1. Anatomy, physiology and
pathology of the kidney
Dr Andrew Potter
Registrar
Department of Radiation Oncology
Royal Adelaide Hospital

2. Anatomy

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. 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. 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. 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. 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. Structure - macro

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. Structure - micro

11. Structure - micro

12. Structure - nephron

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. Position and relations
Left Right
Posterior • 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 surface
Anterior 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
· Peritoneum
Medial · L ad rena gland
l · Right adrenal gland Ð
wedgedbetween super or i
pole andIVC
· IVC

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. 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. Venous drainage
 Renal veins
 Communicate widely
 Eventually form 56 vessels that unit at the
hilum
 Drain into IVC

18. Lymphatic drainage
 Para-aortic nodes at L1/L2
 Surface of upper kidney drains through
diaphragm into nodes in the posterior
mediastinum

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. 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. Physiology

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. 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. Water and electrolyte regulation
 Urine formation - 3 phases
 Simple filtration
 Selective and passive
resorption
 Concentration

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. 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. 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. Acid-base balance
 Tubular acid secretion
 Ammonia secreted by
tubules (combines with
H+ to form NH4+
and passed in urine)

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. Pathology

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

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. 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. 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. 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. 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