Acute Kidney Injury Flashcards
how many nephrons does one kidney have?
1 million
the functional filtering unit of the kidney that also works in reabsorption and secretion
nephrons
what are the 2 types of nephrons?
cortical nephrons
juxta-medullary nephrons
each nephron has a renal _____ and a renal _____
corpuscle
tubule
what is the renal corpuscle comprised of? (2)
bowman’s capsule
glomerular capillaries
what supplies the renal tubules with blood?
peritubular capillaries
the kidney is the only organ that has:
2 sets of arterioles + 2 sets of capillaries
what is the 3-layer filtration barrier present in the glomerulus?
endothelial cells
basement membrane
podocytes
if a spot/random urine is abnormal, what should we get? (2)
albumin/creatinine ratio (ACR)
protein/creatinine ratio (PCR)
benign proteinuria that occurs with a fever or exercise
functional
proteinuria during the day but not with the morning urine
orthostatic
what is the assessment of kidney function if urine sodium concentration is over 20?
intrarenal
what is the assessment of kidney function if urine sodium concentration is 20?
prerenal or postrenal
why will high sodium cause low osmolality?
water follows sodium = low concertation (dilute)
in what 4 situations are hyaline casts present?
concentrated urine
fever
exercise
diuretics
which condition is associated with RBC casts and dysmorphic RBCs?
glomerulonephritis (GN)
which conditions are associated with WBC and WBC casts? (2)
pyelonephritis
interstitial nephritis (AIN)
which condition is associated with pigmented/muddy brown casts?
acute tubular necrosis (ATN)
which condition is associated with granular casts?
acute tubular necrosis (ATN)
which condition is associated with broad, waxy casts?
chronic kidney disease
where does BUN come from? should BUN or creatinine be higher?
protein breakdown
BUN
where does creatinine come from?
muscle break down
what does the BUN/Cr ratio of 20:1 mean?
for every 20 units of BUN that is lost, only 1 unit of creatinine is lost
what does it mean when the BUN/Cr ratio is > 20:1? what 2 conditions can it indicate?
products are not being filtered
prerenal
dehydration
what does it mean when the BUN/Cr ratio is < 10:1? what condition can it indicate?
products are being excreted more than usual
intra-renal
what kind of relationship does GFR have with BUN and serum creatinine?
inverse
what is not affected by muscle mass, is detected earlier, responds faster than creatinine, and is filtered by the kidneys?
cystatin C
what are 3 CIs to measuring a cystatin C d/t yielding inaccurate results?
inflammation
thyroid meds
steroids
what are 5 absolute contraindications to a renal biopsy?
uncorrected bleeding disorder
severe uncontrolled HTN
renal infection
neoplasm
hydronephrosis
what are 4 relative contraindications to a renal biopsy?
solitary kidney
horseshoe kidney
end stage kidney disease
polycystic kidney disease
how much urine do the kidneys produce per hour?
30 ml/hr
rapid decline in renal function, oliguria/anuria, and the inability to eliminate uremic toxins, balance acid base, or maintain fluid levels
acute kidney injury
elevated BUN; holding onto urea
azotemia
what causes uremia symptoms?
build up of waste products in the blood
what is the most common acute kidney injury?
prerenal AKI
what is the patho for prerenal AKI?
decreased blood flow to kidneys = decreased GFR = increased BUN/Cr
why does volume depletion in prerenal AKI lead to?
activation of renin angiotensin system
a patient presents with hypotension, tachycardia, reduce skin turgor, thirst, and cool extremities. Dx?
hypovolemia d/t prerenal AKI
a patient presents with fever, hypotension, tachycardia, fatigue, dyspnea, peripheral edema, splenomegaly, ascites, caput medusa. Dx?
hypervolemia d/t prerenal AKI
what will be seen in UA / urine microscopy of a prerenal AKI?
bland +/- hyaline casts
what is the first line imaging for prerenal AKI? 2nd line?
ultrasound
biopsy
what is the treatment for hypovolemia d/t prerenal AKI?
IV crystalloids (NS or LR)
monitor ins and outs
correct electrolyte disorders
correct acid-base
what is the treatment for hypervolemia d/t prerenal AKI? (4)
lasix (cardio)
albumin (liver)
antibiotics (sepsis)
monitor electrolytes
what is a possible treatment for prerenal AKI?
renal replacement therapy (consult nephrology)
damage to the tubules, interstitium, vasculature, or glomerulus
intrarenal AKI
what are the 2 causes of intrarenal AKI?
acute tubular necrosis
acute interstitial nephritis
what is the patho for acute tubular necrosis (ATN)?
damage to tubule cells = ischemia = backing up filtrate into glomerulus drops GFR + increases BUN/Cr + increase in creatinine
a patient presents with uremia, decreased urine output, edema, hypo/hypertension, SOB, dyspnea on exertion, arrhythmias, anorexia, n/v, metallic taste, and bleeding. Dx?
acute tubular necrosis
what is the first line imaging for acute tubular necrosis?
ultrasound
what labs will indicate acute tubular necrosis?
hyperkalemia
hypermagnesemia
hyperphosphatemia
hyperuricemia
hypocalcemia
what is the treatment for acute tubular necrosis? (4)
treat cause
optimize volume status w/ fluids
electrolytes
acid-base
what is the 2nd line treatment for acute tubular necrosis?
renal replacement therapy
what is the initial phase of ATN?
first week of injury
what is the maintenance phase of ATN? (3)
1-3 weeks of early treatment
renal removal of debris
tubular cells heal
what is the recovery phase of ATN?
diuresis > 3L/day
increased GFR
decreased BUN + SCr
what is the most common etiology of acute interstitial nephritis?
drug-induced
what is the patho for acute interstitial nephritis?
inflammation of renal tissue and tubules = activates type I/IV hypersensitivity reaction
what are the 2 pathologic findings in acute interstitial nephritis?
renal edema
tubular cell damage
a patient presents with fever, rash, arthralgia, with eosinophilia. Dx?
acute interstitial nephritis
what is the diagnostic for AIN?
biopsy
what is the treatment for AIN that is proven by biopsy?
corticosteroids
what is the 2nd line treatment for AIN that is proven by biopsy, if does not respond to corticosteroids?
mycophenolate mofetil
what is the patho for postrenal AKI?
obstruction to outflow of urine = urine reflux into kidneys = increased pressure in tubules
what happens initially in postrenal AKI? what does it mimic?
intact tubules have increased reabsorption of sodium and water
prerenal
what happens over time in postrenal AKI? what does it mimic?
high pressure damages tubules = less reabsorption
intrarenal AKI
a patient presents with flank pain, hematuria, dysuria, and frequency. what could they be experiencing? (3)
postrenal AKI
ureteral stones
clots
cancer
a patient presents with anuria, suprapubic pain/mass, and enlarged prostate. what could they be experiencing? (2)
bladder neck obstruction d/t BPH or cancer
urethral obstruction
a patient presents with urinary incontinence or retention. what could be causing this? (2)
neurogenic bladder
meds
what is the diagnostic for postrenal AKI?
bedside ultrasound
what is the treatment for postrenal AKI? (3) what can be done in the case of BPH? (3)
relieve obstruction
reduce meds
+/- stone removal
in&out catheter / meds / surgery
when should a postrenal AKI patient be referred to nephrology?
if declining or not reversed in 1-2 weeks
