Renal Flashcards
Filtration and ultrafiltrate
Filtration by glomerulus forms ultrafiltrate –> same composition of blood except for protein and cells
Sequential renal blood flow
Aorta –> Renal artery –> Interlobar arteries –> arcuate artery –> interlobular artery –> afferent arteriole –> glomerular capillaries –> efferent arteriole –> post glomerular capillaries –> venules –> interlobular vein –. Arcuate vein –> interlobar vein –> renal vein
Glomerular and postglomerular capillaries
2 capillary beds
Glomerular = filtration
Postglomerular = Absorption
Electrical charge and filtration barriers
Negatively charged substances pass less regularly than positve
Electrostatic restriction
More prominent role? Electrostatic restriction or size restriction
Electrostatic
Hallmark of gomerular injury and why?
Protein in urine
Filtration barrier damaged and more protein being filtered than it can be reabsorbed
Parallel arrangement of filtration barrier capillaries
Minimizes hydrostatic pressure drop between entrance and exit
Large surface area for filtration
Filtration forces
Glomerular capillary hydrostatic pressure - filtration
Bowmans Space hydrostatic pressure - Absorption
Bowmans space oncotic pressure = 0 - Filtration
Glomerular capillary oncotic pressure - Reabsorption
Difference between capillaries in Renal vs non renal
Non renal -
Hydrostatic pressure decreases across length Filtration vs reabsorption changes along length
Filtration = Absorption
Renal - Hydrostatic pressure nearly constant Glomerular oncotic pressure increases along length, never higher than hydrostatic pressure
Bowmans space P is constant and oncotic is 0
NEVER ABSORPTION ALONG GLOMERULAR WALL
Increasing GC plasma flow results in —>
More plasma for filtration which slows buildup of proteins in GC –> Lower GC oncotic pressure –> More filtration –> Higher GFR
Forces in peritubular capillaries
Capillary hydrostatic pressure (efferent arteriole)
High Plasma oncotic pressure
Oncotic pressure > hydrostatic pressure = NET FILTRATION
Vasoconstriction of afferent arteriole = ?
Decreased RBF
Decreased GFR
Increased efferent arteriole resistance = ?
Decreases RBF
Increases GFR
Afferent arteriole dilation = ?
Increased GFR
Increased RBF
Nitric Oxide effect on A and E arteriole
A - Dilate
E - Dilate
Prostaglandin I2 effect on A and E arteriole
A - Dilate
E - Dilate
Prostaglandin E2 effect on A and E arteriole
A - Dilate
E - No effect
Angiotensin II effect on A and E arteriole
A - Constrict
E - Constrict
Vasopressin effect on A and E arteriole
A - Constrict
E - Constrict
NE effect on A and E arteriole
A - Constrict
E - Constrict
Endothelin effect on A and E arteriole
A - Constrict
E - Constrict
Thromboxane effect on A and E arteriole
A - Constrict
E - Constrict
ANP effect on A and E arteriole
A - Dilate
E - Constrict/no effect
Autoregulation mechanisms of RBF and GFR
Myogenic
Tubuloglomerular feedback mechanism
Myogenic
Increased constriction if pressure/flow increased
Tubuloglomerular feedback mechanism
Increased GFR –> increased flow through tubule and macula dense –> Paracrine signal from MD to afferent arteriole –> Constriction –> Increased resistance –> decreased hydrostatic pressure –> Decreased GFR
How much of filtered Na load is reabsorbed
>99%
Proximal tubule Na reabsorption %
67%
Loop of Henle Na reabsorption %
Intermediate capacity 25%
Dista nephron (DCT and CCT) Na reabsorption %
Low capacity ~8%
Proximal tubule Na transporters
Na co-transporters
Na/H exchanger
Thick ascending limb Na transporters
NKCC
DCT Na transporters
Na-Cl co trasporter
Collecting duct Na transporter
ENaC
Basolateral membrane Na tranport
Na/K ATPase
Glucose handling early proximal tubule
Apical SGLT2 - Low affinity, high capacity
Na-glu transport Basolateral - GLUT1
Glucose handling late proximal tubule
Apical SGLT1 - High affinity, low capacity 2Na-Glu Basolateral GLUT2
Glucosuria - DM
Amount of glucose exceeds threshold and Tm = glucose excreted in urine
Glucosuria - Defects in NaGlu tranporters
Familial renal Glucosuria
Glucose-Galactose malabsorption syndrome
Familial renal glucosuria
Mutation in SGLT2 decreases transport capacity –> decrease Tm –> glucose excreted
Can result in decreased plasma glucose concentration
Glucose galactose malabsorption syndrome
Mutation of SGLT1 – decrease transport capacity –> slight lower Tm –> mild glucosuria
Can effect gut absorption
Urea diffusion
Urea remains in renal tubules but concentration increases due to water exit –> travels down concentration gradient to renal venous sytem
PAH and Kidney
PAH is filtered and secreted by renal tubules, not reabsorbed
Good measure of Renal plasma flow
[K]ecf
Very closely regulated
3.9 < Normal < 4.5
[K]ecf depends on…
Total body content of K (input - output)
