Kidney anatomy physiology

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Kidney anatomy physiology

  1. 1. Anatomy, physiology and pathology of the kidney Dr Andrew Potter RegistrarDepartment of Radiation Oncology Royal Adelaide Hospital
  2. 2. Anatomy
  3. 3. Overview Retroperitoneal, paired organs Posterior abdominal wall, largely under cover of costal margin Key organ of urinary system Filtration/ concentration of urine Biochemical balance, hormone production
  4. 4. Structure - macro Enclosed in a strong fibrous capsule which passes over the lips of the sinus and becomes continuous with the walls of the calices. Kidney + capsule are surrounded by pararenal fat Each kidney has superior and inferior poles, medial and lateral borders/margins and anterior and posterior surfaces Reddish-brown in colour when fresh – colour varies between cortex and medulla Measure ~12x6x3cm (left often slightly longer than right) Weigh ~130g each Ovoid in outline but indented medially (the renal sinus)  bean-shaped appearance
  5. 5. Structure - macro Hilum  At the concave part of each kidney  Renal vein exits (anteriorly)  Renal artery enters (posterior to renal vein)  Renal pelvis exits (posterior to artery)
  6. 6. Structure - macro Renal pelvis  Funnel-shaped  Lined with transitional epithelium with a smooth muscle and connective tissue wall  Continuous inferiorly with ureter  Divides into major and minor calyces Urine  collecting tubule  minor calyx  major calyx  renal pelvis  ureters  bladder
  7. 7. Structure - macro Cortex  Beneath capsule, extends towards the pelvis as renal columns lying between pyramids of medulla Apices of several pyramids open together into a renal papilla, each of which projects into a renal calyx
  8. 8. Structure - macro
  9. 9. Strcuture - micro Nephrons  Functional and histological subunit  ~106 per kidney  = glomerulus + tubules  glomerulus  tuft of capillaries surrounded by podocytes  projects into Bowman’s capsule  tubule system  epithelium continuous with Bowman’s capsule  proximal convoluted tubule  Loop of Henle  distal convoluted tubule  collecting tubule and collecting duct  glomeruli and convoluted tubules are in cortex  ducts lie in the medulla  glomerular capillaries supplied by afferent arteriole and drained by efferent arteriole
  10. 10. Structure - micro
  11. 11. Structure - micro
  12. 12. Structure - nephron
  13. 13. Position and relations Lie in a mass of fat (perinephric fat) and fascia, retroperitoneally against posterior abdominal wall Fatty renal capsule is covered by fibroareaolar tissue – the renal fascia Renal fascia  encloses kidney, its surrounding fibrous and fatty capsules  helps maintain organ position  superiorly, is continuous with fascia of inferior diaphragm  medially the left and right fascia blend with each other anterior to abdominal aorta and IVC  posterior layer of fascia blends with fascia overlying psoas Extraperitoneal fat outside the renal fascia is located between peritoneum of posterior abdominal wall and renal fascia
  14. 14. Position and relations Left RightPosterior • Diaph ragm (postero-sup eriorly) · Quad ratus lumborum (postero-laterall y) · Psoa major pos s tero-medially · Transversus abdo minis pos tero-laterall y · Subcos nerve and vesse tal ls · Il iohypog astric andili oinguinal nervesdescenddiagona y ac ll ross pos terior surfaceAnterior Lies with panc s and spleen in rea · Supe riorly related to the stomachbed inferior surface of li ver · Adrena gland l · Descend part of ing · Stomach duodenu m · Spleen · Right coli c (hepa tic) · Panc s (tail ) rea fl exure li es anterior to · Jejunum lateral border and inferior · Descend coloning pole · Posterior wall of omental · Small intestine (inferiorly) bursa · Peritoneum · PeritoneumMedial · L ad rena gland l · Right adrenal gland Ð wedgedbetween super or i pole andIVC · IVC
  15. 15. Surface anatomy Superior poles protected by 11th and 12th ribs Extend from T12 to L3 vertebral bodies Move ~2cm superior-inferior during respiration Right – just below transpyloric plane, 5cm right of midline. Inferior pole ~ finger-width superior to right iliac crest Left – just above transpyloric plane, 5cm left of midline.
  16. 16. Arterial supply Renal arteries  branches of aorta at L1/L2 lie behind pancreas and renal veins  Enter at hilum, giving rise to  Anteriorly – apical, upper, middle and lower segments  Posteriorly – posterior segment No communication between segments
  17. 17. Venous drainage Renal veins  Communicate widely  Eventually form 56 vessels that unit at the hilum Drain into IVC
  18. 18. Lymphatic drainage Para-aortic nodes at L1/L2 Surface of upper kidney drains through diaphragm into nodes in the posterior mediastinum
  19. 19. Innervation Sympathetic  Preganglionic cells in spinal cord T12/L1  fibres to thoracic and lumbar splanchnic nerves  Postganglionic cells in coeliac, renal and superior hypogastric plexuses  Vasomotor function
