Lymphatics of Urinary
System
In both the bladder and ureters, lymph first drains into a submucous
network of lymph capillaries. These capillaries drain into a plexus located
outside of the muscular wall. This plexus, in turn, connects to vessels that
lead to regional lymph nodes. The vessels contain valves, whereas the plexus
and capillaries do not.
Bladder. The apex and body of the bladder drain into
vessels that reach the external iliac nodes (some via prevesical and
paravesical visceral nodes). The fundus and neck drain into vessels that reach
the internal iliac nodes (some via postvesical visceral nodes).
Ureter. The pelvic portion of the ureter is drained by a
few lymph vessels that reach the internal iliac nodes either directly or via
efferent vessels from the bladder. The abdominal portion of the ureter has
channels that drain into the external and common iliac nodes. Near the kidney,
drainage is to the lumbar (caval and lateral aortic) nodes, either by direct
communication or via renal lymphatic trunks.
Kidney
Extrarenal. Beneath the surface of the kidney, a scanty
subcapsular plexus of lymph capillaries anastomoses, by means of perforating
channels, with pericapsular vessels in the perinephric fat. These vessles
eventually drain into superior lumbar nodes. The subcapsular plexus also
communicates sparingly with lymphatics in the deeper layers of the parenchyma.
Intrarenal. In the parenchyma, lymph capillaries accompany
the blood vessels and are found chiefly in the perivascular connective tissue.
The lymph capillaries that surround arterioles are generally larger and more
numerous than those that surround venules.
The great majority of intrarenal lymphatics occur in the cortical and
corticomedullary zones. In the outer cortex most lymphatics are associated with
subcapsular veins and renal tubules, whereas in the midcortex they are
associated with cortical radiate (interlobular) arteries and veins, glomeruli,
and tubules. In the corticomedullary zone, lymphatics pass between loops of
Henle and collecting ducts. In the medulla, sparse lymphatic channels drain
structures in the region of the vasa recta.
The lymph vessels exiting the parenchyma reach the renal sinus, often
accompanying the arteries along the way, and form some four to five trunks that
exit the hilum. They are joined by lymph vessels from the renal capsule and
converge into a few valve-studded renal lymphatic trunks that accompany the
renal vein. These trunks primarily drain to the superior lumbar nodes.
Except as a potential metastatic pathway, renal lymphatic drainage is commonly
overlooked. The volume of lymph that drains from the kidney, however, is
approximately 0.5 mL/min, thus approaching that of urine. Its primary function is probably to return reabsorbed
protein to the blood. Some investigators have determined that the concentration
of renin is greater in renal lymph than in renal vein plasma.
Summary
The lymph drainage of the bladder and ureters passes to the external,
internal, and common iliac groups of nodes
a sequential chain of nodes that drains next to the lumbar (caval/aortic)
nodes. The lymph of the upper ureters and kidneys drains directly into the
superior lumbar nodes. In both cases, lymph from the lumbar nodes ultimately
flows to the thoracic duct via the
lumbar lymph trunks.