Distribution between ICF and ECF (Na/K ATPase)
Hormones that cause K uptake into cells
Insulin B agonists
Aldosterone
Cause increased activation of Na/K ATPase
pH changes and K
Lower pH = Decrease K uptake
Higher pH = Increased K uptake into cels
Glomerular filtration of potassium
Freely filtered
Kidney reabsorption of K
>90% reabsorbed by proximal tubule and Thick ascending limb
Kidney secretion of K
Distal tubule and CCT
Regulation of K excretion
Occurs in Distal tubule and CCT
Based on levels of K secretion
Proximal tubule K transport
Passive reabsorption H20 reabsorption –> increased K concentration –> K reabsorption down concentration gradient
Loop of Henle K transport
Thick ascending limb Apical NKCC
Basolateral K channel
Collecting tubule and collecting duct K transport - a Intercalated cells
ICT, CCT, MCD
Apical uptake via H/K ATPase Basolateral K channel
Collecting tubule and collecting duct K transport - principal cells
ICT and CCT - active secretion K uptake from peritubular interstitium via basolateral Na/K ATPase
Passive apical K flux
Increased Na/K ATPase activity and K handling
Increased intracellular K concentration –> K secretion
Increased tubular flow and K handing
Secreted K flushed downstream –> Low K concentration in lumen –> Increase K secretion
Increased negative charge of lumen
K secretion due to electrical gradient
K wasting diuretics
Agents that block Na reabsorption by proximal tubule of loop of henle Increased tubular flow in distal tubule and collecting duct = K secretion
K sparing diuretics
Agents that inhibit Na reabsorption in distal nephron
Tubular flow secretion effect minimized because of tubular electrical status (more positive)
Physiological regulation of K excretion
Increased [K] intake –> Increased [K] plasma –> Aldosterone –> Increased distal nephron K secretion –> Increased K excretion Increased [K] intake –> Increased [K] plasma –> Increased distal nephron K secretion –> Increased K excretion
Water handling in proximal tubule
AQP1 in apical and basolateral membrane
Promotes water leaving tubules and entering interstitium
Water handling in Loop of Henle
Descending limb = water reabsorption
Ascending limb - Water impermeable DCT - Water impermeable
No ADH - collecting duct cells
Cells impermeable to water - no basolateral AQP
ADH effect
AQP-2 channels inserted onto apical membrane, cells are water permeable
Net effect of kidney response to water intake
Formation of dilute urine
Proximal tubule - Isosmotic reabsorption of Na/water
Descending limb - Water reabsorption due to increasing medullary osmolarity (via TAL)
Turn of Loop - Concentrated tubular fluid that is isosmotic to medullary intersititum
Ascending limb - Solute reabsorption and fluid becomes hyposmotic
Slight Na reabsorption in distal nephron
NET EFFECT: Low osmolarity urine excreted
Net effect of kidney to dehydration
Requires ADH Formation of dilute urine that reaches distal tubule
CCT - Water permeable tubule comes under effect of intersitial osmolarity –> water reabsorption
Medullary collecting duct - Also water permeable, water reabsorbed
Highly concentrated urine excreted
Synthesis and release of ADH
Synthesized in supraoptic and paraventricular neurons of hypothalamus
Stored in nerve endings in posterior pituitary
ADH regulation - osmoreceptors
increases in plasma osmolarity = ADH release
Small plasma changes = large ADH release
Most sensitive ADH regulator
ADH regulation - baroreceptors
Decrease in blood volume sensed by baroreceptors –> increase ADH release
Need large decrease in blood volume
Other factors that increase ADH secretion
Vomiting
Nausea
Morphine
Nicotine
Cyclophosphamide
Factors that decrease ADH secretion
Alcohol Clonidine Haloperidol
SIADH
Excessive ADH secretion for given plasma osmolarity
Retain water in excess of solute = decreased plasma osmolarity
Diabietes Insipidus
Patients produce large volume of dilute urine Increased plasma osmolarity
Neurogenic - Deficient ADH secretion
Nephrogenic - Insensitivity of kidney tubules to ADH
Actions of AngII
Retention of Na
Vasoconstriction
Promote acquisition and retention of water
AngII retention of Na
Aldosterone activation –> Na reabsorption in collecting duct
Stimulate Na/H exchange –> proximal tubular Na reabsorption
AngII Vasoconstriction
Direct effect on vascular smooth muscle
Increase TPR to increase systemic arterial pressure
AngII promote acquisition and retention of water
Stimulate thirst –> acquire water
Stimulate ADH release from hypothalamus –> water retention
Decrease medullary blood flow
Aldosterone: Stimuli, action, mechanism
Stimuli: Increased AngII, decreased plasma [Na], increased plasma [K]
Action: Increase Na reabsorption by collecting duct
Mechanism: Promote Na entry through apical ENaC and basolateral Na/K ATPase.
