Renal Flashcards
Renal Clearance (Cx)
= Ux*V/ Px Volume of plasma cleared per unit time (ml/min) Px, Ux= mg/ml V= urine flow rate Cx reabsorption , etc Cl inulin = GFR Cl pah = RPF
GFR
clearance of inulin
about 100 ml/min
= Kf (Pgc - Pbs)- (oncgc- oncbs) but oncbs = 0 mostly
Ccr = GFR but overestimates by about 10-15% bc of secretion in the PCT
Osmolality
285-295 mOsm/kg water
Water division between body and compartments
60-40-20
60% of body
40% ICF
20% ECF (75% interstitial, 25% plasma)
eRPF (effective renal plasma flow)
Clearance of PAH (para-aminohippuric acid)
100% cleared (secreted by carrier and saturable transport in the PCT)
underestimates RPF by about 10%
RBF
= RPF /(1-Hct)
FF
GFR/RPF
20%
Filtered load
GFR * Plasma concentration
What is the effect of prostaglandins on afferent arteriole?
dilate (increase GFR, increase RPF, FF constant)
NSAIDS block this path
At what plasma glucose does glucosuria begin?
200 mg/dL
Can be decreased in normal pregnancy (decrease ability of PCT to reabsorb glucose)
At what plasma glucose are transporters saturated ?
375 mg/dL
Henderson Hasselbach
pH = 6.1 + log (HCO3-)/ 0.03 PCO2
Winter’s formula
compensation metabolic acidosis
Pco2= 1.5 (HCO3) + 8 +- 2
Anion gap formula
8-12
(Na)- (HCO3- + Cl-)
Correct for albumin
Excreted load
= Px * GFR - [] reabsorbed
Most common site of ureter obstruction in fetus?
Uteropelvic junction (last to canalize)
What is horseshoe kidney associated with?
- uteropelvic junction obstruction, hydronephrosis, renal stones, chromosomal aneuploidy syndromes (turner, wiliams, patau, etc); infection, and rarely renal cancer
Excretion Rate
Ux*V
Reabsorption
Filtered - excreted
Secretion
excreted - filtered
RBC casts
Glomerulonephritis, malignant hypertension
WBC casts
Tubulointerstitial inflammation, acute pyelonephritis, transplant rejection
Fatty casts/oval fat bodies
nephrotic syndrome
Granular casts (muddy brown)
acute tubular necrosis
Waxy casts
ESRD/chronic renal failure
Hyaline casts
nonspecific, can be normal esp in concentrated urine samples
Mechanism of action mannitol?
osmotic diuretic
Increases tubular fluid osmolaltiy –> increases fluid flow
Also decreases intracranial pressure
Clinical use of mannitol?
Increased ICP, drug overdose (increases renal flow)
Toxicity of mannitol?
Pulmonary edema
Dehydration
When is mannitol contraindicated?
HF (pulmonary edema)
Anuria
What is the mechanism of acetazolamide?
Carbonic anhydrase inhibitor
Acts in PCT
Decreases HCO3/Na reabsorption
Decreases total body HCO3 stores
What are the clinical uses of acetazolamide?
Glaucoma (CA in cilliary body in eye)
Urinary alkalinzation (excrete weak acids; cystein and uric acid stones)
Pseudotumor cerebri (CA in choroid plexus)
Altitude sickness
What is the toxicity of acetazolamide?
Hyperchloremic metabolic acidosis Parathesias NH3 toxcity (encephalopathy with hepatic impairment) Sulfa allergy CaPh stones
What is the mechanism of furosemide action?
Blocks the NKCC pump in the TAL
Sulfonamide diuretic
Stimulates PGE release to vasodilate afferent arteriole
What is furosemide used for?
Edematous states
HT
Hypercalcemia
What is the toxicity of furosemide?
OH DANG!
Ototoxicity
Hypokalemia
Dehydration
Allergy to sulfa
Nephritis (interstitial)
Gout
When would you use ethacrynic acid?
Diuresis in sulfa allergic patients
Same action as furosemide
Phenoxyacetic acid derivative
What is the mechanism of HCTZ?
Blocks the NCC pump in the early DCT
Clinical use of HCTZ
HT, HF, idiopathic hypercalciuria, nephrogenic DI, osteoporosis
Toxicity of HCTZ
Hypokalemic metabolic alkalosis Hyponatremia hyperGlycemia hyperLipidemia hyperUricemia hyperCalemia (hyperGLUC) sulfa allergy
Mechanisms of action of Spirnolactone?
competitive MR inhibitors
Mechanism of action of triamterene/amiloride?
Block the ENaC channel
Clinical use of K sparring diuretics
Hyperaldosteronism
K depletion
HF (even without frank edema can be useful to decrease aldosterone and its fibrotic action on the heart)
Ca based nephrolithiasis
Toxicity of K sparring diuretics?
Hyperkalemia (arrythmia)
Hyperchloremia acidosis
Spirnolactone can have actions on other endocrine receptors causing gynocomastia (testosterone) and other anti-androgenic effects
What are the mechanisms of action of ACE inhibitors?
Block ACE which converts ANGI to ANGII and metabolizes bradykinin into inactive metabolites
Clinical uses of Ace inhibitors?
HT HF Proteinuria Diabetic nephropathy (decreases constriction of efferent arteriole caused by NEG, decreased intraglomerular pressure slowing GBM thickening and mesangial expansion) Prevent unfavorable heart remodeling
What are the toxicities of ACE inhibitors?
CATCHH Cough (bradykinin) Angioedema Teratogen (renal malformations) Increase Creatinine (decrease in GFR) Hyperkalemia Hypotension
When are ACE inhibitor counterindicated?
Cl esterase deficiency
Bilateral renal artery stenosis (decrease GFR)
What is the mechanism for ARBs?
Block the binding of ang II to ATI Rs (Gq)
Clinical use of ARBs?
HT
HF
Proteinuria
Diabetic nephropathy with intolerance to ACE inhibitors (angioedema, cough)
Toxicities of ARBs?
Teratogen Increase CK Hypotension Hyperkalemia Decrease renal function
Mechanism of action of aliskiren?
binds and inhibits the action of renin
What is the clinical use of aliskiren?
HT
What is the toxicity of aliskiren?
Hyperkalemia
Decreased renal function
Hypotention
When is aliskiren counterindicated?
Diabetics taking ACEs or ARBs
What are weak acid drugs that are excreted by alkalinization of the urine?
aspirin, phenobarbitol, methotrexate, and TCAs
What are weak bases that are improved by acidification of the urine?
amphetamines
What drugs cause DI?
lithium, demecocycline
What drugs cause Fanconi syndrome?
Expired tetracycline
Hemorrhagic cystitis is caused by which drugs?
cyclophosphamide, ifosfamide
Interstitial nephritis is caused by which drugs?
Methicillin, furosemide, and NSAIDs
What can you administer with cyclophosphomide to prevent hemorrhagic cystitis?
mesna
What drugs cause SIADH?
carbamazipine
Cyclophosphomide
SSRIs
Can’t concentrate Serum sodium
Pentad for TTP?
FAT RN Fever Anemia Thrombocytopenia Renal failure Neurological issues
What is the test for citrate stones?
sodium cyanide nitroprusside +
break disulfide bonds to release cysteine
