Definition: Infiltration of renal interstitium by inflammatory cells.

Types

 renal neutrophilic infiltration

• intratubular PMNs forming plugs
  • acute pyelonephritis

• interstitial PMNs or peritubular PMNs or capillary PMNs
  • nonspecific
  • renal vein thrombosis
  • humoral rejection of renal allograft

 renal lymphocytic infiltration

• and edema: acute interstitial nephritis (associated tubulitis)
• and renal interstitial fibrosis: chronic interstitial nephritis

 renal eosinophilic infiltration

• hypersensitivity reaction

 renal interstitial granulomas

• renal non-necrotizing granulomas
  • hypersensitivity reaction

• renal confluent granulomas
  • renal sarcoidosis

• renal necrotizing granulomas
  • renal infection
    • renal tuberculosis
    • renal fungal infection

 renal interstitial inflammation with positive tubular BM IF staining

• linear positive tubular BM IF staining
  • anti-TBM disease

• granular, discrete, immune complex deposits along TBM by IF and EM
  • lupus nephritis