Urinary Flashcards
Which vertebral level can the kidneys be found?
T11/T12
What is the purpose of the bladder?
Storage of urine that empties periodically via the urethra
What are body fluid compartments?
42L of water split into:
- 28L of intracellular fluid
- 14L of extracellular fluid.
14L of extracellular fluid split into:
- 11L of interstitial fluid
- 3L of intravascular fluid
What is the purpose of the kidney?
- Maintenance of a stable environment to enable function in all parts of the body
- Regulation by controlling the concentrations of key substance in extracellular fluid
- Excretion of waste products
- Endocrine via synthesis of renin, erythropoietin, prostaglandins
- Metabolism though the formation of the active form of vitamin D, catabolism of insulin, PTH and calcitonin
How is kidney function measured?
Glomerular filtration rate
What is the GFR?
Amount of filtrate that is produced from blood flow per unit time
How does advancing age affect the glomerular filtration rate?
- Declines after 30 years of age
- Rate of decline is 6-7mls/min per decade
- Loss of functioning nephrons
- Some compensatory hypertrophy
What is compensatory hypertrophy?
- If the nephron number decreases
- Exisiting nephrons get bigger
- Healthy kidney can also get bigger
- Occurs to much greater extent in childhood
What are the risks associated with compensatory hypertrophy?
- Nephrons have to work harder
- Greater risk of wearing out
- Cortical scarring
What happens to the kidneys and their function in pregnancy?
- GFR increases
- Kidney size increases due to increased fluid volume
- Nephrons number stays the same
What does a decline in GFR show?
- Decline in the number of nephrons
- Decline of GFR within individual nephrons
Overall the kidney function has worsened
A patient arrives with significant kidney damage. Their GFR has been stable but recently has decreased. Upon examination, you notice there is kidney hypertrophy. What does this tell you about the kidney function?
The kidney function has declined slowly so GFR didn’t fall until there was significant kidney damage
Why do we need a surrogate marker?
The actual GFR cannot be measured
What is the formula for clearance?
from the body
C=A/P
C= clearance A= amount of substance eliminated from plasma P= plasma concentration of substrate
What is the formula for Renal clearance?
C=(UxV)/Pa
C= clearance U= amount in urine V= urine flow rate Pa= arterial plasma concentration
What is clearance?
The volume of plasma cleared of a substance per unit time where the substance is denoted as ‘x’.
What are the properties of substances used to measure GFR?
- Produced at a constant rate
- Be freely filtered across the glomerulus
- Not be reabsorbed in the nephron
- Not be secreted into the nephron
Why isn’t inulin used to measure GFR?
- Requires a continuous IV to maintain a steady state
- Requires catheter and timed urine collections
When is 51 Cr-EDTA used clinically?
- In children
- Where indication renal function is required
Approximately 10% lower clearance than inulin. Radioactively labelled and cleared by renal filtration
What is creatinine?
- Endogenous substance
- End product of muscle breakdown
What are the properties of creatine in regards to being an indicator of clearance?
- Produced at a constant rate
- Freely filtered across the membrane
- Not reabsorbed along the nephron
- However it is secreted into the nephron
How is creatinine clearance measured?
- Urine is collected over 24 hours
- The serum creatinine is measured
What are the issues associated with using creatinine as a measurement of clearance?
- Cumbersome and frequently inaccurate
- Overestimates GFR by 10-20% due to creatinine secretion
Which population is creatinine best for in terms of indicators of clearance?
-Pregnant women
What factors lead to increased creatinine measurement?
- Muscle cell break down
- Large muscle bulk
- Black
- Male
- Creatinine supplements
- Certain drugs
What factors lead to reduced serum creatinine?
- Reduced muscle mass
- Old
- Hispanic/Indo-asian
- Female
- Vegetarian
What is the eGFR?
A ‘best guess’ of the GFR which uses models to try and better estimate the GFR from serum creatinine levels. It is not the same as GFR.
What are the variable for the equation for the MDRD eGFR based on?
- Serum creatinine
- Age
- Sex
- Caucasian or Black
When is MDRD eGFR inaccurate?
- People without kidney disease
- Children
- Pregnancy
- Old age
- Other ethnicities
- Amputees
- People with significantly reduced muscle mass
- Patient with higher levels of kidney function
Why is there a risk of patient being labelled as CKD due to the MDRD eGFR?
There is an underestimation of the true GFR when the serum creatinine is close or within normal range
Why is eGFR less accurate with mild kidney disease?
