Flashcards in Lecture 18 - Renal Pathology 1 Deck (43):
Give an overview of the structure of the kidney
• Two per person
• 150g each
• Renal artery & vein
• Cortex & medulla
• Renal pyramids
• Ureteric pelvis
Kidneys & hormones?
The kidney makes hormones:
What are some general functions of the kidneys?
• Excretion of metabolites & waste
• Na+ and H20 balance
• Maintenance of pH
• Hormone production
What are the 'four components' of the kidney?
Describe the anatomy of the glomerulus
How many per adult?
Normal adult: 1x10^6
• Cluster of specialised capillary loops
• Afferent & efferent arteriole
• Fenestrated endothelium
• Specialised basement membrane
Describe basic urine formation
Water and solutes pass through fenestrated wall into urinary space
• Occurs along the tubules
• PCT: bulk reabsorption
• Loop of Henle: concentration of urine
• DCT: fine tuning of urine composition
• Collecting duct: water reabsorption
What is the metabolic demand of the kidney tubule cells?
• Very high demand
• Due to active transport occurring along the tubules
What is the tubulo-interstitium?
Interstitium + kidney tubules
• The function of these two elements is inseparable
What is meant by acute renal disease?
• Quick onset
• Reversible element to abnormalities
NB Some acute renal injury may be reversible
List the clinical syndromes of renal disease
• Acute renal failure
• Nephrotic syndrome
• Nephritic syndrome
• Gross / macroscopic haematuria
• Microscopic haematuria
• Asymptomatic proteinuria
• Chronic renal failure
What is GFR?
Glomerular filtration rate
Describe acute renal failure
What is the aetiology?
NB Not a term for general acute renal abnormality!
• Acute reduction in Glomerular filtration rate (GFR)
• Reflected as reduced creatinine clearance
• Increased serum creatinine
3 aetiological groups:
What is 'pre-renal' acute renal failure?
Not enough blood getting to the kidney for proper function
What is 'renal' acute renal failure?
What is the most common cause of this?
Problem with the kidney itself
• Acute tubular necrosis
• Acute Glomerulonephritis
• Acute interstitial nephritis
What is 'post-renal' acute renal failure?
Necessary urinary drainage isn't happening
• Ureteric obstruction
(calculus in lumen, tumour in wall)
• Urethral obstruction
What is nephrotic syndrome?
• Leaky glomerulus
• Proteins escape into urine
• Oedema (whole body)
- due to reduced plasma oncotic pressure
What are some common causes of proteinuria or nephrotic syndrome?
• Diabetes mellitus
• Amyloid deposition (Amyloidosis)
Describe Acute tubular necrosis
Reversible / irreversible?
Under-perfusion severe and long enough to cause death of tubular epithelial cells
• Necrosis of tubular epithelial cells
• Dilation of tubules
• Tubular casts: sloughing into lumen
• Oedema in interstitium
• Glomeruli and vessels preserved
• May take weeks
What are the sequelae?
• Acute injury to the glomerulus
• Most often immune mediated
• Deposition of immune complexes in the tuft
→ C' activation
→ Formation of MAC
Rare but important minority due to:
• Direct anti-Glomerular Basement Membrane antibodies
• Rapid progression w/ crescents
• Slowly progressive to chronic renal failure
What are crescents?
In which disease are they observed?
Observed in Glomerulonephritis
• Clumps of monocytes & epithelial cells accumulate in capillary tufts
• Clotted blood
• Outside the glomerular capillary
• In the urinary space
What is a 'segmental scar'?
A slower, less acutely damaging glomerulonephritis
Describe acute interstitial nephritis
How does it normally present?
Interstitium and tubules infiltrated by inflammatory cells (eosinophils)
Usually presents as acute renal failure
• +/- blood or protein in urine
• Drug allergy (e.g. antibiotics)
Which cells are often seen in the interstitium in acute interstitial nephritis?
What are three important causes of acute renal injury?
• Acute tubular necrosis
• Acute glomerulonephritis
• Acute interstitial nephritis
How much cardiac output do the kidneys receive?
Why is it significant that the blood in the glomeruli is drained by an arteriole?
The efferent arteriole can vasodilator or constrict, controlled very finely the pressure.
GFR can be very finely controlled
Where is the urinary space?
Inside the Bowman's capsule
What are the mechanisms of control of filtration?
• Foot processes of the podocytes
• Vasodilation & vasoconstriction of the afferent & efferent arterioles to control GFR
What type of cells form the tubules?
What is important about them?
Very high metabolic demand
Where is the basement membrane?
Formed on the outside of the endothelium of the glomerulus
What is mesangium?
= Mesangial cell
• Secrete the amorphous basement membrane-like material known as the mesangial matrix
Contained within the basement membrane
Compare acute renal failure and nephrotic syndrome
Acute renal failure: not enough blood perfusing
Nephrotic syndrome: leaky basement membrane
Explain Starlings forces
Plasma osmotic pressure
Plasma hydrostatic pressure
Interstitial osmotic pressure
Interstitial hydrostatic pressure
This maintains volume in capillaries
The proteins in the blood are the main driver of reabsorption of fluid back into the capillaries
Is filtration active or passive?
What about reabsorption?
Why do tubular epithelial cells rapidly undergo necrosis
• Highly metabolically active; stuffed with mitochondria
• When ischemic, they rapidly undergo necrosis
Is acute tubular necrosis reversible?
After a few weeks on dialysis, the tubules will grow back
What is by far the most common cause of acute renal failure?
Acute tubular necrosis
Where are the foot processes of the podocytes?
Wrap around the outside of the glomerular capillaries
What gets triggered when immune complexes are deposited in the glomeruli?
• Recruitment of inflammatory cells
• MAC formation
What is Goodpasture syndrome?
A very rare form of Glomerulonephritis
• Caused by antibodies directed against their own basement membrane
• 'Anti-Basement membrane' antibodies
→ C' activation, MAC formation etc. (like in normal GN)
There is the same outcome, but extremely rare
Where do crescents form?
In the extra-glomerular space (not in the capillary)
What can trigger acute glomerulonephritis?
• Streptococcal infection in throat
NB Antibiotic use could lead to...*