Nephritic And Nephrotic Syndrome/ PBL B10 W1 Flashcards
Normal kidney GFR
180L of plasma, where 1.5L leaves as urine
How do kidneys affect prostaglandin synthesis?
When there is renal hypoperfusion (low kidney blood flow), increased prostaglandin synthesis to increase vasodilation of vessels.
How does increased sympathetic tone of kidneys occur?
Activation of renal B1 receptors
What is the HCO3-/CL- antiporter channels?
AE2 channels
What is the HCO3-/Na+ symporter channels?
NBC1 channel
Where does urea reabsorption occur?
Half is absorbed in the PCT and the rest is excreted out in the urine.
When is Na+ secreted into the filtrated?
Never
Where does majority of K+ reabsorption occur?
PCT
Where does water reabsorption occur?
1) PCT
2) Loop of Henle
The rest is reabsorbed in the collecting duct
Nephrogenic diabetes insipidus
Excessive urination mistaken for diabetes mellitus- occurs due to ADH deficiency because of lesion in posterior pituitary gland. Or, Mutation in aquaporin channels that leads to excess water loss in urine
When are ANP levels elevated?
Released by atrial myocytes in response to atrial distention. Pathologically, increased levels related to heart failure.
When are BNP levels elevated?
Released by heart ventricles and brain. Pathologically, increased levels are related to heart failure.
How does ADH affect the kidney?
Insertion of aquaporin channels into collecting duct via V2 receptors and permeability of urea. Acts on V1 receptors to cause smooth muscle contraction of blood vessels.
What are the types of primary nephrotic syndromes?
Minimal change disease
Focal seggmental glomerulitis
Membranous nephropathy/ Membranoproliferative glomerulonephritis
Effect of ACE
Induces arteriole constriction and causes elevation of bradykinin levels
Indication of ACE inhibitor
Hypertension
Myocardial infarction
Congestive heart failure
Diabetic nephropathy
Diabetic nephropathy
High levels of glucose of blood entering kidneys causes glycation of type 4 collagen in kidney basement membrane in efferent arteriole, causing damage so increased deposition of type 4 collagen occurs. This leads to vasoconstriction of efferent arteriole and increases the GFR, leading to hyperfiltration which results in renal vessel damage. To relieve this, ACE inhibitors induce vasodilation.
Congestive heart failure
Failure of the heart in systole that cannot pump hard enough or diastole where the pre-load is low, so ventricles do not fill enough. This may cause blood to back up into the pulmonary arteries and cause dyspnoea, systemic congestion, and higher BP.
Cause of L sided congestive heart failure
L sided is caused by ischaemia due to atherosclerosis, hypertension that causes cardiac hypertrophy and narrowing of the arterioles. In response to diastole HF, heart chamber may grow and cause muscles to weaken. L sided causes blood to flow backwards and affect the source in the lungs primarily
Cause of R sided congestive heart failure
Right sided heart failure is generally a byproduct of left sided heart failure. It is also caused by chronic lung disease that causes the pulmonary arteries to constrict and create high BP. This leads to systemic congestion in the body, creating pitting oedema and enlarged JVP.
Contraindication of ACE inhibitor
Foetal toxicity and co-administering with NSAIDS which will result in decreased GFR
Types of acute kidney injury
Pre-renal
Intrarenal
Post renal
Pre-renal AKI
Decreased blood flow entering kidneys.
Lower blood volume caused by hypovolemia (blood loss) and haemorrhage or fluid loss via vomiting or skin burns.
Issue with the heart like congestive heart failure means not enough blood is pumped to the kidney.
The vessel itself may be affected such as stenosis or embolism.
What is pre-renal AKI linked to?
Generally linked to lower BP, so aldosterone is released to increase H20 and Na+ reabsorption in blood for increasing BP, but this also increases urea uptake, worsening azotaemia.
Intrarenal AKI
Issue within the glomerulus
such as:
Acute tubular necrosis
Glomerulonephritis
Vascular diseases
Acute interstitial nephritis
This affects the glomerular integrity and allows large proteins and fluids to leak, reducing GFR and causing oedema, oliguria
Acute tubular necrosis
Intrarenal AKI where epithelial cells of tubular cells of nephrons die due to ischaemia caused by pre-renal injury, affecting mainly the PCT and ascending limb. The dead cells build up and create high pressure area, disrupting filtration down pressure gradient, reducing GFR for removing toxic waste like urea and creatinine and generating urine causing oliguria.
