Renal week 3 Flashcards
Chronic kidney disease
permanent reduction in GFR that lasts more than 3 months
Common causes of chronic kidney disease (6)
- Diabetic nephropathy (most common)
- Hypertensive nephrosclerosis and renal vascular disease
Glomerulonephritis
Polycystic kidney disease
Interstitial nephritis
Obstruction
Stage 1 chronic kidney disease
some kidney damage, normal GFR
GFR>90
Action: diagnose and treat
- aggressively treat BP, lifestyle modifications
- diagnose cause of CKD
Stage 2 chronic kidney disease
kidney damage, mild decrease in GFR
GFR = 60-89
Action: continue BP/lifestyle treatment, estimate progression
Stage 3 CKD
moderate decrease in GFR
GFR = 30-59
Action:
- treat complications (give bicarb, restrict dietary phosphorous)
- select site for dialysis and preserve veins
- continue BP and lifestyle treatments
Stage 4 CKD
severe decrease in GFR
GFR = 15-29
Action: prepare for renal replacement therapy (place and AVF)
Stage 5 CKD
kidney failure
GFR
How come you can lose 90% of your GFR before manifestations of uremic syndrome present?
- Functioning nephrons compensate for damaged nephrons
- Magnify excretion of given solutes to maintain external balance (hormonal/tubular hadndling altered of individual solutes)
- Mechanisms that are magnified to maintain individual solute control may have deleterious effects on other systems
Intact nephron hypothesis
some nephrons damaged, but that are nephrons functioning in diseased kidneys maintain glomerulotubular balance comparable to all other nephrons
Filtration and excretion are coordinated
Magnification phenomenon
although nephrons in diseased kidneys function homogeneously, they alter their handling of given solutes as needed to maintain external balance of that solute if possible
Magnify excretion of a given solute
Individual solute control systems
each solute has specific control system geared to maintain external balance in CKD
Each solute system has individual tubular handling and hormonal influences
Trade-off hypothesis
Mechanisms that are magnified to maintain individual solute control may have deleterious effects on other systems
creatinine and urea handling in CKD
balance/rate of filtration maintained at expense of elevated plasma concentrations of these waste products
Excretion rates for urea and creatinine remain constant despite diminished clearance
water handling in CKD
Problems with concentration and dilution
–> Patients prone to hyponatremia (water excess) and hypernatremia (water deficiency)
Sodium handling in CKD
Kidneys no longer able to rapidly adjust sodium excretion in response to sudden changes in sodium intake or extrarenal losses
Increase sodium intake → edema, decrease sodium intake → volume depletion
Inability to adjust can result in:
→ volume expansion
–> increased tubular fluid flow rate and hyperfiltration at active nephrons
Potassium handling in CKD
-can’t secrete K+ as well
- Increase tubular secretion of K+ by increasing Na+ delivery and aldosterone activity at cortical collecting duct
- Fecal excretion of K+ ramped up to compensate for reduced renal secretion
-Patient susceptible to hyperkalemia from sudden K+ loads
H+ ion handling in CKD
Functioning nephrons produce more NH4+ to compensate for loss of nephron mass (limited to 4x increase) → keep acid balance normal until GFR below 20-25 ml/min
Once GFR falls below that level, there is a retention of H+ ions → non-anion gap metabolic acidosis
Calcium, phosphate, parathyroid hormone, and vitamin D loop in normal people
Calcium:
- Ca2+ absorbed in kidneys –> inhibits production of PTH
- low Ca2+ stimulates PTH
Parathyroid hormone:
- stimulates Ca2+ kidney reabsorption
- stimulates Ca2+ mobilization from bone
- reduces phosphate reabsorption in kidney
Active Vitamin D (1,25 dihydroxyvitamin D):
-stimulates gut absorption of calcium and phosphate and stimulates PTH production
Calcium, Phosphate, and Parathyroid hormone handling in CKD
GFR falls → early increase in phosphate → promote FGF-23 release to maintain phosphate balance
FGF-23 suppresses 1,25 vitamin D production → decreases gut Ca2+ absorption → decreases serum Ca2+ → PTH increases → increase Ca2+ reabsorption and mobilize Ca2+ from bone
GFR falls more → cycle continues
3 main impacts or uremic syndrome
1) Retained metabolic products (urea, etc.)
