[OS 206] E03-T02-Kidney, Ureter, and Bladder Anatomy_compressed

Kidney Functions

• Maintains fluid and electrolyte balance
• Maintains acid and base balance
• Produces renin to regulate blood pressure
• Produces erythropoietin
• Converts Vitamin D precursor into its active form

Kidney Location and Position

• Kidneys rest retroperitoneally on the posterior abdominal wall (PAW)
• They sit at the T12-L3 level
• Kidneys are located posteriorly deep to ribs 11-12
• The renal hilum of the left kidney and the superior pole of the right kidney lie in the transpyloric plane
• The right kidney sits 5.5 cm lower than the left kidney
• Each kidney moves 2-3 cm vertically during respiration

Kidney Size, Shape, and Structure

• The average kidney measures 10cm x 5cm x 5.5cm (LWH)
• Kidneys are smaller in Asians
• Male kidneys average 150g, and female kidneys average 135g
• For pediatric patients needing kidney transplants, kidneys from adult donors can be split to provide half a kidney to two different children
• The kidney's lateral margin is convex and the medial margin is concave
• Kidneys have a bean-shaped appearance
• The renal sinus is the space in the middle through which the vessels pass and accommodates the renal hilum

Gerota Fascia

• It encloses the kidney on the superior, medial, and lateral sides
• The inferior side is open and extends to the contralateral side medially
• The fascia is a thickening of connective tissue that covers the adrenal gland
• This is why adrenal glands sometimes need to be removed along with kidney tumors

Renal Parenchyma

• The renal cortex is light colored
• The renal medulla/pyramid is dark colored/hypoechoic in ultrasounds

Renal Papillae

• The tip or apex of the medullary pyramid
• They are the first gross structures of the renal collecting system
• There are normally 7-8 per kidney

Columns of Bertin

• These are extensions of the cortex in between the renal pyramids
• Renal vessels traverse through these columns

Renal Pelvis

• This is the funnel-shaped superior end of the ureter
• It is where urine collects

Major Calyces

• The inferior/middle/superior (or upper middle/lower) of the kidney
• Divides into 2 or 3 minor calyces

Minor Calyces

• The neck of the calyces
• This is where the urine is emptied (fornices)

Kidney Rotation

• A kidney experiences rotation in 3 planes, in 30° anterior rotation in the coronal plane
• There is an inward tilt of the superior pole and anterior displacement of the lower pole
• The superior poles are located more medially and posteriorly than the inferior poles partly due to the muscle bulk of the psoas major and quadratus lumborum

Arterial Supply

• The right renal artery is longer because the aorta is to the left of the body
• It takes a longer path to reach the kidney and crosses the IVC posteriorly
• The renal artery has 5 segmental end arteries that are end arteries with no collateral circulation, supplying an area that no other artery supplies
• Posterior segmental end artery (1)
• Anterior segmental end artery (4)
  • Apical segmental end artery
  • Upper/Superior segmental end artery
  • Middle segmental end artery
  • Lower/Inferior segmental end artery
• Vasa recta are secondary capillary networks

Flow of Blood in Arteries

• The blood flows in arteries in the following order: renal artery → segmental end arteries → lobar → interlobar → arcuate → interlobular → afferent artery → glomerulus → efferent artery → vasa recta

Watershed Areas

• Located toward the end of the kidney circulation
• They are often susceptible to ischemia
• These areas include the line of Brodel (tectonic break and avascular plane)
• The area is commonly cut when a surgeon is trying to prevent massive bleeding when removing a tumor contained within the kidney

Ureteropelvic Junction Obstruction

• Crossing/aberrant/variant vessel compresses the renal pelvis
• Commonly seen in children experiencing flank pain and frequent UTIs
• Caused by posterior segmental artery, lower segmental artery, or an aberrant inferior segmental artery from aorta

Venous Drainage

• Paired branches adjacent to the SMA
• The left renal vein is longer because the IVC is on the right side (~ 6-10 cm in length). Receives the Inferior phrenic vein, gonadal vein, and the lumbar vein
• Enters the IVC at a slightly more cranial level and a more anterolateral location

Blood flow in Veins (Kidney)

