medical renal pathology Flashcards
what is the role of the kidneys?
to eliminate metabolic waste products, to produce hormones, to regulate fluid or electrolyte balance and to regulate the acid base balance
what hormones does the kidney produce?
renin for fluid balance in RAAS
erythropoeitin for erythrocytes
what is the prevalence of renal disease?
26000 patients per year get acute renal failure in England which account for 15% of all hospital admissions - most will recover but 10000 will need dialysis with a 50% mortality
5500 patients will develop chronic renal failure per year and there are around 43000 cases in England - 50% will have transplant, 40% haemodialysis and 10% peritoneal dialysis
what is the RAAS?
the renin angiotensin aldosterone system
the adrenals release aldosterone. This acts on the kidney to reduce water and sodium excretion and increase potassium excretion. Therefore there is vasoconstriction of blood vessels, increased extracellular fluid volume, effective circulating volume and blood pressure due to Na and H2O, there is also decreased plasma K due to loss of K+. The increase in volumes and BP leads to a decrease in renin (also produced by the adrenals). Therefore there is lerss angiotensin I and II (I-II in lungs by ACE), therefore thirst and ADH decrease. Therefore the hypothalamus releases less corticotropin releasing hormones from pituitary gland meaning that there is less stimulation to the adrenals - negative feedback so less aldosterone produced.
where can donors be sourced?
they can be living or deceased
how will renal disease present?
acute renal failure - unwell due to rapid rise in creatinine and urea, nephrotic syndrome with hypoalbuminaemia, proteinuria and oedema
acute nephritis - oedema, proteinuria, haematuria, hypertension and renal failure
chronic - slow decline in renal function with haematuria and proteinuria
what is diagnosis of renal disease based on?
renal physician - clinical history and examination
radiologist - obstruction, size and structural abnormalities
biochemist - blood tests (urea and creatinine) and urinalysis (protein, blood and electrolytes)
urologist - cystoscopy - obstruction and haematuria
pathologist - renal biopsy - immunofluorescence, light and electron microscopy
what is the glomerulus?
coiled capillary with podocytes covering it. The filter is the podocytes foot processes, endothelial cells and basement membrane
what is the blood flow through the kidney?
branches of the renal artery flow into the afferent arteriole and through the glomerulus and then through the efferent arteriole up to the branches of the renal vein
from the bowmans capsule what is in a nephron?
the capsule leads into the proximal convoluted tubule, down into the descending limb, loop and ascending limb of henle, then into the distal convoluted tubule into the collecting dict to the pelvis of the kidney
what does a nephron span?
the renal cortex (above limbs of henle) and the renal medulla (below LoH)
what are some causes of kidney failure?
tubular, glomerular and vascular damage
outline vascular damage?
there can be thrombotic microangiopathy. This is when there are thrombi in the arterioles or capillaries and therefore there is endothelial damage by bacterial toxins, drugs, complement or clotting system abnormalities. This will lead to haemolytic uraemic syndrome.
There can also be vasculitis where there is acute or chronic vessel wall inflammation with lumen obliteration. There can also be various types affecting different calibre vessles such as in Wegeners granuomatosis
what else contributes to vascular damage?
hypertension, diabetes or atheroma such as in renal artery stenosis
how can glomerular damage occur?
through immunological or non immunological causes
what are the immunological causes of glomerular damage?
circulating immune complexes that deposit in the glomerulus such as in SLE
circulating antigens deposit in the glomerulus
antibodies to BM or glomerular components such as in Goodpastures
this results in complement and neutrophil activation, reactive oxygen species and clotting factors leading to damage
what are the non immunological causes of damage?
endothelial injury such as vasculitis
altered basement membrane such as in DM hyperglycaemia
abnormal BM podocytes due to inherited disease such as Alport
abnormal protein deposition (amyloid) impairing the function such as in myeloma
this results in basement membrane and vessel damage and therefore glomerular damage
what is the issue with diagnosis of renal disease?
the aetiology and pathophysiology may be unclear
conditions relate to histological appearances but more than one disease may look the same, some diseases have variable histology, some names are both diseases when idiopathic and appearances when secondary to known cause
what are the causes of tubular damage?
ischaemic or toxic
what is ischaemia causes of tubular damage?
hypotension due to shock etc
vessel damage due to vasculitis or HTN
glomerular damage
this leads to reduced perfusion and tubular damage
what are the toxic causes of tubular damage?
direct toxins
hypersensitivity reactions from drugs
crystal deposits such as urate
abnormal protein deposition
what determines the degree of renal function?
it correlates with the degree of renal tubule damage
what are direct toxins?
pesticides, ethylene glycol, drugs, heavy metals, contrast medium and organic solvents
what are the conditions that will lead to blood vessel damage?
inflammatory - vasculitis
endothelial damage - hypertension, thrombotic or microangiopathy
abnormal deposits - amyloid or diabetes
what are the conditions that will lead to damage to glomerulus?
immunological - membranous nephropathy, antiGBM disease, IgA nephropathy, SLE or post infective glomerulonephritis
non immunological - minimal change disease or FSGS
what are the conditions that lead to damage to the tubule?
direct toxicity - drugs and poisons such as gentamicin
hypersentivity to drugs
inflammatory - pyelonephritis or sarcoid
ischaemic - shock. glomerular damage or vascular disorders
abnormal deposits - myeloma
what is nephrotic syndrome caused by?
always due to damage to the glomerulus
what is the presentation of nephrotic syndrome?
hypoalbuminaemia, proteinura (>3g in 24 hours), oedema, maybe hyperlipidaemia and hypertension
what are the complications of nephrotic syndrome?
infection or thrombosis
what are the conditions that cause glomerular damage and lead to nephrotic syndrome in adults?
minimal change disease
focal segmental glomerulosclerosis
membraneous nephropathy - commonest
what is the epidemiology of membranous?
usually adults <60 years and more males than females
20-30% will progress to end stage renal failure
what are the causes of FSGS?
various - usually idiopathic but also genetic and in heroin use and HIV
males more than females
what is the presentation of minimal change?
male and female equal
normal histology
diabetes, lupus and amyloid
what are the conditions that cause glomerular damage and lead to nephrotic syndrome in children?
FSGS or minimal change
other causes are very rare
what is the prognosis of minimal change in children?
excellent
what are the clinical effects of acute nephritis?
oedema, haematuria, proteinuria, hypertension and acute renal failure