Renal Flashcards
How do the kidneys regulate acid base balance in the body?
1) Regeneration of bicarbonate in the proximal tubules
2) Removal of fixed acid such a sulphate, sulphuric acid from the blood stream
In what part of the nephron would disease be indicated if amino acids were being lost in the urine?
Proximal tubule
The level of what protein is used to measure kidney function?
Creatinine from the break down of muscle
Which 4 drugs can accumulate in kidney disease?
1) Abx
2) Digoxin
3) Opiates
4) Lithium
The kidneys produce eryhtropoeitin in response to what?
Hypoxia
Kidneys secrete the active form of vitamin D but the first stage of producing active vitamin D occurs in what organ?
Liver
Liver secretes 25-OH-D, Kidneys convert that to calcitriol
Low blood calcium stimulates the release of what hormone which stimulates the secretion of Calcitriol from the kidneys?
Parathyroid hormone
How does PTH increase blood calcium?
Causes release of calcitriol from the kidneys
Causes Release of calcium and phosphorus from bone
How does calcitriol released by the kidney increase blood calcium levels?
Causes increased absorption of calcium from the small intestine
Causes release of calcium and phosphorus from bone
Why can phosphorus levels rise in CKD?
Because the kidneys act to increase excretion of phosphorus
In CKD what 3 problems may occur as a result of decreased activation of vitamin D?
1) Secondary hyperparathryoidism
2) Decreased calcium level
3) Bone disease - renal osteodystrophy
What role do the kidneys have in RAAS and how?
Secrete renin which converts angiotensinogen into angiotensin 1
3 signals activate the release if renin from the juxtaglomerular apparatus of the kidney:
1) A drop in perfusion pressure of the afferent arterioles
2) A decrease in the flux of NaCl past the macula densa
3) Activation of sympathetic nerve supply to the afferent and efferent arterioles in the kidney
Why can the haematological disease myeloma lead to CKD?
Production of an immunoglobulin which is deposited in the kidneys
Why can cardiac failure result in CKD?
Decreased blood supply to the kidneys
After what age do you begin to get a gradual decline in kidney function?
40 years
What percentage of cardiac output is received by the kidneys (and how much is this per minute)?
25%, 1.2L/min
In urinalysis what would nitrites and leucocytes in the urine indicate?
Infection
In urinalysis what is glucose in the urine likely to indicate?
Diabetes
In blood tests to investigate kidney function what 6 substances would you measure the levels of?
1) Sodium 133-146 mmol/L
2) Postassium 3.5-5.3 mmol/L
3) Urea 2.5-7.5 mmol/L
4) Creatinine 64-104 umol/L
(Above 4 are part of urea and electrolytes)
5) Bicarbonate 22-29 mmol/L
6) Chloride 95-108 mmol/L
What 6 things are you likely to be testing for in urinalysis to investigate kidney disease?
1) Haematuria
2) pH varies
3) Proteinuria
4) Glucose
5) Nitrites
6) Leucocytes
When measuring urine what would you measure the protein in reference to?
Protein/Creatinine ratio ( 0.1-13 mg/mmol/L)
When would a midstream urine sample be required?
If infection was suspected
What 4 radiological investigations could be carried out on the kidneys and what would each identify?
1) Abdominal x-ray - may identify calcification
2) Renal tract ultrasound - Assesses the size of the kidneys and bladder and identifies any obstruction
3) CT KUB (Kidneys, ureter, bladder) - Calcification use with iodinated contrast
4) Magnetic resonance angiography (MRA) - Blood supply
What may a kidney biopsy be required to diagnose and under what guidance is it performed?
Required to diagnose AKI
Performed under ultrasound guidance
What is the length of a healthy kidney?
10-11 cm
What is a nephron made up of?
Glomerulus surrounded by Bowman’s capsule
Renal tubule
Interstitium
Enveloped by a vascular network
Where do 80% of the kidney glomeruli lie?
In the cortex
How much urine does a healthy person produce in one day?
1.5-2 L
What are the 4 parts of the renal tubule?
