Kidney Anatomy and Relations

Study Notes

Kidney support is provided by perirenal fat, renal fascia, and pararenal fat.
The kidneys are located on the posterior abdominal wall, behind the peritoneum.
The right kidney is situated slightly lower than the left kidney due to the presence of the liver.
The hilum of the kidney, where the renal artery, vein, and ureter enter and exit, faces slightly forwards and medially.

Right Kidney: Right suprarenal gland, right lobe of liver, second part of duodenum, right colic flexure, coils of jejunum.
Left Kidney: Left suprarenal gland, stomach, spleen, pancreas, left colic flexure, coils of jejunum.

Both Kidneys: 12th ribs (right), 11th and 12th ribs (left), diaphragm, psoas major muscle, quadratus lumborum muscle, subcostal nerve and vessels, ilio-hypogastric nerve, ilio-inguinal nerve.

The renal arteries, branching from the aorta at the level of the second lumbar vertebra, supply blood to the kidneys.
The renal artery divides into segmental, lobar, interlobular, arcuate, and afferent arterioles, leading to the glomerulus.
Efferent arterioles, leaving the glomerulus, form peritubular capillaries around collecting tubules in the nephron.
Blood exits the nephron through interlobular veins, arcuate veins, lobar veins, and finally the renal vein.
The kidney, though only 0.4% of body weight, receives 1.2 liters of blood per minute.

The renal artery branches into five segmental arteries, dividing the kidney into five vascular segments: apical/superior, upper anterior, middle anterior, caudal/inferior, and posterior.
The interlobar artery travels through the renal column, reaching the corticomedullary junction.

The ureter is a muscular tube, approximately 10 inches long, connecting the kidney to the bladder.
Urine is propelled through the ureter by peristalsis and glomerular filtration pressure.
The upper half of the ureter resides in the abdomen, while the lower half is in the pelvis.

The ureter originates in the renal sinus as the renal pelvis, which receives 2-3 major calyces.
It descends vertically behind the peritoneum, along the psoas major muscle, opposite the transverse processes of the lower four lumbar vertebrae.
The ureter crosses the bifurcation of the common iliac artery in front of the sacroiliac joint and enters the pelvis.

Right Ureter: Anteriorly: inferior vena cava, inferior mesenteric vein, second part of duodenum, gonadal vessels, iliocolic vessels, root of mesentery. Posteriorly: psoas major muscle, genitofemoral nerve, bifurcation of common iliac artery.
Left Ureter: Anteriorly: inferior mesenteric vein, left colic vessels, left gonadal vessels, sigmoid colon, sigmoid mesocolon. Medially: left colic vessels. Posteriorly: psoas major muscle, common iliac artery bifurcation.

The pelvic ureter begins at the sacroiliac joint, crossing the common iliac artery bifurcation.
It's divided into three parts: from the pelvic brim to the ischial spine, from the ischial spine to the bladder, and the intramural part.
The ureter has three constrictions: at the pelvi-ureteric junction, at the pelvic brim, and as it enters the bladder wall.

The kidney consists of an outer cortex and an inner medulla.
The medulla contains renal pyramids, with their bases facing the cortex and their apices (renal papillae) directed towards the renal sinus.
Minor calyces surround one or more renal papillae, uniting to form major calyces, which eventually form the renal pelvis inside the renal sinus.
Cortical tissue extends between the pyramids, forming renal columns.
Each pyramid with its surrounding cortex forms a renal lobe.

Fibrous capsule: Surround the kidney, anchors at the hilum, protects from trauma and infection.
Perirenal fat: A layer of adipose tissue that cushions the fibrous capsule.
Renal fascia: A condensation of connective tissue surrounding the kidney and suprarenal glands, continuous laterally with the fascia transversalis, located deep to the parietal peritoneum.
Pararenal fat (Renal Bed): Lies external to the renal fascia, often in large quantities, part of the retroperitoneal fat.