PRINCIPAL CELL OF COLLECTING DUCT
Catecholamine: Stimuli, action, mechanism
Stimuli: Activation of SNS
Action: Increase Na reabsorption by proximal tubule
Mechanism: Activate Na/H exchange
Endogenous digitalis like substance: Stimuli, action, mechanism
Stimuli: Increased ECF volume
Action: Decrease Na reabsorption by all nephron segments
Mechanism: Direct effect to inhibit basolateral Na/K ATPase
Glomerular-tubular balance
Proximal tubule reabsorbs constant fraction, 67%, of filtered Na
Increased GFR –> increased oncotic pressure of peritubular capillaries –> increased reabsorption
Reduces impact of increased filtered load on solute/water delivery to distal nephron
Responses to abrupt increase in Na intake
Increased GFR
Decreased Na reabsorption
Factors that increase GFR in response to Na increase
Increased Na = Increased ECF = decreased plasma oncotic pressure = Increased GFR via Starling
Increased arterial pressure –> increased capillary hydrostatic pressure –> increased GFR
Decreased AngII –> decreased arteriolar resistance –> increased RBF/GFR
Increased arterial pressure –> decreased SNS –> decreased arterioloar resistance –> Increased RBF/GFR
Factors that decrease tubular Na reabsorption in response to abrupt increase in Na intake
Decreased AngII –> decreased proximal tubule Na reabsorption (Na/H)
Decreased aldosterone –> decreased Na reabsorption in collecting duct
Decreased sympathetic tone –> decreased Na reabsorption in proximal tubule
Increased blood volume –> increased ANP –> decreased Na reabsorption in collecting duct
Increased endogenous digitalis like substance –> Decreased Na reabsorption
Pressure Natriuresis
Increase in arterial pressure –> Increased Na excretion
Unknown mechanism
IMPAIRED IN HTN
Increased Na intake –> increased ECF volume –> increased arterial pressure –> increased Na excretion –> decreased ECF
Mechanisms of Renin release
- Low blood volume, JG cells secrete renin into circulation
- Decrease in perfusion across macula dense, message sent to JG to secrete renin
- Increased sympathetic activity (B1) via baroreceptors in carotid sinus
ANP stimuli, action, mechanism
Stimuli: Atrial stretch (High ECF)
Action: Decrease Na reabsorption by collecting duct
Mechanism: ENaC inhibitor
ANP actions
- Inhibit vasopressin release in hypothalamus
- Increase GFR a (vasodilation) and decrease Renin
- Inhibit Aldosterone
- Decrease BP via medulla oblongata
- Decrease Na reabsorption via ENaC inhibition
Aldosterone and Potassium
Aldo increases K secretion via compensation for increasing ENaC In collecting duct principal cells
Osmolality definition
Total solute concentration but comprised mainly of Sodium salts
Tonicity
Effective plasma osmolality
Osmolality of solutes that contribute to water distribution
Requirements to excrete excessive free water
Delivery of water/solutes to nephron dilution sites (TAL, DCT)
Proper function of diluting segments (channel function)
No ADH
Requirements for maximal urine concentration (water absorption)
Concentrated medullary interstitium (functioning TAL channels)
Presence of ADH
Normal response to ADH
Osmoregulation of ADH
Serum osmolality sensed by osmoreceptors in hypothalamus
Increase ADH and thirst Increase urine osmolality, water intake
Volume regulation of ADH
Effective tissue perfusion sensed by baroreceptors and macula densa
Activation of RAAS, Aldo, ANP, NE, ADH
Urine sodium and thirst affected
Hypovolemia definition
Decreased fluid volume due to decreased total body Na
Hypervolemia definition
Increased fluid volume due to increased total body sodium
Determinants of Hyponatremia
Plasma tonicity - water distribution
Volume status - Total body Na
Hypertonic hyponatremia osmolar definitions
Posm > 290
PNa < normal
Hypertonic hyponatremia definition/cause
Increased plasma osmolality with decreased Na concentration
Due to other effective osmole causing fluid movement from ICF –> ECF
Hyperglycemia, glycine, mannitol
Hypertonic hyponatremia treatment
Remove underlying cause
Isotonic hyponatremia
