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What is Acute Interstitial Nephritis (AIN)?
Acute Interstitial Nephritis is a form of Acute Kidney Injury that results from immunologically mediated lymphocytic infiltration of the renal parenchymal interstitium, often with accompanying eosinophils.
Although the classic presentation consists of Acute Kidney Injury accompanied by the triad of fever, rash, and eosinophilia, the complete triad is observed in only a small minority of patients.
What are the causes of Acute Interstitial Nephritis?
Although Acute Interstitial Nephritis may develop as the result of infections, malignancy, and immunologically mediated systemic disease, it is most often associated with medication use.
The most common medications include antibiotics, particularly penicillins, cephalosporins, sulfonamides, rifampin, and proton pump inhibitors. Nonsteroidal antiinflammatory medications are associated with an atypical form of interstitial nephritis, which is usually not associated with fever, rash, or eosinophilia, and is often associated with nephrotic proteinuria.
Common Etiologies of Acute Interstitial Nephritis
- Medications
- Penicillins
- Cephalosporins
- Sulfonamides
- Rifampin
- Proton pump inhibitors
- Phenytoin
- Furosemide
- Nonsteroidal antiinflammatory drugs
- Infections
- Bacterial
- Viral
- Rickettsial
- Tuberculosis
- Systemic diseases
- Systemic lupus erythematosus
- Sarcoidosis
- Sjögren syndrome
- Tubulointerstitial nephritis and uveitis
- Malignancy
- Idiopathic
Does the presence of eosinophiluria mean a patient has AIN?
Although eosinophiluria has been considered a hallmark finding, it is neither sensitive nor specific.
It may be seen in many other conditions including pyelonephritis, prostatitis, cystitis, and atheroembolic disease.
Routine assessment for eosinophiluria in patients with AKI is not appropriate.
