Diagnosis: acute interstitial nephritis

Here is why...

    Acute interstitial nephritis (AIN) can result from an allergic reaction to a drug. Our patient was taking phenoxymethylpenicillin, a type of penicillin, for his mouth abscess. Penicillin is associated with AIN because it commonly causes an immune response in patients. Penicillin is removed from the body when it is filtered through the tubules of the nephron. The immune response of the renal tubular epithelium inadvertently injures the nephron.

Symptoms of AIN due to an allergic reaction

On the body:
fever
skin rash

In the urinalysis:
mild proteinuria
variable degrees of hematuria
variable degrees of leukocyturia
presence of casts (leukocyte, granular, hyaline, and renal cell)
renal epithelial cells
drug crystals