Anatomy of Kidneys and Suprarenal Glands

Kidney Anatomy

• Kidneys are reddish-brown, retroperitoneal organs located high up on the posterior abdominal wall, behind the peritoneum.
• Each kidney has anterior and posterior surfaces, lateral (convex) and medial (concave) borders.
• The medial border has a vertical slit called the hilum, which lies at the level of the first lumbar vertebra.

Coverings of the Kidney

• Fibrous capsule: surrounds the kidney and is closely applied to its outer surface.
• Perirenal fat: covers the fibrous capsule.
• Renal fascia: connects the kidney and suprarenal gland.
• Pararenal fat: forms part of the retroperitoneal fat, lies external to the renal fascia.

Renal Structure

• Each kidney has a dark brown cortex and a light brown inner medulla.
• The medulla is composed of about ten renal pyramids, each with a base directed toward the cortex and its apex (renal papilla) projecting medially.
• The cortex extends into the medulla between adjacent pyramids as the renal columns.
• Medullary rays extend from the bases of the renal pyramids into the cortex.

Relations of the Kidneys

• Right kidney: anterior - suprarenal gland, liver, second part of the duodenum, and right colic flexure; posterior - twelfth rib, diaphragm, and psoas muscle.
• Left kidney: anterior - left suprarenal gland, left colic flexure, spleen, coils of jejunum, stomach, pancreas, and splenic vessels; posterior - eleventh and twelfth ribs, diaphragm, and psoas muscle.

Blood Supply of the Kidneys

• Renal arteries: arise at the level of the second lumbar vertebra, cross the psoas to the kidneys.
• The left artery is shorter than the right artery.

Nerve Supply of the Kidneys

• Renal nerve is derived from both parts of the autonomic system.
• Preganglionic sympathetic fibers from T11 and T12 synapse in the celiac and renal ganglia, and are vasomotor in function.
• Afferent fibers, including those subserving pain, accompany the sympathetic nerves.

Suprarenal Glands

• Yellowish, retroperitoneal organs, lie on the upper poles of the kidneys.
• Surrounded by renal fascia, but separated from the kidney by perirenal fat.
• Each gland has a yellowish cortex and dark brown medulla.
• Right suprarenal gland: pyramidal in shape, cups the upper pole of the right kidney.
• Left suprarenal gland: crescentic in shape, cups the left kidney.

Blood Supply of the Suprarenal Glands

• Superior suprarenal artery from the inferior phrenic artery.
• Middle suprarenal artery from the abdominal aorta.
• Inferior suprarenal artery from the renal artery.

Ureters

• Retroperitoneal, muscular tube extends from the kidney to the posterior surface of the urinary bladder.
• The urine is propelled along the ureter by peristaltic contraction of the muscle coat.
• 25 cm long, with three constrictions along its course.
• Relation of the right ureter: anterior - second part of the duodenum, terminal part of the ileum, right gonadal vessels; posterior - right psoas and bifurcation of the right common iliac artery.
• Relation of the left ureter: anterior - sigmoid colon, sigmoid mesocolon, left gonadal vessels; posterior - left psoas and bifurcation of the left common iliac artery.

Arterial Supply of the Ureters

• Upper part from the renal artery.
• Middle part from the testicular or ovarian artery.
• Lower part from the superior vesical artery.

Venous Drainage of the Ureters

• Venous blood drains into veins that correspond to the arteries.

Nerve Supply of the Ureters

• The nerve supply is the renal, testicular (or ovarian), and hypogastric plexuses (in the pelvis).
• Afferent fibers travel with the sympathetic nerves and enter the spinal cord in the 1st and 2nd lumbar segments.

Ureteric Stones

• Three sites of anatomic narrowing of the ureter where stones may be arrested, namely, the pelviureteral junction, the pelvic brim, and where the ureter enters the bladder.

Renal Colic

• The renal pelvis and the 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.