Lumbar Trunk (Pelvic Lymph Trunk)
The lumbar trunk (Figures 24: 11; 27: 10) has an extraordinarily large number of variations. Usually, there are 2 lumbar trunks, a larger one on the left-dorsal or the dorsal border of the aorta, and a smaller one on the right-ventral border of the aorta (Figure 24: i), as shown in Figure 24.
Each of the two trunks originates from the efferent vessels of the medial iliac lymph node (Figures 24: 7, 71; 27: 4, 41). Both trunks, however, are connected to one another by numerous transverse and oblique connecting branches, which run over the two surfaces of the aorta, particularly the ventral surface, so that a coarse network of lymph vessels is created (Figure 24), which delimits numerous islands. Individual branches that separate from this network usually open directly into the cisterna chyli. It is not unusual for one of the lymphatic trunks to flow around a large island. Sometimes the left dorsal trunk is absent, and only the right ventral trunk is present, which then becomes larger, as Figure 27 shows. Nonetheless, even when the left dorsal trunk is absent, there is still a branched network of lymph vessels surrounding the aorta, as shown in Figure 27. The lumbar trunk may also merge into the cisterna chyli with nearly no distinct boundary (see above). Occasionally, there are 3 connected lumbar trunks: a right-ventral trunk, a right-dorsal trunk, and a left-dorsal or directly dorsal trunk; the latter is larger than the other two.