Proximal convoluted tubule
Distal convoluted tubule
Loop of Henle
Collecting ducts
What pressures contribute to movement of filtrate out of the glomerulus and into the glomerulus?
Out - hydrostatic pressure of capillary
In - Plasma protein oncotic pressure
What is another name for an epithelial foot process?
Podocytes
What is pyelonephritis?
Pus in the kidney
What is reflux nephropathy and why does it occur and what can it lead to?
Occurs in childhood when the kidneys are growing
Have an incompetent vesicoureteric junction
On voiding urine passes back up ureter then back into bladder, there is risk of stagnation and infection
On voiding infected urine passes back up to the kidneys - pyelonephritis - injury and scarring
Can lead to CKD
What is the clinical presentation of reflux nephropathy and what is the treatment?
Child with fever of unknown origin
Fails to meet developmental mile stones - bedwetting at 5-7 years
Family history of reflux nephropathy
Treatment is prophylactic Abx
If haematuria was found in a patient over 45 what would you suspect and who would you refer them to?
Suspect a lesion somewhere in the renal tract
Refer to a urologist
If haematuria was found in a patient under 45 what would you suspect and who would you refer them to?
Suspect Glomerulonephritis
refer to the renal physician
What is glomerulonephritis?
Inflammation in the glomerulus
What 4 things make up nephrotic syndrome?
1) Proteinuria
2) Hypoalbuminaemia
3) Oedema
4) Hypercholesterolaemia
What happens in nephrotic syndrome to the glomerulus?
Injury to the foot processes of the nephron
What 4 things can cause injury to the foot processes of the nephron and therefore nephrotic syndrome?
1) Minimal change disease (children)
2) Membranous nephropathy
3) Focal segmented glomerulosclerosis
4) Amyloid (caused by myeloma, malignancy of the bone marrow)
What is the most important way by which foot processes in health prevent the filtration of albumin from the blood?
Repel them by being negatively charged
What 4 important substances are freely filtered into the nephron?
1) Electrolytes
2) Sugars
3) Amino acids
4) Vitamins
What 3 things affect the filtration of a molecule across the glomerular basement membrane?
1) Molecular weight
2) Surface charge - glomerular basement membrane is negatively charged
3) Hydrostatic pressure in the afferent arteriole
What is a normal glomerular filtration rate?
100-120mls/min/1.73m2
What does accurate glomerular filtration rate measurement require the injection of and when is this carried out?
The injection of a radioactive tracer such as Technetium Tc99
Performed rarely except in the case of live kidney donors to determine accurate kidney function prior to donation
What is performed as an alternative to glomerular filtration rate but is not used often clinically? Is this more or less accurate?
Creatinine clearance
Not as accurate
Requires a blood test and 24 hour urine collection
What is the routinely used measurement of kidney function?
Serum creatinine
Simple blood test
Normal range is 64-104 umol/L
What 4 things are required to calculate eGFR?
1) Serum creatinine
2) Age
3) Sex
4) Ethnicity
What does eGFR correlate with?
Percentage kidney function
At what eGFR do patients need to commence dialysis?
At what level is plasma osmolality maintained at to maintain normal cellular function?
285 mOsm/L
What is a normal urine osmolality?
50-1400mOsm/L
What mechanism is responsible for the kidneys ability to produce concentrated urine during periods of decreased fluid intake?
Counter current mechanism
Establishes a high conc gradient in the medulla and enables water resorption in the proximal tubule and the collecting duct
What are the 3 methods of insensible loss of fluid?
1) Sweat
2) respiration
3) Faeces
How does antidiuretic hormone increase fluid retention?
Inserts channels into the medullary collecting duct to allow reabsorption of water
What 2 things can uraemia (accumulation of waste products) lead to?
1) Pericarditis
2) Encephalopathy
Where is the Na+/K+ATPase in the nephron?
In all sections of the nephron
Located on the apical (blood) side
Pumps 3Na+ out for 2 K+ in
What percentage of glomerular filtrate is recovered at the proximal convoluted tubule?
70% (water and electrolytes)
At what point in the nephron is bicarbonate regenerated?
