Mesenteric adenitis (MA), also called mesenteric lymphadenitis, is an inflammatory condition affecting the lymph nodes located within the mesentery. The mesentery is the fold of tissue that connects the intestine to the back of the abdominal wall. When these lymph nodes become inflamed and swollen, they cause abdominal pain, often mimicking appendicitis. MA is generally self-limiting, meaning it resolves on its own without specific medical treatment.
The Role of Viral and Bacterial Infections
Infectious agents are the most frequent cause of MA, typically developing as a secondary response to a primary infection elsewhere in the body. Inflammation in the abdominal lymph nodes usually occurs after a person has had a recent respiratory illness (such as a common cold or flu-like symptoms) or a gastrointestinal infection. This mechanism involves the body’s immune system reacting to the invading microorganism.
The infectious process begins when a pathogen enters the body, often through the mouth, leading to an initial infection in the digestive tract. The pathogen then travels through the lymphatic vessels. It eventually reaches the lymph nodes located in the mesentery, which are designed to filter out harmful substances.
Viral infections are the most common trigger, especially in children and young adults, often resulting in a milder, self-resolving form of MA. The swelling of the lymph nodes is a localized immune response, where the nodes enlarge as they fill with infection-fighting white blood cells. This type of adenitis is frequently termed “primary” or “nonspecific” because it occurs without an obvious local inflammatory source.
Bacterial infections are less frequent than viral causes but tend to cause more severe symptoms and greater concern due to their potential for systemic illness. Certain bacterial pathogens invade the intestinal lining, gaining direct access to the underlying lymphatic tissue. The resulting inflammation can be intense, leading to significant enlargement of the mesenteric lymph nodes and a more protracted course of illness.
Specific Pathogens Implicated
A variety of specific microorganisms target the lymphatic tissue of the mesentery. The bacterium Yersinia enterocolitica is the most recognized bacterial cause of MA, especially in pediatric populations. Infection with Yersinia can cause symptoms that closely mimic acute appendicitis, often requiring imaging to differentiate the two conditions.
Other bacteria commonly linked to MA are frequent causes of foodborne illness. These pathogens invade the small intestine, causing inflammation that extends into the adjacent mesenteric lymph nodes. Documented bacterial causes include:
- Salmonella species
- Campylobacter species
- Shigella species
- Escherichia coli (E. coli)
On the viral side, Adenovirus is a frequent cause of MA, particularly in children, and is often associated with preceding upper respiratory or gastrointestinal symptoms. Other viral agents implicated include Epstein-Barr Virus (EBV), which causes infectious mononucleosis, and Coxsackieviruses. These viruses initiate an infection that leads to the characteristic swelling of the mesenteric lymph nodes.
Non-Infectious Conditions That May Trigger or Mimic MA
While infection is the main cause, MA can also occur secondary to pre-existing inflammatory conditions or be mistakenly diagnosed as other diseases. Inflammatory Bowel Disease (IBD), particularly Crohn’s disease, involves chronic inflammation of the digestive tract. This can lead to persistent secondary enlargement of the mesenteric lymph nodes, where the lymphadenitis is a consequence of the underlying intestinal inflammation rather than a primary infection.
Conditions affecting the appendix or other abdominal organs can also cause secondary lymph node swelling detected during diagnostic imaging. For instance, a mildly inflamed appendix can result in enlarged lymph nodes in the mesentery, complicating diagnosis. MA can also be a feature of systemic chronic inflammatory disorders, such as systemic lupus erythematosus.
Certain serious conditions can present with symptoms and imaging findings indistinguishable from MA. Malignancies, such as lymphoma, can cause significant mesenteric lymphadenopathy and must be ruled out, especially in adults. While most cases of MA are benign and infectious, diagnosis involves ensuring the lymph node swelling is not due to a more serious inflammatory or neoplastic process.