↓ active vitamin D leads to ↑ PTH → ↑Ca2+ resorption from bone
excessive secretion of PTH in response to hypocalcemia (low blood calcium levels) & associated hypertrophy of the glands OFTEN seen in renal disease
a malfunctioning kidney can't convert vitamin D to its active form, resulting in low blood calcium levels
blood calcium is important for proper nerve & muscle function
low blood calcium levels stimulates the release of PTH to draw on bone Ca2+ stores to rejuvenate & maintain appropriate blood Ca2+ levels
Why do people with end-stage kidney disease (stage 5) often have elevated phosphorous levels?
because unhealthy kidneys are no longer able to remove phosphorus from the blood & filter any excess in urine for excretion
when PTH breaks down bone to liberate Ca2+ & replenish its blood levels, free phosphorous may bind to the Ca2+ (they're highly attracted to each other), preventing Ca2+ blood levels from returning to normal
this only worsens secondary hyperparathyroidism
Chronic Kidney Disease (CKD)
kidney damage for or over 3 months which causes structural or functional abnormalities (possibly with decreased GFR)
manifestations include either pathological damage OR blood or urine markers of kidney damage
can also be detected via imaging
*it's not unusual for people in the early stages of the disease to NOT KNOW they have CKD
CKD becomes more prevalent in older individuals
What are a person's options at Stage 5 CKD after kidney failure?
kidney transplant or dialysis is required
dialysis is MORE common than transplant for treatment
most transplants don't last a lifetime (5-15 years); not unusual for a patient on dialysis to have HAD a transplant
there are different type of dialysis: hemodialysis (HD), peritoneal dialysis (PD), or continuous renal replacement therapy (CRRT)
continuous renal replacement therapy (CRRT)
designed for acutely ill patients in the hospital
What are the 3 main components of treating kidney disease?
1. delay its progression
2. treat any complications: to prevent illness/symptoms
3. RRT: Renal Replacement Therapy
What CAUSES renal failure?
1. primarily metabolic diseases that involve the kidneys (eg. DM or lupus)
2. hypertension → nephroschlerosis → damage to the renal blood vessels
3. disease of the glomeruli causing glomerulonephritis
4. obstructive diseases (eg. kidney stones or polycystic kidney disease)
Diabetes - 45%
Hypertension and RAS - 27%
Other/unknown – 10%
Glomerular Diseases - 8%
Interstitial Diseases - 4%
Cystic Diseases (PKD) - 3%
Lupus - 2%
Other glomerulonephritis - 2%
What would a dietician's overarching goals be for a person with kidney disease?
1. assist nutritionally in the preservation of renal function
2. assist in control of uremic symptoms
3. ensure nutritional adequacy & preservation of lean body mass
Causes of Malnutrition in CKD Patients
unpalatable or inadequate diets
delayed gastric emptying (vomiting is often a problem)
What GFR corresponds to CKD Stage 5, & therefore kidney transplant or dialysis?
a GFR less that 15
removes large volumes of blood, filters out the toxins, then returns it 3x a week
is a time consuming and exhaustive process
there is a large potential for hemodynamic instability - hypotension is common in this procedure, as is cardiovascular instability, nausea, vomiting, post HD fatigue, & protein losses of about 6-8g per treatment
*patients need to eat more protein once the therapy begins if they were previously protein restricted
What are some counterintuitive dietary changes for a person receiving hemodialysis?
fiber is added/important (constipation is a problem in this population)
Ca2+ should be monitored more closely, especially if phosbinders are being used
renal vitamin supplement is recommended (B vitamins are especially important)
fluid = urine output + 1 Liter
intuitive: protein decreases (should be mostly HBV), energy is exactly the SAME, and sodium, potassium, & phosphorous all decrease
Peritoneal Dialysis (PD)
dialysate (fluid) sits within the abdomen & the peritonium acts as a filter; the dialysate is eventually excreted into a drain bag
happens on a daily basis or multiple times a day usually at home
CAPD: continuous ambulatory
CCPD: continuous cyclic
What are the side-effects of peritoneal dialysis?
Glucose Absorption: b/c fluid has dextrose, some of dialysate gets absorbed & increases satiety
Peritonitis: inflammation of the peritoneum due to its constant use
Protein losses of 8-10 g/day (MORE than with hemodialysis)
What are some counterintuitive dietary changes for a person receiving peritoneal Dialysis?
protein is increased: difficult to manage b/c of satiety that comes along with the glucose fluid
more LIBERAL diet (more fluid, Na+, K+)
same thing about fiber & Ca2+
Why do nutritionist WANT nutritional biochem markers such as BUN & creatinine to be high in dialysis patients?
because that's indicative of their TRUE renal function
if they're lower, patients aren't eating adequate protein
Serum BUN (Blood Urea Nitrogen), Serum & Creatinine SHOULD REMAIN ELEVATED IN DIALYSIS PATIENTS
Which can dialysis remove from the blood, phosphorous or potassium?
phosphorous is not well filtered by dialysis machines
blood levels of these molecules are checked to make sure they're not too high