Lymph Drainage of the
Abdomen
The major lymphatic channels
of the posterior abdominal wall are essentially located along the large blood
vessels. Thus the external iliac lymph vessels, interrupted by nodes of
the same name, course with the external iliac arteries and veins. Entering the
pelvis posterior to the inguinal ligament about midway between the anterior
superior spine of the ilium and symphysis pubis, these vessels receive lymph from
the deep (and thereby also superficial) inguinal lymph nodes, through
which pass the lymphatic drainage of the lower extremities, the inferior parts
of the anterolateral abdominal wall, and the perineum (including the external
genitalia and anal region). The internal iliac lymph vessels run,
interrupted by the internal iliac nodes, with the artery and vein of the
same name and drain the larger part of the organs and wall of the true pelvis,
whereas the remaining part of this region releases lymph through the presacral
lymphatics. The external and internal iliac lymphatics join to form common
iliac lymph vessels and nodes of the same name. Common iliac lymph vessels
also receive input from the presacral lymphatics with their lateral and
middle sacral nodes. The latter are situated in the retro- rectal
connective tissue over the anterior surface of the sacrum. In the region of the
aortic bifurcation, the common iliac lymph vessels proceed superiorly along the
lateral walls of the aorta to become the right and left lumbar trunks. These
trunks and the interposed lateral aortic lymph nodes receive afferents
from the kidney and the visceral (preaortic) lymph nodes. The extremely
large area of drainage that the lumbar trunks serve includes, thus, the walls
and organs of the lower abdomen as well as of the lower extremities.
Both lumbar trunks unite in the region of the aortic hiatus, anterior to the vertebral column
(in the majority of cases), at the level of the upper third of L1 and the
intervertebral disc between vertebrae T12 and L1, to form the beginning of the thoracic
duct. In about 50% of individuals, the thoracic duct starts with a
distinctive, elongated, saccular dilatation (≈ 1 to 1.5 cm in diameter and 5 to
7 cm in length), the cisterna chyli. Its three main roots are the single
intestinal trunk and the two lumbar trunks; however, two smaller
tributaries coming from a cranial direction and descending through the aortic
hiatus of the diaphragm also join the cisterna chyli.
The thoracic duct passes first to the right across the posterior surface
of the aorta, through the aortic hiatus of the diaphragm into the mediastinum,
ascending between the aorta and the azygos vein, anterior to the lower thoracic
vertebrae and right intercostal arteries. On reaching the level of the fifth
thoracic vertebra, it courses posterior to the esophagus to the left side of
the spinal column, where it runs for a short distance to the right of the aorta
and then crosses posterior to the aortic arch to continue its ascent. Opposite
the third thoracic vertebra, the
thoracic duct draws away from the spinal column in an anterior direction and
proceeds between the left common carotid artery and the left subclavian artery,
through the superior thoracic aperture, and into the left supraclavicular
fossa. Here it arches superior to the subclavian artery and opens either into
the angle at which the left jugular and left subclavian veins join to form the
left brachiocephalic vein or, less often, into one of the two veins forming this angle. At its point of entry into the
veins, the thoracic duct does not always form a single entity but sometimes
divides into a triangular structure composed of two or more branches. During
its passage through the thorax, the thoracic duct is joined by vessels connecting
with the posterior parietal, tracheobronchial, and posterior mediastinal lymph
nodes, as well as smaller lymph vessels draining the thoracic wall and thoracic organs.
