Kidney pathophysiology Flashcards
What is the general function of the kidney?
Detoxifys blood by filtering everything and reabsorbing only what it needs.
Describe the structure of the glomerular filtration barrier.
Endothelial cells with fenestrae
Basement mambrane
Podocytes (which have foot processes). There are filtration slits with diaphragm.
What is the glomerular filtrate comprised of?
Water, glucose, amino acids and urea.
What are the main features of the glomerulopathy, nephrotic syndrome?
High protein in urine Low albumin in blood Edema Hyperlipidemia Lipiduria
What are the main features of the glomerulopathy, nephritic syndrome?
Mild protein in urine Hematuria Hypertension Blurred vision High blood urea Low diuresis
What are the causes and main features of the glomerulopathy, post-streptococal glomerulonephritis?
Explain treatment.
Occurs 10-14 days after skin/throat infection caused by streptococcus.
Immune complexes deposit at the glomerular membrane and damage the filtration barrier, causing protein and albumin to be lost into the urine.
Symptoms:
Hematuria
Proteinuria
Decreased blood albumin
Edema
Oliguria (Low diuresis)
Hypertension
Treatment:
Antibiotics to destroy any remaining streptococal bacteria.
Diuretics and blood pressure medication to control edema and hypertension.
Limit salt in diet
Explain the action of the osmotic diuretic mannitol.
How is it administered?
What are its uses?
Increases plasma osmolarity.
It is filtered at the glomerulus but poorly reabsorbed. This increases osmotic pressure in the filtrate causing decreased water reabsorption from the nephron.
Administration - Slow IV infusion of 5-20% solution
Uses:
Forced diuresis in poisoning
Acute glaucoma
Cerebral oedema
What is reabsorbed in the PCT?
Sodium (65%), water and bicarbonate.
How is glucose transported out of the PCT?
What happens if the level of filtered glucose exceeds the transport maximum?
SGLT2 transports sodium and glucose into the proximal tubule epithelial cell.
Fcilitated diffusion of glucose from the proximal tubule epithelial cell into the blood capillary with assistance from the Sodium/Potassium ATPase.
If the level of filtered glucose exceeds the transport maximum, the excess is lost in the urine.
What do SGLT2 inhibitors do?
Treatment for diabetes by preventing glucose reuptake
Explain how ions and water are reabsorbed from the PCT?
There is a Sodium/Hydrogen pump on the apical membrane that is dependent on proton availability.
Sodium/Potassium exchanger on the basolateral membrane moves sodium into the blood. Water then follows by osmosis.
What effect will a carbonic anhydrase inhibitor have on the PCT?
Sodium will be unable to leave the lumen, having a diuretic effect.
What is significant about the TAL of the loop of Henley?
What are the characteristics and functions of the loop of henle?
Thick ascending limb is impermeable to water.
Main function of the loop of henle is the reabsorption of water and sodium by establishing an osmotic gradient.
How are ions pumped out of the thick ascending limb?
Sodium is pumped out of the thick ascending limb:
-There is a Sodium/Potassium/Chlorine symporter on the apical membrane
-There is a Sodium/Potassium ATPase on the basolateral membrane
This forms an electrostatic gradient which causes other ions (Sodium, Potassium, Calcium, Magnesium) to move into the blood through the zona occludens.
Explain how the loop of henle diuretic furosemide works.
It inhibits the Sodium/Potassium/Chloride symport meaning there is no electrostatic gradient. Urine is hyperosmolar and drags water from the tubules.
It causes 15-25% of filtered sodium to be excreted and torrential urine production.
It also causes increased osmotic pressure in the filtrate delivered to the distal tubule.
