LYMPHATIC DRAINAGE I—PELVIS
The lymph nodes of the pelvis receive lymphatic drainage from the pelvic organs and the groin. They tend to follow the course of the larger vessels and are named accordingly. The pelvic lymph nodes are shown in the upper picture as they may be visualized in the most frequent surgical approaches, namely, the intraperitoneal and extraperitoneal radical dissection for neoplastic lymph node involvement. More and more, this view is not what is seen surgically because of a growing use of laparoscopic or robotically assisted laparoscopic lymph node dissection. These allow magniﬁcation and a dexterity of dissection that makes up for the more restricted overall ﬁeld of view.
Located in the pelvis, the external iliac nodes are situated about the external iliac vessels superiorly and inferiorly. There are two distinct groups: one situated lateral to the vessels and the other posterior to the psoas muscle. The distal portion of the posterior group is enclosed in the femoral sheath. These nodes receive afferent vessels from the femoral nodes, the external genitalia, the deeper aspects of the abdominal wall, the uterus, and the hypogastric nodes. Some efferent lymphatics extend to the hypogastric nodes, but for the most part they pass upward to the common iliac and periaortic nodes. The majority of lymphatic channels to this group of nodes originates from the vulva, but there are also channels from the cervix and lower portion of the uterus. The external iliac nodes receive secondary drainage from the femoral and internal iliac nodes.
The hypogastric nodes (internal iliac group) lie in close relation to the hypogastric veins. The internal iliac nodes are found in an anatomic triangle whose sides are composed of the external iliac artery, the hypogastric artery, and the pelvic side wall. Included in this clinically important area are nodes with special designation, including the nodes of the femoral ring, the obturator nodes, and the nodes adjacent to the external iliac vessels. This rich collection of nodes receives channels from every internal pelvic organ and the vulva, including the clitoris and urethra.
The number of nodes and their locale are variable; rather constant nodes can be found at the junction of the hypogastric and the external iliac veins, in the obturator foramen close to the obturator vessels and nerve (the obturator node) and at the base of the broad ligament near the cervix, where the ureter runs beneath the uterine artery (ureteral node). The middle sacral nodes (node of the promontory) lie alongside the middle sacral vessels. Lateral sacral nodes may be found in the hollow of the sacrum in relation to the lateral sacral vessels. The hypogastric nodes receive afferents from the external iliac nodes, the uterus, vagina, bladder, lower rectum, and some vessels from the tubes and ovaries. Efferent lymphatics pass to the common iliac and periaortic nodes.
The common iliac nodes lie upon the mesial and lateral aspects of the common iliac vessels and just below the bifurcation of the aorta. Most of these nodes are found lateral to the vessels. Besides those afferents just mentioned, they also receive primary afferents from the viscera, including the cervix and the upper portion of the vagina. Secondary lymphatic drainage from the internal iliac, external iliac, superior gluteal, and inferior gluteal nodes ﬂows to the common iliac nodes. Efferent lymphatics extend upward to the periaortic nodes.
The periaortic chain of nodes lies in front of and lateral to the aorta. These drain into the lumbar trunks, which terminate in the cisterna chyli. They receive afferents from the iliac nodes, the abdomen and pelvic organs, the tubes and ovaries, and the deeper layers of the parietes.