Renal Failure means
reduced GFR (<100ml/min) This can be 'Acute Kidney injury' or 'Chronic Kidney Disease'
How do you know the patient has renal failure?
Mainly done through Blood tests, often no specific symptoms, -Creatinine (from muscles) -Urea
Plasma urea is?
-Main excretory product for waste Nitrogen -~35 g/day formed in liver from aa -Main solute in urinw
What does the amount of formed urea depend on?
1) Dietary protein intake 2) Protein breakdown 3) Bleeding into GIT
Whats the renal handling of urea
-Freely filtered, with a variable fraction reabsorbed -This fraction increases when flow-rate is slow (eg; dehydrated patient) Excretion rate depends on GFR
How does urea change with renal failure and how do we use this change clinically?
Plasma urea rises in renal failure. We can test levels as a rough index of glomerular function (not as good as creatinine as there are so many other variables; protein, hydration, GI bleed etc)
______ rises more then ______ in dehydration
Urea rises more then creatinine in dehydrationn
-Derived from creatine in muscle, no function = WASTE PRODUCT -Rate of production proportional to muscle mass!!!
As creatinine is freely filtered and no tubular reabs./secretion so...
Creatinine clearance rate is proportional to GFR, plasma creatinine rises as GFR falls
How can you get a falsely elevated creatinine?
1. Protein intake 2. Muscle Mass also... 3. Fish/meat meal can cause a rise of 10-40umol/L (as cr. formation occurs in food especially during cooking) This can give a falsely low GFR (blood sample should be take +12hr after meal)
Estimated GFR: via plasma Creatinine (used as other tests are too impractical). Via calculators Done on the basis that it describes the amount if muscle waste product produced, and how well the kidneys get rid of this!!
Factors in eGFR
-Weight (muscle or fat?) -Age -Gender These are done on population norms.
Limitations of eGFR
if muscle mass is unusually high or low (amputees, muscle wasting, body builders) If patients don't have a steady-state creatinine.
Acute Kidney Injury
-Sudden rapid reduction in GFR (days/weeks) -Usually reversible -70% due to non-renal causes (pre-renal, renal, post-renal)
Pre-renal AKI. What is it and what causes it?
Reduction in renal blood flow leading to a reduction in GFR. Due to low BP: -Dehydration, shock, haemorrage, cardiogenic shock, severe bilat. renal art. stenosis
How do we diagnose pre-renal AKI?
1. History: reasons for low BP: hydration, bleeding, infection, chest pain 2. Check urine output: often oliguric <1L/day 3. Blood test: creatinine, high K+, high phosphate, low Ca2+
Treatment for pre-renal AKI. Outcomes??
Fix the underlying problem: eg; rehydrate, treat bleed, fix heart, ABs etc Outcomes: 1) Patient gets better 2) Acute Tubular Necrosis (renal)
80% Acute Tubular Necrosis:
-Mainly due to pre-renal (also drugs and toxins)
-Oliguria and renal failure even after underlying cause is fixed
ATN blood tests will show
-High creatinine -Low urine output (oliguria) -High Potassium
Treatment of renal AKI
Maintain normal BP and treat underlying issue. If it continues to worsen do dialysis ~<10ml/min GFR (NOT TREATMENT JUST KEEPS YOU ALIVE)
Recovery stats of renal AKI
95% Pulyuric phase in Recovery: -tubules can't concentrate -upto 20L urine.day -Need IV fluids to compensate
Rapidly Progressive Glomerulinephritis (RPGN)
-Glomerular disease -Blood and/or protein in urine
Post-renal causes and best way to disagnose
Anything that BLOCKS/SQUASHES -Kidney stones -Tumour -Prostate hypertrophy -Urinary retention Ultrasound very useful!!
Chronic Kidney disease. What would blood tests show?
-Over months/years -Gradual decline in kidney function -IRREVERSIBLE -Elevated creatinine, urea (normal urine output)
Stages of Chronic Kidney Disease and the consequences associated
Causes of CKD. How does it occur?
Gradual increase in creatinine due to underlying disease → scarring of glomeruli and interstitium.
Ureamia: symptoms of kidney Failure
- cold intolerance
Patient Symptoms(feelings)/signs of CKD
Nothing till later stages.
Then ureamai and hypertensive
maybe also oedema, raised JVP
How do you diagnose CKD?
**Haemoglobin (differentiating test): Low and takes ~120 to show
Bone disease and CKD
Kidneys are required to produce the active form of Vit D. If not functioning → bone disease
High serum Phosphate and CKD
Unable to excrete phosphate from preserved food.
Can lead to parathyroid hormone syrdrome