Eosinophils may be found in the urine sediment on Wright's or Hansel staining. Only one third of patients with AIN are oliguric. Immunofluorescence or electron microscopy seldom reveals any changes. In some patients with acute renal failure and TIN unrelated to medications, there is evidence of circulating anti-tubular basement membrane antibodies that may primarily damage the tubules. Studies suggest that the tubulointerstitial immune response consists of phases of immune recognition, regulatory mechanisms, and effector pathways, each with a variety of components.
Most patients regain renal function, and many regain baseline renal function.
Most patients with severe renal failure who receive dialysis and supportive care regain renal function. The use of corticosteroids to treat renal failure associated with AIN remains controversial. No randomized, controlled trials have yet proved that corticosteroid therapy has any advantages over discontinuance of medication. The sulfonamides, including the combination of trimethoprim and sulfamethoxazole, can produce the classic pattern of rash, fever, and eosinophilia. The incidence of AIN with the newer quinolone antibiotics is not known, but AIN has been reported in a number of patients receiving ciprofloxacin.