Organ
Kidney
A retroperitoneal organ for filtration and homeostasis
High-yield
Vein–artery–pelvis is the conventional front-to-back hilar arrangement, but branching vessels frequently alter the pattern; it is not a fixed three-layer order.
Overview
The kidneys lie against the posterior abdominal wall and contain a cortex surrounding medullary pyramids. Blood enters through renal arteries, filtered fluid is modified along tubules, and urine leaves through calyces and pelvis. Endocrine functions complement regulation of fluid, electrolytes and acid-base balance.
Reference facts
- Location
- Retroperitoneal, approximately T12–L3, with the right usually lower than the left. Hilar level is near L1 but varies with side, body habitus and respiration.
- Parts
- Poles, surfaces and borders surround a medial hilum and sinus; internally, cortex and variable numbers of pyramids lead to papillae, calyces and renal pelvis.
- Blood supply
- One or more renal arteries usually arise near L1–L2 and divide into segmental territories with limited effective arterial collateral supply.
- Innervation
- Renal autonomic plexuses provide predominantly sympathetic vascular and tubular control; visceral afferents contribute to referred flank pain.
- Venous/Lymphatic drainage
- Renal veins reach the inferior vena cava; lymph commonly follows hilar vessels toward lumbar nodes near the great vessels.
- Relations
- Posterior relations include diaphragm, lower ribs, psoas, quadratus lumborum and abdominal-wall nerves. Right anterior relations include liver, duodenum and colon; left relations include stomach, spleen, pancreas and bowel.
- Function
- Forms urine, regulates volume and solutes, maintains acid-base balance, releases renin and erythropoietin, and activates vitamin D.
Mnemonic
VAP recalls the conventional hilar map: vein, artery, pelvis; branches can change the view.
Clinical correlation
Renal fascial planes influence the spread of hemorrhage and infection without forming a simple sealed container. A kidney may remain ectopic during development; fused lower poles form the usual horseshoe configuration and can alter ascent and vascular anatomy.
Frequently asked questions
Where is the kidney located?
Retroperitoneal, approximately T12–L3, with the right usually lower than the left. Hilar level is near L1 but varies with side, body habitus and respiration.
What does the kidney do?
Forms urine, regulates volume and solutes, maintains acid-base balance, releases renin and erythropoietin, and activates vitamin D.
What are the parts of the kidney?
Poles, surfaces and borders surround a medial hilum and sinus; internally, cortex and variable numbers of pyramids lead to papillae, calyces and renal pelvis.
What is the blood supply of the kidney?
One or more renal arteries usually arise near L1–L2 and divide into segmental territories with limited effective arterial collateral supply.