Clinical Vignette
A 6-year-old male Old English sheepdog is presented for depression, anorexia, and weight loss of several weeks’ duration. On physical examination, the temperature is mildly increased at 103.7°F. The other vital signs are normal. All peripheral lymph nodes are enlarged, nonpainful, and mobile.
Using the problem-oriented approach, identify the problems in this dog and write an initial plan for each.
Problem Definition and Recognition
Lymphadenopathy is disease of lymph nodes. Clinically, the term usually describes lymph node enlargement, tenderness, or both. Palpable lymph nodes include the mandibular, superficial cervical, auxiliary, popliteal, and inguinal lymph nodes. These nodes should be examined for size, texture, mobility, temperature, and pain. Lymph node enlargement may be localized or generalized.
Pathophysiology
Lymph nodes contain three distinct regions. The cortex is the outer layer and is the region for production of B and T lymphocytes. The next layer, the paracortical region, contains small T lymphocytes and macrophages. The medulla contains lymphocytes, macrophages, and plasma cells. Because of its structure, lymph node function includes lymphatic fluid filtration, phagocytosis of organisms, and lymphocyte and antibody production. Lymph nodes can be a site of extramedullary hematopoiesis.
The causes (rule-outs) of lymphadenopathy are listed in Table 16-1. The basic mechanisms are inflammatory, reactive hyperplasia, and neoplasia. Lymphadenopathy is classified as localized or generalized.
Localized infections cause enlargement of nodes that drain the affected area. In addition to enlargement, nodes may be warm, painful, and adherent to surrounding tissue. Certain bacteria (Pasteurella, Actinomyces, Nocardia, and Yersinia) can cause necrosis and rupture of affected nodes.
Generalized lymphadenopathy is most often associated with immune responses to systemic infection, autoimmune diseases, or lymphoreticular neoplasia. Marked lymph node enlargement in the absence of local inflammation is commonly associated with lymphatic neoplasia.
TABLE 16-1. Causes (rule-outs) for lymphadenopathy
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