Anatomy, physiology and pathology of the kidney

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Anatomy, physiology and pathology of the kidney

• Dr Andrew Potter
• Registrar
• Department of Radiation Oncology
• Royal Adelaide Hospital

Medical ppt
http//hastaneciyiz.blogspot.com
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Anatomy
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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

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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

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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)

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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

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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

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Structure - macro
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Strcuture - micro

• Nephrons
• Functional and histological subunit
• 106 per kidney
• glomerulus tubules
• glomerulus
• tuft of capillaries surrounded by podocytes
• projects into Bowmans capsule
• tubule system
• epithelium continuous with Bowmans 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

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Structure - micro
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Structure - micro
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Structure - nephron
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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

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Position and relations
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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.

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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

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Venous drainage

• Renal veins
• Communicate widely
• Eventually form 56 vessels that unit at the hilum
• Drain into IVC

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Lymphatic drainage

• Para-aortic nodes at L1/L2
• Surface of upper kidney drains through diaphragm
  into nodes in the posterior mediastinum

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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

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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

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Physiology
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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

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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

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Water and electrolyte regulation

• Urine formation - 3 phases
• Simple filtration
• Selective and passiveresorption
• Concentration

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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

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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

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Tubular reabsorption

• 60 of solute isreabsorbed inproximal tubule
• Different partsof tubule systemoptimised to
  absorb differentcomponents of urine
• Distal tubule and collecting duct determines
  final urine concentration
• Regulated by ADH production by posterior pituitary

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Acid-base balance

• Tubular acid secretion
• Ammonia secreted bytubules (combines withH to
  form NH4and passed in urine)

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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

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Pathology
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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

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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 (lt3cm)

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Benign tumours

• Oncocytomas
• Variant of adenoma
• Angiomyolipoma
• Smooth muscle, fat and vessels
• Renal fibroma
• Common small tumours
• 3-10mm
• Arise in medulla

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Malignant tumours

• 90 are renal cell adenocarcinoma (RCC)
• About 3 of all adult cancers
• Usually seen gt50 years of age
• Present with haematuria, pain, loin mass
• Paraneoplastic syndrome
• Hypercalcaemia, hypertension, polycythaemia,
  Cushings syndrome or other hormonal disturbances

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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

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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

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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

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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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Medical ppt
http//hastaneciyiz.blogspot.com