  20. 20. Development Arises from mesoderm Pronephros  Transitory, non-functional structures consisting of a few ducts which persist Mesonephros  Large elongated organs that function as interim kidneys  Glomeruli + tubules open into mesonephric ducts Metanephros  Permanent kidneys  Begin to develop in ~5th week  Arises caudal to mesonephros  Induces a bud from caudal end of mesonephric duct (ureter)  Ureteric bud divides into calyces of pelvis and collecting tubules and medullary pyramids  Develops in anatomic pelvis and migrates to adult position and the new single definitive artery forms
  21. 21. Physiology
  22. 22. Physiology - overview Regulation of the water and electrolyte content of the body Retention of substances vital to the body such as protein and glucose Maintenance of acid/base balance Excretion of waste products, water soluble toxic substances and drugs Endocrine functions
  23. 23. Water and electrolyte regulation Renal blood supply is approx 20% of cardiac output  99% to cortex  1% to medulla 2 capillary beds, arranged in series:  Glomerular  High pressure for filtering  Peritubular  Low pressure for absorption
  24. 24. Water and electrolyte regulation Urine formation - 3 phases  Simple filtration  Selective and passive resorption  Concentration
  25. 25. Filtration Takes place through the semipermeable walls of the glomerular capillaries  almost impermeable to proteins and large molecule Glomerular filtrate is formed by squeezing fluid through glomerular capillary bed Hydrostatic pressure (head of pressure) is controlled by afferent and efferent arterioles, and provided by arterial pressure About 20% of renal plasma flow is filtered each minute (125 ml/min). This is the glomerular filtration rate (GFR).  Autoregulation  With a change in arterial blood pressure, there is constriction or dilatation of the afferent and efferent arterioles, the muscular walled vessels leading to and from each glomerulus
  26. 26. Juxtaglomerular apparatus Macula densa cells  Detect chloride concentration Juxtaglomerular cells  Modified smooth muscle cells  Produce renin  Converts angiotensin to angiotensin I  Angiotensin I converted to angiotensin II by Angiotensin converting enzyme (ACE)  Causes systemic vasoconstriction and increase in BP
  27. 27. Tubular reabsorption 60% of solute is reabsorbed in proximal tubule Different parts of tubule system optimised to absorb different components of urine Distal tubule and collecting duct determines final urine concentration  Regulated by ADH production by posterior pituitary
  28. 28. Acid-base balance Tubular acid secretion Ammonia secreted by tubules (combines with H+ to form NH4+ and passed in urine)
  29. 29. Hormones Renin  Increases production of angiotensin II Aldosterone  Stimulates water and sodium ion resorption in distal tubule Atrial natriuretic hormone (ANP)  Produced when atrial pressure increases (eg heart failure)  Promote Na+, Cl- and water loss Antidiuretic hormone  Increases permability of distal tubule to water, to cinrease water resorption (therfore increases concentration of urine) 1,25 dihydroxy vitamin D3  Promotes calcium absorption from gut Erythropoietin (EPO)  Stimulates marrow to produce red blood cells
  30. 30. Pathology
  31. 31. Benign pathology Vascular disease  Hypertension, diabetes, deposition of immune complexes (eg amyloidosis), coagulation Inflammatory/autoimmune conditions  SLE Infective  Pyelonephritis, tuberculosis Idiopathic  Nephrotoxic drugs - eg. platinum chemotherapy, aminoglicoside antibiotics Congenital/structural  Polycystic kidney, horseshoe kidney, renal agenesis/hypoplasia Metabolic/biochemical  Renal calculi
  32. 32. Benign tumours Frequent incidental findings (up to 20%) Renal adenoma  Bening epithelial tumours arising from tubular epithelium  Difficult to distinguish from renal cell carcinoma - similar histology  Distinguished on size (<3cm)
  33. 33. Benign tumours Oncocytomas  Variant of adenoma Angiomyolipoma  Smooth muscle, fat and vessels Renal fibroma  Common small tumours  3-10mm  Arise in medulla
  34. 34. Malignant tumours 90% are renal cell adenocarcinoma (RCC)  About 3% of all adult cancers Usually seen >50 years of age Present with haematuria, pain, loin mass Paraneoplastic syndrome  Hypercalcaemia, hypertension, polycythaemia, Cushing’s syndrome or other hormonal disturbances
  35. 35. Renal cell carcinoma Rounded masses, yellowish colour with haemorrhage and necrosis Most commonly the ‘clear cell’ variant  Clear cytoplasm because of high lipid and glycogen content
  36. 36. Renal cell carcinoma Spread by local extension/expansion through capsule Blood borne metastases  Bone, lung, brain Lymphatic metastases  Para-aortic chain Prognosis depends on stage  70% ten-year survival of confined to renal capsule  Poor prognosis if metastatic disease at presentation
  37. 37. Nephroblastoma (Wilms’ tumour) Common childhood malignancy Embryonal tumour from primitive metanephros Peak incidence 1-4 years of age Presents as abdominal mass or haematuria Rounded mass largely replacing kidney  Solid, fleshy white with necrosis  Prognosis related to stage at presentation
  38. 38. Summary Paired retroperitoneal/post abdominal organ Cortex, medulla, nephron  Glomerulus, tubule, duct Water/biochemical regulation  Filtration, reabsorption Hormone production Many benign pathological conditions Malignancies predominantly RCC in adults, nephroblastoma in children

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