• Starts with secondary capillary networks -> interlobular veins -> arcuate -> interlobar ->lobar veins -> segmental veins -> renal veins
• Perinephric area and Infundibula have free venous communication
• Unlike the kidneys' arterial supply, the venous return has extensive collateral circulation

Renal Lymphatics

• The left kidney drains into the left para-aortic lymph nodes (including nodes anterior or posterior to the aorta), retrocrural nodes, and directly to the thoracic duct
• The right kidney drains into the right interaortocaval nodes, the right paracaval lymph nodes, and occasionally to the retrocrural nodes of left paraaortic nodes
• Para-aortic nodes are on the left and para-caval nodes are on the right
• General drainage below the thoracic duct drains from right to left

Renal Innervation

• Sympathetic innervation occurs for vasoconstriction
• T8-L1 preganglionic fibers → celiac and aorticorenal ganglia → postganglionic fibers via the autonomic plexus surrounding the renal artery
• Parasympathetic innervation occurs for vasodilation via the vagus → autonomic plexus in real artery
• Kidneys function even without neurologic control and are more hormonally controlled
• This means that the nerves do not necessarily need to be saved in kidney transplants

Embryologic Origin and Variation

• The kidneys develop identically from the intermediate mesoderm regardless of an individual's sex
• Nephrogenesis is complete by weeks 32 - 34
• Mammals develop 3 sets of kidneys in the course of intrauterine life
• Pronephros develops in weeks 3-5 then regresses
  • The pronephric duct becomes the mesonephric duct (name change) and subsequently the urogenital ridge
• Mesonephros develops at weeks 6-16 then regresses
• Mesonephric/Wolffian duct
• Induces growth of the mesonephric tubules
• Metanephros
  • Remnants include efferent ductules, paradidymis, epoophoron, paroophoron
  • Initially the ureteric bud at week 4
  • Co-induction with metanephric mesenchyme
  • Urine production begins at week 10
• The kidneys are segmentally vascularized upon their ascent (weeks 6 - 9) by transient aortic sprouts at progressively higher levels
• Abnormalities in vasculature lead to failure in the ascent of kidneys which causes ascent anomalies (ectopia)
• Pelvic Kidney
• Horseshoe Kidney
  • A branch of the aorta blocks the ascent
  • Kidneys fuse inferiorly

Clinical Correlates

• Case of JMD 13/M
• JMD was riding a motorcycle without a helmet at 4:30AM when he lost control of the vehicle and crashed onto the curb
• Came to the ER with multiple facial fractures, headaches & epistaxis
• Inserted foley catheter's output is gross hematuria
• Fixed structures such as bones and retroperitoneal structures are prone to a special type of injury called Deceleration Injuries
• Unilateral Renal Agenesis can occur (complete absence of one kidney)
• Individuals can live a normal life because the remaining kidney is larger to compensate for the missing kidney

Ureters - Location and Position

• Retroperitoneal structures on the posterior abdominal wall
• Anatomical segments: abdominal ureter (renal pelvis to the iliac vessels), pelvic ureter (iliac vessels to bladder), intramural ureter (within urinary bladder)
  • The ureter pierces the bladder obliquely, travels 1.5-2 cm before terminating into the ureteral orifice, closing during bladder filling (Valve effect: prevents backflow of urine into the kidneys during urination)
• Vesicoureteral reflux (VUR) is deficient valve effect due to shorter intramural ureter, presents as recurrent urinary tract infections
  • Surgical segments: division is the sacrum
• Proximal (P3): renal pelvis to the upper border of sacrum
• Middle (M3): upper to lower border of sacrum
• Distal (D3): lower border of the sacrum to bladder
• Ductus (vas) deferens is the ONLY structure that passes between the ureter and the peritoneum and lies anteromedial to the ureter
• The uterine artery passes lateral to the ureter in its origin (from the internal iliac)

Ureters - Size Shape and Structure

• They are 22-30 cm in the length and NOT uniform in caliber
• There are 3 physiological narrowings: UPJ (ureteropelvic junction), Crossing of the iliac vessels (Approximately at the level of the common iliac bifurcation, external compression/anterior angulation of the ureter), and UVJ (ureterovesical junction)
• The structures from inner to outer include Urothelium (transitional epithelium), Lamina propria, Inner longitudinal muscle, Outer circular smooth muscle, and Adventitia

