Kidney inflammation. Light micrograph of a section through kidney tissue in interstitial nephritis. Nephritis refers to kidney inflammation, while the term interstitial means that the inflammation is of kidney tissue other than the glomerulus tubes (the filtrating structures of a kidney). It may be caused by a bacterial infection or a reaction to a drug or toxic material. Cessation of exposure to the offending drug or toxin is normally sufficient for recovery, though steroid drug therapy may also be required. Magnification unknown.