- Reduction in GFR causes increase in blood flow
- Reduced nephron number lead to nephron hypertrophy so no change in GFR
- Reduced filtration of creatinine results in increased serum creatinine and increased secretion into the tubule
What is the sequence of arteries from the renal artery?
Renal artery > Segmental artery > Interlobar artery > Arcuate artery > Interlobular Artery
What are the 2 types of nephrons found in the kidney?
- Cortical nephrons
- Juxtamedullary nephrons
What are the features of the cortical nephrons?
- Short loop of henle which just enters the medulla
- Peritubular capillaries covering most of the nephron
- Rich sympathetic innervation
- High concentration of renin
- In the outer part of the cortex
- Small glomerulus
What are the features of the juxtamedullary nephrons?
- Glomerulus sits juxtaposed to the medullary boundary
- Loop of henle is very long and penetrates deep into medullary tissue
- Vasa recta runs in parallel to the loop of henle.
- Poor sympathetic innervation
- Almost no renin
- Glomerulus is large
What is renal plasma flow and blood flow?
Renal blood flow = About 1.1 L/min
Plasma flow = (1-haemotocrit) X renal blood flow
What is the renal corpuscle and function of the renal corpuscle?
The glomerulus + bowman’s capsule
To produce ultra filtrate of plasma
What produces the filtration barrier in the renal corpuscle?
- Capillary endothelium - permeable. Water, salts, glucose. Filtrate moves between cells
- Visceral layer of Bowman’s capsule - Acellllar gelatinous later of collagen/glycoproteins which is permeable to small proteins. Glyocproteins repel protein movement
- Podocyte layer - Pseudopodia interdigitate froms filtration slits
Which molecules cannot cross the filtration barrier?
Cells and large proteins
What is the effect as a result of the negative charge on the filtration barrier being lost?
-Proteins are more readily filtered and result in a condition called proteinuria
What is the myogenic mechanism?
- Arterial smooth muscle response to decrease and increase in vascular tension
- Contribute to total auto-regulatory mechanism
- Occurs rapidly
- Property predominantly of the preglomerular resistance vessels
Why do we need Autoregulation of GFR?
Feedback mechanism intrinsic to the kidney to keep RBF and GFR constant. Without this a slight change in the blood pressure would cause a significant change in the GFR
Two mechanism
- Myogenic reflex
- Tubuloglomerular feedback
What is the myogenic response to an increase in blood pressure?
-Constriction of the afferent arteriole predomantly or dilation of the efferent arteriole to decrease the blood volume arriving to be filtered. This keep the GFR unchanged
What is the myogenic response to a decrease in blood pressure?
-Dilation of the afferent arteriole predominantly or constriction of the efferent arteriole in order to increase the blood volume arriving to be filtered. This keep the GFR unchanged.
How does the Tubular glomerular feedback mechanism work?
- Links the sodium and chloride concentration at the macula densa with control of renal arteriole resistance (efferent and afferent)
- Acts in response to acute deviation in the delivery of fluid and solutes to the JGA.
- Control the distal solute delivery and hence tubular reabsorption
What is the action of the Tubular goloemrular feedback when the arterial pressure increases?
- Increase in renal plasma flow and increase in GFR leads to increase in NACl
- Macula densa cells detects NaCl via a concentration-dependant salt uptake through the NaKCC co-transporter and responds to changes in NaCL arriving in the distal convoluted tubule
- Juxtaglomerular apparatus is stimulated to release adenosine which constricts the afferent arteriole by stimulating the Alpha 1 receptors. The efferent arteriole is dilated by stimulation of the Alpha 2 receptors
- This reduces the GFR
When is the sympathetic innerveation of the renal vessels most active?
During haemorrhage, ischamia or the fight or flight response.
Vasoconstriction occurs in order to conserve blood volume and can cause a fall in GFR
How does the parasympathetic nervous system act on the blood vessels?
Release of nitrous oxide for endothelial cells and vasodilation
What is the glomerulotubular balance?
It blunts the sodium excretion in response to any GFR changes which occur do occur despite the Myogenic
and TG feedback response.
What is the short term regulation of blood pressure?
Baroreceptor reflex
- Adjust sympathetic and parasympathetic inputs to the heart to alter the cardiac output
- Adjust sympathetic input to peripheral resistance vessels to alter TPR
What are the hormonal responses to low renal perfusion?
- Renin-angiotensin aldosterone system
- Sympathetic nervous system
- Prostaglandins
- ADH
What is the long term regulation of blood pressure?
