Physiology 4 Flashcards
What is acute renal failure?
Occurring suddenly eg one or several days.
Stop urinating for a period of 24 hours
Is ARF reversible?
ARF is often reversible The longer it lasts…less likely is recovery
What is consistent about chronic renal failure?
It always has the same specific gravity of plasma
What is CRF?
A reduction in GFR - it is considered significant it is less than 50ml/min =
Is the degree of tubular impairment fixed or rlative?
The degree of tubular impairment relative to filtration impairment is highly variable…… from “glomerular” disease to “tubular” disease
what happens when there is a loss of GFR?
Loss of GFR is invariably accompanied by impairment in tubular processes; reabsorption and secretion
What are the most important endocrine dysfunction which occurs in renal failure?
RAS
Vit D
Erythropoeitin
Is urea a good guide to GFR?
No its a poor guide
How much urea is absorbed?
50% - variable
Where does urea come from?
Protein
When are urea levels up?
Elevated in numerous situations other than CRF! Eg catabolic states, steroid Rx
When are urea levels down?
Malnutrition
Liver disease
How is GFR measured?
Creatinine Clearance = UV/P = GFR
Why is creatinine used as a measure of GFR?
1 Creatinine production is constant
2 Filtered, but 15% bound to plasma proteins (underestimates GFR)
3 Not reabsorbed
4 Small amount of secretion (overestimates GFR)
5 (2) and (4) tend to cancel out
What are the normal creatinine levels?
50-120 µM/L
Why is a baseline creatinine important?
It should stay the same, if it rises then GFR is falling
What happens when nephrons are destroyed?
The remaining nephrons tend to filter more. This tends to worsen the failure (i.e. it puts more pressure on the remaining nephrons)
What are the types of acute renal failure?
- Pre-renal
- Renal
- Post-renal
What causes pre-renal ARF?
If the MAP drops far enough the GFR will drop and urine output will be insufficient.
What is olguria?
Is the low output of urine
What is anuria?
No urine output
What is rhabdomyolysis?
Leads to leakage of enough products into the urine which were not present
What are the specific causes of pre-renal ARF?
Shock
Sepsis
Haemolysis Rhabdomyolysis
Nephrotoxic drugs
What is the most common nephrotoxic drug?
Gentomycin
What is acute tubular nephritis?
ARF not due to volume depletion
What Intrinsic acute renal failure
Glomerular disease
Interstitial nephritis (Tubulo-interstitial)
Tubular damage
What are the specific causes of tubular damage?
Ischemia
Toxins
What are the specific causes of interstitial nephritis?
Inflammatory reaction, often drug-related
What is the most common cause of ARF?
Acute tubular necrosis
What is the major concern of someone with Acute tubular necrosis?
acidosis and ↑K+
What is post-renal acute renal failure?
Outlet Obstruction
– Ureteric, cystic or urethral
– stones, clots, fibrosis, tumors
What is chronic renal failure?
Irreversible loss of renal function • Reduction in functional renal mass • Develops over months to years (highly variable rates of decline)
What is another name for chronic renal failure?
uraemia
What happens to nephrons in CRF?
Remaining nephrons hypertrophy
Glomerular hyperfiltration
– loss of functional reserve
– glomerular hypertension
– further damage and glomerulosclerosis
What happens to the fluid in CRF?
The leaves the nephron largely unchanged
What can happen to people with CRF?
Are susceptible to both dehydration and hypertension if their water and salt intake adjusts
What are the symptoms of uremia?
– Fatigue
– Loss of appetite
– Skin pigmentation (lemon)
What causes skin pigmentation?
Crystallisation of urea on the skin surface
What are the causes of CRF?
- Diabetes
- High blood pressure
- Chronic glomerulonephritis
- Cystic disease (poly-cystic kidney disease)
What is uremia?
Accumulation of “uremic” toxins
• Mostly urea
When is uremia symptomatic?
Symptomatic with less than 30% of normal renal function
What are the salt and water imbalances observed in CRF predominantly of the glomerulus?
Sodium retention and hypertension
What are the salt and water imbalances observed in CRF predominantly of the tubules?
– Sodium wasting and low BP
– Impaired concentrating ability & polyuria
What happens to K in CRF?
Tends to rise, esp late-stage (not as fast as ARF)
– Higher in diabetes
What happens to pH in CRF?
falls i.e. H+ accumulates; failure to excrete non-volatile acids • Produced at high rate in normal metabolism • Excretion requires high GFR • reduced ammonia production • low [HCO3-]
What happens to phosphate when GFR falls?
Reduced phosphate excretion
Tubular capacity to reabsorb stays the same concentration secreted reduced which results in a slow rise in [PO4]
Reciprocal reduction in [Ca]
How is phosphate excreted?
Sodium and Phosphate co-transporter
What does [PO4] signal?
Parathyroid —
What happens when there is low vit D?
Reduced renal mass and Vit D activation
– Hyperphosphatemia
– Renal “rickets”: osteomalacia with fractures and subperiosteal resorption
What causes secondary hyperparathyriodism?
Excessive secretion of parathyroid hormone (PTH) by the parathyroid glands in response to hypocalcemia
What affect does 2nd degree have on bone?
hyperparathyroidis (excessive osteoclastic activity)
What is osteomalacia?
Osteomalacia refers to a softening of your bones, often caused by a vitamin D deficiency
What are the symptoms of uremia?
Fatigue
Loss of appetite
Skin pigmentation (lemon)
What are some common causes of CRF?
- Diabetes
- High blood pressure
- Chronic glomerulonephritis
- Cystic disease
