Acute Renal Failure Flashcards
What is acute renal failure?
Acute, severe decrease in renal failure. (Develops within days)
What is the hallmark sign of Acute renal failure?
Azotemia often with Oliguria.
What are the the different forms of Azotemia?
- Prerenal
- postrenal
- Intrarenal
What are the causes of Prerenal Azotemia / Acute renal failure?
Results from decreased bloodflow to the kidneys (hypoperfusion).
What are the consequences of renal hypoperfusion?
- Decreased GFR
- Azotemia
- Oliguria
How is this prerenal Azotemia induced Acute renal failure seen?
- Reabsorption of BUN and Creatinine ensues (serum BUN:Cr ratio > 15)
- Tubular function remains intact (urine osmolality >500 mOsm/kg
What is postrenal Azotemia / Acute renal failure?
Due to obstruction of the urinary tract downstream of the kidney e.g ureters
What are the results of Postrenal Azotemia / Acute renal failure
- Decreased GFR
- Azotemia
- Oliguria
What is the presentation in the EARLY STAGES of Postrenal acute kidney failure?
- Increased tubular pressure forces BUN into the blood Serum BUN:Creatinine >15
- Urine osmolality of >500 mOsm
What is the presentation in the LATER STAGES of Postrenal acute kidney failure?
- Tubular damage ensues resulting in decreased reabsorption of BUN (serum BUN:Creatinine ratio 2%
- Inability to concentrate urine so urine osmolality <500 mOsm
What is the most common cause of acute renal failure (Intrarenal Azotemia)?
Acute Tubular Necrosis
What is acute Tubular Necrosis?
Injury and Necrosis of Tubular epithelial cells
What are the presentations of ACUTE TUBULAR NECROSIS?
- Oliguria with Brown Granular casts
- Elevated BUN and Creatinine
- Hyperkalemia (due to increased renal excretion) with metabolic acidosis due to inability to excrete organic acids as well (increased anion gap)
What are the etiologies of Actute Tubular Necrosis?
- Injury and Necrosis of tubular epithelial cells
- Necrotic cells plug tubules decreasing GFR
- Dysfunctional tubular epithelium results in decreased reabsorption of BUN (serum BUN:Creatinine ratio 2%)
- Urine osmolality <500 mOsm
What is seen in the Urine of patients with acute tubular necrosis?
Brown granular cast