Neurohormonal resposes to affect salt and water balance
What factors stimulate the renin release?
- Reduced NaCl delivery to the macula densa of distal tube
- Reduced perfusion pressure in the kidney causes the release of renin
- Sympathetic stimulation (B1) of the juxtaglomerular increases release of renin
Where is renin released from?
Juxtagomerular cells of the afferent arteriole in response to reduced perfusion pressure and stimulation by the sympathetic nervous system
What are the direct actions of angiotensin 2 on the kidney?
- Vasoconstriciton of the efferent and to a lesser extent the afferent arteriole
- Enhanced sodium reabsorption at the proximal collecting tubule by stimulation of Na-H(NHE3) exchanger in the apical membrane
- Increase in mesangial matrix
- Increase in mesangial cell proliferation
- Glomerular permeability to proteins
What are some indirect effects of angiotensin 2 on the kidney to control blood pressure?
- Release of aldosterone
- Release of ADH
What are the actions of aldosterone on the kidney?
Acts on principal cells of distal convoluted tubule and collecting ducts to:
- Stimulate Na+ and therefore water reabsorption
- Activates apical Na+ channel and apical K+ channel
- Increases basolateral Na+ extrusion via Na/K/ATPase
What are the actions of the sympathetic nervous system in response to low blood pressure?
- Reduction of the renal blood flow by vasocontrcitin of arterioles and decrease in the GFR
- Activates apical Na/H exchanger and basolateral Na/K ATPase in proximal collecting tubule
- Stimulates renin release from JG cells
What are effects of prostaglandins in the kidney?
- Causes vasodilation of the afferent arteriole
- Enhances renin release
What triggers the release of prostaglandins in the kidney?
- Angiotensin 2
- Noradrenaline
- Anti diuretic hormone
What is the net effect of the interaction of prostaglandins and the RAAS system?
- Systematic vasoconstrinon
- Vasoconstriction of the efferent artriole
- Vasodilation of the afferent arteriole
- The GFR is preserved as a result
What is action of ADH?
- Formation of concentrates urine by retaining water to control the plasma osmolarity. Reabsorption of water is increased at the distal nephron
- Vasoconstriction
What stimulate release of ADH?
- Increase in plasma osmolarity stimulates release of ADH
- Severe hypovolaemia stimulates release of ADH
What are the 2 major actions for atrial natriuretic peptide?
- Causes vasodialtion
2. Inhibits Na+ reabsorption especially in the collecting duct causing natriuresis
What triggers the release of ANP?
Low circulating volume. It acts to support the blood pressure
What is hypertension?
-Persistent increase in blood pressure
What is pressure natriuresis?
Increasing blood pressure gradually resets the kidneys for salt concentrations and water volume and this means the regulatory mechanisms aren’t working as well. It is thought to be one of the causes of hypertension
What is hypertension?
-Persistent increase in blood pressure
What are some causes of secondary hypertension?
- Reno-vascular hypertension
- Coarctation of the aorta
- Primary hyperaldosteronism (Conn’s syndrome)
- Cushing’s syndrome
What are the 2 main types of renovascualr disease?
- Atheroma
- Fibromuscular dysplasia
What causes renovascular disease?
-Renal artery stenosis which is narrowing of the renal artery
Why does renovascular disease lead to hypertension?
- Lack of blood supply to the kidney causes the kidney to sense hypovolaemia in the body
- This means that it triggers changes in order to increase the blood pressure
- This causes hypertension because the mechanism are constantly trying to increase blood pressure even though the blood is normotensive
What happens with unilateral renal artery stenosis?
- One kidney triggers mechanism to increase blood pressure by activating the RAAS system because it senses hypovolaemia
- One kidney works normally and sense the increase in sodium so acts to excrete the sodium. It suppresses the RAAS system.
- Net effect is hypertension with no fluid overload and salt as the kidney that works normally excrete the extra salt and water
What happens with bilateral renal artery stenosis?
- RAAS system is activated
- Kidney does not get rid of the extra salt and water and hypertension persists
- Risk of acute pulmonary oedema
What is coarctation of aorta
Stenosis in the aorta vessels
What is the mechanism that causes hypertension due coarctation of the aorta?
- Less renal blood flow
- Kidney triggers the RAAS system as it senses hypovolaemia wrongly
What is primary hyperaldosteronism and the causes?
