Renal Path Flashcards
Pronephros
- Forms at begining and present until week 4 when it degrades.
- Not functional
Mesanephros
- Functional from week 5 to 32-36 weeks.
- Ureteric bud comes off caudal end
Ureteric Bud
- Comes off caudal end of mesenephros and works with metanephric mesenchyme to make definitive kidney.
- Ureters to Collecting duct are made from ureteric bud
Metanephros
- Begins developing at week 5 and functional by week 32-36.
- Contains metanephric mesenchyme
Metanephric mesenchyme
- Works with ureteric bud to form the definitive kidney.
- Forms proximal portion from DCT to glomerulus
Horsehoe Kidney
- Fusion of inferior pole of kidney
- Gets stuck on IMA during ascent.
- Still functional and seen commonly in turners syndrome
Multicystic Dysplastic Kidney
- Impaired communication between metanephric mesenchyme and ureteric bud leads to degradation of kidney.
- Cystic spaces with fibrotic stroma in betweem
- Most commonly unilateral. Contralateral kidney hypertrophies and picks up function.
Potter sequence
- Oligo hydramnios leads to lung hypoplasia (Cause of death), facial deformities, and club feet/arms
- Can be caused by: Posterior urethral valves (Problem with wolfiian duct, bilateral renal agenesis, ARPKD
Uretopelvic Junction
- Last portion to canalize and most commonly impaired.
- will lead to congenital hydronephrosis
Ureters Anatomy
-Retroperitoneal structures that go under the uterine arteries and and ductus deferens
Macula Densa
- Modified cells in association with DCT. In close aproximation with JG cells.
- Works to regulate renin secretion and constriction of afferent arteriole in response to changing Na/Cl concentrations.
Fluid Compartments
- 60% body water, 40% normal tissue
- Of 60%, 2/3 is intracellular and 1/3 is extracellular
- Of extracellular, 3/4 is interstitial and 1/4 is plasma
- Measure plasma with radio-labeled albumin
- Normal osmolarity is 290 (approximately 2xNa)
Glomerular Barrier
- Fenestrated endothelium is size barrier and prevents RBC from penetrating
- BM contains large quantities of heparan sulfate which is highly negatively charged. Proteins will be repeled (loss in nephrotic syndrome leads to proteinuria)
- Podocytes of bowman’s epithelial cells
Substance Filtration
- Small polar molecules are completely filtered and must be reabsorbed
- Large proteins are not filtered
- Lipophilic substances (steroids, bilirubin) will be bound to almbumin and large proteins so won’t be filtered.
- If glucuronidation or sulfation leading to increased water solubility will increase ability to be filtered
Renal Clearance
- The volume of fluid from which all of a substance has been cleared
- Renal excretion/plasma concentration
- Ux*V/Px
- If greater than GFR then net secretion
- Less than GFR net reabsorption
GFR
- Meausured acurately with the celarance of inulin. Freely filtered by not secreted or resorbed
- Clinically done with creatinine
Effective Renal Plasma Flow
- Calculated by PAH clearance
- All of PAH is secreted therefore plasma flow.
- At really high PAH concentrations transporter can be saturated and will no longer be accurate
Renal Blood Flow
-Renal Plasma Flow/ (1-Hct)
Filtration fraction
-GFR/RPF, normally 20%
Filtered Load
GFR* plasma concentration
Prostaglandins effect on filtration and GFR
- Cause dilation of afferent arteriole leading to increased RPF and Increase GFR with no change in filtration fraction.
- NSAIDs oppose this action and will decrease RPF and GFR
Angiotensin 2 effect on filtration and GFR
- Preferentially constricts efferent arteriole leading to decreased RPF with increased GFR and increased FF.
- ACEI will inhibit this leading to an increase in RPF and decrease in GFR and FF. Given to “all diabetics” takes strain off kidneys
Glucose Clearance
- Driven by Na/K symporter. Normally all glucose is reabsorbed, but demonstrates saturation kinetics
- at 160,g/dl there is the start of splay (some saturated) at 350mg/dl is complete saturation of receptors.
- Glucosuria will be seen from 160 onwards.
Glycosuria of Pregnancy
- Increased blood volume leads to increased RPF and GFR which increases filtered load of glucose and saturates glucose transporters at lower glucose levels.
- Is normal and not pathalogic
Amino Acid Clearance
-Saturation kinetics like glucose however rarely saturated
Hartnup disease
- Congenital lack of neutral amino acid transporter leading to impaired tyrptophan reabsorption and absorption from the gut.
- Tryptophan makes niacin and lack of transporter will lead to lack of niacin and pellegra.
Proximal Convuluted Tubule
- Reabsorption of almost everything. Reabsorbs all glucose, amino acids. Most HCO3, 2/3 Na and 2/3 H20
- Generates an isotonic urine (water follows Na)
- Generates NH3 to be used as buffer for acid in collecting duct
- Has CA, HCO3 reabsorbed and H+ secreted and complexes with HCO3 in urine. No net production of HCO3.
Carbonic Anhydrase Inhibitors
- Prevent reabsorption of HCO3 leading to diuresis
- Also can cause slight metabolic acidosis
- Acetazolamide used to treat altitude sickness that is brought on by hyperventalaion induced metabolic alkalosis.
PTH role in PCT
-Cause decrease in function of phosphate transporters.
