Chempath: Renal Flashcards
What are the functions of the kidney?
The kidney has various functions - broadly broken down into;
1. Removal of waste
- Homeostatic -> acid/base, fluid, electrolytes
- Hormonal -> renin, EPO, 1a-hydroxylase
What is GFR? what is the normal level?
Glomerular filtration rate is a measure of kidney function and normal rate is 120ml/min
GS = INSULIN CLEARANCE
How is GFT calculated?
Clearance is used to calculate GFR -> volume of plasma that can be completely cleared of a marker substance per unit time
What makes the ideal marker to be used in assessing GFR?
1) not bound to serum proteins
(2) freely filtered at the glomerulus
(3) not secreted or reabsorbed by tubular cells
What is the gold standard for measuring GFR?
INULIN, however, steady state infusion required, therefore only really used in research
What is used in clical practice to measure GFR?
Endogenous marker aka creatinine
However, creatine isn’t a perfect marker –> factors affecting it + secreted into tubules
What factors can affect creatinine levels?
Muscle mass (↑ with more muscle mass)
Age (↓ with age)
Sex (M > F)
Ethnicity (Black > Caucasian > Chinese)
How can you use creatinine as a better marker for GFR?
By using th CKD-EPI equations equation estimates the creatinine clearance, taking into account age, weight and sex
The old equation (cockgroft gault) may overestimate GFR
What is the better way to measure proteinuria?
Spot urine > 24 hour urine collection when measuring proteinuria
How is protein uria measured?
Spot urine + Protein:creatinine ratio (PCR) = quantitative assessment of amount of proteinuria
What can urine dipstick testing show?
pH Specific gravity (SG) - concentration of urine
Blood:
- If –ve - reliably EXCLUDES haematuria
- If +ve - may be due to blood OR myoglobin
Protein
Nitrites - detects bacteria (coliform)
Leucocyte esterase (-ve result = important)
What microscopy is used in renal tests?
Crystals (calcium oxalate, calcium phosphate, uric acid, cystine, struvite)
RBCs (infections, stones, cancers)
WBCs (bacterial or non bacterial inflammation)
Casts (cellular vs acellular)
Bacteria
+ imaging can be used depending on diagnosis suspected
What is the gold standard for renal issues?
Renal biopsy
What is the definition of AKI?
Rapid reduction in kidney function leading to inability to maintain electrolyte, acid base and fluid homeostasis.
NB - THIS IS A MEDICAL EMERGENCY NEEDS REFERRAL TO NEPHROLOGIST FOR DX + TX
What is the criteria for AKI?
Increase in serum creatinine by >26mmol/L within 48 hours OR
Increase in serum creatinine to 1.5x baseline within 7 days OR
Urine output <0.5mL/kg/hr for 6hrs
What are the different stages of AKI?
Stage 1: ↑ in serum Cr by ≥ 26micromol/L OR by 1.5-1.9 x reference serum Cr
Stage 2: ↑ in serum Cr by 2-2.9 x the reference serum Cr
Stage 3: ↑ in serum Cr by ≥ 3 x the reference serum Cr OR ↑ by ≥ 354micromol/L
What is the most common cause of AKI?
pre-renal + ATN (occurs when a pre-renal AKI isnt treated)
What are the different causes of pre-renal AKI?
Hypotension
Oedematous states
Selective renal ischaemia
Drugs affecting glomerular blood flow
What drugs can cause prerenal AKI and how?
NSAIDs- ↓ afferent dilation
ACEi/ ARBs- ↓ efferent constriction
Diuretics- ↓ preload, affects tubular function
Calcineurin inhibitors- ↓ afferent dilation
How can you distinguish between renal and pre-renal AKI?
RESPONDS TO RESTORATION OF CIRCULATING VOLUME (fluid resus) - this is because there is no structural damage unlike in renal (prlonged insult -> ATN)
What causes pre-renal?
Generally = INTRINSIC DAMAGE
Vasculitis
Glomerular disease (GN-itides)
Interstitial disease (analgesics)
Tubular disease
What are some tubular disease causes of renal AKI?
Ischaemia- MOST COMMON (ACN)
Endogenous toxins
MYOGLOBIN!
