A mixed inflammatory cell infiltrate in a child with acute interstitial nephritis. Image courtesy of Patrick Walker, MD.

Acute interstitial nephritis with associated acute tubular injury. There is interstitial edema and the tubules are not back to back as would be expected, due to the inflammatory and lymphocytic infiltrate in the interstitial compartment. Note the interstitial eosinophils present in the second image (black arrows). Images courtesy of Joseph Gaut, MD PhD.