Leads to phosphate excretion
Ang II role in PCT
-Causes increase in Na/H antiporter leading to increased Na and bicarb reabsportion leading to increased tonicity of blood and increasd blood volume.
Thin Descending limb of henle
-Impermiable to Na and flows down the corticomedullary gradient resulting in reabsortpion of water and concentration of urine
Thick Ascending Limb
- Impermiable to water and dilutes the urine
- Na/K/2Cl pump reabsorbs these ions. Blocked by loop diuretics (ferosumide) (hypokalemia possible)
- Reabsorption of Ca and Mg occurs because of positive luminal membrane potential generated by K backleak
Early DCT
- Na/Cl transporter, blocked by thiazides leads to reduced Na and Cl reabsorption
- Cl can be absorbed paracellularly
- Makes urine more hypotonic (impermiable to water)
How Thiazides increase Ca reabsportion
-Blockage of Na/Cl channel means that all Na pumped out of cell with Na/K pump will then only be able to enter the cell from the basilar side in the Na/Ca exchanger. This leads to increased Na/Ca exchanger function and incresed Ca absorption.
How Thiazides can be used in Nephrogenic DI
-Decresed Na/Cl reabsorption means there is more in the lumen. This is sensed by the JG aparatus as GFR that is too high. This will feedback to the afferent arteriole and cause constriction and reduction in GFR. Decreased GFR leads to decreased diuresis in the collecting Duct
PTH effects on Early DCT
-Cause increased Ca absorption through Na/Ca exchanger
Collecting Duct Principle Cell
- Mainly concerned with water and electrolye absorption
- Contains and inducable (aldosterone) Na channel.
- Contains aquaporins induced by V2 ADH receptors
- K+ leak channel that functions to secrete K with low intraluminal K concentrations
Amilioride/Triamterene
-K sparing diuretcs that block the Na channel in the collecting duct. Decreased intracellular Na leads to decrease in Na/K pump and decreased K leak. Leading to K sparing properties
Sprinolactone
-Blocks aldosterone receptor. Prevents protein synthesis of Na channel. Effects same as K sparing diuretcs
ADH
- Gs receptor that puts aquaporins on luminal membrane leading to increased reabsorption of water.
- Urea follows water and will be reabsorbed too.
Intercalated Cell
- Functions in acid base balance.
- CA splits H20 and CO2 to make HCO3 and H
- HCO3 is generated here and is free. Works to alkalanize plasma (HCO3 in PCT is not free and is complexed with H)
- Main channel is primary active trasport H pump that pumps hydrogen into the lumen.
- Pump is slowed if luminal pH drops. Therefore acid must be complexed with luminal substances to be buffered out.
- Phosphate can absorb H and NH3 (produced in PCT) can absorb H+ (more)
Renal Tubular Acidosis I
- Dysfunction of H+ pump in intercalated cell leads to impaired HCO3 production and impaired H secretion
- Urine will have a high pH
- Fanconi’s syndrome
Renal Tubular Acidosis II
- Impaired HCO3 production in PCT leads to decreased production and transfer into plasma.
- Increased urine pH predisposes to production of calcium phosphate renal stones
TF/P
- Water is resorbed along the length of the PCT at the same rate as K and Na
- Substances that are resorbed more rapidly have a TF/P of less than 1 (glucose, AA, Phosphate, HCO3)
- Substances that are absorbed slower are above 1 (inulin, Cl, Urea, creatinine)
JG Aparratus
- Consists of JG cells (granular cells) That are modifiec smooth muscle cells of the afferent arteriole that secrete renin.
- Macula Densa cells of the DCT that detect Na/Cl concentrations.
- Increased Na/Cl delivery means that GFR is too fast and signals through adenosine to cause constriction of the afferent arteriole to decrease RPF and GFR
- Decreased Na/Cl means GFR is too low signalling a release of renin that results in the preferential constriction of the efferent arteriole and increasing GFR and FF at a lower RPF
RAAS
- Release of Renin from JG (Granular cells) is stimulated by decrease Na/Cl (macula densa), B1 SANS stimulation, decreased BP (decreaed RPF and decreasd GFR)
- Renin converts angiotensinogen to ang 1 which is converted to ang2 in lungs by ace.
ACE
- Enzyme in lungs that activates ang I to ang 2
- Also degrades bradykinin, ACEI can induce massive angioedema and tongue swelling in some patients.
Ang 2
- Main role is to increase BP
- Systemic effects on AT1 receptors cause vasoconstriction
- Causes preferential constriction of efferent arteriole which leads to increase FF and preserves GFR in the face of decreased RPF
- Causes release of aldosterone which will increase Na reabsorption and volume expansion. ADH is primarily concerned with osmolarity
- Causes release of ADH which acts through Gs receptors to place aquaporins in the collecting duct to increase water absorption. Mainly concerned with volume status
- Inhibits reflex bradychardia in baroreceptors of carotid sinus
- Increases Proximal Tubule Na/H activity. Increases Na, HCO3, and H20 reabsorption
- Stimulates thirst sensor in hypothalamus
Aldosterone
- Mainly concerned with volume
- Functions to increase Na reabsoprtion in exchange for K and H.
- Excess leads to hypokalemic alkalosis
- Nuclear receptor that increases Na channel expression in collecting duct
ANP
- Stimulated by stretch in the atria.
- Binds to receptor and increases intracellular cGMP and NO concentrations leading to vasodilation
- Increases GFR and decreases Renin