2) Overproduction of counter-regulatory hormones (PTH in response to low Ca2+, ANP in response to volume overload)
3) Underproduction of renal hormones (EPO, 1-hydroxylation of vitamin D)
Disorders commonly accompanying CKD (3)
1) Anemia
2) Hypertension
3) Mineral and bone disease
Anemia occurs almost universally when GFR falls below ______ and in CKD is caused by…(4)
universal when GFR below 25
1) Decreased EPO production
2) Shortened red cell life span due to a “uremic” toxin
3) Blood loss (Secondary to abnormal coagulation/decreased platelet function)
4) Marrow space fibrosis due to secondary hyperparathyroidism
Hypertension occurs in ______% of CKD patients and is caused by…(4)
in 80-90% of CKD patients
1) Expansion of ECF volume due to reduced Na+ excretion ability
2) Increased RAAS activity
3) ANS dysfunction - insensitive baroreceptors, increased sympathetic tone
4) Diminished presence of vasodilators (prostaglandins)
What causes mineral and bone disease in CKD
-increase in phosphorous –> increase FGR-23 –> decreased 1,25 vitamin D –> decreased Ca2+ reabsorption –> increased PTH release –> mobilization of Ca2+ from bone
Why is renal disease progressive?
4 compensatory changes
Glomerulus and tubule function as a unit but must make compensatory changes to keep up with increased load
Compensatory changes occur in functioning nephrons →
1) Glomeruli hypertrophy
2) Blood flow per nephron increases
3) Intra-glomerular pressure increases
4) Solute flow per tubule increases
Treatment of CKD (4)
**Delay progression:
1) Blood pressure control is MOST important (reduces risk of CVD, reduces proteinuria)
- 3 drug combo: ACEI/ARB + 2 others
- CKD patients in highest risk group for CVD
2) Treat metabolic acidosis (oral NaHCO3-)
3) Treat vitamin D deficiency
4) Maintain serum phosphorus in a near normal range with dietary counseling and phosphate binders
Once uremic syndrome has developed in CKD patients…
–> dialysis or renal transplantation
Select site for dialysis access and preserve veins
Place an AVF around stage 4
Indications for starting dialysis (5)
1) Volume overload unresponsive to diuretics
2) Severe hyperkalemia
3) Uremic Pericarditis
4) Uremic symptoms (lethargy, difficulty concentrating, coma, seizures, nausea, uremic bleeding)
5) Other metabolic derangements - metabolic acidosis, hyperphosphatemia, calcium abnormalities
**Ideally begin dialysis prior to the development of life-threatening symptoms
No hard and fast BUN or eGFR that requires dialysis
Hemodialysis
-most common modality
-done by nurses/health techs
-requires vascular access (need good arteries/veins)
-lots of needle sticks
-usually done in dialysis unit
3x a week, each lasting 3-4 hours
-intermittent –> significant dietary and fluid restrictions
Semipermeable membrane → Rapid removal of small molecular weight solutes (urea), but not very effective at removing larger molecules or solutes that are protein bound
Peritoneal dialysis
- much less common
- done by patient and/or caregiver
- continuous
- requires peritoneal catheter (no hernias or major abd surgeries), no vascular access
- no needles
- usually done at home
- may not need strict fluid restriction
- can be done during sleep
Process of hemodialysis (4)
1) Using specialized vascular access (a-v fistula, a-v graft, or catheter) blood is removed from body and enters hemodialysis filter
2) In dialysis filter, solutes are removed by diffusion into dialysate
- Countercurrent dialysate draws solutes from blood in by diffusion
3) Fluids can also be removed in filter by applying positive transmembrane pressure (ultrafiltration)
4) “Clean” blood is returned to body (via separate port)
3 types of access ports used in hemodialysis
1) Arteriovenous fistula
2) Arteriovenous grafts
3) Dialysis catheter (dual lumen catheters)
Arteriovenous fistula (AVF) -pros and cons
Surgical anastamoses of native artery to vein
Preferable placed in non-dominant arm
Pros: lowest infection rate, longest lifespan, requires fewest procedures to maintain
Cons: takes months to mature, may never be usable, risk of steal syndrome (because diverting arterial blood flow to vein)
Arteriovenous grafts (AVGs)
-pros and cons
synthetic graft connecting artery and vein
Pros: can be used quicker than AVF, good blood flows, lower infection than catheters, but hight than AVFs
Cons: Fail quicker (stenosis) and require interventional procedures to maintain, steal syndrome
Dual lumen catheters (Dialysis Catheter)
-pros and cons
