16.8 Physiology: The pathophysiology of renal function Flashcards
What is the definition of acute renal failure?
Occurs suddenly, urine flow less than 500mL/day
What is the definition of chronic renal failure?
Occurring gradually over 6 months, GFR
What is a lab test marker of chronic renal failure?
Specific gravity of 1.010
What is loss of GFR invariably accompanied by? (2)
Impairment of tubular processes- reabsorption and secretion
What can GFR loss be due to?
Glomerular or tubular disease
In CRF, what kind of endocrine impairment can occur?
RAS
Vit D activation
Erythropoeitin
What predictably increases in concentration in chronic kidney disease?
How much of it is normally reabsorbed?
Urea (50%)
-but not so reliable, can occur in situations other than CRF
Why can we use creatinine to assess GFR?
Production is constant, it is not reabsorbed
What is the formula for creatinine clearance? What is a normal range?
UV/P=GFR
P: 50-120uM/L
What is daily production (and excretion) of creatinine proportionate to?
Muscle mass
GFR inversely proportional to plasma creatinine concentration
What is the net filtration pressure equal to?
10mm Hg
Which is the most common cause of acute renal failure?
Pre-renal (e.g. shock, haemorrhage, dehydration)
What are some pre-renal causes of ARF? (5) When does it occur?
Systemic perfusion pressure
What causes intrinsic acute renal failure? (3)
Glomerular disease, interstitial nephritis, tubular damage (ischaemia or toxins)
What is the most common cause of renal origin ARF?
What are 3 features?
Acute tubular necrosis
Oliguria
+/- acidosis and increase in K+
What is a cause of post-renal ARF?
Outlet obstruction (ureteric, cystic or urethral; stones, clots, fibrosis, tumours)
What happens to the remaining nephrons in CRF?
What happens to the glomeruli?
Hypertrophy
Hyperfiltration and hypertension–>glomerulosclerosis
When is uremia symptomatic? What can it result in?
What are some common causes of CRF?
Diabetes, high blood pressure, chronic glomerulonephritis, cystic disease
What are the differences in CRF salt and water imbalances for predominantly glomerular or tubular disease?
Glomerular:
Sodium retention and hypertension
Tubular:
Sodium wasting, low BP, impaired ability to concentrate and polyuria
What happens with potassium and pH in CRF?
K+
-Tends to rise, higher in diabetes
pH
-falls (H+ accumulates), failure to excrete non-volatile acids
What happens with calcium and PO4 in CRF?
Rise in PO4, reciprocal reduction in Ca
Why does renal osteodystrohpy occur?
Low Vit D3 (reduced Vit D activation, hyperphosphatemia, renal rickets)
High PTH (excessive osteoclastic activity)
