Chempath: Renal Flashcards by D J

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

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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

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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

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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

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What is the gold standard for measuring GFR?

INULIN, however, steady state infusion required, therefore only really used in research

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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

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What factors can affect creatinine levels?

Muscle mass (↑ with more muscle mass)

Age (↓ with age)

Sex (M > F)

Ethnicity (Black > Caucasian > Chinese)

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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

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What is the better way to measure proteinuria?

Spot urine > 24 hour urine collection when measuring proteinuria

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How is protein uria measured?

Spot urine + Protein:creatinine ratio (PCR) = quantitative assessment of amount of proteinuria

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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)

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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

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What is the gold standard for renal issues?

Renal biopsy

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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

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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

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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

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What is the most common cause of AKI?

pre-renal + ATN (occurs when a pre-renal AKI isnt treated)

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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