Mesenteric lymphadenitis is an inflammation of the abdominal lymph nodes, characterized by white blood cells moving into organs near the nodes to help fight infection. Lymph nodes filter the blood of infectious agents, and as a result, the nodes are the target of those agents. The condition occurs when an infection sets in and the node is overwhelmed by white blood cells. This is not a genetic disease, although dogs that have lowered immunity are often victims.
Bacteria such as Pasteurella, bacteroides, and fusobacterium are possible causes of this condition as they create colonies within the lymph node. Normally, lymphadenitis is a swollen node due to nearby infection but in this case, the infection is within the node. Yersinia pestis, also known as bubonic plague, and Francisella tularensis are particularly likely to be present in the lymph nodes and are major causes of lymphadenitis. Nodular lymphadenitis occurs in dogs thanks to Bartonella vinsonii bacteria.
Certain fungi such as blastomyces, cryptococcus, histoplasma, coccidiodes and sporothrix are common fungal infections of organs near the lymph nodes. Viral infections are unusual with this disease but when they are present they most commonly colonate near the mesenteric lymph nodes of the abdominal wall. Protozoa infestations also cause lymphadenitis as dogs with leishmaniasis and toxoplasmosis frequently also have swollen lymph nodes. Noninfectious causes such as pulmonary disease or systemic eosinophilic disease are common as well.
The pet owner will not be able to see the enlarged nodes but a veterinarian feels for them by palpating the nodes. This is painful for the dog who may also have a fever, and anorexia, depending on where the infected node is located. He may have abscessed lymph nodes, caused by bacterial infection, which can open through the skin and drain. The organs causing the infection cause the lymph nodes nearest to them to swell.
The veterinarian performs a complete blood count and urinalysis to locate any traces of bacteria and fungus. X-ray and ultrasound imaging are used to determine swelling of the lymph nodes of the abdomen and a fine needle might be inserted directly into the infected node to gather a sample of the node's fluids and tissues. Antibiotics are given to treat bacterial infections and antifungal medications are given to the dog to treat fungal infections of the nodes.
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