Renal: Lecture 1 Flashcards
Clearance in healthy individual?
100-120ml
Afferent arteriole
Brings blood in, slightly thicker
Efferent arteriole
Brings blood out, but more constricted to increase pressure and push filtrate through Glomerulus
Kidney functions
Regulatory Function
Excretory Function
Hormone Function
Metabolic Function
Regulatory Function of Kidney
Control composition and volume of blood volume
Maintain acid-base balance
Excretory Function of Kidney
Produce urine
Remove metabolic waste
Hormone Function of Kidney
Produce renin for BP control
Produce erythropoietin which stimulates RBC production
Activate Vitamin D
Metabolic Function of Kidney
Gluconeogenesis
Metabolize drugs and endogenous substances
Kidneys role in Regulation of BP
Decreased blood coming through afferent stimulates renin from juxtaglomerular cells of kidney
Renin turns A-> A1, A1 -> A2 by ACE, A2 = vasoconstriction, stimulates Na retention, release of ADH to increase Na
Prostaglandin will decrease efferent in HTN
Primary function of kidneys are….
Filtration (Glomerulus)
Reabsorption and Secretion (Tubule)
Pre-renal event
Any injury to Arterioles/vasculature
change in volume/tone of either afferent or efferent
Where can kidney injury occur
Arterioles
PCT
DCT
Collecting duct
Injury in PCT will lead to sodium….
waste
What to look for in Afferent Arteriole that influence perfusion pressure
Volume and tone
What aspect of Efferent Arteriole influences perfusion pressure
Tone
Meds/conditions that impact Volume/tone of afferent arteriole
Anything affecting diameter of afferent arteriole (DM,HTN)
Disease that limit perfusion pressure to kidney (HF,Cirrhosis)
Meds that alter volume or tone (Diuretics + meds w/ constrictive properties)
Meds/Conditions that impact tone of Efferent arteriole?
ACE/ARB = dilate
RBC or protein in urine is. sign of
renal damage in glomerulus or the tubule
If tubular cells are damaged then….
Na and other electrolytes will be wasted and increased urine sodium
FeNA
Fraction of excreted Sodium
want 1% or less
BUN
Often high in dehydration
Extent of rise in BUN is a marker of a change in perfusion pressure (rapid rise in pre renal injury)
Creatine Clearance
Tendency to over estimate GFR, ~10 points
What is AKI
acute increase in creatinine with or without decrease in urine output over a short period of time
over ~24-48hrs
AKI 3 categories of Kidney Injury
Prerenal = decreased renal blood flow
Intrinsic/intrarenal = structural damage within Glomerulus,tubule, interstitium
Postrenal - obstruction within urine collection system
RIFLE Classification of AKI is….
Doubling Cr
AKIN Stage 2 classification is….
increased Cr X 2
KDIGO Classification of AKI is….
Doubling Cr
Nonoliguria
Urine output > 500ml per day
Oliguria
Urine output 100-500ml per day
Anuria
Urine output <100ml per day
Markers of AKI
2 X increase in Cr
Posible Change in Urine Output
Time frame, short period of time
What to NOT use to measure AKI
Cockcrof and Gault eq = CrCL
MDRD and MDRD4 eq = GFR
CKD-EPI eq = GFR
Who develops AKI?
Pt on high meds = increase risk
Community generally <1% risk
Inpatient setting = risk ~10%
Critically ill = ~25%, survival rate 10-30%
% of AKI cases thought to develop in hospital?
50%
increase risk of death, length of stay, move to ICU
AKI Risk Factors
Non-modifiable: CKD Diabetes Older age Cirrhosis CHF Renal artery stenosis PVD
Modifiable: Major surgery/anesthesia Sepsis/shock Volume depletion Hyper/Hypotension Nephrotoxic meds
Tenting of skin suggests….
Prerenal
Dark “Tea colored” Urine suggests….
Prerenal
Fever and High WBC count suggests….
AIN and Glomerulonephritis
Fever and rash Suggests….
AIN and Glomerulonephritis
Blood in Urine suggests…
Post renal or Glomerulonephritis
Causes of pre renal AKI
Hypovolemia
Decrease Cardiac output
Decreased circulatory volume
NSAIDs = Vasoconstriction of AA ACEi/ARBs = vasodilation of EA
Prerenal AKI risk factors
Advanced Age Diuretic Use Poor oral intake GI Fluid Loss CHF Renal Artery Stenosis ACEi/ARBs NSAIDs
Prerenal AKI treatment
Fluid replacement with NaCl
Counseling and prevention of pre renal AKI
Avoid NSAIDs (ASA 81 OK) Maintain adequate hydration
Look for darkening urine, “tea” color and less urine output
Intrarenal AKI Diagnostics
BUN/Scr: 16/1 ratio Urine output: Down **Urine Sediment: (ATN = muddy brown casts)(AIN = WBC casts +/- eosinophil cast)(Glom = RBC casts)** Urine RBC: 2-4 (in Glomerulonephritis) Urine WBC: 2-4 (in AIN) Urine Na: >40 mEq/L Urine protein: none FeNA % = >2%
Markers of intrinsic/intrarenal AKI
KEY: damage inside glomerulus, tubule or interstitium
Leads to cell death, and debris (cell casts) which cause obstruction
present as a wasting order of sodium (FeNA >2%)
ATN (acute tubular necrosis) causes
Tubular Disease
prolonged ischemia from pre renal AKI, infection, nephrotoxins
AIN (Acute interstitial nephritis) causes
Injury to interstitial space but can also affect tubules
Ischemia, infection, connective tissue damage, nephrotoxins
Glomerulonephritis
inflammation of glomerulus
Form RBC casts
AIN causes….
infection or drug-induced
Glomeruloneophritis causes…
Immune reaction or Drug induced
Prerenal Diagnosis parameters
BUN/Scr: 20/1 ratio Urine output: Down Urine Sediment: none Urine RBC: none Urine WBC: none Urine Na: < 20 mEq/L Urine protein: Variable FeNA % = <1%
Postrenal Diagnosis parameters
BUN/Scr: 16/1 ratio Urine output: Down Urine Sediment: Possible Urine RBC: Variable Urine WBC: 1+ Urine Na: >40 mEq/L Urine protein: Variable FeNA % = >2%
AIN Findings
Sediment: WBC + Eosinophils Cells: WBCs 2-4, + Eosinophils Crystals: None Protein: Mild, <0.5/day Timing: Slower develop, 7-10 days after "insult" event
Glomerulonephritis Findings
Sediment: RBC Casts
Cells: RBC
Crystals: Urate and or calcium crystals maybe present
Protein: Mod - Large proteinuria
Timing: Slower develop, 7-10 days after “insult” event
Treatment for ATN
Restoring Volume/BP
Treating for AIN
Discontinue cause of infection, need corticosteroids
Postrenal Kidney injury also known as….
post-obstructive AKI or obstructive uropathy
Physical obstruction along urinary tract
Common drug induced Postrenal AKI
acyclovir, indinavir, sulfadiazine
drugs can cause crystals
Kidney Stones
might cause Postrenal AKI
Largely impacted by diabetes
Prevention: hydration and low oxalate/urate foods
