Kidneys and Suprarenal Glands
The two kidneys lie behind the peritoneum on either side of the
upper lumbar vertebrae (Fig. 4.79).
They are embedded in fat in the paravertebral gutters of the posterior abdominal
wall and are placed obliquely, with their anterior surfaces directed slightly laterally (Fig. 4.80). The left kidney usually lies at a
higher level than the right.
Each kidney is bean-shaped, flattened anteroposteriorly and
approximately 11 cm long. The anterior and posterior surfaces are gently convex
and the superior and inferior poles are rounded. The lateral border is convex,
while the indented medial border bears an aperture, the hilum (Figs 4.81 &
4.82), which is traversed by the renal pelvis or ureter, the renal vessels,
lymphatics and autonomic nerves. The hilum
leads into a cavity within the kidney, the renal sinus, which is occupied by
the calices and renal pelvis (Fig. 4.83),
the renal blood vessels and a quantity of fat.
Covered by a thin capsule, the kidney comprises an outer cortex
and an inner medulla. The medulla contains numerous pyramids, the apices of
which project into the renal sinus as the renal papillae. Urine discharged from
the papillae is collected by about 10 trumpet-shaped chambers, the minor
calices (Fig. 4.83),
which unite to form two or three major calices. These fuse into the single,
funnel-shaped renal pelvis, which lies posterior to most of the vessels and is
continuous with the ureter. Either of the
kidneys and ureters may be duplicated and the two embryonic organs may fuse
resulting in a ‘horseshoe kidney’.
Perirenal tissues
Each kidney is surrounded by a layer of perinephric (perirenal)
fat enveloped in a thin sheet of connective tissue, the renal fascia (Fig.
4.84). This fascia also encloses the suprarenal gland and the proximal part of
the ureter. From the inferior pole of the kidney, the renal fascia tapers
downwards into the iliac fossa. Around the fascia is a further layer of fat
(paranephric or pararenal fat) lying against the posterior abdominal muscles
and covered anteriorly by the peritoneum. The perirenal fascia can impede the
spread of infection or cancer.
Relations of kidneys
The right and left kidneys have similar posterior relations (Fig.
4.80). The superior poles lie against the diaphragm and the twelfth ribs, below
which run the subcostal nerves and vessels. On the left the upper pole is also
related, through the diaphragm, to the pleura and eleventh rib. The medial
border of each kidney overlaps psoas major (Fig. 4.79), while the inferolateral
portion is related to quadratus lumborum and transversus abdominis and to the
first lumbar nerve.
The anterior relations of the kidneys
are asymmetric. On the right, from above downwards, they include the bare area
of the liver, the second part of the duodenum (Fig. 4.80), the right flexure of
the colon and coils of jejunum. The medial border of the right kidney is
related to the inferior vena cava, the renal vessels and the upper part of the
ureter (Fig. 4.84).
On the left, from above downwards, the anterior relations include
the stomach and spleen, the splenic vessels, the tail of the pancreas, the left
colic flexure and coils of jejunum. The medial border relates to the suprarenal
gland, the renal and suprarenal vessels, the left gonadal vein and the proximal
part of the ureter (Fig. 4.87).
Renal vessels
At the level of the first lumbar vertebra the aorta usually
supplies one renal artery to each kidney (Fig. 4.85). Each artery lies behind the
corresponding vein, and the artery on the right crosses behind the inferior
vena cava. However, there are often supernumerary (anomalous, aberrant or
accessory) renal arteries arising from the aorta above or below the typical
vessel. Regardless of its origin, each renal artery divides as it approaches
the kidney and all the branches usually traverse the hilum. However, a polar
artery may occasionally be found entering the medial border of the organ above
or below the hilum (Figs 4.81 & 4.87). Stenosis of a renal artery can lead
to systemic arterial hypertension.
Several veins unite near the renal hilum, anterior to the
arteries, forming the renal vein. On the right, the vein runs a short course to
terminate in the inferior vena cava. The left renal vein is longer and usually
receives the suprarenal and gonadal veins before passing in front of the aorta
to reach the inferior vena cava (Fig. 4.79). Because of its termination, the
left gonadal vein may become dilated if the renal vein is obstructed. In the
male, this can lead to swelling of the pampiniform plexus within the scrotum (varicocele;
p. 150).
The suprarenal glands lie adjacent to the superior poles of the
kidneys, embedded in the perinephric fat. On the right, the gland is
tetrahedral and occupies the angle between the superior pole of the kidney and
the inferior vena cava (Fig. 4.86).
The left gland is crescentic and is applied to the medial border of the kidney
above the hilum (Fig. 4.87).
The blood supply
to the suprarenal glands is
provided by branches of the renal and inferior phrenic arteries and the aorta.
The right suprarenal vein is very short and enters the inferior vena cava
directly while that on the left descends to enter the left renal vein.
The medulla of each suprarenal gland is richly innervated by
preganglionic sympathetic nerves from the adjacent part of the sympathetic
trunk.
Abdominal parts of ureters
From the pelviureteric region, each ureter descends through the
retroperitoneal tissues of the posterior abdominal wall as far as the pelvic
brim. Here it crosses in front of the external iliac vessels and continues down
the lateral wall of the pelvis (p. 222). Within the abdomen, the ureter lies on
psoas major (Fig. 4.84), behind which are the lumbar transverse processes (Fig.
4.82).
The right ureter commences behind the descending duodenum and is
crossed by the root of the mesentery, the gonadal vessels and branches of the
superior mesenteric artery and accompanying veins. This ureter is also related
to coils of small intestine, and sometimes to the caecum and appendix. The left
ureter is covered initially by the pancreas and is subsequently crossed by the
gonadal vessels, branches of the inferior mesenteric artery and vein (Fig.
4.76) and coils of small intestine and sigmoid colon. At the pelvic brim, it
passes behind the root of the sigmoid mesocolon.
Renal calculi may impact where the ureters narrow at the
pelviureteric junction, near the pelvic brim and at the entrance to the
bladder.
The blood supply to the abdominal part of the ureter is derived
from branches of the renal artery, supplemented by minute peritoneal vessels.
