9. Acute tubulointerstitial nephritis

Question 1

What are the general characteristics of acute interstitial nephritis?

Answer 1

• Inflammation involving intersitium (tissue that surrounds glomeruli and tubules)
• Accounts for 10-15% of cases of AKI

Question 2

What is the etiology of acute interstitial nephritis?

Answer 2

• Acute allergic reaction to medication (e.g. penicillin, cephalosporins, diuretics, anticoagulants, phenytoin, …)
• Infections (mainly in children)
  
  • Streptococci, Legionella
• Collagen vascular disease (e.g. sarcoidosis)
• Autoimmune disease (e.g. SLE, Sjögren)

Question 3

What are the clinical features of acute interstitial nephritis?

Answer 3

• AKI
• Rash, fever, eosinophilia
• Pyuria and hematuria (may be present)

Question 4

How do we diagnose acute interstitial nephritis?

Answer 4

• Renal function test (increased BUN and Cr levels)
• Urinalysis: eosinophiles, hematuria, mild proteinuria
• Renal biopsy: distinguishes between ATN and AIN (not often done due to invasiveness)

Question 5

What is the treatment of acute interstitial nephritis?

Answer 5

• Removal of offending agent
• Treat infection
• Corticosteroids if autoimmune disorder

Question 6

What is the prognosis of acute interstitial nephritis?

Answer 6

• 40% of patients with drug­-related AIN will be left with CKD
• 10% will progress to ESRD
• Final GFR does not correlate with the maximal value during the early acute phase.
• Of those with milder disease, the majority will return to baseline renal function. Even those requiring renal replacement therapy for AKI usually regain independent renal function.