Lab artifact
Increased protein/lipid concentration that is sensed as decreased Na concentration
Old lab testing
Brain response to hyponatremia
Immediate effect - water gain (cerebral edema) and altered mental status (low osmolality)
Rapid adaptation - Loss of sodium/K/Cl to reduce edema (low osmolality)
Slow adaptation - Loss of organic osmolytes (low osmolality)
THERAPEUTIC INTERVENTION:
Slow correction = brain returns to normal osmolality
Rapid correction = Osmotic demyelination - no chill
Hypotonic hyponatremia - Definition and types
POsm < 290
PNa < 140
Due to excessive water either because of ADH or impaired water excretion
Hypovolemic Euvolemic Hypervolemic
Hypovolemic hypotonic hyponatremia - Pathogenesis
True volume depletion (ECF loss, Na and water)
ADH stimulation –> water retention –> restored ECF volume but NOT Na
Hypovolemic hypotonic hyponatremia - physical exam
Signs of volume depletion
Flat neck veins
Tachycardia
Hypotension
Orthostatic hypotension
Hypovolemic hypotonic hyponatremia - Causes
Volume losses: GI, blood
Insensible losses - sweating/burns
Renal losses - Loop diuretics, adrenal insufficiency, salt wasting nephropathies
Insensible losses in Hypovolemic hypotonic hyponatremia
Burns and sweating
Low Urine [Na] because RAAS active and Na reabsorption is maximal
Renal losses in Hypovolemic hypotonic hyponatremia
High urine [Na]
Sodium reabsorption not functioning
Euvolemic hypotonic hyponatremia
Euvolemic on exam
SIADH:
High urine Osm
High urine [Na]:
ADH –> water reabsorption –> volume increase –> decrease renin –> decrease RAAS –> decrease Na reabsorption
Primary polydipsia
Cause of euvolemic hypotonic hyponatremia
Excessive water intake that overwhelms excretory capacity of kidney
Urine Osm low due to ADH suppression
Hypervolemic hypotonic hyponatremia
ECF volume excess with decreased intravascular volume
EDEMATOUS STATES
Hypervolemic hypotonic hyponatremia causes - non renal
Heart failure
Liver cirrhosis
Nephrotic syndrome
ADH activated b/c low circulating volume
Urine Osm high b/c ADH
Urine [Na] low b/c RAAS activation
Hypervolemic hypotonic hyponatremia causes - renal
Advanced renal failure
Impaired free water excretion
Effective plasma Osm low b/c water retention
Total Plasma Osm may be high b/c excessive urea
Hypovolemic hypotonic hyponatremia treatment
Correct intravascular volume w/ isotonic fluid
Euvolemic hypotonic hyponatremia treatment
Correct underlying cause
SIADH - Water restrict, increase solute intake, V2 antagonist
Hypervolemic hypotonic hyponatremia treatment
Diuretics
Fluid restriction
Hyponatremia management risks
DO NOT TREAT QUICKLY
Avoid osmotic demyelination syndrome
Hypernatremia definition and general cause
Serum Na >145
Loss of free water
Occurs in patients who cannot express thirst of don’t have access to water
Diabetes insipidus
Decreased ADH action - nephrogenic or neurogenic
Central DI
Neurogenic
Insufficient release of ADH in response to increased Na osmolality
Lesion in hypothalamic osmoreceptors, supraoptic nuclei, or trauma/surgery
Nephrogenic DI
Reduced action of ADH at collecting tubule to due receptor/aquaporin mutation
Lithium
Hypernatremia etiology
Hypotonic fluid loss - Na/water loss but solute concentration is hypotonic to plasma osmolality If free water not replaced –> hypernatremia
Hypertonic sodium gain
4 Mechanisms of K balance
K intake through diet
GI losses (5-10% absorbed K secreted in GI)
Renal losses (90-95% K regulation)
Transcellular K shift (ECF vs ICF distribution)
Renal handling of K - PCT
Freely filtered in glomerulus 65-70% reabsorbed in proximal tubule via passive transport
Renal handling of K - TAL
NKCC channel reabsorption of K
K pumped into lumen in TAL to enhance K recycling and NKCC function
Apical K channel inhibited by ATP - More Na enters cell –> transported out by Na/K ATPase –> low ATP –> apical K activation –> NKCC function and more Na absorbed
Renal handling of K - Principal cell
K transported into cell by Na/K ATPase
Secreted into tubule via ROMK
