Acute interstitial nephritis vs Acute tubular necrosis
How to tell Acute interstitial nephritis and Acute tubular necrosis apart when a board question makes them look alike.
AIN: WBC casts, eosinophils, and a recent drug; ATN: muddy brown granular casts after ischemia or a toxin.
Side by side
AKI after NSAIDs, PPIs, beta-lactams, sulfonamides, or another new drug; fever/rash/eosinophilia can occur but are often absent.
AKI after ischemia or toxin exposure with muddy brown granular casts.
Hypersensitivity inflammation targets the renal interstitium and tubules.
Tubular epithelial cells are injured, slough, and obstruct tubular flow.
WBC casts support interstitial inflammation; eosinophiluria is suggestive when present but low-sensitivity.
Muddy brown casts, FeNa above 2%, and urine sodium above 40 support tubular necrosis.
The trap
A medication history does not automatically mean allergy; some drugs directly injure tubules.
Watch it explained
The repair move
Sort AKI by exposure, sediment, and sodium handling: WBC casts suggest AIN; muddy brown casts plus FeNa above 2% suggests ATN.
Try a free question
CoreA patient develops AKI one week after starting a beta-lactam antibiotic. Fever, rash, eosinophilia, sterile pyuria, and WBC casts are present. What is the most likely diagnosis?
Show answer and explanation
Answer: A. Acute interstitial nephritis. Drug exposure plus sterile pyuria/WBC casts points to AIN; fever, rash, and eosinophilia are supportive when present.
Why the other choices are tempting
- B. ATN causes muddy brown granular casts after ischemic or toxic tubular injury.
- C. Prerenal azotemia has intact tubular sodium conservation and bland sediment.
- D. Postrenal obstruction causes hydronephrosis and urinary retention clues.
- E. RPGN causes nephritic sediment with RBC casts and rapid renal decline.
Flashcards
Tap a card to flip it.
What urine sediment separates AIN from ATN fastest?
WBC casts support interstitial inflammation, while muddy brown granular casts point to tubular epithelial injury.
Which drug classes are classic AIN triggers?
NSAIDs, PPIs, beta-lactams, and sulfonamides are high-yield medication triggers for interstitial nephritis.
Quick answers
What is the fastest way to tell Acute interstitial nephritis from Acute tubular necrosis?
AIN: WBC casts, eosinophils, and a recent drug; ATN: muddy brown granular casts after ischemia or a toxin.
What is the key clue for Acute interstitial nephritis?
AKI after NSAIDs, PPIs, beta-lactams, sulfonamides, or another new drug; fever/rash/eosinophilia can occur but are often absent.
What is the key clue for Acute tubular necrosis?
AKI after ischemia or toxin exposure with muddy brown granular casts.
What is the common trap with Acute interstitial nephritis vs Acute tubular necrosis?
A medication history does not automatically mean allergy; some drugs directly injure tubules.