Renal: 12.2: Acute Renal Failure Flashcards
BUN:Cr ratio is greater than 15:1. Dx?
prerenal azotemia
How does acute interstitial nephritis present?
- Days to week after starting a drug:
- oliguria
- fever
- rash
- hematuria
- CVA tenderness
- Eos in the urine
What are the clinical features of acute tubular necrosis?
- oliguria with brown, granular casts
- elevated BUN and Cr
- Hyperkalemia
- Metabolic acidosis
Why does acute tubular necrosis cause hyperkalemia?
decreased renal excretion of K+
What are the consequences of renal failure?
MAD HUNGER
- Metabolic Acidosis
- Dyslipidemia (esp. triglycerides)
- Hyperkalemia
- Uremia
- Na+/H2O retention (HF, pulmonary edema, HTN)
- Growth retardation and developmental delay
- Erythropoietin failure (anemia)
- Renal osteodystrophy
What do all of the following have in common?:
- Chronic analgesic use (ie phenacetin, aspirin, NSAIDs)
- Diabetes mellitus
- Sickle cell trait or disease
- Severe acute pyelonephritis
they can cause renal papillary necrosis
What is the most common cause of acute renal failure?
acute tubular necrosis
What are the 2 major causes of acute tubular necrosis?
- ischemia
- nephrotoxic
What is allopurinol used for?
- to prevent uremia/tumor lysis syndrome kidney damage
- tx for gout
Which parts of the kidney are particularly susceptible to toxins?
proximal tubule
What is the ratio of BUN:Cr in acute tubular necrosis?
less than 15
What items are very nephrotoxic?
- aminoglycosides
- heavy metals (ie lead)
- myoglobinuria (ie crush injury)
- ethylene glycol (antifreeze)
- radiocontrast dye
- urate/uric acid (ie tumor lysis syndrome)
What is azotemia? How is it measured?
- an increase of nitrogenous waste products in the blood
- increased BUN and Cr
What is post-renal azotemia?
obstruction of the urinary tract downstream from the kidney
Which parts of the kidney are particularly susceptible to ischemia?
- proximal tubule
- medullary segment of the thick ascending limb
What happens to the tubular function in acute tubular necrosis? What will the tests of tubular function show?
- decreased
- FENa greater than 2%
- urine osm less than 500
What does post-renal azotemia do to the GFR?
decreases it
What is prerenal azotemia?
decreased blood flow to the kidney
What does pre-renal azotemia do to the GFR?
decreases it
What happens to the tubular function in prerenal azotemia? What will the tests of tubular function show?
- it’s normal
- FENa = less than 1%
- urine osm = greater than 500
What is renal papillary necrosis?
necrosis of the renal papillae –> sloughing –> gross hematuria and proteinuria
What happens to the tubular function in post-renal azotemia? What will the tests of tubular function show?
- early: remains intact
- FENa = less than 1%
- urine osm = greater than 500
- late: decreased resorption of Na
- FENa greater than 2%
- urine osm less than 500
How can acute tubular necrosis be reversed?
- tubular cells can regenerate (although slowly)
- often req’s supportive dialysis
What is oliguria?
low urine production
How does renal papillary necrosis present?
- gross hematuria
- flank pain
- proteinuria
What kind of casts are seen in acute tubular necrosis?
brown, granular
How is acute interstitial nephritis treated?
cessation of the drug
What is found in the urine in acute interstitial nephritis?
Eosinophils
What happens to the GFR in acute tubular necrosis?
it decreases
What is the hallmark of acute renal failure?
azotemia
This is a drug-induced hypersensitivity rxn of the interstitium and tubules (inflammation).
acute interstitial nephritis
Dx?
- Days to week after starting a drug:
- oliguria
- fever
- rash
- hematuria
- CVA tenderness
- Eos in the urine
acute interstitial nephritis
What is the ratio of BUN:Cr in post-renal azotemia?
- early: BUN:Cr greater than 15
- late: BUN:Cr less than 15
- *** Late = LESS than
This is an increase of nitrogenous waste products in the blood.
azotemia
What is acute interstitial nephritis?
a drug-induced hypersensitivity rxn of the interstitium and tubules (inflammation)
What are the s/s of uremia?
- increased BUN
- Nausea and anorexia
- Pericarditis
- Asterixis
- Encephalopathy
- Platelet dysfunction
This is necrosis of the renal papillae –> sloughing –> gross hematuria and proteinuria.
renal papillary necrosis
What causes renal papillary necrosis?
- Chronic analgesic use (ie phenacetin, aspirin, NSAIDs)
- Diabetes mellitus
- Sickle cell trait or disease
- Severe acute pyelonephritis
What category of azotemia is acute tubular necrosis?
intrarenal azotemia
Dx?
- injury of tubular epi cells –> necrosis –> plug tubules with brown, granular casts –> decreased GFR
acute tubular necrosis
What does acute interstitial nephritis cause?
intrarenal acute renal failure
Is acute tubular necrosis fatal? Why/why not?
- it can be
- electrolyte imbalances
Dx?
- oxalate crystals in the urine
ethylene glycol poisoning
What is acute tubular necrosis?
injury of tubular epi cells –> necrosis –> plug tubules with brown, granular casts –> decreased GFR
What is the ratio of BUN:Cr in prerenal azotemia?
greater than 15:1
What is Fomepizole? What is it used to treat?
- an alcohol dehydrogenase inhibitor
- tx for methanol or ethylene glycol poisoning
What is the tx for ethylene glycol poisoning?
Fomepizole
Pts that have ingested ethylene glycol often have _____ in their urine.
oxalate crystals
What do the following drugs have in common?:
- NSAIDs
- penicillin
- diuretics
- PPIs
- sulfonamides
- rifampin
they all can cause acute interstitial nephritis
Are BUN and Cr reabsorbed?
only BUN is
What is asterixis?
a recurrent flapping tremor of the arms, like the action of a bird’s wings
This is a recurrent flapping tremor of the arms, like the action of a bird’s wings. When is it seen?
- asterixis
- hyperammonemia (liver or kidney dysfunction)
What is the normal ratio of BUN:Cr?
15:1
How is tumor lysis syndrome prevented?
- hydration
- allopurinol
How is tubular function measured? What are the normal values?
- FENa = less than 1%
- urine osm = greater than 500
What do all these items have in common?:
- aminoglycosides
- heavy metals (ie lead)
- myoglobinuria (ie crush injury)
- ethylene glycol
- radiocontrast dye
- urate (ie tumor lysis syndrome)
they’re all nephrotoxic
Is acute tubular necrosis reversible?
yes
What causes acute interstitial nephritis?
- drugs, including:
- NSAIDs
- penicillin
- diuretics
- PPIs
- sulfonamides
- rifampin
Why does acute tubular necrosis cause metabolic acidosis? What kind of metabolic acidosis is it?
- decreased excretion of organic acids
- anion gap metabolic acidosis
What can acute interstitial nephritis progress to?
renal papillary necrosis
