Kidneys
Location & Description
The waste products leave the kidneys as
urine which passes down the ureters to the
urinary bladder which is located within the
pelvis. The urine leaves the body in the
urethra.
The kidneys are reddish brown and lie
behind the peritoneum high up on the
posterior abdominal wall on either side of
the vertebral column. They are largely under
cover of the costal margin.
The right kidney lies slightly lower than the
left kidney because the large size of the right
lobe of the liver.
With contraction of the diaphragm during
respiration, both kidneys move downward in
a vertical direction by as much as 1 inch (2.5
cm ) .
On the medial concave border of
each kidney is a vertical slit that is
bounded by thick lips of the renal
substance and is called the hilum.
The hilum extends into a large cavity
called the renal sinus.
The hilum transmits from front
backward:
The renal vein; two branches of the
renal artery; ureter; the 3rd branch of
the renal artery ( V.A.U.A. ) ; lymph
vessels and sympathetic fibers .
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Covering:
1. Fibrous capsule: It surrounds the kidney and is closely applied to its outer surface.
2. Perirenal fat: It covers the fibrous capsule.
3. Renal fascia: It is a condensation of connective tissue that lies outside the perirenal fat
and enclose the kidneys and suprarenal glands. It is continuous laterally with the fascia
transversalis.
4. Pararenal fat: It lies external to the renal fascia. It is in a large quantity. It forms part of
the retroperitoneal fat.
N. B. 2 & 3 and 4 support the kidneys and hold them in position on the posterior abdominal
wall.
Renal Structure
Each kidney has a dark brown outer cortex and a light brown inner medulla.
The medulla is composed of about a dozen ( 12 ) renal pyramids, each having its
base oriented toward the cortex and its apex ( renal papilla ) projecting medially.
The cortex extends into the medulla between adjacent pyramids as the renal
columns.
Extending from the bases of the renal pyramids into the cortex are striation
(medullary rays ).
The renal sinus is the space within the hilum. It contains the upper expanded end
of the ureter ( renal pelvis ) which divided into 2 or 3 major calyces, each of which
divides into 2 or 3 minor calyces. Each minor calyx is indented by the apex of the
renal pyramid ( renal papilla).
Anterior Relations of the Right Kidney
The suprarenal gland; liver; second part of the duodenum; right colic flexure and
coils of small intestine.
Anterior Relation of the left Kidney
The suprarenal gland; spleen; stomach; pancreas; left colic flexure and coils of
the jejunum.
N.B. many of the structures are directly in contact with the kidneys, whereas other
are separated by visceral layers of peritoneum.
Posterior Relation of the Right Kidney
The diaphragm; costodiaphragmatic
recess of the pleura; 12th rib; psoas;
quadratus lumborum; transversus
abdominis muscles; subcostal (T 12 );
iliohypogastric and ilioinguinal
nerves ( L1 ).
Posterior Relation of the Left Kidney
As the right except that it lies higher
than the right. So, it is related to 11th
and 12th ribs.
N.B. the right kidney lies at a slightly
lower level than the left kidney and
the lower pole may be palpated in the
right lumbar region at the end of deep
inspiration in a person with poorly
developed abdominal musculature.
Arteries
The renal artery arises from the aorta at
the level of the 2nd lumbar vertebra. Each
renal artery usually divides into 5
segmental arteries that enter the hilum of
the kidney, 4 in front and one behind the
renal artery.
Lobar arteries arise from each segmental
artery one for each renal pyramid. Before
entering the renal substance each lobar
artery gives off 2 or 3 interlobar arteries.
The interlobar arteries run toward the
cortex on each side of the renal pyramid.
At the junction of the cortex and medulla,
the interlobar arteries give off the
arcuate arteries which arch over the
bases of the pyramids.
The arcuate arteries give off several
interlobular arteries that ascend in the
cortex.
The afferent glomerular arterioles arise
as branches of the interlobular arteries.
Veins
The renal vein emerges from the hilum in front of the renal artery and drains into the inferior
vena cava.
Lymph Drainage
Lateral aortic lymph nodes ( para- aortic ) around the origin of the renal artery.
Nerve Supply
Renal sympathetic plexus. The afferent fibers that travel through the renal plexus enter the
spinal cord in the 10th ; 11th and 12th thoracic nerves.
Clinical Notes
Renal Pain
It varies from a dull ( not sharp ) ache to a severe pain in the flank that may radiate
downward into the lower abdomen.
It can result from stretching of the kidney capsule or spasm of the smooth muscle in the
renal pelvis.
The afferent nerve fibers pass through the renal plexus around the renal artery and ascend
to the spinal cord through the lowest splanchnic nerve in the thorax and the sympathetic
trunk. They enter the spinal cord at the level of T12 .
Pain is commonly referred along the distribution of the subcostal nerve ( 12 ) to the flank
and the anterior abdominal wall.
Renal Mobility
The kidney are maintained in their normal position by intra- abdominal pressure
and by their connections with the perirenal fat ; renal fascia and pararenal fat .
Each kidney moves slightly with respiration. If the amount of the perirenal fat be
reduced , the mobility of the kidney may become excessive and produce
symptoms of renal colic caused by kinking of the ureter.
Excessive mobility of the kidney leaves the suprarenal gland undisturbed because
both kidney and suprarenal are enclosed within a separate compartment in the
renal fascia. Also, any of them can separate easily during operations.
Kidney Trauma
The kidney are well protected by the lower ribs; lumbar muscles and vertebral
column. However, a severe blunt applied to abdomen may crush the right kidney
against the last rib & the left kidney against the last 2 ribs and vertebral column.
Because 25 % of the cardiac outflow passes through the kidneys, renal injury can
result in rapid blood loss.
