Interstitial nephritis

Etiology

Drugs

• Nonsteroidal antiinflammatory agents (NSAIDs)
  • Includes selective cyclooxygenase (COX)-2 inhibitors and mesalamine
• Antimicrobials
  • Penicillins and cephalosporins
  • Rifampin
  • Trimethoprim-sulfamethoxazole
  • Ciprofloxacin
  • Indinavir
• Diuretics, including furosemide and thiazides
• Cimetidine
• Allopurinol
• Proton pump inhibitors (PPIs)

Infections

• Long list, including Legionella, Leptospira, cytomegalovirus, streptococci, Mycobacterium tuberculosis, Corynebacterium diphtheriae, Epstein-Barr virus, Yersinia, polyomavirus, Enterococcus, Escherichia coli, adenovirus, and Candida

Autoimmune Disorders

• Systemic lupus erythematosus
• Sarcoidosis
• Sjögren syndrome
• IgG4 disease

Clinical Manifestations

• Can be asymptomatic, presenting with renal dysfunction
• Nausea, vomiting, malaise, and oliguria
• May have arthralgias
• With drug-induced AIN, can have an allergic syndrome that includes fever, eosinophilia, and rash

Investigations

• Creatinine, showing AKI
• CBC, showing eosinophilia
• Urine studies
  • May have pyuria and white cell casts and RBCs, and eosinophiluria
  • Usually around 1 g/day of proteinuria
  • FENa >1%