Excess secretion of aldosterone
- Adrenal adenoma
- Adrenal hyperplasia
What are the clinical features of primary hyperaldosteronism?
- Hypertension
- Can cause hypokalemia
What is used in the diagnosis of the the primary hyperaldosteronism?
- Aldosterone:renin ratio is high
- Look for adenoma with a CT scan and remove if present
- If no adenoma treat by blockage of aldosterone
What is the effect of excess liquorice on the blood pressure?
- Blocks an enzyme
- Cortisol can’t be converted to cortisone
- Cortisol interacts with mineralocorticoid receptor triggering the same effect as aldosterone
- Blood pressure increase
- Similar mechanism as Cushing’s
What is chronic kidney disease?
Irreversible and sometime progressive loss of renal function over a period of months to years. Renal injury can cause renal tissue to be replaces by extracellular matrix in response to tissue damage
Leads to hypertension and fluid overload (oedema)
What are the indications of nephrotic syndrome?
- Proteinuria
- Hyperalbuminaemia
- Oedema
- High cholesterol
Which ion primarily affects the effective circulating volume?
- Sodium ions
- Water in the extracellular fluid compartment depends on the sodium ion content.
What would be the effect of changing the amount of sodium that is ingested (without kidney action)?
- Amount of water in the extra cellular fluid would change
- Effective circulating volume would also change
- Blood pressure also changes as a result
Why does the kidney Na+ excretory rates have to vary over a wide range?
- The kidney needs to match excretion of sodium to ingestion to remain sodium balance.
- Urinary water excretion can be varied physiologically
What can you do to increase the plasma volume?
-Add an isosmotic solution
Adding water alone affect plasma osmolarity
How can we add or remove an isosmotic solution?
- Movement of osmoles
- Water will follow
What can affect the proximal tubule Na+ reabsorption?
- Changes in osmotic pressure and hydrostatic pressure
- RAAS system can stimulate proximal tubule Na+ reabsorption
What causes pressure natriuresis and pressure diuresis when renal blood pressure increases?
- Increased renal artery blood pressure
- Reduced number of Na-H and reduced Na-K ATPase activity in proximal tubule
- Causes reduction in sodium and water reabsorption in proximal tubule
- Leads to pressure natriuresis and pressure diruresis together in order for the ECF volume to be decrease and diminish the BP rise.
What are the sodium channels in the proximal tubule?
Na-H antiporter
Na-Glucose symporter
Na-AA co-transporter
Na-Pi
What are the sodium channels in the loop of henle?
NaKCC symporter
What are the sodium channels found in the early distal tubule?
NaCl symporter
What are the sodium channels found in the late distal tubule and collecting tubule?
ENaC (epithelial Na channels)
What are the histological features of the proximal tubule?
- Brush border
- Large outside diameter
- Lots of mitochondria (incredibly active)
What are the solutes transported in the 1st segment of the proximal tubule?
-Apical Na-H exchange Co-transport with glucose Co-transport with amino acid or carboxylic acids Co-transprt with phosphate
-Basolateral
3 Na-2K ATPase
NaHCO3- co transporter for acids and bases
- Aquaporin channels
- Chloride concentration increases
What are the solutes transported in the 2nd segment of the proximal tubule?
Basolateral
3Na-2K ATPase
Apical
Na+ is reabsorbed via Na-H exchanger
Paracellular and transcellular transport of Cl-
What is the overview of the function of the proximal collecting tube?
- Highly water permeable so bulk transport of water reabsorption
- Reabsorption is isosmotic with plasma
- Reabsorbs 65% water, 100% glucose and amino acids, 67% of sodium
- Driving force for reabsorption is osmotic gradient established by solute absorption, hydrostatic force in the interstitum, oncotic force in peritubular capillary due to loss of 20% filtrate at glomerulus but cells and proteins left in blood
What are the features of the thin descending limb?
- Lots of aqua porin channels
- No mitochondria
- Loose junctions
- No brush border
- Thin
- Flattened
- Passive in nature
What are the features of the thick segment of the ascending limb?
- Impermeable to water
- Many mitochondria
- No aqua porin
- Lots of active transport for sodium reabsorption
What is the function of the thick and thin descending limb?
- Paracellular reuptake of water due to increased intercellular concentrations of sodium
- Concentrates sodium and chloride ions in the lumen of the descending limb ready for active transport in the ascending
- Highly permeable to water due to AQP (1 channels always open)
- Impermebale to Na
What is the function of the thin ascending limb?
