Post midterm content

renal onwards

what are the three kidney functions?

excretory, metabolic, endocrine

what is a nephron, how does it work?

• functional unit of the kidney responsible for filtering blood

• filtration: takes stuff out of blood

• Reabsorption: put useful stuff back into blood

• secretion: waste from blood goes out in the urine

what is the glomerulus, how does it work?

• blood capillaries at the star of the nephron, that helps the kidney to filter

• two blood vessels connect to it

  • afferent arteriole: brings blood into the glomerulus (arrive)

  • efferent arteriole: brings blood out of the glomerulus (exit)

whats the proximal tubule, how does it work?

• takes useful substances back into the blood

• things that reabsorbed include:

  • glucose

  • amino acids

  • Na+

  • water

  • phosphate

• it can also get rid of extra substances by moving them from the blood into the tubule:

  • H+

  • NH3

  • organic acids and bases

  • certain drugs (penicillin)

what’s the loop of henle, how does it work?

• main job is to control how concentrated or diluted your urine becomes

• descending limb (water leaves)

  • water moves out of the tubule

  • the surrounding area is salty, so water gets pulled out

  • water goes back into the blood

• ascending limb (salt leaves, not water)

  • Na, K, Cl leave the tubule

  • water does not follow

what is the distal tubule, how does it work?

• tube after the loop of henle

• helps regulate Na, K, H, Cl

• adjusts amounts of sats and acids in your body

what is the collecting duct, how does it work?

• where fluid from several nephrons comes together

• decide how much water your body should keep

where does urine go?

• collecting duct → urine leaves the nephron

• ureter → carries urine to the bladder

• Bladder → stores urine

• urethra → urine exits your body

what are the excretory functions of the kidneys?

• removing waste products

• components of the blood in excess or that are toxic are removed

• excretion is the net results of filtration, reabsorption and secretion

explain the diagram on pg 179 of coursepack (filtration, reabsorption, secretion)

• blood enters afferent arteriole

• glomerulus filters water and solutes which et excreted into urine

• proximal tubule knows how much stuff we need in our bodies and will increase or decrease transporters (either excrete into pee or reabsorb into blood)

• blood cells and proteins leave the efferent arteriole and go to the rest of the body

• 
  

what is ultrafiltrate?

when water and small solutes go from the capillaries of the glomerulus into the bowman’s capsule

• small solutes = glucose, electrolytes, waste products are filtered out of the blood

• large particles like. blood cells and proteins are left in the blood

why is reabsorption beneficial in terms of the nephron?

we still want some of the good stuff that is in the ultra filtrate, resorption is the movement of the good stuff back into the blood

• we sometimes want glucose and electrolytes

• waste products and excess electrolytes stay in the ultra filtrate

what happens to ultra filtrate AFTER the final filtration process?

it gets secreted in the urine

what can happen if the kidney’s excretory functions aren’t working properly?

• edema

• excess toxins circulating

• getting rid of too much good stuff

• glucose and protein in urine

• too many electrolytes

• high BP

what are the main metabolic functions of the kidneys?

balancing electrolytes and pH

how is acid-base balanced in the body?

• excretion of excess H+

• generation of bicarbonate (HCO3)

what is metabolic acidosis

• blood pH becomes acidic (drops below 7)

• can cause stupor, coma, seizures, arrhythmias, death

• kidney can make HCO3 or get rid of H+

• lungs can partially compensate by breathing out more CO2 (bc CO2 is acidic)

what is metabolic alkalosis

• blood pH becomes basic (above 7) due to too much bicarbonate (HCO3) production

• can cause confusion, muscle twitching, nausea, coma, difficulty breathing, death

what to the kidney synthesize and secrete (endocrine functions)

• renin

• EPO

• 1,25-dihydroxyvitamin D

what does the renin-angiotensin system do?

resorption (reabsorption) of Na and water

• this increases blood volume and blood pressure

what does erythropoietin (EPO) do?

makes red blood cells

what happens with the activation of vitamin D

activates to 1,25-dihydroxyvitamin D

what are some possible nutrition implications of altered endocrine function of the kidneys?