Principal cell K transport governing factors
- Luminal electrical charge
- Luminal concentration gradient
- K permeability of luminal membrane
4 Main factors that affect K secretion into tubular fluid
- Aldosterone
- Plasma [K]
- Distal flow rate
- Distal Na delivery
Aldosterone and K secretion
Increases # open Na (ENaC) and K (ROMK) channels
Enhances Na/K ATPase activity
Plasma [K] and K secretion
Increased plasma K = enhanced Na/K ATPase activity
Increased # open K & Na channels
Distal flow rate and K secretion
Increased flow = more K washed away = increased K secretion via favorable gradient
Distal Na delivery and K secretion
Na through ENaC = more negative lumen = K secretion More ENaC absorption = more intracellular Na = enhanced Na/K ATPase = more K secreted
a-Intercalated cells and K handling
Reabsorption of K via apical H/K ATPase
Main etiologies of hypokalemia
Transcellular shift
GI losses
Renal losses
Poor intake
Hypokalemia and transcellular shift etiologies
Insulin B2 agonists
Alkalosis
Hypokalemic periodic paralysis
Hypokalemia and insulin
Stimulates Na/K ATPase –> more K secretion
Hypokalemia and B2 agonist
Increase Na/K ATPase activity –> K secretion
Hypokalemia and alkalosis
Alkalosis = high extracellular pH –> H will leave cell –> K enters cell to maintain electroneutrality
Hypokalemic periodic paralysis
Acute attacks precipitated by sudden movement of K into cells
Lowers plasma K significantly
Rest after exercise, stress (catecholamines), high carb meal (insulin)
Familial - autosomal dominant mutation Acquired - Thyrotoxicosis
Hypokalemia - GI losses
Associated with metabolic alkalosis due to HCL loss –> K entry into cells b/c H exit
Concurrent urinary losses: -
Aldosterone activation
Plasma Bicarb increase = too much Bicarb that can be absorbed –> Na pairs with bicarb –> increased distal delivery of Na –> K secretion
Hypokalemia renal losses categories
Metabolic alkalosis
Metabolic Acidosis
Magnesium
Hypokalemia w/ metabolic alkalosis categories
Normo-hypotension
Hypertension
Hypokalemia w/ metabolic alkalosis and normo-hypotension
Diuretics - Loop/Thiazide
Activation of aldosterone by volume depletion Increased distal delivery of Na (blocked absorption more proximally)
Salt wasting nephropathies
Bartters syndrom
THINK LOOP DIURETIC
Defect in solute reabsorption in TAL NKCC2, Luminal K channel, Basolateral Cl channel can be affected
Gitelman’s syndrome
THINK THIAZIDE DIURETIC
Defect in thizide sensitive NaCl cotransporter in DCT
Hypokalemia with metbolic alkalosis - Hypertension
Mineralocorticoid excess:
Primary hyperaldosteronism (adrenal tumor, BAH)
Glucocorticoid remedial aldosteronism
Renal artery stenosis
11BHSD2 deficiency
CAH
Liddle’s syndrome
Gain of function mutation in ENaC
Triad:
Hypertension - Metabolic alkalosis - Hypokalemia
Hypokalemia with metabolic acidosis types
Renal tubular acidosis
Nonreabsorbable anion
Hypokalemia with metabolic acidosis - Renal tubular acidosis
Hyperchloremic, non anion gap metabolic acidosis
- Distal hypokalemic RTA (type I): Impaired distal urine acidification. No protons pumped out = more K secreted
- Proximal (type II): Reduction in bicarb reabsorptive capacity –> all bicarb reabsorbed –> metabolic acidosis that inhibits Na reabsorption –> hypokalemia
Hypokalemia with metabolic acidosis - Nonreabsorbable ion
Non reabsorbable anion paired with Na –> reduced Na –> Increased distal delivery of Na
Diabetic ketoacidosis - Beta hydroxybuterate pairs with Na
Hypokalemia and Magnesium
Hypokalemia occurs in 40-60% of hypoMg diseases
Diseases that waste both K and Mg: Diarrhea, diuretics
Correct Mg to restore K
CV clinical manifestations of Hypokalemia
Cardiac arrhythmias:
Sinus bradycardia, AV block, Vtach/Vfib
Decrease amplitude of T wave, increase U wave amplitude
Muscular clinical manifestations of hypokalemia
Weakness and muscle cramps
Low K = hyperpolarized skeletal muscle cells = impaired contraction
Reduce blood flow by impairing NO release
