Fever occurs in most cases and may be accompanied by an urticarial rash. The urine sediment usually reveals WBCs, RBCs, and WBC casts but is occasionally bland. Proteinuria is usually minimal. The kidneys usually are large because of interstitial edema and avidly take up radioactive gallium or radionuclide-labeled WBCs. However, a negative radionuclide scan with gallium-67 does not preclude the diagnosis.
Diagnosis involves stopping the suspected offending drug and observing the response.
No further evaluation is required if renal function begins to improve within several days. Glomeruli usually are normal. The earliest finding is interstitial edema, typically followed by interstitial infiltration with lymphocytes, plasma cells, eosinophils, and few PMNs. The presence of noncaseating granulomas suggests sarcoidosis. Immunofluorescence or electron microscopy seldom reveals any pathognomonic changes.