• anemia

• osteoporosis (lack of vit D)

• increased renin production (high BP)

what is GFR (glomerulus filtration rate)?

• volume of blood filtered by the glomerulus per minute

• standard marker of kidney/renal function

• normal filtration is 132-200L/d

  • Male 110-150 mL/min

  • female 103-132 mL/min

what are creatinine and BUN?

• creatinine is a product of muscle breakdown

• urea is a product of protein breakdown

• in a healthy kidney, both are excreted in the urine

what do GFR, creatinine, and BUN levels tells us?

as GFR decreases, serum creatinine and urea increase

• elevated levels can occur in muscle loss, low protein intake

what happens as GFR goes down and BUN/creatinine go up?

1. decreased renal reserve

2. renal insufficiency (not on dialysis, almost no symptoms, gradually loosing function)

3. renal failure (some uremia symptoms)

4. dialysis, transport, or death

what are the primary causes of CFR

diebetes and hypertension

how does diabetes lead to CFR?

• high blood glucose causes damage to fine capillaries in the glomerulus

  • BG attaches to proteins in blood vessels and damages them

• thickening of the vessel cell membranes lead to loss of function

  • glomerulus → thicker walls → fluid can’t move thru the nephrons as well

how does hypertension cause CFR?

high pressure damages fine capillaries

what is glomerulonephritis?

• also can cause CRF

• inflammation of glomerulus/nephron

• infection

whats the clinical definition and pathophysiology of CFR?

• clinical definition: low GFR, decreased creatinine clearance, high blood creatinine

• 1 in 10 Canadians has kidney disease

• CFR is associated with marked reduction in excretory, metabolic, and endocrine functions of the kidney

• marked by progression

• develops over months to years

what is polyuria, oligouria, and anuria?

• polyuria: increased urination

• oligouria: decreased urination

• absence of urine

what even is urea

byproduct of amino acids being metabolized

what happens when the excretory functions of the kidney begin to fail?

increase of toxins in the blood

what is uremia? why is it bad?

• uremia is the buildup of urea (build up of protein in the blood)

• can cause enlarged heart (cardiomegaly)

• also

  • tiredness

  • nausea

  • high BP

  • anorexia

  • itchy skin

  • numbness/cramps in legs “restless legs”

• excretory dysfunction

what is nephrotic syndrome?

• happens when there is excretory dysfunction

• it is categorized by albumin in the urine

  • this causes damage to the glomerulus which leads to leaky glomeruli and albuminuria

• causes PEM, low serum albumin, edema

what is volume expansion?

• happens when there is metabolic dysfunction

• Na is retained, leading to water retention, edema, and high BP

• Distal convoluted tubule damage increases Na retention

• Loss of albumin leads to edema

what is hyperkalemia?

• metabolic dysfunction

• high potassium in blood

• impaired filtration of extra K

• Damage to tubule cells results in high K

• metabolic acidosis shifts K out of cells to help counteract acidosis

• some other causes

  • catabolism

  • hemorrhage

  • constipation (causes higher absorption)

  • medication

• results in muscle weakness, cardiac irritability, cardiac arrest

how does phosphorus play a role in bone health for pts with CFR?

• hyperphosphatemia leads to hyperparathyroidism and bone problems because:

  • the kidneys fail to get rid of extra phosphorus

  • calcium then binds to this extra phosphorus, forming CaPO4, which decreases blood calcium levels

  • the body tries to increase blood calcium levels but:

    • it can’t stop excreting Ca in the urine, can’t make vitamin D to help absorb more Ca