Proximal convoluted tubule
What channels are present in the proximal convoluted tubule to enable reabsorption of large amounts of water?
Aquaporins
What enzyme is bicarbonate regeneration in the proximal convoluted tubule dependent on and what drug inhibits this enzyme?
Carbonic anhydrase
Inhibited by acetazolamide
Why do you get acidaemia in kidney disease and how may you compensate for this?
Failure to regenerate bicarbonate
Respiratory compensation - tachypnoea to blow off CO2
How does carbonic anhydrase help in the regeneration of bicarbonate?
For bicarbonate to pass into the podocyte from the filtrate it must be neutral
In filtrate converted to H20 and CO2 so it can pass through the podocyte membrane
When in the cell carbonic anhydrase converts CO2 + H2O back to bicarbonate
How is Na+, K+, Cl- and H2O absorbed in the ascending limb of Henle?
Through a K+,2Cl-, Na+ co transporter using the Na+ gradient set up by Na+/K+ATPase and water then follows
Where is the site of action of loop diuretics such a furosemide, what could this lead to the development of?
Act on the K+,2Cl-,Na+ co transporter in the ascending limb of Henle
Could lead to the development of hyponutraemia
What is reabsorbed at the cortical collecting duct and how?
Na+ (with Cl-, H20) is reabsorbed in exchange for K+
This is controlled by aldosterone
How do potassium sparing diuretics such as spironalactone work and what do they increase the riskl of?
Aldosterone antagonist
Block the absorption of Na+ in exchange for K+
High risk of hyperkalaemia
What is diabetes insipidus and what can it cause?
Central failure to secrete ADH or a peripheral resistance to ADH Large volume of water output - polyuria Hypovolaemia Hyponatraemia
What 2 things can hyponatraemia lead to?
Confusion and fits
What are the 3 types of AKI?
Pre renal AKI, Intrinsic AKI, Post renal AKI
Over what time period would a reduction in kidney function be considered AKI rather than CKD?
Abrupt reduction in kidney function occurring over hours to weeks
With a SCr increase of >26umol/L or SCr increase >1.5 to 1.9 fold from baseline what stage AKI is this?
Stage 1
With a SCr increase of >3 fold from baseline or >354 umol/L what stage AKI would this be?
Stage 3
With a SCr increase of >2-2.9 fold from baseline what stage kidney disease would this be?
Stage 2
If a patient commenced on renal replacement therapy what stage AKI would this be?
Stage 3
If a patient produced 6 consecutive hours what stage kidney disease would this be considered to be?
Stage 1
If a patient produced 12 hours what stage kidney disease would this be?
Stage 2
If a patient produced 24 hours or was anuric for 12 hours what stage kidney disease would this be considered to be?
Stage 3
What does pre renal AKI refer to?
AKI due to inadequate blood flow to perfuse the kidneys
What are the causes of pre renal AKI? 5
1) Haemorrhage
2) Severe sepsis (vasodilation)
3) Vomiting and diarrhoea
4) Over diuresis with diuretics
5) Burns (excessive fluid loss through the skin)
What does intrinsic AKI refer to?
Intrinsic renal disease where there is structural damage to the renal tissue (glomeruli/tubules/interstitium) - most intrinsic AKI cause blood and our protein to leak out through the kidney which can be detected using a urine dipstick
What are some causes of intrinsic AKI? 5
1) Nephrotoxic medication
2) Interstitial nephritis
3) Gomerulonephritis
4) Vasculitis
5) Tubulo nephritis
Name 4 nephrotoxic drugs/ substances?
1) Gentamicin
2) Contrast media
3) NSAIDs
4) ACE-I
What does post renal AKI refer to?
Post renal AKI is caused by obstruction to the renal tract, this can be anywhere from the renal pelvis to the urethra
What 8 things could cause post renal AKI?
1) Retroperitoneal fibrosis
2) Renal stone disease
3) Bladder carcinoma
4) Prostatic enlargement
5) Cervical carcinoma
6) Intra Abdominal hypertension
7) Urethral stricture
8) Obstructed urinary catheter
What is hydronephrosis?
Large kidneys on ultrasound