Lymph Node - Congestion

Congestion of blood vessels (e.g., capillaries or venules) may be seen in lymph nodes of rodents, particularly associated with angiectasis (Figure 1 and Figure 2, arrows). Congestion is characterized by excessive accumulation of blood within a vessel, due either to increased afflux or to obstruction of return flow. Congested vessels may or may not be dilated (angiectatic). In the lymph node, congestion should be distinguished from sinus erythrocytosis, hemorrhage, hemangioma, and hemangiosarcoma. Congestion differs from sinus erythrocytosis in that the accumulation of blood is within blood vessel lumens and not lymphatic sinuses. Congestion differs from hemorrhage in that erythrocytes and other blood components are intravascular and not extravasated. Congestion may accompany a hemangioma or hemangiosarcoma; however, the lesion is secondary and typically consists of normal blood components. Extravasated erythrocytes may be present with congestion, but in the absence of necrosis or other lesions, they are attributed to necropsy technique and considered to be a dissection-induced artifact.