A 27-year-old man comes to the physician because of a 1-day history of fever and joint pains. He is being treated with cephalexin for a skin infection. His urine has turned darker. His temperature is 38.5° C (101.3° F), blood pressure is 125/70 mm Hg, pulse is 90/min, and respirations are 15/min. Examination shows a skin rash; examination otherwise shows no abnormalities. Urinalysis shows: 8 RBCs/HPF, 12 WBCs/HPF with white cell casts, eosinophiluria, and a mild degree of proteinuria. Laboratory studies show a BUN of 40 mg/dl and serum creatinine of 2.2 mg/dl. Which of the following is the most appropriate next step in management?
The patient presented in this clinical vignette is most likely suffering from drug-induced interstitial nephritis. Drug-induced interstitial nephritis occurs with many drugs such as penicillins, cephalosporins and sulfonamides. Clinical features include fever, rash and arthralgias. Other features are peripheral eosinophilia, hematuria, sterile pyuria and eosinophiluria. WBC casts may be present in the urine, but red cell casts are rare. Discontinuing the offending agent is the treatment of drug-induced interstitial nephritis.
(Choice D) Steroids may hasten recovery in cases of drug-induced interstitial nephritis, but they may aggravate the underlying infection.
(Choice C) Oral ciprofloxacin or IV ampicillin and gentamicin are used to treat acute pyelonephritis.
Educational Objective:
70% of cases with interstitial nephritis are caused by drugs such as cephalosporins, penicillins, sulfonamides, sulfonamide containing diuretics, NSAIDs, rifampin, phenytoin, and allopurinol. Discontinuing the offending agent is the treatment of drug-induced interstitial nephritis.