Urinary

• Kidney coverings


  • Fibrous capsule
  • Perirenal fat
  • Renal fascia
  • Pararenal fat

  
• Fibrous capsule


  Surrounds the kidney itself, closely applied to its outer surface, innermost covering, condensation of fibrous connective tissue in the peripheral part of the organ, easily stripped off from the face of normal kidney, goes through the hilum to line the renal sinus and becomes constant with all the walls of calyces

  
• Perirenal fat


  Aka perinephric fat, covers the fibrous capsule, separates renal gland and kidney, thickest at the edges of the kidney and is prolonged via hilum into the renal sinus, depletion in chronic debilitating diseases can cause downward displacement of the kidney
• Renal fascia


  Aka Gerota's fascia, condensation of the connective tissue that lies outside the perirenal fat, encloses the kidneys and the suprarenal glands, laterally continuous with the transversalis fascia, fibroareolar sheath with two layers - fascia of Toldt (ill-defined anterior layer) and fascia Zuckerkandl (well-defined posterior layer)

  
• Pararenal fat


  External to the renal fascia, part of the retroperitoneal fat, substantial volume of fat, more plentiful posteriorly and toward the lower pole of the kidney, fills the paravertebral gutter and creates a "pillow" for the kidney

  
• The perirenal fat, renal fascia, and pararenal fat support the kidneys and hold them in position on the posterior abdominal wall

  
• Order of kidney coverings from outermost to innermost

  • Pararenal fat
  • Renal fascia
  • Perirenal fat
  • Renal fibrous capsule (true capsule)

  
• Kidney


  • Color: Reddish brown
  • Weight: Adult male ~150g, Adult female 135g
  • Dimensions: Length 10cm, Width 5cm, Thickness 2.5cm
  • Right kidney 129g, Left kidney 137g

  
• Functions of the kidney

  • Maintenance of water, electrolyte, & acid-base blood balance
  • Excrete products of metabolism
  • Regulate body fluid osmolality & volume
  • Hormone production: Renin (blood pressure regulation), Erythropoietin (red blood cell production)
• Kidney location


  Both kidneys found at the level of T12-L3 vertebrae, lie behind the parietal peritoneum (retroperitoneal) high up on the posterior abdominal wall on either side of the vertebral column, right kidney slightly lower than left due to presence of liver

  
• Kidney relations


  • Anterior: Right suprarenal gland, right lobe of liver, right colic flexure, duodenum, colon, jejunum; Left: Left suprarenal gland, stomach, spleen, pancreas, left colic flexure, colon, jejunum
  • Posterior: 12th rib, 11th and 12th rib, costodiaphragmatic recess of pleura, psoas, quadratus lumborum, transversus abdominis, diaphragm, subcostal (T12), iliohypogastric (L1), ilioinguinal nerves (L1)

  
• Hepatorenal recess (Morison's pouch)


  Subhepatic space between right lobe of liver and right kidney, site of spread for peritonitis and appendicitis

  
• Structures in the renal hilum

  • Renal vein
  • 2-4 branches of renal artery
  • Ureter (renal pelvis)
  • 1 branch of renal artery
  • Lymph vessels
  • Sympathetic nerve fibers

  
• Renal sinus


  Space within the hilum, contains renal pelvis, renal blood vessels, lymphatics, and nerves

  
• Renal arteries


  • Arise from aorta at L2, right renal artery longer due to aorta oriented to left, left renal artery usually higher, blood flow 1L/min, divide into segmental arteries at renal sinus

  
• Renal artery divisions


  Renal artery -> 5 segmental arteries -> lobar arteries -> 2-3 interlobar arteries -> arcuate arteries -> interlobular arteries -> afferent glomerular arterioles

  
• Hilum


  • Contains the following:
  • Renal pelvis
  • Expanded part of the ureter
  • Divided into 2 to 3 major calyces which further divided into 2 or 3 minor calyces
  • Renal blood vessels, lymphatics, and nerves

  
• The perinephric fat is continuous to the hilum and sinus surrounding the VAUALS
• Renal Arteries


  • Arise from the aorta at L2
  • Located behind the renal vein and inferior vena cava
  • Right renal artery is longer due to the abdominal aorta more oriented to the left side of the vertebral bodies
  • Left renal artery usually a little higher
  • Blood flow is 1 L/min
  • Renal artery → 5 segmental arteries → lobar arteries → 2 to 3 interlobar arteries → arcuate arteries→ interlobular arteries → afferent glomerular arterioles

  
• Segmental Arteries


  • Renal arteries divide into segmental arteries at the renal sinus → renal column
  • Do not significantly anastomose with each other, each supply an independent, surgically resectable unit or renal segment
  • Anterior section (4 segmental branches) are often bigger and named after the segment they supply
  • Posterior section (1 segmental branch) only supplies the posterior portion of the kidney

  
• Brödel's bloodless line is a relatively avascular (though still vascular) line where the anterior and posterior segmental branches meet, used as a surgical landmark

  
• Lobar arteries


  Given off by segmental arteries

  
• Interlobar arteries


  Emerge when lobar/segmental arteries bifurcate into the renal columns, run over the base of the pyramids where they will become arcuate arteries

