Flashcards in Acute Kidney Injury Deck (39)
What is the definition of acute kidney injury?
An abrupt (within 48 hours) reduction in kidney function, defined as:
• Increase in serum creatinine of > 0.3mg/dL OR
• % increase in serum creatinine of 50% OR
• Oliguria of 6 hours
What is the relationship between acute kidney injury and critical illness?
AKI is often found in critically ill patients
What are the 3 groups of AKI causes?
- Prerenal Azotemia
- Intrinsic Renal Disease
- Postrenal Obstruction
What are the causes of prerenal azotemia?
i. True hypovolemia
ii. Decreased effective circulating volume
iii. Renal artery stenosis/occlusion
iv. NSAID/ACE-I/ARB mechanism
What are the causes of intrinsic renal disease?
i. Vascular causes
ii. Glomerular disease
What are the causes of postrenal obstruction?
i. Bladder outlet obstruction
￼ii. Bilateral ureteral obstruction
iii. Unilateral ureteral obstruction in a solitary kidney
What are the 2 most common causes of AKI?
- Prerenal Azotemia
- Ischemic ATN
What can prerenal azotemia progress to if it is not corrected?
What is prerenal azotemia?
It is an appropriate response to renal hypo perfusion that leads to a build up of nitrogen compounds in the blood
What are some of the causes of prerenal azotemia?
- Decreased ECV
- Renal artery stenosis
- Drug-induced impaired renal autoregulation
What is the normal renal response to drop in BP?
- Afferent vasodilation
- Efferent vasoconstriction
What is the effect of NSAIDs on the GFR?
NSAIDs decrease the GFR by causing afferent arterial vasoconstriction
What is the effect of ACE-I/ARBs on the GFR?
They do not affect the GFR that much. They dilate the efferent arterioles which has a protective effect.
What are some of the risk factors for postern disease?
• Older men with prostate disease
• Solitary kidney
• Intra-abdominal (pelvic) cancer
What are the 4 categories of intrinsic renal disease?
- vascular causes
- glomerular diseases
- acute interstitial nephritis
- acute tubular necrosis
What are some of the causes of ATN?
• Nephrotoxic exposures
What is the major cause of intrinsic renal disease?
What are the classical features of ATN?
- Muddy brown urine
- Oliguric Phase (HTN/Hyperkalemia/Volume Overload)
- Polyuric Phase
What are the two types of ATN?
What are some of the vascular causes of intrinsic renal failure?
• Thromboembolic disease
• Malignant HTN
• Scleroderma renal crisis
What is the main vascular cause of intrinsic renal failure?
Malignant HTN - which causes impending/progressive organ dysfunction
What are the two class of acute interstitial nephritis (AIN) that lead to intrinsic renal failure?
Drug Associated (NSAIDs and antibiotics)
Non-drug Associated (Infectious/Autoimmune)
What is the triad of signs in AIN?
Fever, peripheral eosinophilia, rash
Pushing on the umbilicus leads to jugular vein rising of more than 4 cm
What are signs that the body is too dry?
• Dry mucous membranes
• Skin tenting (only useful if positive in adults)
• Neck veins flat at 0 degrees
What are signs that the body is too wet?
• Abdominojugular reflux at 30-45 degrees
• S3 gallop
Prerenal Azotemia Urinanalysis
Prerenal Azotemia Urine Specific Gravity
It will be high - 1.020
Prerenal Azotemia Osmolality
It will be high - greater than 500
Prerenal Azotemia FE of Na
It will be low - less than 1%
Prerenal Azotemia FE of Urea
Less than 35%
Tubular Epithelial Casts
ATN Urine Specific Gravity
It will be low - less than 300
ATN FE of Na
Greater than 2%
ATN FE of Urea
Greater than 35%
What is the BUN:Cr ratio in prerenal azotemia?
Greater than 10:1
What is the BUN:Cr ratio in ATN?