Acute Renal Failure - Pathoma Flashcards
What is Acute Renal Failure?
- Acute
- Severe decrease in renal function
What is the hallmark of acute renal failure?
- Azotemia
- increase in nitrogenous waste products in the blood
- causes increased BUN and Creatinine
- Often have oliguria
- low production of urine
What are the three types of acute renal failure?
- Pre-renal
- decreased blood flow
- Intra-renal
- problem within kidney
- Post-renal
- ureteral blockage (block outflow)
What happens in pre-renal azotemia?
- Decreased Blood Flow →
- decrease GFR
- azotemia
- oliguria
- reabsorption of fluid and BUN ensues
- serum BUN:Cr > 20
- tubular function remains intact
- FeNa <1%
- urine osm >500
What happens in post-renal azotemia?
- Obstruction of the urinary tract downstream from the kidney →
- back up in pressure
- decreased GFR
- azotemia
- oliguria
How do the early stages of post-renal azotemia compare to late stages?
- Early:
- increased tubular pressure “forces” BUN into the blood stream
- serum BUN:Cr >15
- tubular function remains intact
- FeNa <1%
- urine osm <350
- increased tubular pressure “forces” BUN into the blood stream
- Late:
- tubular damage
- decreased reabsorption of BUN
- serum BUN:Cr <15
- Decreased reabsorption of sodium
- FeNa >2%
- Inability to concentrate urine
- urine osm <500
What are the causes of Intra-renal azotemia?
- Acute renal necrosis
- Acute interstitial nephritis
- Renal papillary necrosis
What is the most common cause of Acute Renal Failure?
- Acute Tubular Necrosis
- injury and necrosis of tubular epithelial cells
How does Acute Tubular Necrosis cause problems?
- Necrotic cells plug tubules
- Obstruction decreases GFR
What are the urine findings on UA in Acute Tubular Necrosis?
- Brown, granular casts
- Decreased reabsorption of BUN
- serum BUN:Cr <15
- Decreased reabsorption of sodium
- FeNa >2%
- Inability to concentrate urine
- urine osm <500 mOsm/kg
What are the two possible etiologies of Acute Tubular Necrosis?
- Ischemia
- Nephrotoxic
What etiologic theory of Acute Tubular necrosis states that decreased blood supply results in necrosis of tubules?
Ischemic
(often preceded by prerenal azotemia)
What tubular segments are particularly susceptible to ischemic damage?
- Proximal tubule
- Medullary segment of Thick Ascending Limb
What etiologic theory of Acute Tubular Necrosis states that toxic agents cause necrosis of tubules?
Nephrotoxic
What tubular segment is particularly susceptible to Acute Nephrotoxic Tubular Necrosis?
proximal tubule