Severe K depletion = respiratory weakness –> respiratory failure GI muscle weakness = ileus
Hormonal clinical manifestations of hypokalemia
Impaired insulin release and end organ sensitivity to insulin
Worsened glucose control in diabetic patients
Renal clinical manifestations of hypokalemia
Tubulointerstitial and cystic changes in parenchyma
Polyuria: Increased thirst and mild nephrogenic DI, concentrating ability impaired
HTN: Increased renal vascular resistance
Hypokalemia diagnosis: Metabolic acidosis + Low urinary K:creatinine
Stool losses
Hypokalemia diagnosis: Metabolic acidosis + High urinary K:creatinine
RTA
Nonreabsorbable ion
Hypokalemia diagnosis: Metabolic alkalosis + Low urinary K:creatinine
Vomiting
Hypokalemia diagnosis: Metabolic alkalosis + High urinary K:creatinine
Check BP and volume status
Low-normal BP/volume depleted - diuretics, salt wasting nephropathies
High BP/volume overload - Mineralocorticoid excess, Liddle’s
Main etiologies of hyperkalemia
Transcellular shift
Psuedohyperkalemia
Renal - Decreased urinary excretion
Pseudohyperkalemia
Elevation in measured serum K due to K movement out of cells during/after blood draw
Hemolysis Thrombocytosis Leukocytosis
Hyperkalemia transcellular shift - etiologies
Metabolic acidosis
Hyperglycemia and hyperosmolarity
Nonselective B antagonists
Exercise
Tissue breakdown
Digitalis toxicity
Hyperkalemic familial periodic paralysis
Hyperkalemia - metabolic acidosis
H will enter cell in order to buffer extracellular pH –> K will leave and enter ECF/blood vessels
Hyperkalemia - hyperglycemia/hyperosmolarity
Elevation in serum osmolality = H20 movement from ICF –> ECF = More K in cell –> K will move out of cell
Hyperkalemia - non selective B antagonists
Interfere with K uptake by B receptors
Hyperkalemia - Tissue breakdown
Rhabdomyolysis
Lysis of large tumor burden after chemo
Burns
Hyperkalemia and digitalis
Block Na/K ATPase
Hyperkalemia - renal etiology categories
Renal failure
Volume depletion with decreased distal Na delivery
Functional hypoaldosteronism
Hyperkalemia - renal failure
Able to maintain K with distal flow rate and aldosterone secretion is maintained
Hyperkalemia occurs in patients with decreased flow rate + excess K load/Aldo blocker
Hyperkalemia - decreased distal delivery of Na with volume depletion
Hypovolemia
Effective arterial volume depletion with ECF excess
Heart failure/liver cirrhosis
Hyperkalemia - functional hyoaldosteronisms
Low aldo or resistance to aldo effect
Mineralocorticoid deficiency: primary adrenal insufficiency, hyporeninemic hypoaldosteronism (low renin/aldo)
Tubulointerstitial disease: Sickle cell and urinary tract obstruction -
Distal hyperkalemic RTA - Impaired Na reabsorption reducing K/H secretion
Drug MoA that result in hyperkalemia
Block aldo activity - ACE-I, ARB, Aldo antagonists
Decreased renin release - B blocker, NSAIDs
Bind to ENaC - Amiloride, triamterene Calcineurin inhibitors
Clinical manifestations of hyperkalemia
Severe muscle weakness/paralysis
Cardiac arrhythmias/ECG abnormalities: BBB, AV block, sinus bradycardia, sinus arrest, Vtach/fib
Early - Tall T waves, short QT
Late - prolonged PR/QRS
Hyperkalemia diagnosis - High renin/low aldo
Adrenal insuffieciency
Hyperkalemia diagnosis - Low renin and aldo
Type IV RTA
Diabetic nephropathy
Hyperkalemia diagnosis- normal renin/high aldo
Aldo resistance
Tubuloinsterstitial disease - sickle cell/urinary obstruction
Treatment methods for hyperkalemia
Antagonizing membrane effects of K with Ca
Drive ECF K into cells
Remove excess K from body
Hyperkalemia treatment - Antagonize membrane effects of K with Ca
ONLY for patients with ECG changes or acute rise in serum K
CaCl2
Hyperkalemia induces membrane depolarization and inactivation of Na channels –> Ca antagonizes this effect
Hyperkalemia treatment - Drive K into cells
Insulin + glucose:
Insulin will activate Na/K ATPase, glucose prevents hypoglycemia
B2 agonist: Stimulate Na/K ATPase
Hyperkalemia treatment - K removal - Diuretics
Diuretics: Loop/thizides.
