Which scenario most strongly suggests acute interstitial nephritis?

• A. Eosinophils in urine with NSAID exposure
• B. Proteinuria and edema due to glomerulonephritis
• C. Urinary tract infection with bacteriuria
• D. Stone passage with flank pain

Answer: (A)

Acute interstitial nephritis is a drug-induced hypersensitivity reaction that inflames the renal interstitium and tubules. A classic clue is eosinophils in the urine (eosinophiluria), which reflects the interstitial inflammatory process. NSAID exposure repeatedly pairs with this pattern, so seeing eosinophils in the urine after NSAID use most strongly supports AIN.

In contrast, proteinuria with edema points toward a glomerular problem like glomerulonephritis, which involves the glomerulus rather than the interstitium. Urinary tract infection with bacteriuria indicates an infectious process rather than an allergic interstitial reaction. Stone passage with flank pain suggests obstructive uropathy from calculi, not interstitial inflammation.