Kidney Anatomy and Structure

Kidney Anatomy

• The kidneys are reddish-brown organs located behind the peritoneum on the posterior abdominal wall.
• One kidney is on each side of the vertebral column, extending from the 12th thoracic to the 3rd lumbar vertebra.
• The right kidney is slightly lower than the left due to the larger size of the right lobe of the liver.
• The hilum of the kidney is opposite the L1 vertebra (transpyloric plane).
• The upper end of the right kidney reaches the 11th intercostal space, and the left kidney reaches the 11th rib.
• The lower end of the right kidney is 1.5 inches above the iliac crest, and the lower end of the left kidney is 2 inches above the iliac crest.
• The upper poles of the kidneys are closer to the midline than their lower poles.

Kidney Shape

• Kidney shape is bean-shaped.
• It has two poles (ends). The upper end is thick and opposite T12(1 inch from midline), and the lower end is thin and small and opposite L3 (3 inches from midline).
• Two surfaces:
  • Anterior: irregular, related to organs.
  • Posterior: flat, resting on the posterior abdominal wall.
• Two borders:
  • Lateral: convex.
  • Medial: concave, with a hilum at its middle part.

Kidney Hilum

• A vertical slit at the middle of the medial border of the kidney, where vessels enter the kidney.
• The hilum extends into a large cavity inside the kidney called the renal sinus, which receives vessels.
• It transmits the following structures from front to back:
  • Renal vein (anterior).
  • Renal artery (middle).
  • Pelvis of the ureter (posterior).
  • Lymphatics and autonomic nerve fibers.

Kidney Coverings

• Fibrous capsule: the true capsule, closely surrounding the outer surface of the kidney.
• Perirenal fat (fatty capsule): surrounds the fibrous capsule, derived from the transversalis fascia.
• Renal fascia: a false capsule, derived from the transversalis fascia, which surrounds the kidneys and suprarenal glands, remaining separate below to enclose the ureter.
• Pararenal fat: lies outside the renal fascia, supporting the kidneys on the posterior abdominal wall.

Kidney Relations (Anterior)

• Right kidney:

  • Suprarenal gland.
  • Right lobe of the liver.
  • Second part of duodenum (anterior to medial border and hilum).
  • Right colic flexure (lower lateral part of anterior surface).
  • Jejunum (lower medial part of anterior surface).

• Left kidney:

  • Suprarenal gland.
  • Jejunum (lower medial part of anterior surface).
  • Spleen (upper lateral part of anterior surface).
  • Pancreas and splenic vessels (middle part of anterior surface).
  • Stomach (upper part of anterior surface, between spleen laterally, suprarenal medially, and pancreas below).
  • Descending colon and left colic flexure (lower lateral part of anterior surface).

Kidney Relations (Posterior)

• Left Kidney

  • Diaphragm.
  • Costodiaphragmatic recess of the pleura.
  • 11th and 12th ribs.
  • Psoas, quadratus lumborum, and transversus abdominis muscles.
  • Subcostal (T12), iliohypogastric, and ilionguinal nerves (L1) run downward and laterally.

• Right Kidney

  • Similar relations to the left kidney.

Kidney Stability

• Attachment of the renal fascia to surrounding fasciae.
• Renal vessels connecting the kidney to major vessels (aorta and IVC).
• Intra-abdominal pressure.
• Surrounding viscera.
• Perirenal and pararenal fat (support and hold kidneys in position on the posterior abdominal wall).

Kidney Blood Supply

• Arteries: arise from the aorta at the level of the second lumbar vertebra. The right artery is longer, running behind the IVC and renal vein. The left artery is shorter, behind the left renal vein. Accessory renal arteries occur in 30% of cases, arising from the aorta above or below the origin of renal arteries.
• Veins: emerge from the hilum in front of the renal artery, draining into the inferior vena cava.

Kidney Lymphatic Drainage

• Lymph passes directly to the para-aortic lymph nodes.

Kidney Nerve Supply

• The nerve supply is the renal sympathetic plexus.

Kidney Surface Anatomy

• Hilum is at the transpyloric plane (L1 vertebral level), 2 inches from the midline.
• Upper pole is approximately 2 inches above the hilum, 1 inch from the midline.
• Lower pole is approximately 2 inches below the hilum, 3 inches from the midline.

Ureter Course

• Each ureter descends downward behind the peritoneum, opposite the transverse processes of L2, 3, 4, and 5 vertebrae, in front of the psoas major muscles.
• It enters the pelvis, crossing the bifurcation of the common iliac artery (at the sacroiliac joint).
• Then passes downward and backward along the internal iliac artery.
• Curves medially and opens into the postero-superior angle of the urinary bladder (pelvic part).

Ureter Parts

• Abdominal part.
• Pelvic part.
• Intramural part (inside the urinary bladder wall).

Ureter Relations (Abdominal Part)

• Right ureter:

  • Right psoas major
  • Right gonadal artery
  • Right colic artery
  • Ileocolic artery
  • Superior mesenteric artery
  • Right genitofemoral nerve

• Left ureter:

  • Left psoas major
  • Left gonadal artery
  • Left colic artery
  • Inferior mesenteric artery
  • Left genitofemoral nerve
  • Sigmoid arteries
  • Bifurcation of the common iliac artery

Quiz Questions

• Anterior relation of the left kidney: second part of the duodenum.
• Most anterior structure of the kidney hilum: pelvis of the ureter.

This quiz covers the anatomy of the kidneys, including their location, shape, and key measurements. Test your knowledge on the specific characteristics of the renal organs and their relation to the vertebral column.