SM 195 Flashcards
What are the effects of AKI on renal function?
AKI is responsible for:
Excretion of nitrogenous waste products
Maintain fluid balance
Maintain electrolyte balance
What populations are AKI more common in?
Hospitalized patients who are septic and critically ill are more likely to develop AKI
Especially those with pre-existing CKD
What changes in serum creatinine define AKI?
Serum creatinine increases of 0.3 mg/dL within 48hrs or an increase in serum creatinine by 1.5x baseline within 7 days
What changes in urine volume define AKI?
Urine volume decreases of 0.5mL for 6 hours
What defines oliguria?
< 500 mL urine output over 24hrs
What defines anuria?
< 50 mL urine output over 24hrs
What systemic manifestations effect AKI?
Hyperkalemia due to Metabolic Acidosis inhibiting the Na/K ATPase
Anemia due to decreased EPO from kidney injury
ECV expansion such as HTN, CHF
What defines prerenal AKI?
Reduced GFR from decreased renal perfusion that can be reversed with a restoration of renal perfusion
How does a loss of renal perfusion setup prerenal AKI?
RAAS is activated in response to decreased NaCl delivery to the Macula Densa from lower perfusion, causing vasoconstriction to the Kidney in an attempt to restore perfusion to the heart and brain
What can cause prerenal AKI?
DHPS
Decreased CO
Hypovolemia
Peripheral Vasodilation
Selective Renal Ischemia
How can prerenal AKI be diagnosed, in terms of history and PE.?
HPI: diarrhea, diuretics
PE: signs of dehydration
How can prerenal AKI be diagnosed, in terms of labs?
BUN:Cr > 20:1
FENa < 1%
What FENa suggests prerenal disease?
FENa < 1% suggests prerenal disease
FENa > 2% suggests ATN
What are limitations of the FENa?
FENa only suggests a disease and is not diagnostic
What is postrenal kidney failure?
Obstruction in the urinary tract that causes renal failure, due increased capsule hydrostatic pressure lowering GFR
What can cause postrenal kidney failure?
Bladder obstruction from prostate hypertrophy, uretrhal obstruction, ureter obstruction
What are the HPI and PE for a patient with postrenal kidney failure?
Distended bladder, enlarged prostate
How is postrenal kidney failure managed?
Rapid diagnosis and relief of urinary obstruction leading to postobstructive diuresis is essential to preserve kidney function
What can cause intrinsic renal failure?
ATN (tubular), interstitial vascular, and glomerular issues can cause intrinsic renal failure
What do muddy brown casts in urinalysis suggest?
Acute Tubular Necrosis
What do red blood cell casts in urinalysis suggest?
Glomerulonephritis
What do white blood cell casts in urinalysis suggest?
Infection, allergies
How should acidosis be managed?
Bicarbonate therapy
How should hyperkalemia be managed?
Modify Diet (low K) Insulin and Epinephrine Kalexylate to promote Na/K exchange in the gut
How should hyperphosphatemia be managed?
Calcium Containing Binders
Sevelamer (anti-phosphatemia drug)
How do creatinine levels compare during the initial injury period and while the injury is ongoing?
Creatinine levels increase as GFR falls during the injury itself
After the injury, a steady state of constant Creatinine level is re-established with elevated GFR and an increased Serum Creatinine, relative to before the injury
How does AKI vary among stages?
AKI at higher stages has higher increases in serum creatinine and lower urine output for longer periods of time
What are the 4 possible outcomes of AKI?
AKI can progress to:
Full recovery
AKI to CKD
Acute on Chronic Kidney Disease (AKI on pre-existing CKD)
AKI to ESRD
How can AKI present?
Most people are asymptomatic, but:
Malaise, flank pain, edema, HTN, and SOB are possible
What type of AKI is produced by abnormalities of renal perfusion?
Pre-renal AKI
What type of AKI is produced by abnormalities within the kidney?
Intrinsic AKI
What type of AKI is produced by abnormalities of urine output?
Post-renal AKI
Does pre-renal AKI involve structural injury to the kidney?
No, the Kidney is just hypoperfused, so it recovers quickly after perfusion is restored
What can cause hypovolemia?
Intravascular volume depletion
Third Spacing
Decreased CO
How do prostaglandins and angiotensin II regulate GFR?
Prostaglandins dilate the afferent arteriole to increase blood flow to the glomerulus and raise GFR
Antiogensin II constricts the efferent arteriole to decrease blood flow
How does aldosterone effect glomerular filtration?
Aldosterone stimulates sodium reabsorption in the CD, raising the ECV
How does ADH effect glomerular filtration?
ADH prevents the insertion of sodium channels in the CD, lowering sodium reabsorption and promoting fluid loss
Orthostatic hypotension, poor skin turgor, dry mucosa and edema suggest which type of AKI?
Pre-renal AKI
What is Hepatorenal Syndrome?
Liver failure that causes AKI due to systemic vasodilation that is compensated by profound vasoconstriction in the Kidneys, leading to impaired sodium/water handling and oliguria that does not respond to volume repletion
What are the types of ATN?
Ischemic and Toxic ATN
What is the most common cause of Intrinsic AKI?
ATN, due to reduced oxygen supply causing ischemia and cell death of tubular cells
What class of drugs can cause Tubular ATN?
Aminoglycosides
What syndromes can cause Tubular ATN?
Rhabdomyolysis, Hemolysis, Tumor Lysis Syndrome, Myeloma drugs
What type of sediment does ATN produce on urinalysis?
Dark, muddy brown sediment = ATN
What can cause Interstitial ATN?
Autoimmune diseases (Sjorgens, Lupus, Sarcoid)
HIV
Penicillins, Rifampin, NSAIDS
What is glomerulonephropathy?
A type of Intrinsic AKI (like ATN)
What are the types of glomeruloneprhapthy?
Rapidly Progressive Glomerulonephritis (RPGN) IgA Nephropathy Post Infection (PIGN after Strep) Immune-complex mediated FSGS Minimal Change Disease
What does the ANA test diagnose?
Lupus
What can cause Vascular Intrinsic AKI?
Small or medium vessel inflammation due to:
Cholesterol atheroembolisms
Hemolytic Uremic Syndrome (E coli infections)
Scleroderma
