Anatomy of urinary tract

• You need about 2/3 kidney function to live - any less than this renal replacement therapy or dialysis will be required.
• Kidney function

  • regulation of fluid volume
  • regulation of osmolarity
  • regulation of ion concentrations
  • regulation of pH
  • excretion of waste and toxins
  • production of hormones
• The trigone is a smooth triangular region within the internal urinary bladder, formed by the two ureteric orifices and the internal urethral meatus (opening of urethra).
• Polycystic kidneys - developing nephrons fail to connect to collecting tubule in development/collecting ducts fail to develop.
• The kidneys are retroperitoneal
• The kidneys lie at approximately T12-L3 on either side of the vertebral column.
• The hila of the kidney is about 5cm from the midline.
• The right kidney is slightly lower than the left because of the liver.
• The transpyloric plane at L1 is roughly the level of the hilum of the left kidney.
• Retroperitoneal organs (SAD PUCKER)

  • suprarenal glands
  • aorta/IVC
  • duodenum
  • pancreas
  • ureters
  • colon
  • kidneys
  • esophagus
  • rectum
• Anterior relations of left kidney

  • spleen
  • stomach
  • pancreas
  • left colon
  • small gut
• Anterior relations of right kidney

  • liver
  • duodenum
  • right colon
• Posterior relations of left kidney

  • 11th and 12th ribs
  • diaphragm
  • psoas major
  • quadratus lumborum
  • subcostal, iliohypogastric and ilioinguinal nerves
• Posterior relations of right kidney

  • 12th rib
  • diaphragm
  • psoas major
  • quadratus lumborum
  • subcostal, iliohypogastric and ilioinguinal nerves
• Psoas sign - pain on extension of hip
• Four layers covering kidney

  • renal capsule (fibrous, tough)
  • layer of fat (perirenal)
  • Gerota's fascia (encloses kidneys and suprarenal glands)
  • 2nd layer of fat (pararenal)
• Kidney fascia opens anteriorly so that pus or extravasated urine can track down alongside the ureter.
• Blood supply of kidneys - renal arteries (L1/L2)
• The right renal artery is longer than the left.
• The left renal vein is longer than the right.
• Front to back kidney hilum structures

  • vein
  • artery
  • ureter
• Five vascular segments of kidney

  • apical/superior
  • caudal/inferior
  • upper anterior
  • middle anterior
  • posterior
• Segmental > interlobular > cortical
• The renal artery splits into 5 segmental branches when it enters the kidney and the segments have no collateral circulation between them.
• The ureters arise from the renal pelvis and descend retroperitoneally to the bladder.
• The ureters run approximately 5cm lateral to spinous processes of lumbar vertebrae
• 3 areas of constriction in ureter - stones get stuck here

  • pelviureteric junction (where the renal pelvis meets the bladder)
  • pelvic brim
  • uretero-vesical junction (where ureter enters the bladder)
• Ureter

  A) Adventitia

  B) Muscularis

  C) Urethral mucosa

  
• The bladder is a hollow organ which changes shape according to fullness.
• Ureters enter the bladder and run in submucosa for approximately 2cm which helps reduce likelihood of reflux.
• In infants and young children:

  • lies in the abdomen even when empty
  • enters the greater pelvis by the age of 6
  • enters the lesser pelvis after puberty
  • retroperitoneal behind pubis
  • neck rests on prostate or vagina
• Peritoneum peels off upper part of posterior bladder surface (rectovesical pouch) and lower part contacts anterior abdominal wall.
• 2 types of peritoneum - parietal and visceral. Parietal lines abdominal cavity. Visceral covers organs. Behind the visceral peritoneum = retroperitoneal.
• Subperitoneal = inferior to peritoneal cavity e.g. last part of rectum, bladder (when empty)
• Preperitoneal = anterior to peritoneal cavity e.g. bladder extending into preperitoneal space when filled.
• What layers of the body will be incised to access a kidney for a nephrectomy? Where will the incision be located?

  Oblique incision midway between 12th rib and iliac crest.
• Horseshoe kidneys - inferior poles of left and right kidneys fuse and get caught on the inferior mesenteric artery.
• Double ureter due to duplicated metanephric bud
• Abnormal renal artery known as aberrant, compresses ureter - hydronephrosis
• Failure of one kidney to develop altogether = renal agenesis