Nephrology: Acute Renal Failure

Question 1

Allergic Interstitial Nephritis

Answer 1

70% due to medications

can happen in first dose (don’t need build up)

penicillins, cephalosporins, sulfa drugs, allopurinol,rifampin, quinolines

(same drugs that cause all allergies of meds)

can have rash, fever, eosinophils, joint pains
(more common to have eosinophils in urine than blood - most sensitive)

may have IgE in blood (not as sensitive)

can be caused by infections

can be caused by autoimmune dz

urinalysis is most sensitive, but cannot distinguish eosinophils from other white cells (still best initial test)

most accurate test for eosinophils in urine is called Hansel’s Test or Wright’s stain (most accurate other than biopsy)

tx: stop the drug, may use steroid if this doesn’t work

Question 2

Acute Tubular Necrosis

Answer 2

Direct tubule damage

or decreased perfusion

or decreased drainage

or toxic injury

or combination of all of these

BUN/Cr 10:1

osmolality close to serum (isostenouria can’t concentrate and can’t dilute <350)

proximal tubule and thick ascending loop of henle concentrates and dilutes

muddy brown casts (deal epithelial cells)

Question 3

ATN: Pigments

Answer 3

pigments - hemoglobin, myoglobin

myoglobin - dipstick positive for blood, but don’t see any blood on urinalysis (best initial test)

hypokalemia - causes rhabdomyalosis

with pigments - hydrate and mannitol (to decrease the contact time)

(protect heart first with crush injuries, because of hyperkalemia - if EKC changes - give calcium chloride, calcium gloconate - increased CPK not as important, must be elevated 10 times or more) insulin and glucose or bicarb can be drive potassium into cells otherwise.
alkalnization prevents precipitation in tubule

Question 4

ATN: Meds

Answer 4

no specific tests, no specific cure. stop the meds. must exclude other problems.

aminoglycocides, amphoteracin, cephalosporins, contrast agents, chemotherapy, radioactive agents, NSAIDS

these needs time to build up.

low potassium and low magnesium can provoke aminoglycoside toxicity

Question 5

ATN: NSAIDS

Answer 5

directly toxic,

allergic interstitial nephritis,

constrict afferents,

membranous glomerulonephritis,

papillary necrosis

particularly bad in already damaged kidneys (old too)

Question 6

ATN: Crystals

Answer 6

ethylene glycol (antifreeze) metabolized to oxalic acid which binds calcium to make crystals - envelope shaped crystals
treat with ethanol or fermethazol to prevent formation of oxalic acid. dialysis. 

crohn’s disease also causes oxalic acid because calcium binds with fat in gut, and oxalate is absorbed at higher rate

Uric acid crystals - tumor lysis syndrome (cell nuclei have purines and pyrimidines) not negative birefringement like in joints

hypercalcemia - stones, distal RTA, blocks effect of ADH on tubule

most common cause is increased PTH

if no stones or renal insufficiency does not need to be treated

Question 7

ATN: Proteins

Answer 7

proteins - Bence-Jones directly toxic to tubules

myeloma makes bence-jones, hypercalcemia, amyloid - all bad for kidney - renal failure 2nd most common cause of death in myeloma

Question 8

oligourea

Answer 8

< 600 ccs per day urine output

Question 9

ATN: Treatment

Answer 9

correct underlying problem

hydration

supportive care

don’t do these:
low dose dopamine
diuretics
mannitol

Question 10

Stones

Answer 10

< 5 mm can pass spontaneously

> 5 mm use lithotripsy

staghorns must be removed surgically

Question 11

Papillary Necrosis

Answer 11

looks like pyelonephritis except no white cells -

flank pain, fever, pieces of necrotic material in urine.

associated with sickle cell dz. and diabetes

dx: spiral ct.
tx: no specific therapy

Question 12

ATN: Contrast induced

Answer 12

prevent this by hydration, N-acetylcysteine, bicarb

Question 13

ATN: atheroembolic disease

Answer 13

• after angiogram
• blue toes, livido reticularis, low complement, eosinophils,
  tx: no treatment