Acute Kidney Injury - Exam 1 Flashcards
What are the normal culprits behind an acute kidney injury?
inability to manage: fluid, electrolytes and acid base balance
decreased excretion of urea and creatinine
In an acute kidney injury, by the time _____ rises, ____ usually has already fallen significantly!
serum Cr
GFR
What criteria for dx AKI is used most commonly?
KDIGO
What is normal urine output? **What is anuria? **oliguria? polyuria?
normal: 800-2000 mL/day
**anuria: less than 50mL
**oliguria: less than 400mL
polyuria: excessive urine 2500-3000mL +
What does anuria make you think is the underlying cause?
Acute obstruction, cortical necrosis, aortic dissection
aka very bad finding!!
Define azotemia
Define uremia
Azotemia - ↑ nitrogenous wastes in the blood (no symptoms present)
Uremia - nonspecific SYMPTOMS caused by elevated nitrogenous waste (especially urea) in the blood (symptoms will be vague and basically the pt does not feel well)
What are the 3 broad categories of acute kidney injury? What is the MC cause of AKI? What is the underlying cause?
**Pre-renal azotemia- MC due to renal hypoperfusion
intra-renal
post-renal
What is intrinsic kidney injury due to? What is the LEAST common cause of AKI? What is the underlying cause?
intrinsic kidney: direct injury
postrenal obstruction- LEAST common
caused by obstruction of urinary flow
What is the underlying cause of prerenal azotemia? Give 3 examples
inadequate renal perfusion aka anything that changes the blood flow to the kidneys
- hypovolemia due to dehydration, hemorrhage, GI loss, diuresis, pancreatitis, burns, peritonitis.
- Decreased cardiac output - decompensated HF, cardiogenic shock, PE, pericardial tamponade, arrhythmias, liver failure
- Changed vascular resistance
↓ - sepsis, anaphylaxis, anesthesia
↑ - epinephrine, high-dose dopamine, renal artery stenosis
Meds that interfere with renal vascular autoregulation
NSAIDs, iodinated contrast, ACEIs/ARBs
What arteriole does angiotensin II prefer?
works on both but prefers Efferent arteriole
What affect do NSAIDs have on the kidney?
NSAIDs work on the Afferent arteriole by blocking the action of prostaglandins that would normally dilate the afferent arteriole. Blocking this action harms the kidney because it leads to decreased perfusion
In prerenal azotemia what is the BUN/Cr ratio? What should the FENa+ be? Describe the urinary sediment? What is the urine osmolality
BUN:Cr ratio > 20:1 usually
If oliguric, there should be a low fractional excretion of sodium (FENa+) in the urine - <1%
urine sediment is usually normal, may see some hyaline casts
urine osmolality is normal
In prerenal azotemia, hyaline casts are formed from ______ secreted by tubule
Tamm-Horsfall mucoprotein
What is the treatment for prerenal azotemia?
treat the underlying cause to why the kidneys are having decreased blood flow
Maintain euvolemia
Correct abnormal electrolytes
Avoid nephrotoxic drugs
What is the MC cause of postrenal obstruction in men? What are some generic causes?
BPH
devices such as an obstructed foley catheter, medications, cancer, retroperitoneal fibrosis, neurogenic bladder
Anuria or polyuria possible
May have lower abdominal pain
May see large prostate, distended bladder, pelvic/abdominal mass
What am I?
What are the dx studies/procedure of choice?
post renal obstruction
Bladder catheterization and/or abdominopelvic US can be helpful to look for hydroureter and obstruction
What am I?
renal US showing hydronephrosis
What is the BUN/Cr ratio in postrenal obstruction? What is the urine osmolality? What may be seen in the urine sediment?
Lab Findings:
↓ GFR and ↑ BUN/Cr with BUN:Cr > 20:1 usually
Urine sodium - varies
Urine osmolality - 400 mosm/kg or less
Urine sediment - often normal; may see RBCs, WBCs, crystals
In postrenal AKI where is the obstruction more common?
in the lower abdomen
In many cases, what does prerenal azotemia lead to ? What are 3 forms of intrinsic kidney injury? Which one is MC?
tubular injury
**Acute Tubular Necrosis- MC
Acute Glomerulonephritis
Acute Interstitial Nephritis
What are the 3 major causes of acute tubular necrosis?
ischemia
nephrotoxins
sepsis
in ATN, what is ischemia characterized by?
by inadequate GFR and inadequate blood flow to maintain perfusion
Prolonged hypotension or hypoxemia
endogenous or exogenous more commonly cause ATN?
Exogenous more commonly cause damage
Name the top 3 common exogenous nephrotoxins. Give a few others
- Aminoglycosides : examples -> gentamicin, tobramycin, amikacin, plazomicin, streptomycin, neomycin, and paromomycin (gentamicin is the WORST and streptomycin in the least harmful)
- Amphotericin B (hurts kidneys after 2-3 grams)
- Vanc
sulfonamides, cephalosporins, tetracycline, acyclovir, foscarnet, IV contrast, methotrexate, cyclosporine, cisplatin, heavy metals, ethylene glycol, insecticides, herbicides
For aminoglycosides, how long does the medication remain in the renal tissue? What is used to predict toxicity?
Can remain in renal tissues up to 1 month
Trough levels are most useful to predict toxicity
Give some examples of endogenous nephrotoxins
myoglobinuria due to rhabdomyolysis
hemoglobinuria
hyperuricemia
bence jones protein