Tubulointerstitial Nephritis (TIN)

Treatment

• Stop offending medication

• If sCr high treat with steroids, may need MMF

• Ensure adequate hydration

• BP is usually normal

Workup/Diagnosis

• KFP: high sCr, sAlb and other mainly normal

• CBC: eosinophilia

• Inflammatory markers: high ESR and CRP

• UA “bland”: dilute, mild proteinuria (non-nephrotic, no albuminuria), glucosuria, no hematuria, may have many WBCs due to inflammation (sterile pyuria)

• Urine eosinophil stain: may be positive

• Urine Beta-2-microglobulin: high, marker of tubular damage

• Complements, ANA, ANCA: negative in drug-induced TIN

• Kidney US: shows enlarged kidneys

• Biopsy:

  • usually not needed

  • indicated if no known offending drug, sCr very high and/or not improving

  • lymphocytic and eosinophilic tubulointerstitial inflammatory infiltrate

Prognosis/Follow up

• Mark offending med as “drug allergy”

• Can resolve fully with or without steroids/MMF as offending med stopped

• Irreversible damage/chronic TIN if offending drug ongoing

• If no clear drug etiology, must look for other causes of TIN:

  • Systemic illness (i.e. IBD, sarcoidosis)

  • TINU Syndrome (TIN+uveitis, autoimmune)

  • Infectious (granulomatous areas on biopsy)

• TIN is an under-recognized cause of AKI, remember to think of TIN if sCr disproportionately high + bland urine