Acute Renal Failure Flashcards
What is acute renal failure? What are the hallmarks? What are the three classifications? What is the most common cause?
Acute, severe decrease in renal function (develops within days). Hallmark is azotemia (increased BUN and creatnine [Cr]), often with oliguria. Divided into prerenal, postrenal and intrarenal azotemia based on etiology. Prerenal aotemia.
What causes prerenal azotemia? What does it result in? What happens to serum BUN:Cr ratio? Tubular function and urine osmolality?
Due to decreased blood flow to the kidneys. Decreased blood flow results in low GFR, azotemia and oliguria. Reabsorption of fluid and BUN ensues (serum BUN:Cr >15); intact tubular function (FENa 500mOsm/kg).
What causes postrenal azotemia? What does it result in? What happens to serum BUN:Cr ratio? Tubular function and urine osmolality in early obstruction?
Due to obstruction of urinary tract downstream from the kidney (e.g. ureters). Decreased outflow results in low GFR, azotemia and oliguria. During early stage , increased tubular pressure forces “BUN” into the blood (serum BUN:Cr >15); intact tubular function (FENa 500mOsm/kg).
What causes postrenal azotemia? What does it result in? What happens to serum BUN:Cr ratio? Tubular function and urine osmolality in late obstruction?
Due to obstruction of urinary tract downstream from the kidney (e.g. ureters). Decreased outflow results in low GFR, azotemia and oliguria. With long-standing obstruction, tubular damage ensues resulting in decreased reabsorption of BUN (serum BUN:Cr ratio 2% and inability to concentrate urine (Urine osm
What causes prerenal azotemia? What does it result in? What happens to serum BUN:Cr ratio? Tubular function and urine osmolality?
Due to decreased blood flow to the kidneys. Decreased blood flow results in low GFR, azotemia and oliguria. Reabsorption of fluid and BUN ensues (serum BUN:Cr >15); intact tubular function (FENa 500mOsm/kg).
What causes postrenal azotemia? What does it result in? What happens to serum BUN:Cr ratio? Tubular function and urine osmolality in late obstruction?
Due to obstruction of urinary tract downstream from the kidney (e.g. ureters). Decreased outflow results in low GFR, azotemia and oliguria. With long-standing obstruction, tubular damage ensues resulting in decreased reabsorption of BUN (serum BUN:Cr ratio 2% and inability to concentrate urine (Urine osm
What is the most common cause of acute renal failure? What does it cause? What is seen in the urine? What are the two etiologies?
Acute tubular necrosis which is injury and necrosis of tubular epithelial cells. Necrotic cells plug tubules. Obstruction decreases GFR. Brown, granular casts are seen in the urine. Etiology may be ischemic or nephrotoxic.
In acute tubular necrosis, what is the serum BUN:Cr ratio? Tubular function and urine osmolality?
Decreased reabsorption of BUN (serum BUN:Cr ratio 2% and inability to concentrate urine (Urine osm
In acute tubular necrosis, what is the serum BUN:Cr ratio? Tubular function and urine osmolality?
Decreased reabsorption of BUN (serum BUN:Cr ratio 2% and inability to concentrate urine (Urine osm
What is ischemia in acute tubular necrosis preceded by? Which two structures are particularly susceptible?
Decreased blood supply results in necrosis of tubules. Often preceded by prerenal aztemia. Proximal tubule and medullary segment of the thick ascending limb are particularly to ischemic damage.
Which structure is particularly susceptible in acute tubular necrosis caused by nephrotoxic agent? What causes it? How is it treated?
Proximal tubule. Causes include aminoglycosides, heavy metals, myoglobinuria, ethylene glycol, radiocontrast dye and urate (tumor lysis syndrome). Hydration and allopurinol are used prior to initiation of chemotherapy to decrease risk of urate-induced ATN.
A patient presents with oliguria with elevated BUN and creatnine. his Potasium is elevated and his pH is low. His urine has brown granular casts. What doe she have? Is this a reversible disorder? How is it managed?
Acute tubular necrosis. Reversible, but often requires supportive dialysis since electrolyte imbalances can be fatal.
Why does oliguria in acute renal failure take 2 - 3 weeks to recover?
Tubular cells take time to reenter the cell cycle and regenerate.
A patient presents with oliguria, fever and rash 2 weeks after starting on a course of penicillin. Hs urine is notable for eosinophils. What is causing this presentation? What structures are affected? What can it lead to? What are the usual suspects? How does it resolve? What can it progress to?
Acute interstitial nephritis which is a drug-induced hypersensitivity involving the interstitium and tubules. Results in acute renal failure (intrarenal azotemia). Causes include NSAIDs, penicillin and diuretics. Resolves with cessation of drug. May progress to renal papillary necrosis.
A patient presents with oliguria, fever and rash 2 weeks after starting on a course of penicillin. His urine is notable for eosinophils. What is causing this presentation? What structures are affected? What can it lead to? What are the usual suspects? How does it resolve? What can it progress to?
Acute interstitial nephritis which is a drug-induced hypersensitivity involving the interstitium and tubules. Results in acute renal failure (intrarenal azotemia). Causes include NSAIDs, penicillin and diuretics. Resolves with cessation of drug. May progress to renal papillary necrosis.