Causes of acute tubular necrosis
Damage from external factors like contrast dyes for X-rays, aminoglycosides, heavy metal, myoglobin (from damaged muscles) and uric acid. Uric acid is a waste product of cancer cell death in treatment.
Acute interstitial necrosis
Type 1 or Type 4 hypersensitivity affecting connective tissue of interstitium. Caused by NSAIDS, diuretics or penicillin.
Post renal AKI
Caused by obstruction to the ureter. Congenital malformations and neurogenic bladder that leads to multiple sclerosis
Features of AKI
Urea retention as azotemia resulting in uremic frost, neurological symptoms and GI issues. Urea and creatinine levels in the blood are measured in a ratio called BUN. Most of creatinine is excreted in the body but urea levels undergo more regulation in increase and decrease, because it is reabsorbed passively via Na+ and H20 uptake. Urea levels in the blood are higher than creatinine.
What happens in post renal AKI?
Backflow of fluid and urine, increasing pressure and disrupts the pressure gradient. This reduces GFR and causes retention of urea in the blood because it can’t enter nephron.
Nephron categories
Short cortical nephrons: majority of all kidney nephrons located in cortex
Juxtamedullary nephrons: located mainly in medulla and have a greater effect at concentrating urine
Vasopressin/ADH
Produced from the posterior hypophysis and released into circulation in response to low Na+ and H20 levels and increases polypsia. It causes insertion of aquaporin channels in the DCT and collecting duct. Causes vasoconstriction and increase in peripheral resistance.
Aldosterone
Released via action of angiotensin 2 on adrenal medulla. It acts on the DCT and the principal cells of the collecting duct to increase expression of the Na+/K+ ATPase pump. Also increases expression of Na+ channels.
Nephrotic syndrome
Damage to the podocytes of the glomerulus which results in the loss of proteins into the urine which becomes frothy. Proteins leak into urine filtrate causing hypoalbumeniemia. This induces increased liver production of proteins which increases lipid levels as a byproduct, causing hypercholesterolemia. The loss of albumin disrupts oncotic pressure and leads to peripheral oedema.
Proteinuria, hypoalbuminuria, Hyperlipidaemia and oedema. Complications are thrombosis due to low albumin
Cause of nephrotic syndrome
Minimal change disease
Focal segmental glomerulosclerosis
Membranous nephropathy
Diabetes mellitus
Amyloidosis
Common cause of nephrotic syndrome in children
Minimal change disease: commonly occurs after viral infection, with cytokine mediated damage of podocyte foot processes, disrupting protein retention. There is sudden onset and sudden offset and this disease is responsive to steroids.
Minimal change disease has little change when seen under an electron microscope.
What are the features of minimal change disease on electron microscopy?
Extensive podocyte foot process effacement, however this is non-specific. Corticosteroids are the main staple of treatment.
Most common cause of primary nephrotic syndrome in adults
Focal segmental glomerulosclerosis which is assoicated with triggers like podocyte injury; scar tissue formation occurs on regions of the glomerulus and hyaline occlusion of capillary loops occur. Primary FSG is idiopathic and secondary FSG is related to Congenital defects or autoimmune conditions. It must be diagnosed by
What are the secondary causes of focal segmental glomerulosclerosis?
Viruses like HIV and parvovirus
Other glomerular diseases with increased risk of podocyte injury like minimal change disease
Sickle cell disease, obesity, renal agenesis
What are the features of focal segmental glomerulosclerosis on imaging?
FSG shares similarities with minimal change disease, however has a worse prognosis as adults have a poorer response to steroids. Light microscopy shows focal segmental sclerosis. Electron microscopy shows effaced podocyte food process
What is the treatment of focal segmental glomerulosclerosis?
Immunosuppressive medication such as corticosteroids like prednisone in combination with cyclosporine and maintaining blood pressure control with ACE inhibitors and ARB