5.11 Kidneys,
Ureters, Adrenals
High on posterior wall of retroperitoneum.
Under costal margin such that lower poles only palpable bit.
Oblique (such that longitudinal pole parallel with psoas) and in gutter (such that hilum faces a little forward as well as medially).
Each normally 12x6x3cm and 130g.
Right: lower (liver). hilum just below transpyloric plane 5cm from midline; upper pole at 12th rib.
Left: hilum just above transpyloric plane 5cm from midline; upper pole at 11th rib.
- each moves 2cm with resps.
Capsule covers them. smooth and convex. pelvis emerges behind vessels --> ureter.
Posteriorly: diaphragm (arcuate lig fibres), quadratus lumborum, medially overlaps psoas, and importantly a bit of costodiaphragmatic recess (and hence pleura) is included in that (at risk in lumbar approach). See 312.
- subcostal nerves emerge below the lateral arcuate ligament and ilioinguinal and iliohypogastric from behind psoas; hence these are relations (250)
- note that lat fem cut nerve of thigh too low and upper lumbar bundles too deep to relate.
- the convexity of the lateral border lies over the start of aponeurosis of transversus abdominus.
Anteriorly: suprarenals overlap superior poles and part of anterior, rest of upper halves sit under peritoneum (hepatorenal pouch on right Ð ie in greater sac under liver; in lesser sac on left beneath spleen & stomach).
- hilum is separated from peritoneum, on right by 2nd part duodenum, on left by pancreas & splenic vessels
- lower pole: separated laterally from peritoneum by hepatic and splenic flexures of large bowel and medially does abut the peritoneum, except where right and left colic arteries run.
Perinephric fat lies outside renal capsule, and helps retain kidney position; nephroptosis (Ôfloating kidneyÕ may develop after severe weight loss.
- the renal fascia (of Gerota) then sits outside this. Is a condensation of fatty fascia between posterior abdo wall and peritoneum and restrains extension of an abscess.
- although the renal fascia does extend over the adrenal a fascial septum separates the two, thus the gland should not be disturbed.
- at the lateral renal border, the anterior and posterior layers fuse, while at the hilum the fascia is attached to renal vessels and ureters. Inferiorly, fades into ureter (complete but weak here, such that if an abscess did develop, its liable to rupture.
Funnel shaped. Most posterior (though 1 tributary may lie behind). Capacity <5ml.
20% of CO at 1L/min, renal arteries leave aorta horizontally behind pancreas and renal veins.
Supply kidney in 5 segments (315), from an anterior and posterior branch.
- anterior branch -> apical, upper middle, lower (aka superior, ant sup, ant inf, inferior)
- posterior branch -> posterior segment
No collateral circulation.
Aberrant vessels off aorta, eg to lower segment, are in fact segmental arteries of atypical origin.
Veins do communicate (unlike arteries) and -> 4-5 vessels at front of hilum.
Para-aortic nodes at L2, though surface of upper pole may go through nodes to post mediastinum.
Sympathetics: from spinal cord from T12-L1. Are vasomotor.
- preganglionics --> thoracic and lumbar splanchnic nerves.
- postganglionics are in coeliac and renal ganglia.
- afferents go with sympathetics (like for most viscera), ie go along splanchnics to sympathetic trunk and then via white communicantes into T12-L1, hence pain referred to back and groin
Possibly some afferents go with vagus to explain renal pain.
Capsule, cortex on outside.
Renal columns and pyramids (of medulla) next most deep.
- pyramids open together into a renal papilla, which meets a minor calyx, which unite to form a major calyx.
Histologically, there are 1 million nephrons, with a glomerulus and tubule as we know.
- glomerulus and convoluted tubule are in the cortex
- loops of henle and collecting tubules / ducts are in medulla.
- the jga apparatus is between distal convoluted tubule cells and arteriolar cells.
Pelvis is lined by transitional epithelium, and there is a pacemaker in the minor calyceal walls.
From Wheaters:
- renal corpuscle is responsible for filtration (is BowmanÕs capsule and glomerulus together).
- Fig 16.6 shows cortex, RCÕs are dense & round, and few in proportion to tubules.
- Fig 16.16 shows prox convoluted tubule, has simple tall cuboidal epithelium and a rich network of surrounding capillaries
- Fig 16.17 shows Loop, thin with squamous epithelium, thick with low cuboidal and with surrounding vasa recta throughout. Collecting tubules have same low cuboidal, while collecting ducts have larger diameter. Distal convoluted tubule similar to thick ascending limb.
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Medulla, Fig 16.21, has many collecting tubules,
Henle deep loops and vasa recta.
Pronephros and mesonephros develop first: arranged segmentally and empty into same duct, while metanephros is not arranged segmentally and has a new duct (the ureter).
- pronephros is brief, but duct persists
- mesonephros tubules then appear and empty into the same duct, now called the mesonephric or Wolffian duct, forms bladder, and male bits: ductus deferens and associated structures
- metanephros develops caudally as a big cell mass, with a separating ureteric bud, which grows up to form the pelvocalyceal system. This is supplied by internal iliac initially, but gains successively higher supplies as it rises to its position from its start in the pelvis.
- The kidney then rotates 90o medially.
Anomalies include persistence of fetal arteries (30%), horseshoe (1:800), polycystic (1:500) or only one kidney (agenesis; 1:500).
Nephrectomy and nephrolithotomy require a lumbar approach.
- renal fascia and perirenal fat incised, adrenal left in its own little fascial compartment.
Renal vessels and arteries next ligated (artery first), then ureter transacted.
- beware the very near IVC on the right.
For biopsy lower pole entered 2.5cm below 12th rib, radiologically determined distance.
- pt must hold breath.
Transplantation requires kidney to be inserted into retroperitoneum in the iliac fossa, hilum parallel to external iliacs. Renal artery attaches to internal or external iliacs, ureter implanted to bladder.