Combine with saline to maintain distal Na delivery and distal flow rate
Hyperkalemia treatment - K removal - Cation exchange resins
Uptake of K in exchange for cation
Hyperkalemia treatment - K removal - dialysis
Warranted when other measures are ineffective
Use when K rises too rapidly
Acute Kidney injury - definition
Abrupt loss of kidney function Retention of urea and other nitrogenous waste products Dysregulation of extracellular volume and electrolytes
AKI general categories
Pre renal
Intrinsic renal
Post renal
Pre renal AKI - major causes
True volume depletion
Decreased effective arterial blood volume
Pre renal AKI - true volume depletion
Loss of Na from ECF
GI losses, hemorrhagic shock, renal losses, cutaneous losses
Pre renal AKI - decreased effective arterial blood volume
Increased ECF but decreased blood volume sensed by baroreceptors –> edematous states: HF, cirrhosis, sepsis
Pre renal AKI GFR
Renal perfusion decreases –> homeostatic mechanisms activated
Afferent arteriolar vasodilation
Efferent arteriolar vasoconstriction
Increased filtration fraction = increased post glomerular oncotic pressure = increased salt/water
Activation of AngII and ADH = Low urine Na and concentrated urine
Pre renal AKI history/chart review
Vomiting Diarrhea GI bleed
HF, liver disease, sepsis
Pre renal AKI physical exam
Orthostatic hypotension, skin tenting, dry mucous membranes
Elevated JVP, edema, hypotension
Pre renal AKI lab workup
BUN:Creatinine >20:1
Urine osmolality > 500
Urine Na <10 Urine Cl <10
Urinalysis: No protein/blood/WBC, no casts no cells
FENa
Measures percent of filtered Na excreted in urine
<1% = patient will be responsive to volume therapy
Intrinsic Renal AKI types
Tubulointerstitial Vascular Glomerular
Acute tubular necrosis - Definition, affected area, risk factors
Most common cause of acute intrinsic kidney injury
Patch necrosis of proximal tubule and TAL: High metabolic activity so very sensitive to changes in renal perfusion
Risk factors: Volume depletion, CKD, NSAIDs, DM
Pathophysiology of acute tubular necrosis
Endothelial/epithelial injury
Intratubular obstruction
Changes in microvascular blood flow
Immunological factors
Tubular cells damaged so cannot absorb salt/water –> increased delivery of salts to macula densa –> afferent vasoconstriction to reduce salt wasting
No TGF = salt wasting and volume depletion = DEATH
Causes of acute tubular necrosis
Ischemia - Low BP, volume depletion, sepsis
Toxin - Radiocontrast media (risk with CKD, DM, hypotension)
Toxins
History/chart review for acute tubular necrosis
Prolonged hypotension in ICU –> ischemia
Radiocontrast exposure
Sepsis (infections)
Drugs - aminoglycosides, amphotericin B
Crush injuries
Acute tubular necrosis lab evaluations
BUN:Creatinine = 10-15:1
Urine Na and Cl >20
FENa >2% (more filtered Na being excreted)
Urine osm <450 May have low grade proteinuria (deficient protein reabsorption in proximal tubule)
Casts and epithelial cells
Acute interstitial nephritis definition and main causes
Inflammatory cell infiltration in kidney interstitium caused by immune response -
Medication -
Autoimmune -
Infection
Acute interstitial nephritis drug causes
NSAIDs Penicillins Cephalosporins Sulfonamides Rifampin Cipro PPI
Acute interstitial nephritis autoimmune and infection causes
Sjogrens Sarcoidosis Legionella, leptospira, CMV
Acute interstitial nephritis clinical presentation
Rash, fever, eosinophilia
Full triad only in ~10% patients
Acute interstitial nephritis lab evaluation
Acute rise in serum creatinine that temporarily correlates with drug administration
Peripheral eosinophilia
Eosinophiluria
Proteinuria
WBC and WBC casts
Acute tubular obstruction
Precipitation of substances in tubules:
Immunoglobulins
Calcium phosphate
Urate
Intratubular crystal precipitations from medications
Volume depletion and acidic urine
Acute tubular obstruction - Cast nephropathy
Occurs in multiple myeloma
Overproduction of immunoglobulin light chains that get filtered into urine, can block tubule
Acute tubular obstruction - Tumor lysis syndrome
