Renal Disease Flashcards
AKI
A sudden loss of kidney function (often reversible, but can be permanent if precipitating factor is not corrected)
Common cause: dehydration (BUN:SCr ratio > 20:1 + decreased urine output, dry mucous membranes, tachycardia)
CKD and ESRD
CKD = A progressive loss of kidney function over months or years (assessed by GFR, CrCl, albumin in urine, most common causes are diabetes and HTN)
ESRD = Total and permanent kidney failure (fluid and waste accumulate, dialysis/transplant needed)
Nephron
Control the concentration of Na and water
Reabsorb what is needed back into the blood (the rest is excreted in the urine) - regulates blood volume and blood pH
Glomerulus
Large filtering unit located in Bowman’s capsule (afferent arteriole delivers blood INTO the glomerulus, exits through efferent arteriole)
If the glomerulus is healthy, larger substances (proteins, protein-bound drugs)
are not filtered and stay in the blood
If the glomerulus is damaged, some albumin passes into the urine (albumin in urine and GFR used to assess kidney disease)
Proximal Tubule
Na, Ca, Cl, water that was initially filtered out of the blood is reabsorbed here
Blood pH is regulated by the exchange of hydrogen and bicarbonate ions
Medications that work here include SGLT2is
Loop of Henle
Descending limb = Water reabsorption (NOT Na and Cl, which increase the concentration of Na and Cl in filtrate)
Ascending limb = Na and Cl are reabsorbed (NOT water, unless ADH is present aka anti-diuresis )
Site of 25% of Filtered Na
= The ascending limb of the Loop of Henle
When loop diuretics inhibit the Na-K pump in the thick ascending limb of the loop of Henle, less Na is reabsorbed (and Ca = decrease bone density)
Distal Convoluted Tubule
Involved in regulating K, Na, Ca and pH
Thiazide diuretics inhibit Na-Cl pump here
-Thiazides increase Ca reabsorption (protective effect on bones)
Collecting Duct
Involved with water and electrolyte balance (affected by ADH and aldosterone)
K-sparing diuretics (like spirono/epelernone) work in DCT and CD to decrease Na/water reabsorption and increase K retention
Select Drugs That Can Cause Nephrotoxicity
- Aminoglycosides
- Amphotericin B
- Cisplatin
- Cyclosporine
- Loop diuretics
- NSAIDs
- Polymyxins
- Radiographic contrast dye
- Tacrolimus
- Vancomycin
BUN
BUN measures the amount of nitrogen in the blood that
comes from urea
Because urea is excreted by the kidneys, as kidney function declines, BUN increases
Not used alone to estimate kidney function (other factors can increase BUN = dehydration)
Creatinine
Creatinine, a waste product of muscle metabolism, is mostly filtered by the glomerulus and is easily measured
As kidney
function decreases, SCr increases
Normal range 0.6 - 1.3 mg/dL
Creatinine Clearance
Cockcroft-Gault equation for CrCl is most commonly
used to estimate kidney function when dosing medications
Accuracy is
decreased when a patient has very low muscle mass, like in frail elderly patients (low muscle mass
= low SCr = overestimation of CrCl)
CrCl Equation
CrCl (MIN/ML) =
(140 - age) / (72 x SCr) x wt in kg
x 0.85 if female
-Use actual body weight if less than IBW
-Use IBW if normal
weight
-Use adjusted body weight if overweight (by BMI)
CKD Criteria
- eGFR < 60 ml/min/1.73m2
or - Albuminuria (urine AER > 30 m/24 hours or UACR > 30 mg/g)
= Decreased eGFR or albuminuria present for 3 months to be considered CKD
GFR Categories
> 90 + kidney damage = G1 = CKD Stage 1
60-89 + kidney damage = G2 = CKD Stage 2
45-59 = G3a = CKD Stage 3
30-44 = G3b = CKD Stage 3
15-29 = G4 = CKD Stage 4
< 15 or dialysis = G5 = CKD Stage 5
Degree of Albuminuria
ACR (mg/g) or AER (mg/24hr)
< 30 = A1 (normal to mild increase)
30-300 = A2 (moderate increase)
> 300 = A3 (severe increase)
Delaying CKD: HTN
Target SBP < 120 mmHg
1. ACEi or ARB is first line
-Baseline SCr may increase up to 30%, but tx should not be stopped (if >30% then d/c)
-Avoid K supplements and salt substitutes (KCl)
-Monitor BP, SCr, K 2-4 weeks after initiation and maximize dose if possible (K normal, SCr increased <30%)
Delaying CKD: Diabetes
- SGLT2i if eGFR > 20
-Canagliflozin, dapagliflozin,
empagliflozin, sotagliflozin have demonstrated a reduction in CV events and/or CKD progression - GLP1-RAs if CI or additional glycemic control
- Finerenone can be added to SGLT2i and max-tolerated ACEi/ARB in patients with eGFR 25+, albuminuria, and normal K
Select Drugs CI in CKD
Nitrofurantoin (Macrobid, Furadantin, Macrodantin) = CrCl < 60
TDF containing (Complera), Voriconazole IV = CrCl < 50
TAF containing (Biktarvy), NSAIDs, Dabigatran = CrCl < 30
Metformin = eGFR < 30
CKD and Hyperphosphatemia
Monitoring of parathyroid hormone, phosphorus, Ca, and Vitamin
Tx
1. Restricting dietary phosphate (dairy, cola, chocolate, nuts)
2. Phosphate binders (block absorption of dietary phosphate, have to be taken before or at start of each meal)
-If dose is missed and food is absorbed, then phosphate binder should be skipped
-Ferric citrate is systemically absorbed (others are not)
3. Tenapanor (Xphozah) for dialysis pts with inadequate response/intolerance to binders
Aluminum Hydroxide Suspension
300-600 mg PO TID with meals
AE: aluminum intoxication (CNS and bone toxicity = confusion/seizures), osteomalacia
Tx duration limited to 4 weeks
Calcium Acetate (Calphron, Phoslyra)
1,334 mg PO TID with meals (titrate based on PO4 levels)
AE: hypercalcemia, constipation
Calcium Carbonate (Tums)
500 mg PO TID with meals (titrate based on PO4 levels)
AE: hypercalcemia, constipation
TDD of elemental Ca should be ≤ 2,000 mg
(from diet and supplements)
Hypercalcemia is especially problematic with concomitant use of Vitamin D (due to increased calcium absorption)
