the mesentery fuses with the retroperitoneum, the remaining segments become the small bowel mesentery, transverse mesocolon, and sigmoid mesocolon. These mesenteries serve as the primary pathways to and from the bowel for arterial, venous, lymphatic, and neural structures.

The small bowel mesentery originates as the root of the mesentery, located at the fourth part of the duodenum and posterior border of the pancreas. It courses along the medial border of the jejunum and ileum in a fan-like projection. The transverse mesocolon connects the transverse colon to the retroperitoneum, and the sigmoid mesocolon connects the sigmoid flexure to the inferior retroperitoneum and pelvis.

Acute Mesenteric Lymphadenitis

Acute mesenteric lymphadenitis (AML) is the marked focal inflammation of mesenteric lymph nodes and has been associated with viral illness and other infectious processes.1,2 AML most commonly occurs in children, with an equal distribution in males and females. The most common presenting symptoms are abdominal pain, mild fever, nausea, and occasionally vomiting. Both laboratory and systemic symptoms are less severe in comparison to those seen with acute appendicitis.3

Given the young age at presentation, most children undergo ultrasound rather than computed tomography (CT) for diagnosis. Diagnostic criteria by either ultrasound or CT include clusters of enlarged (>5-8 mm) hypervascular mesenteric lymph nodes with a normal appendix.1,3 While imaging findings are often suggestive, true diagnosis is often made at the time of negative appendectomy, when mesenteric lymphadenopathy is noted.1,4

When AML is suspected, one can proceed with supportive care, as the disease is self-limiting and typically resolves without invasive measures.1,3,4 Given that the inciting agent is typically viral, there is no indication for antimicrobial agents.

Mesenteric Panniculitis/Sclerosing Mesenteritis

Mesenteric panniculitis was first described in 1927 by Jura as an infiltration of plasma and polymorphonucleated cells into the mesentery.5 The condition, now more vigorously investigated, has many names throughout the literature including sclerosing mesenteritis, retractile mesenteritis, and mesenteric lipodystrophy. The disease process of marked mesenteric inflammation and fibrosis more commonly affects the small bowel mesentery and can be asymptomatic or present as diffuse, nonspecific abdominal pain.6-8 Most cases present in the sixth decade, with a slight male predominance.8,9 The etiology is not well understood and has been related to various sources including autoimmune, infectious, ischemic, and traumatic causes.8-10 In one study, 35% of patients with sclerosing mesenteritis were noted to have a history of abdominal surgery, and therefore, surgical trauma may be a predisposing factor.6

The inflammation and fibrosis originate at the root of the mesentery and proceed to involve varying amounts of the mesentery. Histologically, the disease is classified into 3 stages, based ...

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