Nephritis, Interstitial

Interstitial inflammatory response with edema and possible tubular cell damage, responsible for ~10–15% of cases of intrinsic renal failure

Causes of acute interstitial nephritis

• Drugs (> 70% of cases), including

  • Penicillins

  • Cephalosporins

  • Sulfonamides

  • Nonsteroidal anti-inflammatory drugs

  • Proton pump inhibitors

  • Rifampin

  • Phenytoin

  • Allopurinol

• Infectious diseases, including

  • Streptococcal infections

  • Leptospirosis

  • Cytomegalovirus

  • Histoplasmosis

  • Rocky Mountain spotted fever

• Immunologic disorders, including

  • Systemic lupus erythematosus

  • Sjögren syndrome

  • Sarcoidosis

  • Cryoglobulinemia

• Idiopathic

Causes of chronic interstitial nephritis

• Obstructive uropathy

• Vesicoureteral reflux (reflux nephropathy)

• Analgesic nephropathy

• Heavy metals (lead, cadmium, mercury, bismuth)

• Multiple myeloma

• Gout

Fever (> 80%)

Transient maculopapular rash (25–50%)

Arthralgias

Peripheral blood eosinophilia (80%)

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

Peripheral blood eosinophilia (80%)

Acute or chronic kidney disease

White cells (95%), red cells, and white cell casts in urine

Proteinuria usually modest (< 2 g/24 h)

Kidney biopsy is diagnostic

Differential diagnosis

• Acute tubular necrosis

• Acute glomerulonephritis

• Prerenal azotemia

• Chronic glomerulopathy (eg, diabetes)

• Hypertensive nephrosclerosis

• Obstructive uropathy

Supportive measures

Removal of inciting agent

In more severe cases of drug-induced interstitial nephritis,

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

• Prednisone (60 mg/day orally for 1–2 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 renal disease

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