Renal function Flashcards
Meaning of Polyuria, Oliguria, Anuria
Polyuria: urine vol. >3000ml
Oliguria: urine vol. <400ml
Anuria: urine vol. <100ml
total body of water in extra- & intracellular fluid
ICF: 2/3
- 10.5L interstitial fluid
ECF: 1/3
- 3.5L plasma
How many
a) times does the kidney filtrate the blood per day?
b) liters of blood does the kidney filter per day?
c) av filtrate produced per min
a) 25-30
b) 180L / day
c) 125ml/min
3 Function of kidney
- regulate fluid & electrolytes
- excrete metabloic wastes
- endocrine function (make Vit. D)
Each nephron filters ~__ µL of urine per day.
100uL
percentage the following is excreted
a) Creatinine
b) Glucose
c) Urea
a) 100% (bc toxic waste made by muscle)
b) Glucose (if <11mM in blood)
c) 50% (form breakdown of AA)
The osmolality (mOsmol/kg) can be approximately calculated from the equation:
osmolality = 2*(Na + K) + Glucose + Urea
how osmolality is affected w/ overhydration & dehydration
Overhydration = dec (bc dilute) = swell Dehydration = inc (bc [ ]trated)
common causes of hyponatremia
- Diuretic therapy = inc Na excretion
- Diabetes mellitus = Na low
- High lipids or protein = psuedohyponatremia
- SIADH (secretion inappropriate ADH)
- Addisons = low aldosteron = inc Na excretion
common causes of hypernatremia in terms of water & salt
- Decreased circulating volume = loss water
- Decreased fluid intake = “ “
- Vomiting/Diarrhoea = “ “
- Ventilation (e.g. ICU) = “ “
- Diabetes insipidus = “ “
- Mineralocorticoid excess (top of normal range) = gain salt
In case of low urine Osmolality. How can you tell if it is due to kidney problem or lack of ADH?
- give desmopressin (ADH analogue = work like ADH)
= If urine [ ]trated = lack ADH
OR
= urine non-[ ]trated = kidney problem
body’s response to hypovolemia & inc osmolality
- Renin secretion by kidneys => activate aldosterone secretion = stimulate eNAC enzyme =inc Na reabs. = water reabs.
- ADH in thypothalumas = water reabsorption
Characteristic of Barter’s syndrome and Describe its affect on ion/waster secretion/excretion
Hi Na in blood bc defect in Na+ transport
Characteristic of Cushing’s syndrome and Describe its affect on ion/waster secretion/excretion
inc Cortisol w/ inc eNAC (enzyme responsible for reabs Na & excrete K)
Characteristic of Liddles syndrome and Describe its affect on ion/waster secretion/excretion
high eNAC => inc Na & dec K & dec H+ intake
[Na] is higher in _CF while [K] is lower in _CF
[Na] is higher in ECF while [K] is lower in ICF
ATPase pump push _x Na [out/in] and take _x K [out/in]
3x Na out
2x K in
hyperkalemia is likely to be caused by
- hypoxia
- acidosis (H+ go in cell & K go out)
- diabetics = low insulin = gluc not fuel pump = Na/K pump works less (coming in < come out)
- tissue injury
psuedohyperkalemia is causes by
- haemolysis
- Leukocytosis
- Phelobotomy
- KEDTA anticoagulant
difference b/w Factitious hyponatremia & pseudohyponatremia
Factitious hyponatremia: water moves out of cells
pseudohyponatremia: water doesn’t move out of cells
- osmolality & tonicity normal
- lab errors due to multiple myeloma bc hyperlipidemia & hi protein = contain Na (trapped)
Factors INCREASING K+ excretion
- Aldosterone
- Increased sodium and water delivery (flow rate): eg such as in diuretic use.
- High K+ diet
- Alkalosis
- Tubular damage (eg acute tubular necrosis)
Factors DECREASING K+ excretion
- Hypoaldosteronism (Eg Addisson’s disease)
- Reduced glomerular filtration rate
- Acidosis
- Reduced fluid delivery to the distal tubule
The following are the major symptoms of acute/chronic renal dysfunction.
- inc urea, inc creatinine, hyperkalaemia, metabolic acidosis
- Urine volume may be high in polyuric phase.
- Urine osmolaity ~ plasma osmolality;
- FENa>1
consequence of renal dysfunction in plasma
- inc K, PO4, Mg
- dec pH
- inc urea, creatinine, uric acid
Proteinuria is the term used when the concentration of albumin exceeds ——— gram per day.
> ~0.3 g/day in urine
Nephrotic syndrome is a group of symptoms including
- protein (Alb) in the urine (> 3.5 g/day)
= low Alb in blood = swelling - high cholesterol levels
- high triglyceride levels [when mild, elevated LDL, and in more severe cases VLDL]
Nephrotic syndrome caused by
immune complexes in glomerulus
why is glomerular filtration rate (GFR) important?
- INDICATOR of functioning renal mass.
- MONITORING progression/resolution of renal disease: acute/chronic.
- PREDICT time left to development of end-stage renal failure, (In chronic renal failure)
- ADJUST DOSE of renally excreted drugs.
Equation for GFR when doing the creatinine clearance test
[plasma creatinine] x 24hr x 60 min
Cockcroft–Gault equation “Body weight – Age - Sex” to give Creatinine clearance (mL/min)
[140 - age(yrs)] x weight(kg)
- 23 (OR 1.04 fem.) x serum creatinine (mmol)
What circumstances would force the use of GFR test (e.g. 24hr creatinine test) instead of eGFR?
- malnutrition or obesity
- disease in skeletal muscle
- extreme body size & age
marker for kidney disease, why & equ it uses
- cyastin made my cells (endogenous)
- more accurate than creatinine in children & elderly
- use Larson equ. = 77.24 x sCystatin C^(–1.2623)
Difference b/wCockcroft-Gault equation & MDRD equation
C-G equ: “Body weight-Age-sex”
MDRD equ: “Ethnicity-age-sex”
___ levels are altered in patients with:
Cancer
__ dysfunction
__ therapy
a) Cyastin
b) Thyroid
c) Glucocorticoid
gold std for measuring glomerulus filtration rate & why
inulin bc completely excreted
a) What is Fractional Excretion of Urinary sodium (FeNa)? b) & what does it mean if FENa >1%
c) FENa <1%
a) The amount of Na filtered by the glomerulus but escapes tubular reabsorption (more sodium is excreted in urine)
b) acute tubular necrosis (intrinsic renal damage)
c) prerenal problem from hypovolemia = dec blood flow
