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Acute interstitial nephritis

Definition
AIN is an acute disease characterized by the presence of inflammatory infiltrates and edema within the interstitium that is associated with a decline in renal function.
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Pathophysiology
AIN is mostly caused by drugs (> 75%) such as NSAIDs, allopurinol, acyclovir, furosemide, famotidine, omeprazole, phenytoin; infections (5-10%) such as viruses (HIV, CMV, EBV), Mycobacterium tuberculosis, Mycoplasma, Rickettsia, Toxoplasma, Leptospira, Schistosoma; idiopathic (5-10%) such as tubulointerstitial nephritis and uveitis syndrome; and associated with systemic diseases (10-15%) such as sarcoidosis, Sjogren's syndrome and SLE.
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Disease course
The delayed hypersensitivity immune reactions to foreign antigens result in AIN, which leads to the clinical features of AKI, acute renal failure requiring dialysis, arthralgias, fever, skin rash, and gross hematuria.
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Prognosis and risk of recurrence
AIN is not associated with an increase in mortality.
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Key sources
The following summarized guidelines for the evaluation and management of acute interstitial nephritis are prepared by our editorial team based on guidelines from the American Academy of Family Physicians (AAFP 2003).
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Guidelines

1.Diagnostic investigations

Laboratory investigations: basic laboratory investigations (urinalysis and microscopy, serum chemistry profile, CBC, liver function tests) may provide evidence suggestive of AIN and help guide conservative management or empiric treatment with steroids. Unfortunately, none of these tests have sufficient predictive value to be diagnostically reliable.
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  • Renal ultrasound

2.Diagnostic procedures

Kidney biopsy
Consider implementing a trial of supportive management in patients in whom the diagnosis seems likely, for whom a probable precipitating drug can be easily withdrawn, or who improve readily after withdrawal of a potentially offending drug.
Consider obtaining a renal biopsy in patients who do not improve following withdrawal of the likely precipitating medications, who have no contraindications to renal biopsy, and who are being considered for steroid therapy.

3.Medical management

Withdrawal of offending agents: discontinue any potential precipitating medications in patients with AIN.

More topics in this section

  • Supportive care measures

  • Immunosuppressive therapy