Occurs following chemotherapy
Dead tumor cells release chemicals Intracellular release of uric acid, phosphate, potassium –> all levels high in blood
Acute tubular obstruction - phosphorus containing enemas
Bowel preparation for colonoscopy
Acute calcium deposition in tubules with associated interstitial inflammation
Highest risk in patients with underlying CKD
Lab evaluation - tumor lysis syndrome
Elevated serum uric acid, potassium, phosphorus
Lab evaluation - phosphate nephropathy
High phosphorus
Low calcium
Lab evaluation - Cast nephropathy
Elevated free light chains in serum
Vascular intrinsic renal disease causes
Renal atheroembolic disease
Vasculitis
Thrombotic microangiopathies
Renal atheroembolic disease
Occurs in patients with atherosclerotic disease who undergo aorta/large artery manipulation –> plaque breaks off and can occlude multiple small arteries
Low serum complement, eosinophilia, rash
Intrinsic vascular renal disease - vasculitis
Inflammation and necrosis of small arteries
Thrombotic microangiopathies
Endothelial injury –> platelet thrombi occluding small vessels –> ischemia Low platelets, hemolytic anemia -
HUS -
Thrombotic thrombocytopenia purpura -
Malignant HTN
Schistocytes (RBC fragments)
Post renal disease - obstructive uropathy
Obstruction of the flow of urine anywhere from renal pelvis to urethra
Calculi
Anatomic abnormalities (children)
BPH
Urethral stricture
Malignancy
Proteinuria and hematuria = ?
Glomerular disease
Muddy brown casts in sediment review
Acute tubular necrosis
White Blood cell casts in sediment review
Acute interstitial nephritis
Dysmorphic RBC, RBC casts, WBC casts in sediment review
RPGN
AKI complications - uremia
Nausea
Vomiting
Anorexia
Dysguesia
Altered cognition
Pericarditis
AKI electrolyte abnormalities
Hyperkalemia (aminoglycosides and cisplatin = hypokalemia via increased flow)
Metabolic acidosis
ECF volume excess
Renal causes of Secondary HTN
Renovascular HTN
Renal parenchymal HTN
Renovascular HTN
HTN caused by renal artery stenosis
Atherosclerosis (75-90%)
Fibromuscular dysplasia (10-25%)
Renovascular HTN pathophysiology
Reduced renal perfusion –> RAAS activation –> AngII mediated vasoconstriction, ADH, Aldo
Renovascular HTN patient history/physical exam
Onset in 3-5th decade = FMD
>55yo = Atherosclerotic disease
Sudden onset of uncontrolled HTN
Malignant HTN
Physical: Epigastric bruit
Acute unexplained rise in serum creatinine induced
Asymmetric renal size
Renovascular HTN lab evaluation and imaging
Elevated renin and Aldosterone
MRA to asses vessels, contraindicated in high stage CKD
Renovascular HTN treatment - FMD
BP meds Lipid lowering meds
FMD - ACE-I or ARB –> percutaneous transluminal angioplasty if ineffective
Renovascular HTN treatment - atherosclerotic disease
ACE-I or ARB Lipid lowering meds
Anti platelet therapy
Renal Parenchymal HTN
Common feature in acute and CKD
Renal parenchymal HTN - Acute glomerular disease
Volume overload and suppression of RAAS
Renal parenchymal HTN - acute vascular disease
Ischemic activation of RAAS
Renal parenchymal HTN - CKD
Multifactorial pathogenisis
Volume expansion via Na/water retention SNS activation RAAS activation
Secondary hyperPTH Endothelial cell dysfunction
Renal parenchymal HTN - CKD treatment
ACE-I/ARB slow GFR decline
Diuretic for volume removal
CCB if neeed
Primary hyperaldosteronism
Autonomous production of aldosterone
Adrenal adenoma
Bilateral adrenal hyperplasia
Adrenal carcinoma
Triad: HTN, unexplained hypokalemia, metabolic alkalosis
Primary hyperaldosteronism diagnosis
[Plasma aldosterone] : Plasma renin activity Ratio >35-50 and PAC >15 = primary hyperaldosteronism
Discontinue aldo antagonists for accurate results
Primary hyperaldosteronism confirmatory testing
Na loading test: If Aldo still high then primary hyperaldosteronism
Isotonic saline administration: Aldo should fall <5
Primary hyperaldosteronism treatment - unilateral adenoma, BAH
Unilateral adenoma - Laparoscopic surgical removal
BAH - Spironolactone/other aldo antagonists