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REGUB Medicine: CKD/Nephritic/Nephrotic Syndrome (i) (Classifying CKD…
REGUB Medicine: CKD/Nephritic/Nephrotic Syndrome (i)
Function of kidneys
ECF vol homeostasis
osmoregulation
K homeostasis
Acid-base balance
excretion of waste products incl drugs
Ca + phosphate homeostasis
production of hormones (e.g. erythropoietin)
Podocytes
cells in Bowman's capsule that wrap around capills of glom
make up epithelial lining
3rd layer through which filtration of blood occurs
GFR
main marker of kidney function
normal approx 100-120 ml/min
if 5 or less - dialysis
methods to measure
iothalamate clearance: laborious, only done in potential donors, needs to be 100%
inulin clearance
24hr urine creatinine clearance
most common
overestimated as some creatinine secreted by tubules
eGFR
calculated from SERUM CREATININE
formula factors in muscle mass by age, sex, race (blacks have more muscle)
Classifying CKD
Stage 1: GFR normal (>90) or increased, other evidence of kidney damage
Stage 2: kidney damage + GFR 60-90mls/min
Stage 3: GFR 30-59
3A: 45-60
3B: 30-44
morbidity + mortality being to rise when GFR < 45
anaemia begins to become more common
progression more likely
usually only present from this stage
Stage 4: 15-29
Stage 5: < 15
if transplanted: 3t, 4t, 5t etc
stage implies a step or progress
can delay progression using RAAS blockers
GP register: screen people with risk factors, esp PVD - CKD a/w high mortality for CVD so use cardiac prophylaxis (chol control, aspirin)
joint care by GP + nephrology
CKD risk factors
HTN (did HTN come 1st or did CKD cause HTN)
DM
atheroma (CVD, IHD, PVD)
old age
asian/afro-caribbean
family hx
prolonged hosp admission
significant co-morbidities
CKD causes
diabetic nephropathy (most common cause)
hypertensive nephropathy
GN
IgA most common
membranous: ANCA, anti-GBM (Goodpasture's)
ADPKD
TIN
obstructive nephropathy
chronic pyelonephritis (reflux nephropathy)
CKD prevalence increasing
obesity
DM
longevity (people living longer with it)
Care of patients with CKD
smoking cessation
discontinuation od nephrotoxic medications
limit iodinated contrast admin or adequate pre-hydration + N-acetylcysteine pre-imaging (hard to prevent contrast nephropathy)
Manage HTN
target < 130/80, <125/75 if proteinuria
esp NB with proteinuria
delays progressive renal disease
check creatinine + K before start
ACEis or ARBs
expect eGFR to fall by <25%
if hyperkal occurs >6, review drugs
frequently need 2/3 drugs
Ca antagonist (amlodipine)
alpha blocker (doxazosin)
beta blocker (bisprolol)
combined alpha + beta blocker (labetolol)
vasodilators (hydralazine)
loop diuretics (furosemide)
Manage anaemia of renal disease
less erythropoietin production when GFR<35
exacerbated by Fe deficiency - ensure Fe stores are adequate
ferritin > 300 (APR so not a great marker)
serum Fe + transferrin sat normal
Tx = erythropoietin (wkly/monthly subcut injection)
aim Hb 11.5-12.5: patients usually not too active so don't need high Hb, also increases clotting (increased PCV)
oral Fe poorly absorbed by gut in CKD
fluid balance
need for high doses of loop diuretics in CKD (reduced GFR)
low Na diet
prep for RRT
don't restrict protein
Metabolic acidosis
inability of failing kidney to excrete acid load (H+) in diet
may mediate faster CKD progression
Tx = NaHCO3 tablets
caution with salt load
Progressive renal disease
eGFR < 30
worsening kidney function despite removal of initial kidney insult
a/w proteinuria, HTN, increasing serum creatinine
patients ultimately progress to dialysis - a/w bad prognosis, shortened lifespan
can be put on transplant list when GFR<15 (transplant lengthens lifespan)
When to start dialysis
based purely on symptoms - non-specific so look for a collection
uraemic symptoms
N+V, retching, anaemia - low energy, diffuse itch (uraemic pruritus hard to tx), insomnia, anorexia, weightloss
generally eGFR < 10
acidosis, hypocalcaemia, hyperphosphataemia