Abdominal and Retroperitoneal Lymphadenopathy

Lymphadenopathy, the abnormal enlargement of lymph nodes, can result from a wide variety of infectious and noninfectious causes. Acute enlargement of superficial lymph nodes caused by infection can occur over a period of days, accompanied by pain and tenderness to palpation, resulting in lymphadenitis. Alternatively, the enlargement of nodes can occur over weeks to months, with little tenderness, representing a more chronic inflammatory process. Abdominal and retroperitoneal lymphadenopathy is a diagnosis made by imaging techniques such as ultrasonography (US), CT, or MRI and is defined as lymph nodes >8–10 mm diameter. Without sequential imaging studies, it can be unclear whether enlargement represents a new, rapidly evolving process or a more prolonged, chronic, relatively stable one. Without the ability to examine the lymph nodes directly, the clinician must rely on clues from the history and physical examination to formulate a diagnosis.

Inflammation in lymph nodes may be the direct result of infection in the tissues (or other lymph nodes) that the nodes drain or a consequence of dissemination of an organism through the bloodstream. Tissues and organs of the abdomen and retroperitoneal space can be infected by a variety of pathogens and through various routes (see Chapters 66 and 67 ).