Passive sodium reabsorption due the actions of the descending limb.
Epethelium permits passive reabsorption by paracellular route
What is the function of the thick ascending limb?
- NKCC2 transrptoer that transports sodium, (2)chloride and potassium from lumen to cells
- Na+ ions move into the interstitum due to the action of 3Na-2K-ATPase
- ROMK channels move potassium from the cell into the lumen to allow the NKCC2 channels to work
What is the clinical significance of the thick ascending limb?
Sensitive to hypoxia due to the amount of energy use
Give an overview of the loop of henle reabsorption.
- Descending limb reabsorbs water and not NaCl
- Ascending limb reabsorbs NaCl but not water
- The tubule fluid leaving the loop is hypo-osmotic compared to plasma
Outline features of reabsorption in the distal convoluted tubule
- Hypo-osmotic fluid enters (100 mOsm/Kg)
- Active transport of 5-8% of Na+
- Water permeability is low
- Has 2 regions DCT1 and DCT1
What are the channels present in DCT1?
Apical
-NaCl enters via electro-neutral NCC transporter which is sensitive to thiazides diuretics
Basolateral
-3Na-2K-ATPase
What are the channels present in the distal convoluted tubule 2?
Apical
- Na+ enter via ENaC
- NaCL enters by the NCC
Basolateral
- 3Na-2K-ATPase
- KCC4
Which channels are affected by amiloride diuretics?
ENaC channels
What detects changes in plasma osmolarity?
Hypothalmic osmoreceptors
What are the 2 efferent pathways to regulate plasma osmolarity and their effect?
- ADH: Acts on the kidney to control renal water excretion
- Thirst: Trigger brain for drinking behaviour to cause an effect on the water intake
Where are osmoeceptors found?
- Located in the OVLT of the hypothalamus.
- Leaky endothelium is exposed directly to the systemic circulation to sense the changes in plasma osmolarity
What physiologically inhibits ADH?
-Decreased osmolarity inhibits ADH
What happens to the osmotic and haemodynamic relationship in circulatory collapse?
- Kidney continues to conserve H2O even though this will reduce osmolarity of body fluids
- Volume is more important than osmolarity if volume crashes
Describe the efferent pathway of thirst?
- Stimulated by an increase in fluid osmolarity
- Salt ingestion is the analogue of thirst
- Large deficits in water only partially compensated for in the kidney and ingestion is the ultimate compensation.
- Stop when sufficient fluid has been consumed
What is central diabetes insipidus?
- Plasma ADH levels are too low
- Damage done to the hypothalamus or pituitary gland
- Brain injury
What is nephrogenic diabetes insipidus?
-Acquired insensitivity of the kidney to ADH
How are problems with ADH secretion managed?
- In both water is inadequately reabsorbed so a large quantity of urine is produced
- Managed clinically by ADH injections or by ADH nasal spray
What is SIADH?
Syndrome of inappropriate ADH secretion
- Characterised by excessive release of ADH from posterior pituitary gland or another source
- Dilutional hyponatraemia in which the plasma sodium levels are lowered and total body fluid is increased
What happens to the aqua porin channels when plasma osmolarity decreases?
- No ADH stimulation
- No stimulation of Aqua porin 2 in apical membrane
- AQP3 and 4 on basolateral membrane only of the latter DCT and collecting ducts and act as an exit for water entering AQP2
- Limited water reuptake in latter DCT and collecting duct
- Loss of large amount of hypo osmotic urine
- Diuresis
What happens to the aqua porin channels when plasma osmolarity increases?
- Release of ADH causes the insertion of AQP2 channels into the apical membrane
- Water moves out of the collection duct into hyper osmotic environment if there are AQP in both the apical and the basolateral epithelium of the tubule cells
Which part of the kidney loop is crucial to generate the medullary gradient?
-Thick ascending limb of the loop of henle
What is the maximum osmolaitly at the tip of the Loop of Henle?
1200 mOsm/Kg in medulla
What is counter current multiplication?
- Na+ is actively transported out of the ascending limb of LH
- Concentration increases in the interstitial fluid surrounding the loop of Henle
- Increased concentration in the interstitial fluid achieved by loop of Henle
What is the range for the vertical osmotic gradient in the kidney?
- 300 mOsm/kg at corticomedullary border
- 1200 mOsm/kg in medullary interstitum at papilla
What are the essential mechanisms to maintain the vertical osmotic gradient?
