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Structure

Kidney

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The kidneys are paired retroperitoneal organs that filter blood, form urine and regulate fluid, electrolyte and acid-base balance. Each also contributes to blood pressure control, erythropoietin production and vitamin D activation.

Terminologia Anatomica (Latin): Ren · Open in the 3D atlas

Location

Lie on the posterior abdominal wall on either side of the vertebral column, roughly from T12 to L3; the right kidney is usually slightly lower because of the liver. The hilum lies near L1 (transpyloric plane) and is surrounded by perirenal fat within renal fascia.

Structure

Each kidney has a cortex and a medulla organised into renal pyramids, with renal columns between them; pyramid apices (papillae) drain into minor then major calyces and the renal pelvis. The functional unit is the nephron (glomerulus, proximal tubule, loop of Henle, distal tubule) draining into collecting ducts; there are about one million per kidney, a figure that varies.

Blood supply

The renal artery arises from the aorta at about L1-L2 (the right passes behind the inferior vena cava) and divides into segmental arteries, then interlobar, arcuate and interlobular arteries; segmental arteries are end-arteries. The renal veins drain to the inferior vena cava, and the left is longer and receives the left gonadal and suprarenal veins. Accessory renal arteries are common.

Innervation

Sympathetic fibres from T10-L1 reach the kidney through the renal plexus (coeliac and aorticorenal ganglia) and regulate renal blood flow and renin release. Parasympathetic supply is from the vagus nerve; visceral pain travels with sympathetic afferents to T10-L1, so renal pain is felt in the loin and flank.

Function

The kidneys filter plasma at the glomerulus, then reabsorb and secrete along the nephron to excrete waste and control volume, osmolality, potassium, sodium and pH. Endocrine functions include renin, erythropoietin and calcitriol production.

Clinical correlations

Common problems include renal calculi (colic), pyelonephritis, renal cell carcinoma, polycystic kidney disease, acute kidney injury and chronic kidney disease (see KDIGO staging by GFR and albuminuria). Renal trauma and the retroperitoneal position matter in imaging and surgical approach; management follows local guidelines.

Common exam points

  • Hilum at about L1; right kidney usually lower than the left.
  • Hilar structures from front to back: renal vein, renal artery, renal pelvis.
  • Segmental arteries are end-arteries (five segments); the left renal vein crosses anterior to the aorta below the superior mesenteric artery.
  • Renal pain: T10-L1 dermatomes, loin to groin.
  • Layers around the kidney from inside out: fibrous capsule, perirenal fat, renal fascia, pararenal fat.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Brenner and Rector's The Kidney. Elsevier, 11th edition (2019) — Tier 3 (textbook)

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