Placed in internal jugular vein and terminates in SVC
Pros: immediate use, no needles, does not require surgery
Cons: highest infection risk, high rate of dysfunction/low blood flows, requires insertion site care
Associated with high mortality
Process of peritoneal dialysis (3)
1) Catheter placed in peritoneal cavity that exits the abdominal wall
2) Sterile fluid with a high glucose concentration (high oncotic pressure) instilled in peritoneal cavity
3) Water pulled into dialysate and solutes with it
Patients perform at least 3-4 exchanges per day
Limitations of dialysis (3)
1) Uremic symptoms markedly improved, but some patients do not completely recover pre-illness health status
2) Difficulty achieving euvolemia → chronic heart failure because can’t remove enough volume
3) Abnormal bone and mineral disorders persist
Complications of hemodialysis
*Infection (#1) (bloodstream infection with Staph. Aureus)
Hypotension Muscle cramps Angina Myocardial ischemia Disequilibrium syndrome: headache, somnolence, seizures coma Air emboli (rare) Anaphylaxis
Complications of peritoneal dialysis (4)
1) Increased intra-abdominal pressure → hernias
2) Infectious peritonitis
3) Catheter problems (kinking, malposition)
4) Metabolic complications (hyperglycemia, hypertriglyceridemia, hypokalemia)
Risks/Benefits if transplant over dialysis
Transplant improves long term patient survival vs. dialysis, but has a higher mortality in the peri- and immediate postoperative period (reduced risk after a few months)
- Improves quality of life
- Financial benefits
-Requires immunosuppression → infection, cancer, drug-specific side-effects
Warm ischemia
time from cardiac death to cold perfusion (max 60 min)
Cold ischemia
time from cold perfusion to recipient anastomosis (max 24-36 hours)
MHC and kidney transplant
MHC = genes that encode proteins that present antigens to T cells (HLA in humans)
- T cells don’t recognize free antigens, only recognizes when when presented on HLA
- highly variable throughout the population (very small chance of two people having the same HLA genotype) → REJECTION of non-self
Class I vs. Class II HLA
Class I: HLA A, B, C → all nucleated cells present intracellular antigens to CD8+ cytotoxic T cells
Class II: HLA DR, DP, DQ → only on antigen presenting cells → present extracellular proteins to CD4+ helper T cells
2 ways organ transplants can be rejected by T cells
1) direct activation
2) Indirect activation
Direct activation
recipient T cells recognize intact donor HLA antigens on donor APCs → early rejection
Indirect activation
recipient T cells recognize donor HLA antigen fragments presented by host APCs → “normal” mechanism of T cell activation, usually via class II MHC
B cells and organ transplant rejection
B cells also activated by T cells → production of IgG for foreign donor HLA molecule
B cell rejection (antibody mediated + complement)
HLA matching
Match for 3 antigens: A, B, and DR (1 from mom, 1 from dad = 6)
The better the match, the better the survival
3 layers of immunosuppression used in kidney transplantation
1) Calcineurin Inhibitor
2) Proliferation Signal Inhibitor
3) Prednisone
Calcineurin Inhibitor
cyclosporine
Side effects: **Highly nephrotoxic, HTN, diabetes
Proliferation Signal Inhibitor
2 different drugs
Mycophenolate Mofetil (MMF) - inhibits purine synthesis
mTOR Inhibitors - inhibit mTOR proliferation signaling
Side effects: cytopenias, GI toxicity
Prednisone side effects
Side effects: weight gain, HTN, diabetes, hyperlipidemia, bone loss, cataracts
Kidney transplant AKI
Can be just like normal AKI, but must consider transplant specific etiologies
Prerenal
Postrenal
Intrarenal
Causes of Prerenal AKI in kidney transplant patients
Volume depletion from post-op fluid shifts, blood loss
Thrombosis of transplanted renal artery or vein
Calcineurin inhibitor effects on afferent arteriole
Causes of Post renal AKI in kidney transplant patients
Transplant ureter obstruction
Causes of Intrarenal AKI in kidney transplant patients (3)
Recurrence of primary renal disease
Infection: UTI, pyelonephritis, CMV virus, BK virus nephropathy
Rejection
Two types of nephrosis that commonly reoccur in a transplanted kidney
MPGN → 100% recurrence
Primary FSGS → 20-50% recurrence
T cell vs. B cell rejection in kidney transplants
T cell → tubular and/or large vessel inflammation
B cell → ab directed against HLA antigens
What drugs and endogenous effectors cause afferent arteriolar dilation? (4)
effect on GFR and RBF?