- Active NaCl transport in thick ascending limb
- Recycling of urea (effective osmole)
- Unusual arrangement o blood vessels in medulla descending components in close opposition to ascending components
Why is urea an effective osmole?
- Doesnt cross the membrane easily
- Urea reabsorption from medullary collecting duct
- Cortical collecting duct cells are impermeable to urea
- Movement into interstitum and diffusion back in Loop
- Under the influence of ADH fraction excretion of urea decreasing and urea re-cylcing increases
How does the vasa recta maintain the concentration gradient?
Flow in vasa recta is in the opposite redirection to fluid flow in the tube, the osmotic gradient is maintained. Vasa recta acts as a counter current exchanger.
Vasa recta can actively transport. True/False
False
What happens in the descending limb of the vasa recta?
- Isoosmotic blood in vasa recta enter hyper osmotic medullary region
- Na+,Cl- and urea diffuse into the lumen of vasa recta
- Osmolarity of the blood in vasa recta increases as it reaches tip of hairpin loop
Why is blood flow in the vasa recta slow?
Blood flow is compromised to :
- Deliver nutrients
- Maintain medulaary hyper tonicity
How does the shape of the vasa recta and loop of henle allow for the courter current exchange?
-Both hairpin configurations
What happens in the ascending limb of vasa recta?
- Blood ascending towards cortex will have higher solute content than surround interstitum
- Water moves in from the descending limb of the loop of henle
What is a diuretic?
A substance that promotes a diuresis by increase in renal excretion of water and sodium to reduce ECF volume
When are diuretic used clinically?
Conditions where sodium and water retention cause expansion of ECF volume
What is the effect of diuretics reducing ENaC activity on K+ secretion?
Reduction of K+ secretion
How do Diuretic work? (4 ways)
- Direction action on cell to block Na+ transporters in luminal membrane (Loop diuretic, Thiazide Diuretics, K+ sparing diuretics)
- By antagonising the action of aldosterone
- By modification of filtrate content
- By inhibiting activity of enzyme carbonic anhydrase
How do loop diuretics work?
- Block apical NKCC transporter
- Na and Cl not absorbed so medullary tonicity is less
- This reduces water reabsorption further down the tubule
- Leads to Na+ and water loss
Very potent diuretics
What are the effect of loop diuretics in heart failure?
Used in heart failure for treatment of symptoms
- Diuretic effect
- Vaso and veno dilation to decreased after load/preload
- Reduces symptoms but no effect on reducing mortality
What is given in acute pulmonary oedema?
-IV Furosemide
When are loop diuretics used?
- Heart failure
- Nephrotic syndrome
- Renal failure
- Cirrhosis of liver
- Hyper calcaemia
What are the effect of loop diuretics on calcium absorption?
Blockage of the NKCC channels:
- Impairs calcium reabsorption as lumen positive potential isn’t created by K+ drifting into the lumen
- More calcium is exerted in urine
- Furosemide given together with IV fluids
What are the effects of Thiazide diuretics?
- Secreted into lumen in PCT
- Block Na-Cl transporter in DCT
- Travel downstream to act at DCT
- Increase Na+ loss in urine
- Reduces Ca2+ loss in urine
When are thiazide diuretics used?
-Widely used in hypertension
ineffective in renal failure as less potent compared to loop diuretics
What are the side effects of thiazide diuretics?
-Higher incidence of hypokalaemia
What are the type of K+ sparing diuretics?
Act on late distal tubule and collecting duct
- Inhibitors of ENaC (amiloride)
- Aldosterone antagonists (spironolactone)
What are the mechanism of action for potassium sparing diuretics?
- Reduces ENaC activity directly or indirectly
- Reduce loss of K+
- Both can produce life threatening hyperkalaemia especially if used with ACE inhibitors, K+ supplement or in patients with renal impairment
- Both are mild diuretics affecting only 2% of Na+ reabsorption
What are the non diuretic situations that feature the use of aldosterone antagonists?
- Reduction of mortality in heart failure (used in the long term treatment of heart failure)
- Preferred duct for ascites and oedema in cirrhosis
- Used as additional therapy in hypertension if other treatment aren’t effective
- Treatment of hypertension in Conn’s syndrome
What are ENaC blockers like amiloride used in combination with?
K+ losing diuretics
How can diuretics contribute to hypokalaemia?
- Diuretics may lead to reduced circulatory volume
- Activtion of RAAS
- Increase in Aldosterone secretion
- Increase in Na+ absorption and K+ secretion
- Hypokalaemia