Treatment for Acute Interstitial Nephritis (NSAID-induced)
The primary treatment for NSAID-induced acute interstitial nephritis is immediate discontinuation of the offending agent, followed by corticosteroid therapy initiated within 7 days of diagnosis to improve recovery and decrease the risk of chronic renal impairment. 1
Diagnostic Approach
- Assess temporal relationship between NSAID administration and AKI onset
- Evaluate urinalysis findings:
- Pyuria, hematuria, white cell casts, and possible eosinophiluria
- Fractional excretion of urea (FEUrea) <28% (sensitivity 75%, specificity 83%)
- Consider renal biopsy for definitive diagnosis, especially in severe or atypical cases
- Kidney biopsy will show interstitial inflammation, tubulitis, and edema 2
Treatment Algorithm
Step 1: Immediate Management
- Discontinue the causative NSAID immediately 2
- This is the most critical intervention as continued exposure significantly worsens outcomes
- Avoid all nephrotoxic medications during recovery 3
Step 2: Corticosteroid Therapy
Based on severity of renal dysfunction:
| Grade | Treatment |
|---|---|
| Mild (Grade 1) | Monitor creatinine weekly |
| Moderate (Grade 2) | Prednisone 0.5-1 mg/kg/day orally, taper over 4-6 weeks if improved |
| Severe (Grade 3-4) | Methylprednisolone 1-2 mg/kg/day IV; consider pulse methylprednisolone in severe cases; taper over at least 4 weeks once improved [1] |
Step 3: Supportive Care
- Maintain euvolemia
- Adjust medication dosages based on renal function
- Monitor for electrolyte imbalances
- Consider renal replacement therapy for:
- Hyperkalemia
- Refractory acidosis
- Volume overload
- Uremic symptoms 1
Step 4: Advanced Therapy for Refractory Cases
- If no improvement after 3-5 days of corticosteroid therapy, consider additional immunosuppression:
Important Considerations
Timing of Treatment
- Early administration of corticosteroids (within 7 days of diagnosis) is associated with better outcomes 1
- Delayed treatment significantly increases risk of progression to chronic kidney disease 2
Risk Factors for Progression to Chronic Disease
- Prolonged NSAID use (>1 month) prior to diagnosis increases risk of permanent renal insufficiency by 88% 5
- Presence of interstitial granulomas on biopsy (found in 31% of cases with permanent damage) 5
- Tubular atrophy on histology 5
Prevention of Recurrence
- Avoid re-exposure to the causative NSAID and all other NSAIDs due to high risk of recurrence 1
- Educate patients to avoid taking NSAIDs or any new medications without consulting their nephrologist 3
- Use ACE inhibitors, decongestants, antivirals, antibiotics, and herbal products with caution during recovery 3
Prognosis
- NSAID-induced AIN has a 56% risk of causing permanent renal insufficiency if not properly managed 5
- Early recognition and discontinuation of the offending agent significantly improves outcomes
- Patients should be monitored for development of chronic kidney disease following AIN 2
Pitfalls to Avoid
- Misdiagnosing as other forms of AKI (check for allergic manifestations and eosinophiluria)
- Continuing NSAID therapy during evaluation (discontinue immediately upon suspicion)
- Delaying corticosteroid therapy (initiate within 7 days for best outcomes)
- Using the "triple whammy" combination of NSAIDs, diuretics, and ACE inhibitors/ARBs during recovery 3
- Restarting NSAIDs after recovery (high risk of recurrence)