Renal Intro Flashcards
3 main functions of kidneys?
- Maintain homeostasis
- Excretion of metabolic end products
- Production of enzymes and hormones
Maintain homeostasis?
- Control of fluid (water)
- pH
- Electrolyte balance
- Blood pressure
Excretion of metabolic end products?
- Uric acid, creatinine, urea, drugs
- Urea and excess water from blood excreted into the urine
- *Most important function**
Production of enzymes and hormones?
- Renin (BP)
- EPO (RBC synthesis)
- 1,25-dihydroxycholecalciferol (Calcitriol)
What is glomerular filtration?
Non-discriminent filtration of a protein free plasma from the glomerulus into the Bowmans capsule
What is tubular reabsorption?
Selective movement of substances from the tubular lumen into the peritubular cavities
What is tubular secretion?
Selective movement of non-filtered substances from the peritubular capillaires into the tubular lumen
What do the walls of the glomerulus allow for?
Free flow of water soluble materials into the bowmans capsule
The pressure in the glomerulus is ____ higher than other capillaries
3-4 x higher
Which arteriole is narrower?
Efferent
What does glomerular filtration discriminate on?
Size and charge
What is a normal GFR?
120 ml/min or 105-135 ml/min
What substances are normally filtered?
-Water, electrolytes, glucose, nitrogenous wastes such as urea and creatinine
Which substances are normally excluded from filtration?
- Substances >79 kDA
- Plasma protein bound to substances
How can we evaluate kidney function via lab tests?
- Microalbuminuria
- GFR
- Tubular function tests
- Morphological evaluation (Microscopic, radiologic, biopsy)
What is the GFR
The expression of the quantity of glomerular filtrate formed each minute, in the nephrons of both kidneys, calculated my measuring the clearance of specific substances (inulin or creatinine)
What may influence creatinine measurement? (Serum)
- Antibiotics inhibit secretion
- Tubular secretion overestimates GFR by 10%
- Filtration decreased with age
- Muscle breakdown and diet
When using the MDMR, Which population is GFR decreased?
Females
When using the MDMR, Which population is GFR increased?
Black ethnicity
When is CKD-EPI more accurate than MDRD for estimating GFR?
When GFR >60
When is CKD-EPI just as accurate as MDRD for estimating GFR?
When GFR <60
3 ways to estimate GFR?
1) Crock-fold and Gaut
2) MDRDPreferred
3) CKD-EPI
When will CKD-EPI overestimate eGFR?
In patients with low BMI
When will CKD-EPI underestimate eGFR?
In patients with muscular hypertrophy
How does the CKD-EPI equation work to estimate eGF?
By estimating creatinine clearance
What does the CKD-EPI adjust for?
Age and gender and ethnicity
Which equation does not adjust for weight?Why?
MDRD
-As the final number is based on 1.73 m^2 of body surface area, which is an accepted average adult surface area
What does the MDRD adjust for?
Age, gender and ethnicity
AKI and ARF?
Acute Kidney Injury/ Acute Renal failure
Stages of AKI/ARF?
-Prerenal, Postrenal, Intrarenal
CKD and CRF?
Chronic Kidney Disease, Chronic Renal Failure
CRI?
Chronic renal insufficiency
Key renal disorders
- AKI
- CKD
- Nephrotic syndrome
- Urolithiasis
Potassium restriction in HD
2-3 g/day
Potassium restriction in PD?
No restriction, +/- supplement
Normal serum potassium?
3.5-5.5 mmol/L
3 non-nutritional causes of hyperkalemia?
- GI bleeding
- Acidosis
- Hypoaldosteronism
Which drugs may raise potassium?
- ACEi
- ARBs
- SARS (Selective Aldosterone Receptor Antagonists)
- Potassium-sparing diuretics
- Antifungals
Increases in serum potassium up to ____can be expected when ACEi or ARB initiated with dosage increases
0.5 mmol/L
High potassium foods?
- Fruits (dried, juice, banana, avo)
- Vegetables
- Bran products, chocolate milk, molasses, nuts and seed, potassium salt (sodium replacements)
Low potassium foods?
- Apples, berries, grapes, pineapples
- Some vegetables
- Rice, noodles, pasta, coffee and tea
How are fluid and sodium needs dictated by?
- Needs according to urine output
- Needs according to type of dialysis
If urine output is less that 1L/day, what is fluid and sodium restriction?
1-1.5 L and 2g of sodium
If urine output greater than 1L per day, what is fluid and sodium restriction?
2L and 2-4 g of sodium
Interdialytic weight gains should not exceed ____ of BW in HD
5%
What is important to consider about fluids?
Anything that is liquid at room temperature is considered a fluid, including jello, ice-cream, smoothies etc.
What is a practical suggestion to limit fluid intake?
- But lemon/lime in water to attenuate thirst
- Freeze grapes and snack on them , low in K+ and refreshing
Between dialysis, how will weight change?
Fluid will accumulate (as it cannot be excreted into the urine), which will impact blood pressure. This is expected to occur during both PD and HD
-We must interpret true dry weight with blood pressure, edema
If we have high serum sodium, what is this indicative?
- NOT diet
- Dehydration
When is there no need for fluid or sodium restriction per patients BP?
Pre-dialysis
Restriction of phos in HD and PD?
800-1000 mg/day or <17 mg/kg of IBW
High phosphorus products?
- Dairy products
- Livers, oysters, sardines
- Beans, lentils, chick peas
- Bran, seeds, whole grains
- *Many plant proteins**
What is the goal regarding serum calcium?
Maintain between 8.4-10.12 mg/dl
Calcium intake should not exceed ____
2,000 mg/day
Caution with Phos binders (<1500 mg/day)
When we supplement calcitriol, what does it do? What is the negative impact?
- Will suppress PTH excretion, which may be causing the excessive release of calcium and phosphate from the bones
- However, the calcitriol could increase absorption of calcium and phosphate from the GIT, which would be counterintuitive
Water-soluble vitamin supplementation?
- Increases losses during PD and HD, often due to anorexia and poor intake
- Difficult maintain with diet restriction and impaired synthesis, therefore supplementation can be ideal
Which vitamin is not recommended to be supplemented in PD and HD?
Vitamin A, as serum levels are already elevated
(T/F) Improper use of phosphate binders can increase the uptake of both calcium and phosphate
T, they will absorb on their own if they don’t have the chance to combine in the GI tracts to form the CaPO4 precipitate for excretion
Which organ is responsible for the maintenance of serum magnesium?
Kidney
What should be avoided to avoid excess mg?
-Laxatives
-Enemas
-Phos binders
As these commonly contain magnesium
What is an unsuspected source of magnesium?
Water, check that water is low in Mg (hard water)
How will we supplement for iron?
According to serum markers of ferritin, iron, total iron binding capacity and transferrin saturation
What are patients undergoing maintenance HD know to have decreased levels of?
-Decreased levels of zinc in serum, hair and kidneys
What amount of zinc supplementation may be appropriate in improving dysgeusia and impotence in male HD patients?
15 mg/day
Is there selenium supplementation in dialysis?
Not right now, however plasma levels are low
Are antioxidant supplements recommended?
Not yet
What is the role of carnitine?
Involved in the transfer of FA into the mitochondria for oxiation
-Carnitine is removed by dialysis
Carnitine supplementation?
Evidence insufficient for use, however may improve symptoms in certain patients
What is the most promised application of carnitine tx?
Treatment of EPO-resistant anemia
What is the proposed order of diet calculation?
- Milk
- Meat
- F&V
- Starches according to protein left
- Fat