Nephritis, Interstitial

KEY FEATURES

• Acute interstitial nephritis accounts for ∼10–15% of cases of intrinsic acute kidney injury (AKI)

• Interstitial inflammatory response with edema is the typical pathologic finding; tubular damage may be present as well

• Causes of acute interstitial nephritis

  • Drugs (> 70% of cases), including

    • Penicillins

    • Cephalosporins

    • Immune checkpoint inhibitors

    • Sulfonamides

    • Nonsteroidal anti-inflammatory drugs

    • Proton pump inhibitors

    • Rifampin

    • Allopurinol

  • Infectious diseases, including

    • Streptococcal infections

    • Leptospirosis

    • Cytomegalovirus

    • Histoplasmosis

    • Rocky Mountain spotted fever

  • Autoimmune disorders, including

    • Systemic lupus erythematosus

    • Sjögren syndrome

    • Sarcoidosis

    • Cryoglobulinemia

CLINICAL FINDINGS

• Fever (> 80%)

• Rash (25–50%)

• Arthralgias

• Peripheral blood eosinophilia (80%)

• The classic triad of fever, rash, and arthralgias is present in only 10–15% of cases

• Differential diagnosis

  • Acute tubular necrosis

  • Acute glomerulonephritis

  • Prerenal azotemia

  • Chronic glomerulopathy (eg, diabetes)

  • Hypertensive nephrosclerosis

  • Obstructive uropathy

DIAGNOSIS

• Peripheral blood eosinophilia (80%)

• Acute or chronic kidney disease

• Urine microscopy reveals white cells (70%), red cells (50%), and white cell casts (15%)

• Proteinuria usually modest (< 2 g/d)

• Kidney biopsy is sometimes needed

TREATMENT

• Supportive measures

• Prompt removal of the inciting agent

• Corticosteroids

  • Consider giving if kidney injury persists despite removal of culprit drug

  • Efficacy is diminished if started more than 1–2 weeks after onset of AKI

  • For severe cases of drug-induced interstitial nephritis

    • Short-term, high-dose methylprednisolone (0.25–0.5 g/d intravenously for 1–4 days) or

    • Prednisone (60 mg/d orally for 4–6 weeks) followed by a taper can be used

• Prognosis good; recovery occurs over weeks to months

• Dialysis may be necessary in up to 33%

• Patients rarely progress to end-stage kidney disease

• Prognosis worse in those with prolonged courses of oliguric failure and advanced age