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

A mixed inflammatory cell infiltrate in a child with acute interstitial nephritis. Image courtesy of Patrick Walker, MD.
WBC casts (black arrows) in a biopsy specimen of a patient with acute interstitial nephritis. Images courtesy of Patrick Walker, MD.
Gross pathology and low-power light microscopy of kidney tissue in a neonate with ARPKD. The kidneys are enlarged but maintain their reniform shape, and are full of microscopic cysts derived from dilated distal tubules and cortical collecting ducts. Images courtesy of Patrick Walker, MD.
Microscopic renal cysts. Note the flattened to cuboidal epithelium lining the cysts. Images courtesy of Patrick Walker, MD.