    • Ca releasing from the bones also releases phosphorus

• ppl with kidney disease should take Vitamin D supplements

explain bone and endocrine dysfunction relating to the kidneys

• involves Vit D, renin, EPO

• decreased GFR will increase renin and blood volume

  • the kidneys release renin when they sense the glomeruli are not being perfused

• decreased EPO leads to decreased production of RBCs and ultimately anemia

  • give EPO as a supplement to renal pts

which hormones are recommended to be replaced as much as possible for the medical management of renal disease

• EPO

• vitamin D

what are some common tests in renal disease management

• body wt

• BP

• Markers of renal function

  • GFR

  • creatinine clearance

• electrolytes

• measures of acid base balance

• assessment of anemia

• assessment of hormone levels

  • Vit D, EPO, PHT

• urinalysis

  • volume

  • pH, glucose, urea, electrolytes

  • albumin excretion

• BIA

what are the main important meds used in the management of renal disease?

• BP meds

  • renin system modulators

  • angiotensin converting enzyme (ACE inhibitors)

• diuretics

  • thiazides

  • loop

  • K sparing

• SGLT2 inhibitors

• Hormones

  • calcitriol

  • EPO

• K and P binders

  • CaCO3 (K binder)

  • Na polystyrene sulfonate (kayexalate) (K binder)

• anticoagulants

  • heparin

  • warfarin

what is dialysis, why do we do it?

• artificial kidney

• removes excessive toxic by-products of metabolism from the blood

• indications:

  • low GFR

  • nasty side effects 😉

what are the two main components of dialysis?

• dialysate

  • fluid with electrolytes and solutes of a very specific concentration, does not come in contact with the blood

• semipermeable membrane

  • allows movement between blood and dialysate

how does dialysis create a concentration gradient?

• waste products move out of the blood and into the dialysate

• nutrients move from dialysate to blood

• things want to move from high concentration to low concentration, so the dialysate needs to have a specific concentration

what is hemodialysis, how does it work?

• most common type used

• vascular access thru:

  • fistula: surgically linking blood vessels together in the arm so they can take blood out

  • graft: surgical insertion of artificial vessel

  • permacatheter: access line placed in subclavian vein (chest area)

what is peritoneal dialysis?

• when fluid sits in the peritoneal cavity (where your internal organs are)

• the peritoneum acts as a semipermeable membrane where solute and water cross between blood vessels found in the peritoneum and dialysate

HD vs PD

• hemodialysis

  • membrane is man made

  • dialysate constantly filtered for the 4 hour treatment

  • fistula in the forearm

  • less glucose

  • build up of toxins in the 2 days between treatments

  • done in clinic

• peritoneal dialysis

  • peritoneal membrane is naturally occurring

  • dialysate sits against the peritoneal membrane

  • sits there for 4-6 hours then gets changed

  • lots of glucose

  • done at home

short term complications of hemodialysis

• blood loss

• BP variations

• bone disease

• infection

• inflammation

• amino acid loss (pts will have higher protein needs

what are the short term complications of peritoneal dialysis

• bloating

• infections

• inflammation

• intestinal perforation

• hyperglycemia

• protein loss

longterm complications of dialysis

• anemia

• coagulopathy (being prone to blood clots)

• dyslipidemia

• malnutrition/fat and muscle loss

• wt gain (peritoneal dialysis)

what should we monitor for in dialysis

• urea

• creatinine

• body wt pre and post dialysis

what are some general recommendations for diets of ppl with kidney disease?

• reduce sodium

• increase fibre, whole grains, F/V

• count carbs, spread throughout the day

what are they key nutrition diagnoses of kidney disease?

PES statements include the following:

• malnutrition

• protein

• sodium

• Vit D, P, K

• fluid

explain the different in nutrition therapy based on what stage of CKD they are in

• CKD stages 1-2

  • focus on controlling comorbidies (diabetes/HTN)

• CKD stages 3-4

  • prevent malnutrition

  • manage fluid balance

  • not too much protein

  • trat vitamin and mineral abnormalities

  • treat blood lipids

• CKD stage 5

  • prevent malnutrition

  • manage fluid balance

  • treatment depends on dialysis

roles of renal RD