Kidney Anatomy Quiz

The Kidney

• Paired retroperitoneal structures
• Located on either side of the vertebral column, between T12-L3 vertebrae
• Right kidney positioned 2 cm lower than the left due to the right hepatic lobe
• Kidney's long axis is directed downward and laterally, parallel to the psoas muscle
• Upper poles are more medial and posterior than lower poles
• Adult kidney size: 9-15 cm long, 3-5 cm wide in males
• Left kidney is usually slightly larger than the right (not exceeding 1.5 cm)
• Bean-shaped
• Two poles (superior, inferior)
• Anterior and posterior surfaces, medial and lateral borders
• Surrounded by perirenal fat
• Covered by outer fibrous capsule

Kidney Structure

• Renal parenchyma consists of renal cortex and medulla
• Renal sinus contains renal pelvis, calyces, renal vessels, nerves, lymphatics, and perirenal fat
• Renal cortex is 2.5 cm thick, containing glomeruli and renal tubules
• Renal medulla is comprised of 10-14 renal pyramids
• Renal pyramids have bases to the periphery, conical tips towards the renal hilum (papillae)
• Renal columns separate the pyramids
• Renal lobe consists of renal pyramid, overlying renal cortex and adjacent renal columns
• Collecting system (calyces)
• Medulla in fornix of minor calyx (sharp and concave)
• Papillae drain into minor calyces
• Minor calyces coalesce to form 3-4 major calyces
• Major calyces form renal pelvis
• Renal pelvis is a broad, dilated portion within the renal hilum
• Can be intrarenal or partially/entirely extrarenal
• Drains into the ureter

Ureters

• 25-30 cm long
• Three parts: abdominal, pelvic, intravesical/intramural
• 3 mm diameter
• Narrowing sites (most common calculus obstruction): pelviureteric junction (PUJ), ureter entering pelvis (crossing common iliac artery bifurcation), vesicoureteric junction (VUJ) (oblique entry to bladder wall)

Urinary Bladder

• Pelvic, extraperitoneal site
• Pyramidal shape, base posteriorly
• Four surfaces: superior, inferolateral, and posterior-inferior
• Features:
  • Apex (superior surface), connected to umbilicus by median umbilical ligament (urachus remnant)
  • Fundus (base, posteroinferior surface), triangular, tip pointing posteriorly
  • Neck: confluence of fundus and inferolateral surfaces (2-3 cm funnel-shaped extension into urethra)
• Trigone region sits at bladder base between ureteral and urethral openings

Male Urethra

• 15-20 cm long
• Three parts:
  • Posterior urethra: prostatic and membranous
  • Anterior urethra: bulbous and penile
• Parts of prostatic urethra contain ejaculatory duct orifices
• Membranous urethra is the shortest and contains external urethral sphincter
• Bulbous urethra traverses penis root, and Cowper's glands open into it
• Penile urethra extends to glans penis, with a fossa navicularis dilation

Female Urethra

• Much shorter than male urethra (~4cm)
• Not divided into segments
• Contains Skene's glands, homologous to male prostate, secreting mucus into urethra

Radiological Anatomy

• Kidney shadows easily identified due to perirenal fat
• Kidney length is ~3-4 lumbar vertebrae
• Kidneys move with respiration
• Ureters not normally visualized; radiopaque calculi can be located