Ureters, Arteries, Veins and, Lymphatics

• Arterial Supply (Abdominal ureter): Medial
• Arterial blood supply for Pelvic ureter: lateral
• Terminal ureter (uterine artery (F)/inferior vesical artery (M) is the MOST consistent
• NOTE: arterial vessels located longitudinally WITHIN THE ADVENTITIA for safe mobilization
• Venous Drainage parallels the arterial supply
• Lymphatic drainage: Abdominal ureter (LEFT: Left para-aortic LN and RIGHT: Right paracaval, interaortocaval)
• Pelvic: internal/external/common iliac LNs

Ureters - Clinical Correlations and Stones

• Visceral receptors creates somatic pain, often Referred pain
• Upper/Proximal ureter stone
• Ureter stone (SRP 60/F case)
• Findings: dilatation of the left collecting system. Plain CT scans showed, Left Kidney stone sits before the sacrum at the left upper ureter

Endopelvic Fascia

• Table detailing endopelvic fascia is shown
• Puboprostatic (Male)
• Females: Pubourethral
• Arcus tendineus fascia pelvis: Tendinous arch of the pelvic fascia, Pubovesical
• Lateral/Posterior Vesical ligaments: Lateral attachments to the anterior bladder wall
• Female only: Cardinal & uterosacral ligaments

Bladder - Location, Size, Shape, and Structure

• Hollow viscus for temporary reserve of urine with strong muscular distensible walls
• Bladder fixed to the pubic bone from areolar tissue
• Bladder are tetrahedral when empty
• Superior surface covered by peritoneum on the intra-peritoneal surface
• Retropubic Space of Retzius/Perivesical space exists between the bladder and the pubic bone and during conditions such as pathology
• Space such Pouch of Douglas/Retrovesical space/Rectovaginal space occurs behind the vagina/uterus in females and males
• When filled it can reach 500ml, ovoid in structure
• The bladder's tetrahedral superior apex is the urachus and the lowest pint is known as the bladder neck
• Medial: is anchored to the bladder and is a longitudinal ligament.
• Lateral: is in the peritonal veins with no defined attachment.

Urinary Tract - Microscopic Structures

• The pathway of urinary flow is shown
• Pathway: Penile urethra --> bulbar urethra - narrow slit, --> membranous urethra;
• *Narrowest orifice, which continues through the →: to reach Seminal
• colliculus* (Urethral crest)--> Prostatic utricle → "Kissing prostate lobes"
• Superifical surface created with smooth muscle from the ureter
• Deep trigrone has the "waldeyer sheath" NOTE! Each exit and entry from the Urinary tract can be drastically different depending on the patient. In instances where the bladder contracts The tract closes NOTE! Among patients with bladder cancer, the whole trigone is edematous as well which may take more than an hour to evaluate or difficult to find the ureter

Bladder Vasculature

• Vessels which run superiorly from the ladder (anterioly) from the superior vesical artery.
• Minor contricution comes from obturatory artery with the infeiror gluteal artery.
• Veinous drainage in the vesicles run down through.
• INFO!* The plexus is a great reference through the hypogastric nerves as it is heavily invested in the prostate and bladders for urination and ejaculation.

Robotic - Steps

Ascending steps and structures are shown with descending colons

• note!:*
• Be cautioned not to cut the Lumbar Artery when exposing renal vein*
• If this step goes south it becomes a open surgical*

Bladder

• Distended state has internal smooth serface. Contraction: causes internal surface to appear smooth
• Micro structures from inside/out, the Urothelium basement membrane
• Lamina propria* Longintudinal layers Middle circular layer of muscle. The Circular Pre-prostatic Sphincter (internal urtheral in males)
• Cystoscopy: Procedure to invesigate bladder using
• This procedure is great for bladder analysis passing through the the penis during the scrotum*
• Note!!* The scrotum is a great reference through the hypogastric nerves has it is invesitive thru urination+ ejaculation

This lesson explores kidney anatomy, including location, size, and structure. It also details kidney functions such as fluid and electrolyte balance, blood pressure regulation via renin, erythropoietin production, and Vitamin D conversion.