hi let's talk about the renal vasculature in this video we'll discuss the flow of blood two
and through the kidney as well as the peculiarities of the tributaries of
the left renal vein and how that relates to left renal vein entrapment syndrome
so first of all kidneys are supplied by renal arteries they're frequently about a
third of the time also supplied by accessory renal arteries but for the time being let's ignore those
so a renal artery is typically going to multifurcate into five segmental arteries we
call them segmental arteries because they supply renal segments so there is an apical renal segment
an inferior renal segment an anterior superior renal segment an anterior inferior renal segment
and then posterior or deep to these but corresponding with their relative positions
as i'll outline here there's also a posterior segment as well now these segmental arteries
are end arteries meaning they don't anastomose or share blood in any way so there is no open
anastomosis typically nor are there overlaps of capillary beds so each segment has its own
dedicated arterial supply which allows for the removal of that segment we would call that a
partial nephrectomy without affecting the other remaining segments it probably also
bears relating much like in the lungs where we have an analogous system the intrarenal veins
do typically anastomose so arteries won't cross from segment to segment but veins may
as we move forward it probably would be useful to also define what a renal lobe and lobule are
a renal lobe consists of a renal pyramid as well as all of the cortex surrounding that pyramid so
half a column as well as the entire cortical arch here a lobule is a way of
subdividing the lobe and a lobule consists of all of the cortex
here this would be a cortical arch surrounding a single medullary or in line with a single
single medullary ray so that's roughly going to be between these vessels here
these are called the cortical radiate arteries also known as the interlobular arteries
these are helpful as we describe the nomenclature of subsequent branches of the segmental arteries
so let's walk through that and we'll just follow any old segmental artery let's let's follow this
one here serving the the apical segment so coming off of segmental arteries are interlobar arteries
so we can see there's an interlobar artery there there's an interlobar artery there
and there and there these interlobar arteries are going to enter into the parenchyma in the regions
dividing the cortical arch from the medulla so there's the pyramid of the medulla here's
a cortical arch and they will ascend between those two tissues and as they ascend they will
branch off cortical radiate arteries these arteries radiate out into the cortex
they're also known as interlob arteries because they're also defining lobules
now as an interlobar artery rounds the bend from the lateral side of a pyramid here to the base of
the pyramid it becomes known as an arcuate artery so if it's on the side of the pyramid it's an
interlobar artery and if it's on the base of the pyramid it is an arcuate artery arcuate arteries
much like interlobar arteries also give off cortical radiate arteries these
cortical radiate arteries are then going to supply afferent arterioles which supply the glomeruli
those are the specialized capillary beds that are part of the renal corpuscles where we have
glomerular filtration or the movement of materials from the cardiovascular system into the nephron
from there blood is going to travel through efferent arterioles
and these efferent arterials are going to supply both peritubular capillaries as well as vasorecta
these vasorecta are specialized vessels within juxtamedullary nephrons and then we'll have
a similar drainage pattern so there will be peritubular venules going into cortical
radiate veins into arcuate veins interactive lobar veins and then finally into renal veins
now as we move to more granular levels so here we have
the arcuate artery that arcuate artery is giving off a cortical radiate artery and here we can see
afferent arterioles going out to supply the glomeruli here as part of the
renal corpuscle and then coming off of that glomerulus will be the efferent
arteriole now this is interesting because uh glomeruli are capillary beds and efferent
arterioles supply peritubular capillaries so we have a capillary bed
connected to a capillary bed by a vessel
any time that we have that situation it's called a portal system and so this is the basis of the
renal portal system these peritubular capillaries which are surrounding the nephron tubes are going
to be involved with the processes of tubular secretion and tubular reabsorption the vasa recta
are specialized vessels that are going to be basically elaborations of peritubular capillaries
surrounding the nephron loops of juxtamedullary nephrons and so these are going to be involved in
moving water out of the medulla to create a hyperosmotic gradient within the medulla
so to continue to pull water out from the nephron loop so peritubular veins
are then going to feed into cortical radiate veins which will feed into arcuate veins which
are going to mirror the the various hierarchy of the arteries as they supplied the nephrons
in terms of what we could expect to see in lab much of what i just discussed can only be seen
on a microscopic level with the the help of a light microscope or other imaging techniques
but reliably we will be able to see renal arteries we will reliably be able to see segmental arteries
and interlobar arteries reliably also and this is going to depend on a dissection we can see
arcuate arteries and of course if accessory renal arteries are present we can oftentimes see them so
about a third of the time accessory renal arteries will be present if they're present going into the
hilum they'll be known as hilar arteries if they are associated with either the superior
or the inferior poles they'll be known as polar arteries so anything cortical radiate and beyond
will not be visible in the laboratory so if uh if you don't see it don't don't
have your feelings hurt and i wouldn't waste much time looking for it because
without um without special technology um you're not going to be able to view them
on the other side of things is the venus return and we have a really interesting situation here
but let first let's let's kind of get the lay of the land within that retroperitoneal space so
here is the inferior vena cava the inferior vena cava the ivc is sort of the the clearing house
of the return of blood from the lower limbs the pelvis and the the abdomen and so there are
various tributaries to it so here we can see the right renal vein here we can see the left renal
vein and we can get a sense that the left renal vein is significantly longer than the right renal
vein it's about three times longer than the right renal vein here is the abdominal aorta coming down
and it will have various branches as we'll see this major branch here is known as the superior
mesenteric artery or the sma for short and we can see that that sma has a unique relationship
with the left renal vein here so that left renal vein is going to be found between the
sma and the abdominal aorta and that's going to be significant but let's go back to veins here
on the left side structures on the left are further from the inferior vena cava then
their counterparts on the right and what we'll see are left inferior phrenic veins
oftentimes combining with left suprarenal veins and there's a common trunk here draining
into the left renal vein we'll also have left gonadal veins draining into the left renal vein
and all of these structures so the the left uh hemi diaphragm the inferior surface the
hemidiaphragm the left supra renal gland and the left gonad on the right side
their respective veins drain directly into the ivc but on the left side they drain into the
left renal vein which is again located between the sma and the abdominal aorta so let's go back to
here's our abdominal aorta looking at this in profile here is the sma
and then between the two of these we have the left renal vein if
there is an aneurysm such as an abdominal aortic aneurysm a triple a here
that can squeeze that left renal vein and oftentimes occlude the return of blood
from the regions drained by the left renal vein so the left kidney the left inferior surface of
the hemidiaphragm the left supranal gland and the left gonad so that's going to be problematic you
know it likely is going to present as hematuria that's blood in the urine uh flank or gonadal pain
and varicocele which is the expansion of the plexus of veins surrounding the scrotum
and this
condition is sometimes referred to as nutcracker syndrome not because of the left gonadal pain
but because of the resemblance of the sma and abdominal aorta to a nutcracker but oftentimes
this is mistaken by uh the the lesser minds which sometimes the lesser personalities haunt us all
so don't uh don't feel ashamed there but do have an appropriate amount of decorum professionalism
and empathy for patients so we've discussed the flow of blood from the renal arteries to
and through the kidneys out to the renal veins as well as the peculiarities of the
left renal vein tributaries this is your summary slide thank you for your time