  
• Arcuate arteries


  Arch over the bases of the pyramid, give off branches towards the cortex to form interlobular arteries
• Interlobular arteries


  Branch off as afferent glomerular arterioles, ascend to the cortex
• Arterial blood flow of the kidney

  • Abdominal Aorta (L2) → Renal Artery → (5) Segmental Arteries → hilum → Lobar Arteries (pyramid) → (2-3) Interlobar Arteries (toward the cortex on each pyramid) → Arcuate Arteries (arching over pyramid bases) → Interlobular Arteries (ascend in the cortex) → Afferent Glomerular Arterioles

  
• Renal Veins


  • Emerges from the hilum anterior to the renal artery and drains into inferior vena cava
  • Left renal vein is longer than the right, crosses anterior to the abdominal aorta, enters in front of the aorta immediately below the origin of the inferior mesenteric artery and beneath the superior mesenteric artery

  
• Venous blood flow of the kidney

  • Peritubular plexus → interlobular veins (anastomosis with each other) → Arcuate veins → Interlobar veins → Renal vein

  
• Lateral Aortic Lymph Nodes

  Lies on the side of the abdominal aorta, anterior to the medial margins of the psoas major, diaphragmatic crura, and sympathetic trunk, around the origin of the renal artery

  
• Renal lymphatic vessels


  Follow the renal veins and drain into the right and left lumbar (caval and aortic) lymph nodes

  
• Renal Plexus


  • Lies on the sides of the abdominal aorta and distributed along the branches of the renal artery, regulates the vascular tone and secretion of renin
  • Combination of sympathetic and parasympathetic fibers
  • Parasympathetic fibers come from the Vagus Nerves
  • Sympathetic outflow come from T10- L1
  • Afferent fibers will accompany the vagus nerve towards the spinal cord, enter at T10-T12 segments, at the area of costovertebral angle

  
• Pain elicited through kidney punch will be referred to the costovertebral area (somatic pain)
• Preganglionic fibers


  From the least splanchnic nerve (T12) → Aorticorenal ganglion (junction of aorta and renal artery) → Renal Plexus

  
• Radiographic appearance of kidney

  • Usually visible on anteroposterior radiograph of the abdomen
  • Perirenal fat surrounding kidney produces a transradiant line
  • Renal pelvis up to the minor calyces are easily observed (more opaque)

  
• Ureter


  • Muscular tubes from the kidneys to the posterior surface of the urinary bladder
  • Only excretory duct of the kidney
  • Conveys urine by peristaltic contractions of the muscle coat assisted by the filtration pressure of glomeruli towards the bladder
  • Average length: 25-30 cm, with three constrictions resembling esophagus
  • Lumen diameter: approximately 3 mm
  • Composed of outer circular and inner longitudinal layer of smooth muscles, with tunica adventitia

  
• Course of the Ureter in Males and Females

  • Renal pelvis - Expanded upper end of the ureter
  • Emerges from the hilum of the kidney
  • Runs vertically downward behind the parietal peritoneum (adherent to it) on the psoas muscle with the genitofemoral nerve behind it and the vessels of the gonads in front
  • Enters the pelvis by crossing the bifurcation of the common iliac artery in front of the sacroiliac joint
  • Runs down the lateral wall of the pelvis in front of the internal iliac artery to the region of the ischial spine
  • Turns forward to enter the lateral angle of the bladder (males)
  • Turns forward and medially beneath the base of the broad ligament where it is crossed by the uterine artery (females)
  • Near its termination, it is crossed by the vas deferens (males)
  • Runs forward, lateral to the lateral fornix of the vagina to enter the bladder (females)
  • Termination: Passes obliquely through the wall of the bladder for about 0.75 in, (1.9 cm) before opening into the bladder

  
• Ureteric constrictions


  • Widest at renal pelvis and narrow progressively as it enters the urinary bladder and the concavity of true pelvis
  • Ureteropelvic junction (UPJ) is the first anatomical constriction where the renal pelvis joins the ureter
  • Pelvic brim / iliac vessels is where the ureter is kinked as it crosses the pelvic brim
  • Ureterovesicular junction (UVJ) is the narrowest constriction where the ureter pierces all the urinary bladder

  
• Ureteric stones


  • Kidney stones that have passed to the ureters with the aim of expelling them with the urine through the urethra
  • If too large in diameter, can get arrested especially at the constrictions of the ureter, causing spasm of the wall of ureter and colicky pain

  
• Relations of ureter


  • Anterior: Duodenum, Terminal part of ileum, Right colic and right ileocolic vessels, Right testicular or ovarian vessels, Root of the mesentery of the small intestine (right); Sigmoid colon, Sigmoid mesocolon, Left colic vessels, Left testicular or ovarian vessels, Inferior mesenteric vein (medially) (left)
  • Posterior: Right psoas muscle, Bifurcation of the right common iliac artery (right); Left psoas muscle, Bifurcation of the left common iliac artery (left)

  
• Blood supply of ureter

  • Upper part: supplied by the renal artery
  • Middle part: supplied by the testicular or ovarian artery
  • Lower/pelvic part: supplied by the superior vesical artery