Immunoglobulins (paraprotein)
Exogenous toxins
Aminoglycosides
Amphotericin
Aciclovir
What is the triad of rhabdomyolysis?
New onset AKI + bruising + dark urine
What causes post-renal AKI?
Obstruction to urine flow
- Intra-renal
- Ureteric (bilateral)
- Prostatic
- Blocked urinary catheter
Severe obstruction -> hydronephrosis
What happens in post-renal AKI depending on length of obstruction?
Immediate relief of obstruction:
- Restores GFR
- NO structural damage
Immediate relief of obstruction:
- Restores GFR
- NO structural damage
What are the indications for emergency dialysis?
Acidosis -> metabolic acidosis Electrolytes -> refractory hyperkalaemia Intoxication -> lithium, aspirin Oedema -> pulmonary oedema Uraemia -> encephalopathy, pericarditis
AEIOU
Which drugs / toxins are dialysable?
I STUMBLED
Isopropyl alcohol (antifreeze)
Salicylates TheophyllineUraemia Methanol Barbiturates Lithium Ethylene glycol Dabigatran
What suggests a pathological response to AKI?
Hallmark of pathological response to AKI = imbalance between scarring and remodelling
Replacement of renal tissue with scar tissue causes chronic kidney disease.
What is CKD?
Abnormalities of kidney function >3 months with implications for health.
GFR < 60 OR 1+ of:
- Albuminuria/proteinuria
- Urine sediment abnormalities (haematuria)
- Electrolyte abnormalities
- Histological abnormality
- Structural abnormalities (on imaging)
- History of kidney transplantation
What are the different causes of CKD?
Diabetes mellitus (commonest) Hypertension (2nd commonest)
Atherosclerotic renal disease
Obstructive or infective uropathy
Glomerular nephrotic and nephritic syndromes
Polycystic kidney disease
What are the different stages of CKD?
G1 : GFR >90 +evidence of kidney damage G2: GFR 60-89 G3: GFR 45-59 G4: GFR 15-29 G5: GFR <15
What consequences of CKD affect the kidneys function to Excrete of waste
Uraemia + death
Uraemic cardiomyo/encephalopathy
What consequences of CKD affect the kidneys function to Acid-base balance
Metabolic acidosis
What consequences of CKD affect the kidneys function to electrolyte balance? ECG changes?
HyperK -> ECG: Tented T waves, broad QRS, flat/ loss of P waves, U waves
What consequences of CKD affect the kidneys function to endocrine function?
Vit D hydroxylation:
Renal bone disease - E.g. Osteomalacia, osteitis fibrosa cystica, mixed osteodystrophy etc.
EPO production:
Anaemia- Normocytic, normochromic
RAAS:
CVD - Calcified vascular plaques
How can problems in CKD due to issues with waste excretion be treated?
Dialysis
How can problems in CKD due to issues with acid-base balance be treated?
PO Sodium bicarbonate
Dialysis
How can problems in CKD due to issues with electrolyte balance be treated?
Calcium gluconate Insulin (+ dextrose) Nebulised salbutamol Calcium resonium Dialysis
How can problems in CKD due to issues with endocrine function be treated?
Vit D:
PO4 limiting control: diet, PO4 binders
Vit D receptor activators: 1a-calcidol
PTH suppression: Cinacalcet
EPO:
Erythropoiesis stimulating agents: EPO alpha, EPO beta, Darbopoietin
RAAS:
Control risk factors, e.g. cholesterol, BP
What does renal replacement therapy involve?
Dialysis - haemodialysis (3x w dialysis centre -av fistula / tesio line) + peritoneal (at home but infection risk - tenckoff catheter)
Transplant = only definitive mx - lasts 25y (needs lifelong immunosupressants)
Indications for renal replacement therapy:
G5 CKD
Uraemia
What are absolute CI for renal transplant?
Active HIV infection
Uncontrolled malignancy
Life expectancy <2yrs due to other cause
DIfferences between AKI and CKD?
AKI:
Abrupt decline in GFR
Potentially reversible
Treatment: precise diagnosis and reversal
CKD:
Longstanding decline in GFR
Irreversible
Treatment: prevention of (1) progression and (2) complications