increase GFR, increase RBF
NO, Prostaglandins
Dopamine –> D1 agonist
Caffeine –> adenosine antagonist
What drugs effectors cause efferent arteriolar dilation? (2)
effect on GFR and RBF?
decrease GFR, increase RBF
ACEIs/ARBs –> decrease AngII
What drugs and endogenous effectors cause efferent arteriolar constriction? (2)
effect on GFR and RBF?
increase GFR, decrease RBF
AngII, NE
What drugs and endogenous effectors cause afferent arteriolar constriction? (4)
effect on GFR and RBF?
decrease GFR, decrease RBF
AngII (sorta), NE, Adenosine
NSAIDs –> decrease PGs
______, _______, and ________ drugs can cause acute renal failure
ACEI/ARBs (if hypovolemic)
NE
NSAIDs
________ can be renal protective via increase in RBF
dopamine
________ has a well-describe diuretic effect via increase in GFR
caffeine
Treatment of CKD associated anemia?
recombinant EPO (Epoetin and Darbepoetin)
Iron supplements
Treatment of CKD associated renal osteodystrophy (3)
(caused by hyperphosphatemia)
1) Phosphate binding agents
2) Vitamin D compounds
3) Calcimimetics
Phosphate binding agents
bind dietary phosphate in GI tract to form insoluble phosphates which are excreted in feces
Prevents increases in phosphate and increase in FGF-23
-treatment for renal osteodystrophy
Vitamin D compounds
-treatment for renal osteodystrophy
suppress PTH secretion and synthesis by stimulating intestinal calcium absorption
- Calcitriol → hypercalcemia
- Paricalcitol acts selectively at D3 receptors on parathyroid gland NOT intestine → no hypercalcemia
Calcimimetics
-treatment for renal osteodystrophy
binds calcium-sensing receptors on parathyroid cells → reduce release of PTH directly
Drugs that can cause hyperkalemia
1) K+ Sparing diuretics
- Aldosterone antagonists - spironolactone, eplerenone
- Collecting duct ENaC channel blockers - triamterene, amiloride
2) ACEI and ARBs
3) Digoxin
Effect of CKD on insulin
half life prolonged, dose must be reduced
Effect of CKD on diuretics
1) Thiazides may lose effectiveness as renal function declines
- As GFR falls, less drug reaches site of action in nephron → diuretic efficacy decreases
- GFR less than 30 → use loop diuretic
2) Avoid using K+ sparing diuretics
Effect of CKD on ACEIs/ARBs
used through all CKD stages
- Causes dilation of efferent
- Monitor for hyperkalemia
- May cause ARF in hypovolemic patients
Effect of CKD on beta blockers
Atenolol: half life prolonged
Metoprolol preferred
Treatment of acute hyperkalemia (3 strategies)
1) Calcium gluconate or chloride (IV) → antagonize cardiac conduction abnormalities (immediate onset)
2) Shift K+ intracellularly
Insulin/Glucose (IV)
B2 agonist → albuterol (inhaled)
NaHCO3 (IV)
3) Remove K+ from body (kayexalate) (1-2 hours for onset)
Patiromer
exchanges Ca2+-sorbitol counterion for K+ in gut
Used in non-life threatening hyperkalemia
May allow patients with comorbid conditions (CKD, HF, diabetes) to continue taking K+ sparing agents (ACEI/ARB, spironolactone)
Routes of Urinary tract infections (2)
Hematogenous:
a. Less common
b. Distant source - septicemia or infective endocarditis
c. Usually presence of ureteral obstruction, immunosuppressive therapy
d. Staphylococci, fungi, viruses
- Ascending:
a. Most common
b. Fecal flora (E. Coli usually, also proteus, klebsiella, enterobacter)
Virulence factors UTI
- Bacterial adhesion → Pili
- O antigens (Certain strains more resistant)
- Endotoxin → decreased ureteric peristalsis