The lower pole of the right kidney can be
palpated in the right lumbar region at the end
of deep inspiration in a person with poorly
developed abdominal muscles.
The normal left kidney which is higher than
the right is not palpable.
Surface Anatomy:
On the anterior abdominal wall the hilum of
each kidney lies on the transpyloric plane,
about 3 fingerbreadths from the midline.
On the back, the kidneys extend from the 12
thoracic spine to the 3rd lumbar spine. The hili
are opposite the spine of the 1st lumbar
vertebra.
Draw oblique line, so that:
Its upper end is 2.5 cm lateral to the median
plane.
Its center is 5 cm lateral to median plane.
Its lower end is 7.5 cm lateral to the median
plane.
Ureter
The 2 ureters are muscular tubes that extend from
the kidneys to the posterior surface of the urinary
bladder.
The urine is propelled along the ureter by
peristaltic contractions of the muscle coat which
are assisted by the filtration pressure of the
glomeruli.
Each ureter measures about 10 inch ( 25 cm ) long.
It has 3 constrictions along its course:
Where the renal pelvis joins the ureter
Where it is kinked as it crosses the pelvic brim.
Where it pierces the bladder wall.
The renal pelvis is a funnel- shaped expanded
upper end of the ureter. It lies within the hilum of
the kidney and receives the major calyces.
It emerges from the hilum of the kidney and runs
vertically downward behind the parietal
peritoneum which is adherent to it on the psoas
muscle which separates it from the tips of the
transverse processes of the lumbar vertebrae.
It enters the pelvis by crossing the bifurcation of
the common iliac artery in front of the sacroiliac
joint.
The ureter then runs down the lateral wall
of the pelvis to the region of the ischial
spine and turns forward to enter the lateral
angle of the urinary bladder.
Posterior Relations of the Right Ureter
Right psoas muscle which separates it
from the lumbar transverse processes.
The bifurcation of the right common iliac
artery.
Posterior Relations of the Left Ureter
Left psoas muscle and the bifurcation of
the left common iliac artery.
Anterior Relation of the Right ureter
The 2nd part of the duodenum; terminal part of the ileum; right colic and ileocolic
vessels; right testicular or ovarian vessels and the root of the mesentery of the
small intestine.
Anterior Relation of the Left ureter
The sigmoid colon; sigmoid mesocolon; left colic vessels and the left testicular or
ovarian vessels.
N.B. The inferior mesenteric vein lies along the medial side of the left ureter.
Arteries
The upper end is supplied by the renal
artery
The middle portion is supplied by the
testicular or ovarian artery.
The pelvic part is supplied by the
superior vesical artery.
Veins
Venous blood drains into the
corresponding veins.
Lymph Drainage
The lymph drains into the lateral aortic
nodes and the iliac nodes.
Nerve Supply
Renal; gonadal in the abdomen and
hypogastric plexuses in the pelvis.
Afferent fibers travel with the
sympathetic nerves and enter the spinal
cord in the 1st & 2nd lumbar segments
Clinical Notes
Ureteric Stones
There are 3 sites of anatomic narrowing of the ureter where stones may be arrested. Most
stones, although radiopaque, are small enough to be impossible to see definitely along the
course of the ureter on plane radiographic examination.
An intravenous pyelogram is usually necessary. The ureter runs down in front of the tips of
the transverse processes of the lumbar vertebrae, crosses the region of the sacroiliac joint,
swings out to the ischial spine and then turns medially to the bladder.
Renal Colic
The renal pelvis and ureter send their afferent nerves into the spinal cord at segments T11
and 12 and L1 and 2.
In renal colic, strong peristaltic waves of contraction pass down the ureter in an attempt to
pass the stone onward.
The spasm of the smooth muscle causes an agonizing colicky pain which is referred to the
skin areas that are supplied by these segments of the spinal cord ( flank; loin and groin ).
When a stone enters the low part of the ureter, the pain is felt at a lower level and is often
referred to the testis or the tip of the penis in the male and labium majus in the female.
Sometimes ureteral pain is referred along the femoral branch of the genitofemoral nerve ( L1
and 2 ) to the front of the thigh .
The pain is often so severe that afferent pain impulses spread within the central nervous
system giving rise to nausea.
Suprarenal gland
They are yellowish; ductless and retroperitoneal
glands. They lie on the upper poles of the
kidneys.
They are surrounded by renal fascia, but are
separated from the kidneys by the perirenal fat.
Each gland has yellow cortex and a dark brown
medulla.
The cortex of the glands secretes hormones that
include mineral corticoids which are concerned
with the control of fluid and electrolyte balance.
Glucocorticoids which are concerned with the
control of the metabolism of carbohydrates; fat;
and proteins and small amounts of sex hormones
which probably play a role in the prepubertal
development of the sex organs.
The medulla of the suprarenal glands secretes
the catecholamines epinephrine and
norepinephrine.
The right suprarenal gland:
It is pyramidal shaped and caps the upper pole of the right kidney. It lies behind
the right lobe of the liver and extends medially behind the inferior vena cava. It
rests posteriorly on the diaphragm.
The left suprarenal gland:
It is crescentic in shape and extends along the medial border of the left kidney
from the upper pole to the hilus. It lies behind the pancreas; lesser sac and
stomach and rests posteriorly on the diaphragm.
Arteries
They are inferior phrenic artery; aorta and renal artery.
Veins
A single vein emerges from the hilum of each and drains into the inferior vena
cava on the right and into the renal vein on the left.
Lymph Drainage
The lymph drains into the lateral ( para ) aortic nodes.
Nerve Supply
Preganglionic sympathetic fibers derived from the splanchnic nerves supply the
glands. Most of the nerves end in the medulla of the gland.