FA 2011 pg 470
Can someone please explain the difference between drug-induced interstitial nephritis vs diffuse cortical necrosis vs acute tubular necrosis vs renal papillary necrosis. I've had a few questions where I've had to choose which process is occurring in a particular scenario, and I have no idea how to tell the difference between those 4 renal problems.
Thanks!
Drug induced interstitial nephritis is a hypersensitivty rxn. The drug is attaching itself to cells and you get a type1/type 4 rxn and you are going to see eosinophils in any casts. Drugs that cause this include Penicillins like methicillin, nsaids, allopurinol, sulfa drugs of all sorts, cephalsporins, PPIs, rifampin...I'd say the penicillins are the most "testable" out of all of em.
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Diffuse cortical necrosis, some sort of bad event like DIC from abruptio placenta or something along those lines is going to cause a bunch of clots in cortex and only the cortex. Medulla is spared. I think the reason for this is that the cortex gets like 90% of blood flow and so all the clots are gonna muck up the cortex.
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ATN, two general causes. Ischemic and Nephrotoxic.
Most common cause of ischemic is prerenal, as in hypovolemia or lack of blood flow to the kidneys. This means no ATP for the tubules to do stuff and since the medulla only gets a fraction of bloodflow, in any ischemic problem they are going to be messed up.
Nephrotoxic is due to poisons. Most common cause is aminoglycosides. Other causes include myoglobinuria, other drugs, shock, multiple myeloma, etc...
3 phases to ATN.
1st phase is that the kidney gets injured and starts sloughing off debris and dead stuff into the tubules. You get oliguria within like 24 hrs and muddy brown casts is how they characterize the urine. Those muddy brown casts are all the debris.
2nd phase is maintenence, the kidneys maintain that oliguria and the biggest worry during this period is that they can't get rid of stuff. Hyperkalemia can occur during this period which can lead to arrythmias and other stuff that go along with hyperK.
3rd phase is recovery. This is what the kidneys start pissing out everything and so you get tons of urine volume and so you get volume depleted and you get hypokalemic.
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Renal Papillary Necrosis. This is destruction of the renal pyramids, and common causes are diabetes, analgesics, sickle cell, and acute pyelonephritis. Common sign is a "ring sign" where the dead cells in the renal papillae don't pick up contrast on an intravenous pyelogram.
TLDR
Drug induced Interstitial Nephritis: Eosionphils, recent drug use
Diffuse Cortical Necrosis: DIC, recent trauma or something that could induce tons of clots. Medullary sparing.
ATN: Ischemic or Nephrotoxic. Muddy Brown casts. 3 phases Initiation, Maintenece, Recovery
Renal Papillary Necrosis: Diabetes, using both aspirin and acetomenophin, sickle cell, recent pyelonephritis, and ring sign....
Hope that helps.
