The omental lymph node (Figure 25: 1) is 4 to 10 mm in size, and is found in only about half of all cases. It is sometimes found as a double lymph node and may even be tripled. It is embedded in the dorsal wall of the omental bursa about 2 to 5 cm from the duodenum. It was found 6 times in 12 examined dogs; 1 lymph node was found in 3 dogs, 2 lymph nodes were found in 2 dogs, and 3 lymph nodes were found in 1 dog.
The omental lymph node drains the lymph vessels of the omentum (but not the lymph vessels of the duodenum).
Efferent drainage (Figure 25)
The efferent vessels of the omental lymph node usually merge to form a single small vessel that travels over the pancreas to either a right hepatic or right colic lymph node, uniting along the way with one of the efferent vessels of the duodenal lymph node. Because of this connection, retrograde flow can be observed from the duodenal lymph node to the omental lymph node. Another efferent vessel of the omental lymph node may also be found to drain directly to the duodenal lymph node.